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255 S. King Street, Suite 800, Seattle, WA 98104 | 206.426.2600 | JACOBSONENGINEERS.COM TECHNICAL INFORMATION REPORT Hazen High School Improvements 1101 Hoquiam Ave NE Renton, WA 98059 July 11th, 2025 PREPARED FOR: Renton School District 7812 South 124th Street Seattle, WA 98178 PREPARED THROUGH: Integrus Architecture Alexandra Forin 117 S Main St, Suite 100 Seattle, WA 98104 PREPARED BY: Jacobson Consulting Engineers Sascha Eastman 206.426.2600 sascha@jacobsonengineers.com DEVELOPMENT ENGINEERING msippo 08/07/2025 Surface Water Enginering jfarah 08/11/2025 i Technical Information Report for HAZEN HIGH SCHOOL IMPROVEMENTS JCE Project No. C240033-0208 July 11, 2025 TABLE OF CONTENTS 1. PROJECT OVERVIEW ........................................................................................................................... 3 GENERAL DESCRIPTION .............................................................................................................................. 3 EXISTING CONDITIONS ................................................................................................................................. 3 PROPOSED DRAINAGE SYSTEM ................................................................................................................. 4 WATER QUALITY TREATMENT .................................................................................................................... 4 2. CONDITIONS AND REQUIREMENTS SUMMARY ..................................................................................... 6 CORE REQUIREMENT #1: DISCHARGE AT THE NATURAL LOCATION .................................................. 6 CORE REQUIREMENT #2: OFFSITE ANALYSIS ......................................................................................... 6 CORE REQUIREMENT #3: FLOW CONTROL FACILITIES.......................................................................... 6 CORE REQUIREMENT #4: CONVEYANCE SYSTEM .................................................................................. 7 CORE REQUIREMENT #5: CONSTRUCTION STORMWATER POLLUTION PREVENTION ................... 7 CORE REQUIREMENT #6: MAINTENANCE AND OPERATIONS ............................................................... 7 CORE REQUIREMENT #7: FINANCIAL GUARANTEES AND LIABILITY.................................................... 8 CORE REQUIREMENT #8: WATER QUALITY FACILITIES ......................................................................... 8 CORE REQUIREMENT #9: ON-SITE BMPS .................................................................................................. 8 SPECIAL REQUIREMENT #1: OTHER ADOPTED AREA-SPECIFIC REQUIREMENTS ........................... 9 SPECIAL REQUIREMENT #2: FLOOD HAZARD AREA DELINEATION ..................................................... 9 SPECIAL REQUIREMENT #3: FLOOD PROTECTION FACILITIES ............................................................ 9 SPECIAL REQUIREMENT #4: SOURCE CONTROLS .................................................................................. 9 SPECIAL REQUIREMENT #5: OIL CONTROL .............................................................................................. 9 SPECIAL REQUIREMENT #6: AQUIFER PROTECTION AREA ................................................................10 3. OFFSITE ANALYSIS .......................................................................................................................... 11 FIELD INSPECTION ......................................................................................................................................11 DRAINAGE SYSTEM PROBLEM DESCRIPTIONS .....................................................................................11 UPSTREAM ANALYSIS .................................................................................................................................11 DOWNSTREAM ANALYSIS ..........................................................................................................................11 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS .........................................................................11 4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER QUALITY FACILITY ANALYSIS AND DESIGN .................................................................................................................................................. 12 FLOW CONTROL SYSTEM (PART D) .........................................................................................................13 WATER QUALITY SYSTEM (PART E) .........................................................................................................13 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................................................. 14 6. SPECIAL REPORTS AND SUMMARY ................................................................................................... 17 7. OTHER PERMITS ............................................................................................................................. 18 8. CSWPP ANALYSIS AND DESIGN ......................................................................................................... 19 HAZEN HIGH SCHOOL IMPROVEMENTS ii STANDARD REQUIREMENTS .....................................................................................................................19 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ....................................... 20 BOND QUANTITIES WORKSHEET..............................................................................................................20 FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH .......................20 DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND WQ FACILITIES .....................................................................................................................................................20 10. OPERATIONS AND MAINTENANCE MANUAL ........................................................................................... 21 11. FIGURES ............................................................................................................................................... 22 12. APPENDICES ......................................................................................................................................... 23 APPENDIX A – BOND QUANTITY WORKSHEET .......................................................................................23 APPENDIX B – STORMWATER CALCULATIONS ......................................................................................23 APPENDIX C – STORMWATER POLLUTION PREVENTION PLAN (SWPPP) ........................................23 APPENDIX D – FACILITY SUMMARY SHEET, DECLARATION OF COVENANT ....................................23 HAZEN HIGH SCHOOL IMPROVEMENTS 3 1. PROJECT OVERVIEW GENERAL DESCRIPTION This Drainage Report provides the design narrative and discussion for the Hazen High School Improvements project, which is tentatively scheduled to begin construction in April 2025 and reach final completion in January 2029. The stormwater design for the project follows the requirements outlined in the 2022 City of Renton Surface Water Design Manual (RSWDM). Hazen High School is located within the City of Renton’s jurisdiction at 1101 Hoquiam Ave NE, Renton, WA 98059, and includes the following parcel numbers: 1023059057, 1023059072, 1023059201, 1023059278, 1023059292, 1023059084, 1023059277, and 1023059094, totaling 29.28 acres. The site is bounded by Duvall Ave NE to the west, NE 12th Street to the north, an access road and paved pedestrian pathway along NE 10th Street to the south, and Hoquiam Ave NE to the east. Single-family residential properties border the site to the west. Additionally, the Hazen High School property surrounds an existing church located at 1063 Hoquiam Ave NE (Parcel Number 1023059146) in the center of the campus. The school also shares the eastern parking lot, located north of the tennis courts, with the church. See Figure 2 – Vicinity Map for additional context. The proposed project includes replacement of the existing baseball and softball fields with new synthetic turf fields. In addition to field improvements, the project will include installation of stormwater, geothermal, and electrical utilities, a new security vestibule for the existing school building, temporary classroom portables, and new and replaced paving. Proposed paving includes utility trenching, a new mechanical yard, sidewalk replacement for security bollard installation, and sidewalk replacement surrounding the new main entry security vestibule. EXISTING CONDITIONS The Hazen High School property is currently developed with one large school building located in the northeast portion of the site, surrounded on all sides by associated sidewalks, parking areas, and internal drive aisles. The western portion of the campus includes a baseball field, while the southwest corner features a rubberized track and grass athletic field. A softball field is located directly south of the school building, and tennis courts occupy the southeast corner of the site. Landscaping, trees, and other vegetation are present throughout the campus, particularly between the building and driving surfaces. A notable area of dense existing vegetation is located west of the baseball field. See Figure 4 – Existing Conditions for reference. A geotechnical investigation determined that site soils primarily consist of existing fill from prior development, dense silty Vashon ice-contact deposits, and very dense Vashon Lodgment till. Refer to the project geotechnical report and Figure 8 – Soils Map for further detail. The site's topography is generally flat, with gentle slopes radiating away from the school building in all directions. Due to the site's size and drainage characteristics, the campus is divided into multiple Threshold Discharge Areas (TDAs): · TDA #1 includes the existing baseball field, which is assumed to be underdrained. Stormwater from this area is routed to an existing pond located southwest of the field. From there, water flows to a dispersion trench and discharges westward through native vegetation toward Duvall Ave NE. · TDA #2 comprises central site areas, including the grass play field north of the baseball field, parking lots west and south of the building, the rubberized track and grass field, and the grass softball field. Runoff from this area flows south toward the existing stormwater system in NE 10th Street. · TDA #3 encompasses parking areas north, east, and south of the school building, the existing grass multipurpose field, and the tennis court. A summary of existing land cover characteristics within each TDA planned for redevelopment is provided in Table 1 below and illustrated in Figure 4 – Existing Conditions. HAZEN HIGH SCHOOL IMPROVEMENTS 4 TABLE 1 – DISTURBED AREA EXISTING SITE CONDITIONS Land Cover TDA #1 TDA #2 TDA #3 TOTAL Impervious Surface (SF) 0 436 5,227 5,663 Pervious Surface (SF) 102,802 47,916 0 150,718 Total Area (SF) 102,802 48,352 5227 156,381 % Impervious 0% 0.90% 100% 3.62% PROPOSED DRAINAGE SYSTEM As noted above, the Hazen High School campus is divided into three Threshold Discharge Areas (TDAs). The proposed drainage design maintains the existing discharge points for each TDA to preserve natural hydrologic patterns and comply with flow control requirements in the 2022 City of Renton Surface Water Design Manual. TDA #1 includes the existing baseball field in the western portion of the site. The field is assumed to be underdrained and currently discharges to an existing pond near the southwest corner, which outlets via a dispersion trench to native vegetation west of the site, ultimately draining toward Duvall Ave NE. Recent improvements along Duvall Ave NE include new curb, gutter, sidewalk, and stormwater infrastructure, including water quality treatment and a 12-inch storm main. The redeveloped synthetic turf baseball field, considered to be 100% impervious, will include an underdrain system that conveys runoff to a new Contech CDS Separator for presettling, then to a StormTrap modular detention system located west of the field. The detained stormwater will then discharge through a 54-inch Type II catch basin with a flow control structure, then into a 12-inch storm pipe before connecting to the existing storm main in Duvall Ave NE. See Civil Plan Sheet C203 and Figure 5A – Offsite Drainage for continuation of the downstream system. TDA #2 includes the central portion of the site: the grass play field north of the baseball field, parking areas west and south of the school building, the rubberized track and field, and the softball field. Runoff from this area currently flows south through a 12-inch storm pipe to the existing storm system in NE 10th Street. The proposed synthetic turf softball field will be underdrained and routed to a new StormTech chamber detention system. From there, flow will discharge to a 54-inch Type II catch basin with a flow control structure, then through a 12-inch storm pipe that connects to the existing system conveying flows south to NE 10th Street. See Civil Plan Sheet C205 and Figure 5B – Offsite Drainage for continuation of the downstream system. TDA #3 includes parking areas on the north, east, and south sides of the school building, the existing grass multipurpose field, and the tennis courts. Stormwater from this area discharges to the Hoquiam Ave NE storm system at multiple locations along the eastern property line. Runoff from the new security vestibule, bollard replacements, and driveway improvements will tie into an existing storm connection on Hoquiam Ave NE. See Civil Plan Sheets C205 and C207 and Figure 5C – Offsite Drainage for additional detail. Table 2 below summarizes the land cover characteristics of the proposed project disturbed areas in each TDA. See Figure 3 - New + Replaced Impervious Areas. TABLE 2 – DISTURBED AREA PROPOSED SITE CONDITIONS Land Cover TDA #1 TDA #2 TDA #3 TOTAL New Impervious Surface 102,802 47,916 0 150,718 Replaced Impervious Surface 0 436 5,227 5,663 Total Area 102,802 48,330 5,227 156,381 WATER QUALITY TREATMENT Per the 2022 City of Renton Surface Water Design Manual, water quality treatment is required when a project includes 5,000 square feet or more of pollution-generating impervious surfaces (PGIS) or ¾ acre or more of HAZEN HIGH SCHOOL IMPROVEMENTS 5 pollution-generating pervious surfaces. This project proposes 150,718 square feet (3.46 acres) of new pollution generating impervious surfaces including new synthetic turf fields with pollution-generating infill materials. This exceeds the threshold, and therefore Enhanced Basic Water Quality Treatment is required. To meet this requirement, the project will install two 4'x6' Modular Wetland Systems: One at the baseball field in TDA #1 and one at the softball field in TDA #2. Each Modular Wetland unit will be installed downstream of the respective stormwater flow control facility, providing water quality treatment prior to discharge from the site and is sized based on the 2-year release rate from each respective flow control facility. See Appendix B for MGSFlood water quality facility sizing calculations and Figure 12 – Flow Control Basins for contributing basins to be treated. HAZEN HIGH SCHOOL IMPROVEMENTS 6 2. CONDITIONS AND REQUIREMENTS SUMMARY The proposed Hazen High School Improvements project will result in more than 7,000 square feet of land disturbing activity to construct the proposed improvements and will require Full Drainage Review by the City of Renton as directed in Section 1.1.1 of the 2022 Renton Surface Water Design Manual (RSWDM). See Figure 6 – Project Minimum Requirements Flow Chart for how the level of drainage review was determined for this project. This section of the report will address the (9) nine required minimum requirements and (6) six special requirements for Full Drainage Review as set forth by Section 1.1.2.4 of the 2022 RSWDM. CORE REQUIREMENT #1: DISCHARGE AT THE NATURAL LOCATION All stormwater runoff and surface water from a project must be discharged at the natural location so as not to be diverted onto or away from downstream properties. The manner in which stormwater runoff and surface water are discharged from the project site must not create a significant adverse impact to downhill properties or drainage facilities (see "Discharge Requirements" below). Drainage facilities as described above means a constructed or engineered feature that collects, conveys, stores, treats, or otherwise manages surface water or stormwater runoff. “Drainage facility” includes, but is not limited to, a constructed or engineered stream, lake, wetland, or closed depression, or a pipe, channel, ditch, gutter, flow control facility, flow control BMP, water quality facility, erosion and sediment control facility, and any other structure and appurtenance that provides for drainage. Note: Projects that do not discharge all project site runoff at the natural location will require an approved adjustment of this requirement (see Section 1.4). CED may waive this adjustment, however, for projects in which only a small portion of the project site does not discharge runoff at the natural location and the runoff from that portion is unconcentrated and poses no significant adverse impact to downstream properties. Stormwater runoff is currently discharged from the site at (3) three locations. TDA #1 consists of the existing baseball field, which we assume to be underdrained and routed to an existing pond to the southwest of the field, where water is then routed to a dispersion trench that flows to the west toward Duvall Ave NE through native vegetation. TDA #2 consists of areas at the center of the site, including the grass play field to the north of the baseball field, parking lots to the west and south of the school building, the rubberized track and grass field, and grass softball field, which flow to the south toward the existing storm system in NE 10th St. TDA #3 consists of parking areas north, east and south of the school building, the existing grass multipurpose field, and tennis courts. The proposed drainage systems will continue directing stormwater to these existing points of discharge. See Figure 3 – New + Replaced Impervious Areas and Figure 4 - Existing Conditions. CORE REQUIREMENT #2: OFFSITE ANALYSIS All proposed projects must submit an offsite analysis report that assesses potential offsite drainage and water quality impacts associated with development of the project site, and that proposes appropriate mitigation of those impacts. The initial permit submittal shall include, at minimum, a Level 1 downstream analysis as described in Section 1.2.2.1 of the RSWDM. If impacts are identified, the proposed projects shall meet any applicable problem-specific requirements specified in Section 1.2.2.2 for mitigation of impacts to drainage problems and Section 1.2.2.3 for mitigation of impacts to water quality problems. The project is NOT exempt from performing an Offsite Level 1 Downstream Analysis as the project adds more than 2,000 square feet of new impervious surface, AND does construct or modify a drainage pipe/ditch that is 12 inches or more in size/depth or that receives runoff from a drainage pipe/ditch that is 12 inches or more in size/depth, even though the project will create less than 3/4 acres of new pervious surface, AND does not contain or lie adjacent to a landslide, steep slope, or erosion hazard area as defined in RMC 4-3-050. Additionally, there are no known Drainage Complaints downstream or adjacent to project property that are related to the Hazen High School campus according to the City of Renton GIS and King County iMap. A Level 1 Downstream Analysis has been performed for this project. See Downstream Analysis in Section 3 Off-Site Analysis of this report. CORE REQUIREMENT #3: FLOW CONTROL FACILITIES All proposed projects, including redevelopment projects, must provide onsite flow control facilities to HAZEN HIGH SCHOOL IMPROVEMENTS 7 mitigate the impacts of storm and surface water runoff generated by new impervious surface, new pervious surface, and replaced impervious surface targeted for flow mitigation as specified in the following sections. Flow control facilities must be provided and designed to perform as specified by the area-specific flow control facility requirement in Section 1.2.3.1 of the RSWDM and in accordance with the applicable flow control facility implementation requirements in Section 1.2.3.2. The project is NOT exempt from providing Flow Control Facilities as the project proposes more than 5,000 square feet of new plus replaced impervious surface in each of the three TDAs for this site. Each TDA triggering Core Requirement #3 will have a dedicated flow control system installed, conforming to the forested Flow Control Duration Standard. These systems will be described in greater detail in Section 4 of this report. CORE REQUIREMENT #4: CONVEYANCE SYSTEM All engineered conveyance system elements for proposed projects must be analyzed, designed, and constructed to provide a minimum level of protection against overtopping, flooding, erosion, and structural failure as specified in the following groups of requirements: · "Conveyance Requirements for New Systems," Section 1.2.4.1 · "Conveyance Requirements for Existing Systems," Section 1.2.4.2 · "Conveyance System Implementation Requirements," Section 1.2.4.3 This project is NOT exempt from Conveyance Requirements for New Systems as there are new pipe system additions from the proposed improvements. All new conveyance systems will be designed to meet requirements. See Appendix B for Conveyance Calculations. CORE REQUIREMENT #5: CONSTRUCTION STORMWATER POLLUTION PREVENTION All proposed projects that will clear, grade, or otherwise disturb the site must provide erosion and sediment controls to prevent, to the maximum extent practicable, the transport of sediment from the project site to downstream drainage facilities, water resources, and adjacent properties. All proposed projects that will conduct construction activities onsite or offsite must provide stormwater pollution prevention and spill controls to prevent, reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or watercourses. To prevent sediment transport and pollutant discharges as well as other impacts related to land-disturbing and construction activities, Erosion and Sediment Control (ESC) measures and Stormwater Pollution Prevention and Spill Control (SWPPS) measures that are appropriate to the project site must be applied through a comprehensive Construction Stormwater Pollution Prevention (CSWPP) plan as described in Sections 1.2.5.1 and 1.2.5.3 and shall perform as described in Section 1.2.5.2. In addition, these measures, both temporary and permanent, shall be implemented consistently with the requirements in Section 1.2.5.3 that apply to the proposed project. A Construction SWPPP has been prepared for this project and is included in Appendix C of this report. A concept ESC plan with requirements for the Contractor to provide and implement a design for a system to treat construction runoff to no more than 25 NTU’s over baseline is included with the submittal. A baseline will be established at the start of construction and the contractor will be required to maintain levels no greater than 25 NTU’s above this level. CORE REQUIREMENT #6: MAINTENANCE AND OPERATIONS Maintenance and operation of all drainage facilities is the responsibility of the applicant or property owner, except those facilities for which the City assumes maintenance and operation as described below and in RMC 4-6-030.M. Drainage facilities must be maintained and operated in accordance with the maintenance standards in Appendix A of this manual, or other maintenance standards as approved by the City. An operation and maintenance manual is included in Section 10 of this drainage report and will be provided to the School District for all stormwater BMPs proposed for this project that are maintained by the School District. HAZEN HIGH SCHOOL IMPROVEMENTS 8 CORE REQUIREMENT #7: FINANCIAL GUARANTEES AND LIABILITY In accordance with RMC 4-6-030, CED shall require all persons constructing any surface water facilities (including flow control/water quality facilities, conveyance systems, erosion control, and road drainage), to post with the City of Renton a bond, assignment of funds or certified check. The applicant must also maintain liability insurance as described in this Core Requirement #7. The owner of the proposed project, Renton School District (RSD), is a public agency and is not subject to bonding requirements. The School District will provide a Public Agency Agreement to the City of Renton. CORE REQUIREMENT #8: WATER QUALITY FACILITIES All proposed projects, including redevelopment projects, must provide water quality (WQ) facilities to treat the runoff from those new and replaced pollution-generating impervious surfaces and new pollution-generating pervious surfaces targeted for treatment as specified in the following sections. These facilities shall be selected from a menu of water quality facility options specified by the area-specific facility requirements in Section 1.2.8.1 and implemented according to the applicable WQ implementation requirements in Section 1.2.8.2. The threshold for providing water quality treatment is 5,000 SF of pollution generating impervious surfaces or ¾ of an acre or more of pollution-generating pervious surfaces. This project proposes 150,718 square feet (3.46 acres) of pollution generating surfaces (PGIS) consisting of new turf fields and pollutant generating infill, which exceeds the 5,000 SF threshold. Therefore, water quality treatment is required. This project is required to provide Enhanced Basic Water Quality treatment and proposes to install (2) two 4x6 Modular Wetland Water Quality vaults, which will be installed downstream of each of the stormwater flow control systems. See Appendix B for MGS water quality facility sizing calculations and Figure 12 – Flow Control Basins. CORE REQUIREMENT #9: ON-SITE BMPS All proposed projects, including redevelopment projects, must provide on-site flow control BMPs to mitigate the impacts of storm and surface water runoff generated by new impervious surface, new pervious surface, existing impervious surfaces, and replaced impervious surface targeted for mitigation as specified in the following sections. On-site BMPs must be selected and applied according to the basic requirements, procedures, and provisions detailed in this section, and the design specifications for each BMP in Appendix C, Section C.2. In accordance with the 2022 RSWDM, Flow Control BMPs must be evaluated and implemented to the maximum extent feasible. Per section 1.2.9.2, this project site is over 22,000 SF and is subject to evaluating the Large Lot BMP Requirements as detailed in section 1.2.9.2.2 and described below: 1. Full Dispersion – All available native vegetation for dispersion is over 15% slope and is therefore not feasible to implement Full Dispersion for this project. 2. Full Roof Infiltration – A geotechnical engineer has determined that soils on site are not suitable for infiltration, therefore Full Roof Infiltration is not feasible for this project. 3. Full Infiltration – A geotechnical engineer has determined that soils on site are not suitable for infiltration, therefore Full Infiltration is not feasible for this project. 4. Limited Infiltration – A geotechnical engineer has determined that soils on site are not suitable for infiltration, therefore Limited Infiltration is not feasible for this project. 5. Bioretention – A geotechnical engineer has determined that soils on site are not suitable for infiltration, therefore Bioretention is not feasible for this project. In addition, all proposed pervious surfaces are only for lawn replacement after utility installation and would not be feasible to route to bioretention via gravity. 6. Permeable Pavement – A geotechnical engineer has determined that soils on site are not suitable for infiltration, and all paved surfaces are replacing existing impervious surfaces for utility trenching or are located under roof overhangs, therefore permeable pavement is not feasible for this project. 7. Basic Dispersion – The minimum required flow path and maximum slope requirements cannot be met on this project therefore Basic Dispersion is not feasible. HAZEN HIGH SCHOOL IMPROVEMENTS 9 8. Reduced Impervious Surface Credit – The proposed building and site improvements propose more than 4,000 SF of impervious surface and therefore the Restricted Footprint credit is not feasible for this site. Wheel Strip Driveway credit is not feasible for the proposed driveways on site. The proposed building foundation and requirements for the proposed building vestibule addition function are such that the Minimum Disturbance Foundation credit is infeasible for this project. No open grid decks are proposed with this project therefore the Open Grid Decking credit is not feasible for this project. 9. Native Growth Retention Credit – All native vegetation remaining on site is sloped over 15% or consists of small pockets of existing trees with the vast majority being landscaped, therefore the Native Growth Retention Credit is not feasible. 10. Perforated Pipe Connection – No new downspouts are proposed with this project; therefore, Perforated Pipe Connections are infeasible for this project. SPECIAL REQUIREMENT #1: OTHER ADOPTED AREA-SPECIFIC REQUIREMENTS The RSWDM is one of several adopted regulations in the City of Renton that apply requirements for controlling drainage on an area-specific basis. Other adopted area-specific regulations with requirements that have a direct bearing on the drainage design of a proposed project are found in Section 1.3.1 of the RSWDM. To the best of our knowledge, there are no adopted area-specific requirements in the proposed project site development that would impact the current Renton Surface Water Design Manual (RSWDM) requirements for this project. Therefore, the project will adhere to the requirements outlined in the 2022 RSWDM. SPECIAL REQUIREMENT #2: FLOOD HAZARD AREA DELINEATION Flood hazard areas are composed of the 100-year floodplain, zero-rise flood fringe, zero-rise floodway, FEMA floodway. If a proposed project contains or is adjacent to a flood hazard area as determined by CED, this special requirement requires the project to determine those components that are applicable and delineate them on the project’s site improvement plans and recorded maps. To the best of our knowledge in reviewing both FEMA Flood Insurance Rate Maps and the King County iMap, the proposed project site area is not located within a 100-year floodplain. SPECIAL REQUIREMENT #3: FLOOD PROTECTION FACILITIES Flood protection facilities, such as levees and revetments, require a high level of confidence in their structural integrity and performance. Proper analysis, design, and construction is necessary to protect against the potentially catastrophic consequences if such facilities fail. To the best of our knowledge in reviewing both FEMA Flood Insurance Rate Maps and the King County iMap, the proposed project site area is not located within a 100-year floodplain and not located adjacent to any rivers, streams, creeks, or other water bodies, and does not have any existing flood protection facilities installed on the existing property, nor are any new flood protection facilities proposed to be installed or warranted for this project. SPECIAL REQUIREMENT #4: SOURCE CONTROLS If a proposed project requires a commercial building or commercial site development permit, then water quality source controls applicable to the proposed project shall be applied as described below in accordance with the King County Stormwater Pollution Prevention Manual and King County Code 9.12. No structural improvements are proposed that will require source controls. However, the proposed turf fields are considered PGIS and therefore will require water quality source controls for the turf grass and field infill. Modular Wetland water quality vaults will be placed downstream of all detention systems. SPECIAL REQUIREMENT #5: OIL CONTROL Projects proposing to develop or redevelop a high-use site must provide oil controls in addition to any other water quality controls required by this manual. Such sites typically generate high concentrations of oil due to high traffic HAZEN HIGH SCHOOL IMPROVEMENTS 10 turnover, on-site vehicle or heavy or stationary equipment use, some business operations, e.g., automotive recycling, or the frequent transfer of liquid petroleum or coal derivative products. This project is not considered a high-use site and therefore will not require oil controls to be installed. SPECIAL REQUIREMENT #6: AQUIFER PROTECTION AREA Aquifer Protection Area(s) (APA) are identified in the RMC 4-3-050. If a proposed project is located within the APA, this special requirement requires the project to determine those components that are applicable and delineate them on the project’s site improvements plans. APA zones are depicted in the Wellhead Protection Area Zones layer of COR Maps (<https://maps.rentonwa.gov/Html5viewer/Index.html?viewer=cormaps>). This project is not located in an aquifer protection area according to the online City of Renton COR Maps. HAZEN HIGH SCHOOL IMPROVEMENTS 11 3. OFFSITE ANALYSIS FIELD INSPECTION Multiple site visits have been made to gather information about the existing campus, including, but not limited to, a review of the onsite and downstream drainage, parking lots, baseball field and softball field along with the surrounding areas, the outside of the electrical room on the west side of the building, and the main entrance on the east side of the building. Several visits took place to review the existing site in the Spring of 2023 on 02/02, and in the Summer of 2024 on 07/09, and 07/30, and 08/15. Please refer to Downstream Analysis below for more information. DRAINAGE SYSTEM PROBLEM DESCRIPTIONS There are no known drainage concerns or any existing drainage problems per review of the site with the Renton School District and the King County iMap and City of Renton COR Maps ‘Drainage Complaints’ Layer. As such, no drainage problems are expected to be present in the redevelopment or exacerbate any existing problems. UPSTREAM ANALYSIS The existing school is surrounded by single-family residences on all sides of the property and has an established public right-of-way with curb and gutter that collects stormwater runoff in NE 12th Street to the north, Hoquiam Avenue NE to the east, Duvall Avenue NE to the west, and NE 10th Street to the south in catch basins along the curb flow line and then conveys the stormwater through a series of 12-inch and 18-inch storm pipes that are routed between the existing school classroom building and the existing track then along the north and south sides of the existing classroom building until it heads towards the offsite conveyance locations. To the best of our knowledge, stormwater runoff from the residential properties surrounding the campus flows away from the school property. DOWNSTREAM ANALYSIS According to the project survey, site visits, and the City of Renton COR GIS database, stormwater runoff from the site currently leaves the site at three locations with three separate Threshold Discharge Areas. TDA #1 is part of the May Creek Basin and consists of the existing baseball field, which we assume to be underdrained and routed to an existing pond to the southwest of the field, where water is then routed to a dispersion trench that flows to the west toward Duvall Ave NE through native vegetation. Stormwater is then collected by the existing 12” storm system in Duvall Ave NE and flows to the north for ¼ mile before heading east through the Central Highlands Plaza parking lot and ultimately discharges to Lake Washington. See Figure 5A – Offsite Drainage. TDA #2 is part of the May Creek Basin and consists of areas at the center of the site, including the grass play field to the north of the baseball field, parking lots to the west and south of the school building, the rubberized track and grass field, and grass softball field, which flow to the south toward the existing storm system in NE 10th St. Stormwater flows to the west along NE 10th St for approximately ¼ mile before discharging to an existing City of Renton stormwater pond, and ultimately discharging to Lake Washington. See Figure 5B – Offsite Drainage. TDA #3 is part of the May Creek Basin and consists of parking areas north, east and south of the school building, the existing grass multipurpose field, and tennis courts. Stormwater is collected in multiple stormwater systems along the east side of the site prior to discharging the stormwater to the existing 18” storm main flowing north along Hoquiam Ave NE. This storm main flows north for ¼ mile and discharges to Honey Creek, a non-fish bearing seasonal stream, which flows to the west and ultimately discharges to Lake Washington. See Figure 5C – Offsite Drainage. MITIGATION OF EXISTING OR POTENTIAL PROBLEMS The site is not within or near any FEMA flood zones, no existing problems are known, and no potential problems are expected because of the proposed development. HAZEN HIGH SCHOOL IMPROVEMENTS 12 4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY (PART A) Geotechnical investigation on site has found site soils to primarily consist of existing fill soils from previous development, dense, silty Vashon ice-contact deposits, and very dense Vashon Lodgment till soils. See project geotechnical report and Figure 8 – Soils Map. The topography of the existing site is generally flat, sloping gently away from the existing school building on all sides. Due to the site topography, the school campus consists of multiple Threshold Discharge Areas (TDAs). TDA #1 consists of the existing baseball field, which we assume to be underdrained and routed to an existing pond to the southwest of the field, where water is then routed to a dispersion trench that flows to the west toward Duvall Ave NE through native vegetation. TDA #2 consists of areas at the center of the site, including the grass play field to the north of the baseball field, parking lots to the west and south of the school building, the rubberized track and grass field, and grass softball field, which flow to the south toward the existing storm system in NE 10th St. TDA #3 consists of parking areas north, east and south of the school building, the existing grass multipurpose field, and tennis courts. See Table 1 in Section 1 of this report and Figure 4 – Existing Conditions for a summary of the existing land cover characteristics for the areas in each TDA to be redeveloped with this project. DEVELOPED SITE HYDROLOGY (PART B) Stormwater mitigation will be provided for all new and replaced impervious surfaces, as well as new pervious surfaces, within each TDA. This includes the new synthetic turf play fields, security vestibule roof, and driveways and sidewalks associated with the redevelopment project. Note that impervious surfaces replaced solely for utility installation or maintenance are excluded from the definition of “replaced impervious surfaces” and are therefore not subject to flow control requirements. Stormwater within each TDA will be discharged from the proposed detention facilities and routed to the existing discharge point for that TDA. Table 2 in Section 1 of this report summarizes the land cover characteristics of the disturbed area within the proposed redevelopment site. See Figure 3 – New + Replaced Impervious Areas. PERFORMANCE STANDARDS (PART C) Flow control conforming to Core Requirement #3 meeting the Flow Control Duration Standard for forested site conditions is required for this project. Specifically, flow durations for the developed site must match flow durations for the pre-existing forested site between ½ the two-year and the 50-year storm events. In accordance with the 2022 RSWDM, MGS Flood Version 4, an approved continuous-modeling software, is used to model the existing and proposed site drainage basins. This project proposes to construct two detention systems, one for the baseball field replacement in TDA #1 and one for the softball field replacement in TDA #2, to provide the required flow control volume for each basin. In the existing site pre-development conditions, all areas disturbed by the target surfaces of the proposed development are modeled as having forested surface cover and broken out into flat (0-6%), moderate (6-15%) and steep (15%+) slopes. The proposed detention systems also have a small amount of flow through due to existing areas sloped toward the proposed target surfaces to be collected to meet flow control requirements. This flow through area is modeled in a separate basin and is identical in both the pre- and post- developed conditions, see Table 3 below and Figure 12 – Flow Control Basins. In the proposed conditions, new and replaced impervious areas (excluding utility trenches) are broken out by flat, moderate, or steep slope and surface type such as sidewalk and roof areas. No surface type is available for synthetic turf fields; therefore, they are included in the sidewalk category for modeling purposes. In the proposed conditions for TDA #3, the replaced impervious surfaces will bypass the detention system due to grading constraints. See Table 3 below and Figure 12 – Flow Control Basins. HAZEN HIGH SCHOOL IMPROVEMENTS 13 TABLE 3 – FLOW CONTROL BASINS Land Cover TDA #1 TDA #2 TDA #3 TARGET SURFACES BASIN Flat Sidewalk 2.360 0.977 Flat Sidewalk (Bypass) 0.09 Flat Roof (Bypass) 0.01 FLOW THROUGH BASIN Flat Sidewalk 0.113 0.085 Flat Lawn 0.097 Moderate Sidewalk 0.016 Moderate Lawn 0.146 Steep Lawn 0.076 Total Area 2.808 AC 1.062 AC 0.10 AC FLOW CONTROL SYSTEM (PART D) This project proposes to construct two detention systems, one for the baseball field replacement in TDA #1 and one for the softball field replacement in TDA #2, to provide the required flow control volume for each basin. TDA #1 proposes to install a StormTrap Modular Precast detention vault to provide the required live storage volume. The total live storage volume required is 47,398 CF, with 52,664 CF of total storage volume proposed. TDA #2 currently proposes to install an ADS StormTech MC-3500 chamber detention system to provide the required live storage volume. The total live storage volume required is 22,265 CF, with 27,943 CF of total storage volume proposed. There are no flow control measures proposed for TDA #3 because flow control is not triggered for that TDA and is therefore not required. See Stormwater Calculations in Appendix B of this drainage report for all MGS Flood calculations. WATER QUALITY SYSTEM (PART E) The threshold for providing water quality treatment is 5,000 SF of pollution generating impervious surfaces or ¾ of an acre or more of pollution-generating pervious surfaces. This project proposes 150,718 square feet (3.46 acres) of pollution generating surfaces (PGIS) consisting of new turf fields and pollutant generating infill, which exceeds the 5,000 SF threshold. Therefore, water quality treatment is required. This project is required to provide Enhanced Basic Water Quality treatment and proposes to install one 4x6 Modular Wetland Water Quality vault at the Baseball Field, and one 4x6 Modular Wetland Water Quality vault at the Softball field. Each of the Water Quality Vaults will be installed downstream of each of the stormwater flow control systems. See Appendix B for MGS Flood water quality facility sizing calculations and Figure 12 – Flow Control Basins. HAZEN HIGH SCHOOL IMPROVEMENTS 14 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN PIPE SYSTEMS: 1. New pipe systems shall be designed with sufficient capacity to convey and contain (at minimum) the 25- year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. - New pipe systems are designed to convey and contain the 25-year peak flow rate. 2. Pipe system structures may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a severe flooding problem or severe erosion problem as described in Core Requirement #2, Section 1.2.2 (p. 1-27). Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, this overflow must be contained within an onsite drainage easement, tract, covenant, or public right-of-way. - Pipe systems are designed so that the 100-year runoff event does not create or aggravate a severe flooding or erosion problem. 3. The upstream end of a pipe system that receives runoff from an open drainage feature (pond, ditch, etc.) shall be analyzed and sized as a culvert as described below. - The upstream end of the proposed pipe system does not receive runoff from an open drainage feature. CULVERTS: 1. New culverts shall be designed with sufficient capacity to meet the headwater requirements in Section 4.3.1 and convey (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. - No culverts are proposed with this project. 2. New culverts must also convey as much of the 100-year peak flow as is necessary to preclude creating or aggravating a severe flooding problem or severe erosion problem as described in Core Requirement #2, Section 1.2.2 (p. 1-27). Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, this overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. - No culverts are proposed with this project. 3. New culverts proposed in streams with salmonids shall be designed to provide for fish passage as detailed in Section 4.3.2. Note: The County’s critical areas regulations (KCC 21A.24) or the state Department of Fish and Wildlife may require a bridge to facilitate fish passage. - No culverts are proposed with this project. DITCHES/CHANNELS: 1. New ditches/channels shall be designed with sufficient capacity to convey and contain, at minimum, the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. - No new ditches or channels are proposed with this project. 2. New ditches/channels must also convey as much of the 100-year peak flow as is necessary to preclude creating or aggravating a severe flooding problem or severe erosion problem as described in Core Requirement #2, Section 1.2.2 (p. 1-27). Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, this overflow must be contained within an onsite drainage easement, tract, covenant, or public right-of-way. - No new ditches or channels are proposed with this project. HAZEN HIGH SCHOOL IMPROVEMENTS 15 TIGHTLINE SYSTEMS TRAVERSING STEEP SLOPES: 1. New tightline conveyance systems traversing slopes that are steeper than 15% and greater than 20 feet in height or are within a steep slope hazard area as defined in KCC 21A.06, shall be designed with sufficient capacity to convey and contain (at minimum) the 100-year peak flow, assuming full build-out conditions for all tributary areas, both onsite and offsite. Tightline systems shall be designed as detailed in Section 4.2.2. - Tightline conveyance is designed to effectively convey 100-year storm events. BRIDGES: 1. New bridges shall be designed to accommodate the 100-year peak flow as specified in Section 4.3.3 and in accordance with the floodplain development standards in KCC 21A.24. - No bridges are proposed with this project. CONVEYANCE ANALYSIS The conveyance analysis for the redevelopment has been performed using Autodesk Storm and Sanitary Analysis (SSA) for each sub-basin within the site. This analysis follows the guidance provided in the 2022 Renton Surface Water Design Manual (RSWDM) for conveyance and backwater analysis. This analysis uses the storm network designed in Civil 3D to perform the conveyance analysis and backwater calculations for the designed storm system. From the Civil 3D model, SSA can extract pipe size, length, slope and invert elevations, along with the rim elevation for each cleanout, catch basin, or manhole. City of Renton Compliance – In order to meet RSWDM requirements for conveyance analysis, settings within SSA were updated to reflect the correct analysis options. Because the project site is less than 10 acres, Table 3.2 – Acceptable Uses of Runoff Computation Methods in the RSWDM states that the analysis should be performed using the Rational Method, the time of concentration should be set to a minimum of 6.3 minutes for all runs, and Link Routing is set to “Hydrodynamic” for SSA to calculate backwater analysis within the model. These system settings can be seen in Figure 13 – SSA Settings. With SSA set to use the Rational Method (QR = C * IR * A), the “C”, “IR” and “A” values must be entered into the program in order for it to calculate the QR for the proposed system. The first step in these calculations was to find the catchment area in acres for each structure in the proposed storm system, which can be seen in Figure 12 – Flow Control Basins. These areas are then input as the “A” within the characteristics for each sub-basin in SSA. With the catchment areas calculated for each structure sub-basin, the “C” values could then be found for each of those sub-basins. This value was calculated by first finding the total pervious and impervious surface area for each sub-basin. Using a “C” value of 0.25 for pervious lawn areas and 0.90 for all impervious pavement and roof surfaces (per Table 3.2.1.A – Runoff Coefficients, 2022 RSWDM), a weighted “C” value was found for each area and entered into SSA for each sub-basin. The final value to input for SSA to use the Rational Method is “IR”, which is input as a system setting, rather than a characteristic for each sub-basin. To do this, an IDF curve is created within SSA for the design storm, which in this case is the 100-year 24-hour storm. Using the equations within section 3.2.1 – Rational Method of the RSWDM for “IR” (IR = PR * iR, where iR = aR * Tc -bR) the IDF curve is created within SSA. To begin, PR is calculated to be 3.92 using Figure 3.2.1.D – 100-Year 24-Hour Isopluvials (See Figure 15 – Isopluvial Map). The time of concentration, “Tc”, is set at a constant 6.3 minutes, while aR and bR are values found in Table 3.2.1.B – Coefficients for the Rational Method “iR” Equation within the RSWDM, which are 2.61 and 0.63, respectively. Detailed calculations showing the correlation between RSWDM formulas and the SSA IDF curve can be seen below and in Figure 14 – IDF Curve. KCSWDM: IR = PR * aR * Tc -bR = (3.92in * 2.61 * 6.3 min -0.63) = 3.21 in/hr SSA: i = B / (Tc + D)E = (10.23) / (6.3 + 0)0.63 = 3.21 in/hr HAZEN HIGH SCHOOL IMPROVEMENTS 16 A node referred to as an Outfall is also an important part of computing a conveyance analysis within SSA. This particular site has four outfalls representing one point of connection to the proposed vault downstream of the baseball field, and three points of discharge to the existing storm downstream of each detention system. Outfalls within SSA are where initial tailwater elevations are input to conduct backwater analysis. To provide a conservative analysis, the initial tailwater elevation for the outfall to the detention vault is set to 453.00, which is the 100-year water surface elevation for the vault. Details for the site outfalls can be found in the SSA results in Table 5 – Site Outfalls in Appendix B. Results The results provided by SSA are included in Appendix B. These results are broken down into four tables with the analysis for each pipe, outfall, structure and subbasin in the model. Table 4 – Pipe Analysis includes the length, slope, size, upstream and downstream structures, entrance and exit losses, available capacity, and peak flow within each pipe. Note that pipes labeled as “Surcharged” or “>Capacity” are acceptable in this case because a surcharged pipe does not necessarily mean the structure rim has been overtopped. Table 5 – Site Outfalls shows the results for each outfall on site. This table includes peak flow at the detention inlet and fixed water surface elevation, which in this case is set to the 100-year storm water surface elevation for the detention vault. Table 6 – Structure Analysis is a summary of all cleanouts, catch basins, and manholes within the conveyance system. This table contains the rim elevations, outlet pipe elevations, peak inflow, max HGL, and minimum freeboard. The minimum freeboard attained is critical in this table as any value greater than zero demonstrates that no structure rims have been overtopped. Table 7 – Subbasin Summary lists the total area, structure it drains to, weighted C value, rainfall intensity, and time of concentration for each subbasin. OUTFALLS The proposed redevelopment does not include any new systems which utilize an outfall requiring outfall protection. As flows will be maintained or even reduced by the implementation of the detention system on this project, no upgrades to existing outfalls are included as part of this project. HAZEN HIGH SCHOOL IMPROVEMENTS 17 6. SPECIAL REPORTS AND SUMMARY Please refer to the Geotechnical Engineering Report – by Associated Earth Sciences, dated August 26, 2024 associated earth sciences incorporated Associated Earth Sciences, Inc. www.aesgeo.com Kirkland | Mount Vernon | Tacoma Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report HAZEN HIGH SCHOOL MODERNIZATION Renton, Washington Prepared For: RENTON SCHOOL DISTRICT NO. 403 Project No. 20210251E003 August 26, 2024 Kirkland | Tacoma | Mount Vernon 425-827-7701 | www.aesgeo.com August 26, 2024 Project No. 20210251E003 Renton School District No. 403 7812 South 124th Street Seattle, Washington 98178 Attention: Mike Cato, P.E. Subject: Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report Hazen High School Modernization 1101 Hoquiam Avenue NE Renton, Washington Dear Mr. Cato: We are pleased to present this copy of our geotechnical engineering report for the referenced project. This report summarizes the results of our subsurface exploration, geologic hazard, and geotechnical engineering evaluation, and contains our geotechnical design recommendations for the proposed project. We have reviewed the 100% Design Development set and the plans have accurately incorporated the recommendations presented in this report. If any design changes are made, we recommend that we be allowed to review the recommendations in this report and modify them as necessary. We have enjoyed working with you on this study and are confident that the recommendations presented in this report will aid in the successful completion of your project. If you should have any questions, or if we can be of additional help to you, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ G. Bradford Drew, P.E. Associate Engineer BD/ld – 20210251E003-002 SUBSURFACE EXPLORATION, GEOLOGIC HAZARD, AND GEOTECHNICAL ENGINEERING REPORT HAZEN HIGH SCHOOL MODERNIZATION Renton, Washington Prepared for: Renton School District No. 403 7812 South 124th Street Seattle, Washington 98178 Prepared by: Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, Washington 98033 425-827-7701 August 26, 2024 Project No. 20210251E003 Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 1 I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of Associated Earth Sciences, Inc.’s (AESI’s) subsurface exploration, geologic hazard assessment, and geotechnical engineering recommendations for the proposed building renovations and structural alterations to the existing Hazen High School campus in Renton, Washington. Our understanding of the project at the time of fieldwork was based on email correspondence with the design team and our review of conceptual markups indicated on the “Hazen High School Modernization Existing Plan - Level 1,” prepared by Integrus Architecture, dated January 9, 2024. The site location is shown on the “Vicinity Map,” Figure 1. The approximate locations of explorations completed for this study relative to existing and proposed site features are shown on the “Existing Site and Exploration Plan,” Figure 2. Interpretive exploration logs of subsurface explorations completed for this study are included in Appendix A. 1.1 Purpose and Scope The purpose of this study was to provide subsurface data and geotechnical engineering design recommendations to be utilized in the development and design of the project. Our study included reviewing available geologic literature, advancing six exploration borings, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and shallow groundwater at the site. Geotechnical engineering studies were completed to formulate recommendations for site preparation, temporary cut slopes, erosion control, structural fill, building foundations, seismic site class, floor slabs, and site drainage. This report summarizes our current fieldwork and offers recommendations based on our present understanding of the project. We recommend that we be allowed to review the recommendations presented in this report and revise them, if needed, when a project design has been finalized. 1.2 Authorization Authorization to proceed with this study was granted by means of an agreement for Consulting Services issued by Renton School District No. 403 and executed on December 19, 2023. Our study was accomplished in general accordance with our proposal, dated December 12, 2023. This report has been prepared for the exclusive use of Renton School District No. 403 and their authorized agents for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 2 2.0 PROJECT AND SITE DESCRIPTION The project site is located at the existing Hazen High School in Renton, Washington (Figure 1). We understand the existing school campus was originally constructed in 1969 and includes several classroom buildings near the center of the site with parking lots and driveways surrounding the buildings and grass athletic fields to the west and south. The site has been graded to its current configuration by past earthwork onsite. Topography across the site is generally flat to gently sloping down to the west with an overall vertical relief of less than 10 feet across the footprint of the main school buildings. The project involves the modernization of the existing school buildings including structural seismic upgrades and interior renovations. We understand that modernization elements will include the addition of shear walls, columns, footings, and other structural elements to meet current seismic requirements under the 2021 International Building Code (IBC). Details of the modernization elements were still in progress at the time of this report. We understand that all buildings are currently supported on conventional shallow foundations consisting of spread and strip footings. We understand that foundation improvements are focused near the central-eastern portion of the campus buildings with improvements also planned at the south end of the natatorium building. These areas are outlined on Figure 2. We anticipate that earthwork activities will be minimal for this project as building alterations and foundation improvements will be conducted inside of and/or adjacent to the existing building footprint. 3.0 PREVIOUS EXPLORATIONS AESI previously completed a total of 17 explorations at the school campus in 2009, 2021, and 2022. The approximate locations of our previous explorations onsite are shown on Figure 2, and copies of the exploration logs are included in Appendix B. In addition to previous work completed by AESI, the State of Washington completed a subsurface shear wave transmission velocity survey at the site in October 2020. Additional information regarding that study is included in the “Ground Motion/Seismic Site Class” section of this report. The previous explorations completed by AESI include: Five borings (EB-1 through EB-5, completed in May 2009) located north of the existing natatorium for a new classroom addition. Borings EB-1 through EB-5 were advanced to a depth of about 21.5 feet below site grade. These borings generally encountered about 7 feet of existing fill overlying native soils that included a variable presence/thickness of medium dense recessional outwash, medium dense to dense ice-contact sediments, and Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 3 dense glacial till and/or hard silt at depth. Perched groundwater was encountered above the glacial till and hard silt at depths of 10 to 15 feet in early May. One boring (EB-1, completed in October 2021) located to the west of the existing natatorium for the pool modernization project. This boring was advanced to a depth of 21.5 feet below existing site grade and encountered about 5 feet of existing fill overlying medium dense recessional outwash to 12 feet and dense glacial till to the termination depth of 21.5 feet. Perched groundwater was encountered above the glacial till at about 8 feet below existing grade in late October. Eleven borings (EB-1 through EB-11, completed in March 2022) located within the northern parking lot areas and drive lanes for the parking lot upgrades project. These borings were shallow and extended to depths of 3 to 5 feet below parking lot grades. Most of these borings encountered existing fill to the termination depth. Three of the borings (EB-1, EB-5, and EB-6) encountered native recessional outwash sediments at depths of 1 to 2 feet below parking lot grades. 4.0 SUBSURFACE EXPLORATION Our field study was conducted for this project on January 2, 2024 and included advancing six exploration borings (EB-1 through EB-6) around the perimeter of the school near the locations of the planned improvements (see Figure 2) The conclusions and recommendations presented in this report are based, in part, on the explorations completed for this study. The number, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 4.1 Exploration Borings The exploration borings for this phase of the project were completed by Geologic Drill Partners, Inc., an independent firm working under subcontract to AESI, at the locations shown on Figure 2. The borings were completed by advancing a 6-inch outside-diameter, hollow-stem auger with a track-mounted drill rig. During the drilling process, samples were obtained at generally 2.5- to 5-foot-depth intervals. After completion of drilling, each borehole was backfilled with bentonite chips, and the surface was patched with the excavated soil in landscape areas and with asphalt cold patch in pavement areas. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 4 Disturbed but representative samples were obtained by using the Standard Penetration Test (SPT) procedure. This test and sampling method consists of driving a 2-inch outside-diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance (“N”) or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are plotted on the attached exploration boring logs. The exploration borings were continuously observed and logged by a geologist from our firm. The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification and laboratory testing, as necessary. The exploration logs presented in Appendix A are based on the N-values, field observations, and drilling action. 5.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, our visual reconnaissance of the site, and review of selected geologic literature. The various types of sediments, as well as the depths where the characteristics of the sediments changed, are indicated on the exploration logs presented in Appendix A. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types. If changes occurred between sample intervals in our exploration borings, they were interpreted. The exploration borings completed for this study generally encountered existing fill soils overlying Vashon ice-contact sediments, Vashon lodgement till, Vashon advance outwash (lacustrine) and/or pre-Fraser sediments observed at depth depending on location. The following section presents more detailed subsurface information organized from the shallowest (youngest) to the deepest (oldest) sediment types. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 5 5.1 Site Stratigraphy Asphalt Asphalt was encountered at the surface of exploration EB-3. The asphalt layer was approximately 3 inches in thickness. Topsoil/Mulch We encountered 2 to 3 inches of sod and topsoil at the ground surface in borings EB-1 and EB-2, and 4 to 6 inches of bark/mulch in EB-4 through EB-6. Fill Directly below the asphalt and topsoil/mulch, all borings encountered fill soils (those not naturally placed) to depths ranging from approximately 3 to 4.5 feet below the existing ground surface, except the fill in EB-2 was observed to extend deeper to about 8.5 feet below the ground surface. The fill generally consisted of loose to medium dense, moist, brown to dark brown with occasional orange oxidation staining, silty, fine to medium sand with variable gravel content and scattered to abundant organics (roots/rootlets/fine black organics). Due to the inherent variability of the fill and unknown placement and compaction methods, the fill soils are not considered suitable for direct foundation support and may require remedial measures for support of new hardscapes and slabs-on-grade. Excavated fill material may be suitable for reuse in structural fill applications if such reuse is specifically allowed by project plans and specifications, if excessively organic and any other deleterious materials are removed, and if moisture content is adjusted to allow compaction to the specified level and to a firm and unyielding condition. Fill soils are also likely present in unexplored areas of the site near the existing buildings, within existing utility trenches, and below previously graded/backfilled areas. Vashon Ice Contact Below the existing fill, exploration borings EB-1, EB-3, EB-4, and EB-5 encountered medium dense to dense sand with variable silt content ranging from trace to silty, and stiff to hard silt and sandy silt. These native sediments are interpreted to be representative of Vashon ice-contact sediments and extended to depths of 6.5 to 13.5 feet below the ground surface. Ice-contact sediments were deposited above, adjacent, or within a glacial ice mass and may have been redeposited as the ice melted or was reworked by the ice. Ice-contact sediments can have variable density and grain size and range from stratified to massive; stratification was observed in some of the samples. Some of the ice-contact sediments observed in our exploration borings contained large quantities Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 6 of silt and are considered highly moisture-sensitive. These sediments are suitable for foundation support with proper preparation. We noted a faint petroleum odor was encountered in a sample obtained from 5 to 6.5 feet within EB-3, near the contact between the existing fill and underlying ice-contact sediments. We are available to assist with additional explorations and analytical testing should earthwork be performed in this area or desired by the Owner. Vashon Lodgement Till Directly below the Vashon ice-contact deposits, explorations EB-4 and EB-5 encountered very dense, moist, brown, silty fine sand with some gravel to the termination depth of both borings at about 11 feet. We interpreted these sediments to be representative of Vashon lodgement till. The Vashon lodgement till was deposited by basal, debris-laden, glacial ice during the Vashon Stade of the Fraser Glaciation, approximately 12,500 to 15,000 years ago. The high relative density characteristic of the Vashon lodgement till is due to its consolidation by the massive weight of the glacial ice from which it was deposited. Consequently, lodgement till soils are typically dense to very dense and possess high-shear strength and low-compressibility and low-permeability characteristics. The lodgement till soils are favorable for support of foundations with proper preparation. Lodgement till soils are generally suitable for structural fill applications provided that these materials are placed and compacted at or near optimum moisture content. Vashon Advance Outwash (Lacustrine) Below the ice-contact sediments in EB-1 and EB-3 and below the existing fill in EB-2, we encountered massive to faintly bedded, dense to very dense, very moist to wet, sand and silty sand ranging to hard silt and sandy silt. Based on the density, grain-size distribution, stratification of samples observed and lack of organic sediments, we interpret this unit to be Vashon advance outwash deposited in a lacustrine (low-energy) environment. Vashon advance outwash sediments were deposited in front of an advancing ice sheet and were subsequently overridden. These sediments typically possesses high-strength and low-compressibility attributes that are favorable for support of foundations with proper preparation. The advance outwash sediments extended to depths of 11.5 and 23 feet within EB-1 and EB-3, respectively, and to the termination depth of EB-2 at about 16 feet. Pre-Fraser Sediments Below the advance outwash (lacustrine) sediments in EB-1 and EB-3 and below the existing fill in EB-6, we encountered very dense, very moist to wet, sand and silty sand and hard, slightly moist, Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 7 silt with some sand. Due to their density and stratigraphic position, we infer that these sediments are of pre-Fraser age and were deposited prior to the Fraser Glaciation that occurred from 12,500 to 15,000 years before present and have been consolidated by at least one glaciation. The pre-Fraser sediments extended beyond the maximum depths explored of approximately 26 feet, 25.5 feet, and 14.5 feet at EB-1, EB-3, and EB-6, respectively. This unit also possesses high- strength and low-compressibility attributes that are favorable for support of foundations with proper preparation. 5.2 Regional Geologic and Soils Mapping Review of the regional geologic map of the project area (Geologic Map of King County, Washington, by Derek B. Booth, Kathy A. Troost, and Aaron P. Wisher, GeoMapNW, 2007) indicates that the site vicinity is underlain by Vashon lodgement till with Vashon advance outwash exposed offsite to the northeast. The shallow native sediments observed in our explorations for this study are in partial agreement with this mapping in that we encountered Vashon lodgement till at depth within EB-4 and EB-5 and Vashon advance outwash (lacustrine) at depth within EB-1, EB-2, and EB-3. Directly below the existing fill, we encountered geologic units not depicted on the map which included Vashon ice-contact sediments above the lodgement till and advance outwash in EB-1, EB-3, EB-4, and EB-5, and pre-Fraser fine-grained sediments in EB-6 to the termination depth. 5.3 Hydrology Groundwater was encountered in explorations EB-1 and EB-2 within the Vashon advance outwash (lacustrine) sediments at depths of 7.5 and 10 feet below the existing ground surface at the time of drilling, respectively. We also observed groundwater in EB-3 within the Vashon ice-contact deposits at a depth of 8.5 feet. Where the Vashon advance lacustrine sediments and pre-Fraser sediments were primarily sand, such as EB-1, the water-bearing zone was greater than 15 feet thick and extended beyond the exploration depth. Groundwater elevations in EB-1, EB-2, and EB-3 ranged from about 457.5 to 460.5 feet. No groundwater was encountered in EB-4 and EB-5 which did not encounter the Vashon advance lacustrine sediments, or EB-6 which was located at a slightly higher elevation. Groundwater within the sandy Vashon advance lacustrine and pre-Fraser sediments is interpreted to be perennial. Shallower perched groundwater should also be expected within the fill and silty Vashon ice-contact sediments. Perched groundwater occurs as surface water percolates down through the near-surface, relatively permeable soils, and becomes trapped or “perched” atop underlying, lower-permeable, layers such as silty ice-contact and glacial till sediments. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 8 It should be noted that our explorations were completed in early January when groundwater levels are elevated and possibly rising. Groundwater levels may be higher during the late winter and spring months. The duration and quantity of groundwater seepage can be expected to vary in response to changes in season, precipitation patterns, on- and off-site land usage, site development, and other factors. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 9 II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, slope, and ground and surface water conditions, as observed and discussed herein. The discussion will be limited to landslide, seismic, and erosion hazards. Individual geologic hazard topics are discussed in further detail below. 6.0 LANDSLIDE HAZARDS AND MITIGATIONS Topography across the site is generally flat to gently sloping down to the west with an overall vertical relief of less than 10 feet across the footprint of the existing school buildings. Based on our site reconnaissance and review of Light Detection and Ranging (LIDAR)-based topographic contours as shown on Figure 2, no steep slopes are present within the vicinity of the proposed building improvements. Therefore, it is our opinion that the potential risk of damage to the proposed improvements by landsliding is low and that no mitigation measures are warranted for the project. 7.0 SEISMIC HAZARDS AND MITIGATIONS The following discussion is a general assessment of seismic hazards that is intended to be useful to the project design team in terms of understanding seismic issues, and to the structural engineer for design. All of Western Washington is at risk of strong seismic events resulting from movement of the tectonic plates associated with the Cascadia Subduction Zone (CSZ), where the offshore Juan de Fuca plate subducts beneath the continental North American plate. The site lies within a zone of strong potential shaking from subduction zone earthquakes associated with the CSZ. The CSZ can produce earthquakes up to magnitude 9.0, and the recurrence interval is estimated to be on the order of 500 years. Geologists infer the most recent subduction zone earthquake occurred in 1700 (Goldfinger et al., 20121). Three main types of earthquakes are typically associated with subduction zone environments: crustal, intraplate, and interplate earthquakes. Seismic records in the Puget Sound region document a distinct zone of shallow crustal seismicity (e.g., the Seattle Fault Zone [SFZ]). These shallow fault zones may include surficial expressions of previous seismic events, such as fault scarps, displaced shorelines, and shallow bedrock exposures. The shallow 1 Goldfinger, C., Nelson, C.H., Morey, A.E., Johnson, J.E., Patton, J.R., Karabanov, E., Gutierrez-Pastor, J., Eriksson, A.T., Gracia, E., Dunhill, G., Enkin, R.J., Dallimore, A., and Vallier, T., 2012, Turbidite Event History—Methods and Implications for Holocene Paleoseismicity of the Cascadia Subduction Zone: U.S. Geological Survey Professional Paper 1661–F, 170. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 10 fault zones typically extend from the surface to depths ranging from 16 to 19 miles. A deeper zone of seismicity is associated with the subducting Juan de Fuca plate. Subduction zone seismic events produce intraplate earthquakes at depths ranging from 25 to 45 miles beneath the Puget Lowland including the 1949, 7.2-magnitude event; the 1965, 6.5-magnitude event; and the 2001, 6.8-magnitude event and interplate earthquakes at shallow depths near the Washington coast including the 1700 earthquake, which had a magnitude of approximately 9.0. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides or lateral spreading, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 7.1 Surficial Ground Rupture Seattle Fault Zone The site is located approximately 1 mile south of the mapped limits of the SFZ. The SFZ is a broad east-west oriented zone that extends from approximately Issaquah to Alki Beach, and is approximately 2.5 to 4 miles in width from north to south. The SFZ is speculated to contain multiple distinct fault “strands,” some of which are well understood and some of which may be poorly understood or unknown. Mapping of individual fault strands is imprecise, as a result of pervasive modification of the land surface by development, which has obscured possible surficial expression of past seismic events. Studies by the U.S. Geological Survey (USGS) and others have provided evidence of surficial ground rupture along strands of the SFZ (USGS, 20102; Pratt et al., 20153; Haugerud, 20054; Liberty et al., 20085). According to USGS studies the latest movement of this fault was about 1,100 years ago when about 20 feet of surficial displacement took place. This displacement can presently be seen in the form of raised, wave-cut beach terraces along Alki Point in West Seattle and Restoration Point at the south end of Bainbridge Island. Based on our review of the Washington State Department of Natural Resources (WADNR) website, inferred fault traces associated with the SFZ are located about 1 mile north of the site. Due to the 2 U.S. Geological Survey, 2010, Quaternary Fault and Fold Database for the United States, accessed November 10, 2010, from USGS web site: http://earthquake.usgs.gov/hazards/qfaults/. 3 Pratt et al., 2015, Kinematics of Shallow Backthrusts in the Seattle Fault Zone, Washington State: Geosphere, v. 11, no. 6, p. 1-27). 4 Haugerud, R.A., 2005, Preliminary Geologic Map of Bainbridge Island, Washington: U.S. Geological Survey Open-File Report 2005-1387, version 1.0, 1 sheet, scale 1:24,000. 5 Liberty, Lee M.; Pratt, Thomas L., 2008, Structure of the Eastern Seattle Fault Zone, Washington State - New Insights from Seismic Reflection Data: Bulletin of the Seismological Society of America, v. 98, no. 4, p. 1681-1695. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 11 suspected long recurrence interval, and the distance of the site to the fault traces, the potential for surficial ground rupture along the SFZ is considered to be low during the expected life of the proposed improvements. 7.2 Seismically Induced Landslides Similar to the discussion in Section 6.0, “Landslide Hazards and Mitigations,” it is our opinion that the potential risk of damage to the proposed improvements by seismically induced slope failures is low and that no mitigation measures are warranted for the project due to the lack of steep slopes in the immediate project area. 7.3 Liquefaction Liquefaction is a process through which unconsolidated soil loses strength as a result of vibrations, such as those which occur during a seismic event. During normal conditions, the weight of the soil is supported by both grain-to-grain contacts and by the fluid pressure within the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the grain-to-grain contact, increase the pore pressure, and result in a temporary decrease in soil shear strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported by pore pressure alone. Liquefaction can result in deformation of the sediment and settlement of overlying structures. Areas most susceptible to liquefaction include those areas underlain by very soft to stiff, non-cohesive silt and very loose to medium dense, non-silty to silty sands with low relative densities, accompanied by a shallow water table. The site is generally underlain by unsaturated existing fill overlying medium dense to very dense native sediments at relatively shallow depths. Where native sediments are saturated, they are typically dense to very dense and not considered susceptible to liquefaction. In our opinion, the potential risk of damage to the proposed improvements by liquefaction is low. No detailed liquefaction hazard analysis was performed as part of this study, and none is warranted, in our opinion. 7.4 Ground Motion/Seismic Site Class It is our opinion that earthquake damage to the proposed school improvements, when founded on suitable bearing strata in accordance with the recommendations contained herein, will likely be caused by the intensity and acceleration associated with the event. We understand that structural design of the building improvements will follow the 2021 IBC standards. Based on the subsurface conditions encountered within our exploration borings, we recommend using Site Class “C” as defined in Table 20.3-1 of American Society of Civil Engineers (ASCE) 7-16 Minimum Design Loads and Associated Criteria for Buildings and Other Structures. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 12 It should be noted that the Washington Geological Survey (WGS) conducted a seismic survey at the project site on October 22, 2020. The seismic survey was completed with an array of 48 geophones approximately 308 feet in length to measure the shear wave velocity within the upper 100 feet of soil. This array was located at the northwest corner of the campus near the existing ballfield. The average shear wave velocity was measured at 376 meters per second, which corresponds to Site Class C, near the C/D border. The shear wave velocity results are included in Appendix C. 8.0 EROSION HAZARDS AND MITIGATIONS The sediments underlying the site generally consist of fine to medium sand with varying amounts of silt and gravel. Where exposed to rain and wind, these sediments will be susceptible to erosion and off-site sediment transport when exposed during construction. We anticipate that construction will be contained within the existing building footprint and that earthwork will largely involve trench excavations for new footings. The project should follow best management practices (BMPs) to mitigate erosion hazards and potential for off-site sediment transport. To mitigate the potential for off-site sediment transport, we recommend the following: 1. The winter performance of a site is dependent on a well-conceived plan for control of site erosion and stormwater runoff. The project temporary erosion and sediment control (TESC) should include ground-cover measures, access roads, and staging areas. The contractor must implement and maintain the required measures. 2. TESC measures for a given area, to be graded or otherwise worked, should be installed prior to any activity within that area. The recommended sequence of construction within a given area would be to install sediment traps and/or ponds and establish perimeter flow control prior to starting earthwork. 3. During the wetter months of the year, or when large storm events are predicted during the summer months, each work area should be stabilized so that if precipitation occurs, the work area can receive the rainfall without excessive erosion or sediment transport. The required measures for an area to be “buttoned-up” will depend on the time of year and the duration the area will be left unworked. During the winter months, areas that are to be left unworked for more than 2 days should be mulched or covered with plastic. During the summer months, stabilization will usually consist of seal-rolling the subgrade. Such measures will aid in the contractor’s ability to get back into a work area after a storm event. The stabilization process also includes establishing temporary stormwater conveyance channels through work areas to route runoff to the approved treatment facilities. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 13 4. All disturbed areas should be revegetated as soon as possible. If it is outside of the growing season, the disturbed areas should be covered with mulch, or as recommended in the erosion control plan. Straw mulch provides a cost-effective cover measure and can be made wind-resistant with the application of a tackifier after it is placed. 5. Surface runoff and discharge should be controlled during and following development. Uncontrolled discharge may promote erosion and sediment transport. Soils that are to be reused around the site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but are not limited to, covering with plastic sheeting, the use of low stockpiles in flat areas, or the use of straw bales/silt fences around pile perimeters. It is our opinion that with the proper implementation of the TESC plans and by field-adjusting appropriate mitigation elements (BMPs) throughout construction, the potential for adverse impacts from erosion hazards on the project may be mitigated. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 14 III. DESIGN RECOMMENDATIONS 9.0 INTRODUCTION Our explorations indicate that, from a geotechnical engineering standpoint, the proposed building renovations and structural alterations are feasible provided the recommendations contained herein are properly followed. At the locations explored, we encountered a surficial layer of existing fill underlain by medium dense to very dense native sediments. The native sediments will provide suitable support for conventional spread and strip footings. The existing fill soils are not considered suitable for direct foundation support and may require remedial measures for support of hardscapes and slabs-on-grade. The following sections provide our recommendations for site preparation, temporary cut slopes, structural fill, foundation support, lateral earth pressures on retaining walls, drainage considerations, and slab-on-grade support. 10.0 SITE PREPARATION Erosion and surface water control should be established around the perimeter of the excavation to satisfy City of Renton requirements. After any required demolition is complete, disturbed soils below finished grade should be removed. Existing fill should be removed from below the building foundations until suitable native soils are exposed, and the fill removal should extend laterally at least 2 feet beyond the footing limits. The resulting surface should then be compacted before placing structural fill, as necessary, to reach planned grades. 10.1 Site Disturbance The existing fill and native soils onsite contain substantial quantities of fine-grained material (silt) and are considered to be highly moisture-sensitive. Sediments containing more than approximately 5 percent fines (silt and clay) will be moisture-sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. 10.2 Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, we anticipate that temporary, unsupported cuts into the existing fill or native soils can be made near vertical to a Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 15 maximum depth of 4 feet. If excavations greater than 4 feet are required, then temporary, unsupported cut slopes can be planned at maximum inclinations of 1.5H:1V (Horizontal:Vertical) in existing fill and medium dense to dense native sediments. These slope angles are for areas where groundwater seepage is not present at the faces of the slopes. If groundwater or surface water is present when the temporary excavation slopes are exposed, flatter slope angles may be required. As is typical with earthwork operations, some sloughing and raveling may occur, especially if groundwater seepage is present in the excavation cuts, and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. 11.0 STRUCTURAL FILL We anticipate that placement of structural fill may be necessary to establish desired grades at the site and for backfilling around foundation elements. All references to structural fill in this report refer to subgrade preparation, fill type, and placement and compaction of materials as discussed in this section. 11.1 Subgrade Compaction In areas that will receive structural fill, the upper 12 inches of exposed subgrade should be recompacted to a firm and unyielding condition. If the subgrade contains too much moisture, suitable recompaction may be difficult or impossible to attain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. After recompaction of the exposed ground is tested and approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. 11.2 Structural Fill Compaction Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to at least 95 percent of the modified Proctor maximum dry density using ASTM International (ASTM) D-1557 as the standard. Utility trench backfill should be placed and compacted in accordance with applicable municipal codes and standards. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 16 11.3 Use of On-Site Soils as Structural Fill The existing fill and native sediments consisting primarily of sand and silty sand are suitable for use as structural fill provided the soil is free of roots or other deleterious materials and have a moisture content suitable for achieving the specified compaction. At the time of our exploration, the moisture content for the majority of the near-surface fill and native sediments encountered in our explorations appeared to be near or above optimum for achieving suitable compaction and will likely require drying. On-site sediments consisting primarily of silt and sandy silt are not considered suitable for use as structural fill due to the high silt content and high sensitivity to moisture which may lead to unstable conditions with elevated moisture and disturbance. The presence and thickness of the fine-grained sediments was variable between our explorations. Silt and sandy silt were encountered within EB-2 at 12.5 feet to the termination depth of 16.5 feet, EB-4 at 6.5 to 9.5 feet, EB-5 at 4.5 to 6.5 feet, and EB-6 at 6 to 12 feet. Soils in which the amount of fine-grained material (smaller than No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. The existing fill and native soils contain a substantial amount of silt and are considered highly moisture-sensitive. These soils may require moisture-conditioning before use as structural fill. Good construction practices and erosion control measures will be necessary to protect the fine-grained soils and prevent over-optimum moisture conditions from developing. If structural fill is placed during wet weather or if proper compaction cannot be obtained, a select import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil, with the amount of fine-grained material (silt and clay) limited to 5 percent by weight when measured on the minus No. 4 sieve fraction, and at least 25 percent retained on the No. 4 sieve. 11.4 Structural Fill Testing Compaction testing will likely be required by the City of Renton. We recommend that a representative from our firm observe the subgrades and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 17 12.0 FOUNDATIONS Based on the explorations completed for this study, native sediments that are suitable for support of conventional spread and strip footings were encountered at relatively shallow depths ranging from about 3 to 5 feet below the existing ground surface, except at exploration EB-2 the native sediments were deeper at about 8.5 feet. The suitable native sediments encountered at these depths include medium dense to dense ice-contact deposits, dense to very dense advance outwash (lacustrine), and hard pre-Fraser fine-grained sediments. Spread and strip footings may be used for building foundation support when founded either directly on the native sediments described above or on structural fill placed over native sediments after removal of existing fill. If loose ice-contact or other glacially-derived sediments are encountered below planned foundation areas at the time of construction, we recommend that the upper 12 inches of the material be recompacted to a firm and unyielding condition prior to structural fill placement. For footings founded as described above, we recommend using a maximum allowable bearing pressure of 3,000 pounds per square foot (psf) for design purposes, including both dead and live loads. An increase in the allowable bearing pressure of one-third may be used for short-term wind or seismic loading. If structural fill is placed below footing areas, the structural fill should extend horizontally beyond the footing by at least 2 feet. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all foundations must penetrate to the prescribed bearing strata, and no foundations should be constructed in or above loose, organic, or existing fill soils. Anticipated settlement of footings founded as recommended should be less than 1 inch with differential settlement one-half of the anticipated total settlement. Most of this movement should occur during initial dead load applications. However, disturbed material not removed from footing trenches prior to footing placement could result in increased settlements. All footing areas should be observed by AESI prior to placing concrete to verify that the foundation subgrades are undisturbed and construction conforms to the recommendations contained in this report. Foundation bearing verification by AESI will likely be required by the City as a condition of permitting. Perimeter footing drains should be provided as discussed under the “Drainage Considerations” section of this report. It should be noted that the area bounded by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM D-1557. In addition, a 1.5H:1V line extending down and away from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edges of steps or cuts in the bearing soils. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 18 The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and foundations extended down to competent natural soil. If any foundation excavations will occur during the wet season and exposed to rain, consideration should be given to “armoring” the exposed subgrade with a thin layer of rock to provide a working surface during foundation construction. We recommend a 6-inch layer of crushed rock for this purpose. 12.1 Existing Footing Support Because the project will include foundation work on existing buildings, it may be necessary to excavate adjacent to existing footings that are intended to remain in service. We recommend that no excavations be made into the support zone of existing foundations, as defined by a line projected down and away from existing footings at an angle of 1H:1V. If excavation into the support zone of existing footings is required, we should be allowed to offer situation-specific recommendations for foundation underpinning, sequential partial excavations (slot cuts), or other methods to retain support for existing structures. 13.0 FOUNDATION WALLS The following recommendations may be applied to conventional walls up to 5 feet tall. We should be allowed to offer situation-specific input for taller walls. All backfill behind foundation walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls, which are free to yield laterally at least 0.1 percent of their height, may be designed to resist lateral earth pressure represented by an equivalent fluid equal to 35 pounds per cubic foot (pcf). Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an equivalent fluid of 55 pcf. Walls with sloping backfill up to a maximum gradient of 2H:1V should be designed using an equivalent fluid of 55 pcf for yielding conditions or 75 pcf for fully restrained conditions. If parking areas are adjacent to walls, a surcharge equivalent to 250 psf should be added to the wall height in determining lateral design forces. Retaining wall design should include a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. Considering the site soils and the recommended wall backfill materials, we recommend a seismic surcharge pressure of 10H and 15H psf, where H is the wall height in feet for the “active” and “at-rest” loading conditions, respectively. The seismic surcharge should be modeled as a rectangular distribution with the resultant applied at the midpoint of the walls. Surcharges from adjacent footings or heavy construction equipment must be added to the above values. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 19 Perimeter footing drains should be provided for all retaining walls, as discussed under the “Drainage Considerations” section of this report. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. 13.1 Passive Resistance and Friction Factors Lateral loads can be resisted by friction between the base of the foundation and the natural soils or supporting structural fill soils and by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters which include a factor of safety of 1.5: Passive equivalent fluid = 300 pcf Coefficient of friction = 0.30 14.0 FLOOR SUPPORT Slab-on-grade floors may be constructed directly on native sediments, on structural fill placed over native sediments, or on a minimum of 2 feet of structural fill where deeper existing fill soils are encountered. We recommend that the native sediments and any existing fill to remain in place be recompacted to a firm and unyielding condition prior to placement of the structural fill. All fill placed beneath the slab must be compacted to at least 95 percent of ASTM D-1557. Interior floor slabs should be cast atop a minimum of 4 inches of washed crushed “chip” rock to act as a capillary break. Interior floor slabs should also be protected from dampness by a plastic moisture vapor retarder at least 15 mils thick. The moisture vapor retarder should be placed between the capillary break material and the concrete slab. 15.0 DRAINAGE CONSIDERATIONS Traffic across the on-site soils when they are damp or wet will result in disturbance of the otherwise firm stratum. Therefore, during site work and construction, the contractor should provide surface drainage and subgrade protection, as necessary. Any retaining walls and all perimeter foundation walls should be provided with a drain at the base of the footing elevation. Drains should consist of rigid, perforated, PVC pipe surrounded by washed gravel. The level of the perforations in the pipe should be set at or slightly below the bottom of the footing at all locations and the drains should be constructed with sufficient gradient to allow gravity discharge away from the structures. In addition, any retaining or Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 20 subgrade walls should be lined with a minimum, 12-inch-thick, washed gravel blanket, backfilled completely with free-draining material over the full height of the wall (excluding the first 1 foot below the surface). This drainage aggregate should tie into and freely communicate with the footing drains. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. Exterior grades adjacent to walls should be sloped downward away from the structures to achieve natural surface drainage. Final exterior grades should promote free and positive drainage away from the buildings at all times. Water must not be allowed to pond or to collect adjacent to the foundation or within the immediate building areas. It is recommended that a gradient of at least 3 percent for a minimum distance of 10 feet from the building perimeter be provided, except in paved locations. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structures. 16.0 PROJECT DESIGN AND CONSTRUCTION MONITORING We have reviewed the 100% Design Development set and the plans have accurately incorporated the recommendations presented in this report. If any design changes are made, we recommend that we be allowed to review the recommendations in this report and modify them as necessary. The City may require geotechnical special inspections during construction and preparation of a final summary letter when construction is complete. We are available to provide geotechnical engineering services during construction. The integrity of the earthwork and foundations depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Subsurface Exploration, Geologic Hazard, Hazen High School Modernization and Geotechnical Engineering Report Renton, Washington Design Recommendations August 26, 2024 ASSOCIATED EARTH SCIENCES, INC. BCY/ld – 20210251E003-002 Page 21 We have enjoyed working with you on this study and are confident these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ Brendan C. Young, L.G. Senior Staff Geologist ______________________________ Kurt D. Merriman, P.E. G. Bradford Drew, P.E. Senior Principal Engineer Associate Engineer Attachments: Figure 1: Vicinity Map Figure 2: Existing Site and Exploration Plan Appendix A: Exploration Logs Appendix B: Historical Exploration Logs (AESI 2009, 2021, 2022) Appendix C: Shear Wave Velocity Results (WGS 2020) G:\ G I S _ P r o j e c t s \ a a Y 2 0 2 1 \ 2 1 0 2 5 1 H a z e n H S \ A P R X \ E 0 0 3 \ 2 0 2 1 0 2 5 1 E 0 0 3 F1 V M _ H a z e n H S . a p r x | 2 0 2 1 0 2 5 1 E 0 0 3 F 1 V M _ H a z e n H S | 2 0 2 4 - 0 1 - 2 4 | m t r o p COUNTY LOCALE LOCATION PROJECT NO.DATE FIGURE 11/2420210251E003 HAZEN HIGH SCHOOL MODERNIZATION RENTON, WASHINGTON VICINITY MAP ESRI, USGS, NATIONAL GEOGRAPHIC,DELORME, NATURALVUE, I-CUBED, GEBCO:ARCGIS ONLINE BASEMAP. WADOT STATEROUTES 24K (12/20). KING CO: PARCELS(4/23), ROADS (5/23). NOTE: LOCATION AND DISTANCES SHOWNARE APPROXIMATE. BLACK AND WHITEREPRODUCTION OF THIS COLOR ORIGINALMAY REDUCE ITS EFFECTIVENESS AND LEADTO INCORRECT INTERPRETATION. KLnJ CoXnt\ DU V A L L A V E N E HO Q U I A M A V E N E NE 12TH ST NE 10TH ST CH E L A N A V E N E 00 .I N G C O 8 N T < RENTON NEWCASTLE RE N T O N RENTON RENTON NE W C A S T L E NEWCASTLE 0 2,000 FEET ± SITE BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAYREDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION.LOCATION AND DISTANCES SHOWN ARE APPROXIMATE. G:\ G I S _ P r o j e c t s \ a a Y 2 0 2 1 \ 2 1 0 2 5 1 H a z e n H S \ A P R X \ E 0 0 3 \ 2 0 2 1 0 2 5 1 E 0 0 3 F2 E S _ H a z e n H S . a p r x | 2 0 2 1 0 2 5 1 E 0 0 3 F 2 E S _ H a z e n H S | 2 0 2 4 - 0 1 - 2 4 | mt r o p PROJECT NO.DATE FIGURE ± 21/2420210251E003 HAZEN HIGH SCHOOL MODERNIZATION RENTON, WASHINGTON EXISTING SITE AND EXPLORATION PLAN DATA SOURCES/REFERENCES:KING COUNTY: ROADS (5/23), PARCELS (4/23).EAGLEVIEW TECHNOLOGIES, INC.: AERIAL IMAGERY (2021).WA DNR LIDAR: KING_COUNTY_WEST_2021, ACQUIRED 4/21, 1.5'CELL SIZE. CONTOURS DERIVED FROM LIDAR. 0 150 FEET Du v a l l A v e N E Ho q u i a m A v e N E NE 10th St NE 12th St NE 12th St NE 11th Pl NE 11th Ct NE 10th St NE 10th Pl NE 11th St Du v a l l P l N E EB-1 EB-1 EB-2 EB-3 EB-4 EB-5 EB-1 EB-2 EB-3 EB-4 EB-5 EB-6 EB-7 EB-8 EB-9 EB-10 EB-11 EB-1 EB-2 EB-3 EB-4 EB-5 EB-6 +$=(1+,*+ 6&+22/ 47 0 46 0 45 0 44 0 43 0 420 460 450 480 470 460 450 45 0 44 0 470 47 0 470 44 0 44 0 LEGEND SITE EXPLORATION BORING, 2024 EXPLORATION BORING, 2022 EXPLORATION BORING, 2021 EXPLORATION BORING, 2009 FOUNDATION WORK POTENTIAL FOUNDATION WORK CONTOUR 10 FT CONTOUR 2 FT PARCEL APPENDIX A Exploration Logs Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual-manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System. OH PT CH OL MH CL ML SM SC GW SP GC SW GM GP Well-graded gravel and gravel with sand, little to no fines Poorly-graded gravel and gravel with sand, little to no fines Clayey gravel and clayey gravel with sand Silty gravel and silty gravel with sand Well-graded sand and sand with gravel, little to no fines Poorly-graded sand and sand with gravel, little to no fines Clayey sand and clayey sand with gravel Organic clay or silt of low plasticity Organic clay or silt of medium to high plasticity Peat, muck and other highly organic soils Silty sand and silty sand with gravel Silt, sandy silt, gravelly silt, silt with sand or gravel Clay of low to medium plasticity; silty, sandy, or gravelly clay, lean clay Elastic silt, clayey silt, silt with micaceous or diatomaceous fine sand or silt Clay of high plasticity, sandy or gravelly clay, fat clay with sand or gravel (1 ) Hi g h l y Or g a n i c So i l s Fin e - G r a i n e d S o i l s - 5 0 % o r M o r e P a s s e s N o . 2 0 0 S i e v e (1 ) Co a r s e - G r a i n e d S o i l s - M o r e t h a n 5 0 % R e t a i n e d o n N o . 2 0 0 S i e v e Gr a v e l s - M o r e t h a n 5 0 % o f C o a r s e F r a c t i o n Re t a i n e d o n N o . 4 S i e v e 12 % F i n e s 5% F i n e s Sa n d s - 5 0 % o r M o r e o f C o a r s e F r a c t i o n Pa s s e s N o . 4 S i e v e Si l t s a n d C l a y s Li q u i d L i m i t L e s s t h a n 5 0 Sil t s a n d C l a y s Li q u i d L i m i t 5 0 o r M o r e (1 ) (1 ) 12 % F i n e s 5% F i n e s (2 ) (2 ) (2 ) (2 ) Terms Describing Relative Density and Consistency Estimated Percentage Moisture Content Percentage by Weight <5 5 to <12 12 to <30 30 to <50 Component Definitions Component Trace Some Modifier (silty, sandy, gravelly) Very modifier (silty, sandy, gravelly) Size Range and Sieve Number Larger than 12" Descriptive Term Smaller than No. 200 (0.075 mm) 3" to 12" Coarse- Grained Soils Fine- Grained Soils Density Very Loose Loose Medium Dense Dense Very Dense SPT blows/foot 0 to 4 4 to 10 10 to 30 30 to 50 >50 (3) 0 to 2 2 to 4 4 to 8 8 to 15 15 to 30 >30 Consistency Very Soft Soft Medium Stiff Stiff Very Stiff Hard SPT blows/foot(3) Test Symbols No. 4 (4.75 mm) to No. 200 (0.075 mm) Boulders Silt and Clay Gravel Coarse Gravel Fine Gravel Cobbles Sand Coarse Sand Medium Sand Fine Sand Dry - Absence of moisture, dusty, dry to the touch Slightly Moist - Perceptible moisture Moist - Damp but no visible water Very Moist - Water visible but not free draining Wet - Visible free water, usually from below water table G = Grain Size M = Moisture Content A = Atterberg Limits C = Chemical DD = Dry Density K = Permeability No. 4 (4.75 mm) to No. 10 (2.00 mm) No. 10 (2.00 mm) to No. 40 (0.425 mm) No. 40 (0.425 mm) to No. 200 (0.075 mm) 3" to No. 4 (4.75 mm) 3" to 3/4" 3/4" to No. 4 (4.75 mm) Symbols Sampler Type and Description Blows/6" or portion of 6"15 10 20 California Sampler Ring Sampler Continuous Sampling Grab Sample Portion not recovered Split-Spoon Sampler (SPT) Cement grout surface seal Bentonite seal Filter pack with blank casing section Screened casing or Hydrotip with filter pack End cap ATD At time of drilling Static water level (date) (1)Percentage by dry weight(2)Combined USCS symbols used for fines between 5% and 12%(3)(SPT) Standard Penetration Test (ASTM D-1586)(4)In General Accordance with Standard Practice for Description and Identification of Soils (ASTM D-2488) Groundwater depth i n c o r p o r a t e d e a r t h s c i e n c e s a s s o c i a t e d EXPLORATION LOG KEY FIGURE:A1Blo c k s \ d w g \ l o g _ k e y 2 0 2 2 . d w g L A Y O U T : L a y o u t 5 - 2 0 2 2 L o g d r a f t 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 Sod/Topsoil - 3 inches Fill Upper 8 inches: Moist, brown to dark brown, silty, fine to medium SAND, some gravel; scattered organics (rootlets) (SM). Vashon Ice Contact Lower 10 inches: Moist, gray with orange oxidation staining, fine SAND, some silt (SP-SM). Very moist, brown to grayish brown, fine to medium SAND, some silt, some gravel; less silt with depth (SP-SM). Advance Outwash (Lacustrine) Wet, tan transitioning to gray, silty, fine to medium SAND, trace to some gravel; faintly bedded with silty, fine sand (SM). Very moist, brown with orange oxidation staining, silty, fine to medium SAND, some gravel, transitioning to gray, fine sandy, SILT, trace gravel; some medium sand present at tip of sample (SM). Pre-Fraser Non-Glacial Very moist to wet, gray, fine to medium SAND, trace to some gravel; massive (SP). 11 8 14 12 13 15 27 27 21 17 27 50/5" 3150/4" 22 28 48 50/5" 50/4" Associated Earth Sciences, Inc. Exploration Boring EB-1 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.8 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):7.5,14 Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 1 of 2 20 22.5 25 27.5 30 32.5 35 37.5 6 7 Wet, gray, fine to medium SAND, trace to some gravel; occasional layer (up to 0.5 inches thick) of medium to coarse sand (SP). Wet, gray, fine to coarse SAND, trace to some gravel; occasional interbed (up to 0.25 inches thick) of silty, fine sand; occasional red sand grains (SP/SP-SM). Driller notes refusal due to hard drilling. Groundwater encountered at 7.5 feet and 14 feet ATD. 50/6" 3750/4" 50/6" 50/4" Associated Earth Sciences, Inc. Exploration Boring EB-1 Hazen High School Modernization 2 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.8 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):7.5,14 Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 2 of 2 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 Sod/Topsoil - 3 inches Fill Moist, dark brown with brown, silty, fine to medium SAND, some gravel; abundant organics (fine organics/rootlets/bark) (SM). Moist, tan to brown with orange mottling from oxidation staining, very silty, fine SAND; occasional gravel; rare organics (rootlets); disturbed texture (SM). Upper 9 inches: As above. Vashon Advance (Lacustrine) Lower 9 inches: Very moist, brown, fine SAND, trace silt (SP). Wet, brown, fine SAND, trace silt; occasional lamination of gray silt (SP). Slightly moist, tan, SILT, some fine sand; silt becomes gray and blue gray at tip of sampler (ML). Driller notes refusal due to hard drilling. Groundwater encountered at 10 feet ATD. 10 9 4 4 7 9 8 11 12 21 34 50/5" 273350/5" 13 16 23 50/5" 50/5" Associated Earth Sciences, Inc. Exploration Boring EB-2 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):16.4 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):10 Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 1 of 1 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 Asphalt - 3 inches Fill Moist, brown to dark brown, silty, fine to medium SAND, trace to some gravel; abundant organics (fine black organics/rootlets) (SM). Vashon Ice Contact Moist, gray, fine SAND, trace silt; faint interbeds of silty, fine sand; faint petroleum odor (SP). Upper 12 inches: Very moist becoming wet, gray transitioning to tan, fine SAND (SP). Lower 6 inches: Wet, gray, fine to coarse SAND, some gravel, trace silt (SP). Wet, tan and light brown, fine to medium SAND, some silt, some gravel; broken gravel in spoon; blow count may be overstated (SP-SM). Vashon Advance Outwash (Lacustrine) Wet, brown heavily oxidized to orange, fine SAND, some silt; massive (SP- SM). 5 4 6 8 9 9 10 13 20 33 50/5" 1850/6" 10 18 33 50/5" 50/6" Associated Earth Sciences, Inc. Exploration Boring EB-3 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.4 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»466 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):8.5 Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 1 of 2 20 22.5 25 27.5 30 32.5 35 37.5 6 7 Wet, tan to light brown with occasional orange oxidation staining, fine SAND, some silt; faintly bedded (SP-SM). Pre-Fraser Non-Glacial Moist to very moist, gray, silty, fine to coarse SAND; some gravel material coarsening with depth and becoming less moist; occasional organics; faint stratifications (SM). Driller notes refusal due to hard drilling. Groundwater encountered at 8.5 feet ATD. 18 34 47 50/5" 81 50/5" Associated Earth Sciences, Inc. Exploration Boring EB-3 Hazen High School Modernization 2 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):25.4 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»466 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):8.5 Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 2 of 2 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 Bark/Mulch - 6 inches Fill Upper 6 inches: Moist, dark brown, silty, fine to medium SAND, some gravel; abundant organics (SM). Lower 12 inches: Moist, tan with orange oxidation staining, silty, fine SAND, some gravel; rare organics (bark) (SM). Vashon Ice Contact Moist, brown to gray with irregular orange mottling, silty to very silty, fine SAND (SM). Moist, gray with some orange oxidation staining, SILT, some fine sand, rare gravel; occasional interbed (up to 1/3-inches) of fine sand (ML). Vashon Lodgement Till Moist, brown, silty, fine SAND, some gravel; broken gravel in spoon; blow count may be overstated (SM). Driller notes refusal due to hard drilling. No groundwater encountered. 3 4 6 3 4 7 16 30 50/6" 50/6" 10 11 50/6" 50/6" Associated Earth Sciences, Inc. Exploration Boring EB-4 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):11 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):Not encountered Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 1 of 1 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 Bark/Mulch - 6 inches Fill Upper 6 inches: Moist, dark brown, silty, fine to medium SAND, some gravel; abundant organics (rootlets/fine organics) (SM). Lower 12 inches: Moist, tan to gray with large amounts of sub-horizontal orange oxidation staining, silty, fine SAND; rare gravel (SM). Vashon Ice Contact Very moist, tan to gray with minor orange oxidation staining, fine sandy, SILT; occasional interbeds of silty, fine sand (ML). Moist, brown, silty, fine to medium SAND, some gravel; unsorted; large lenses of gray, silty, fine sand at center of sample (SM). Vashon Lodgement Till Moist, brown, silty, fine SAND, some gravel; broken gravel in spoon; blow count may be overstated (SM). Driller notes refusal due to hard drilling. No groundwater encountered. 6 5 8 3 3 5 14 21 33 39 50/4" 13 8 54 50/4" Associated Earth Sciences, Inc. Exploration Boring EB-5 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):10.8 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»468 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):Not encountered.Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 1 of 1 0 2.5 5 7.5 10 12.5 15 17.5 1 2 3 4 5 6 Bark/Mulch - 4 inches Fill Moist, brown, silty, fine to medium SAND, some gravel; scattered organics (roots/rootlets) (SM). Moist to slightly moist, brown with gray inclusions, silty, fine SAND, some gravel; occasional lenses of gray, sandy, silt; broken gravel in spoon (SM). Pre-Fraser Fine Grained Slightly moist, brownish gray with some gray, very silty, fine SAND ranging to sandy, SILT; occasional interbed of gray silt (SM/ML). Slightly moist, grayish brown transitioning to gray with depth, SILT, some fine sand, some gravel (ML). Slightly moist, gray, SILT, some fine sand, trace gravel (ML). Slightly moist, gray to bluish gray, silty to very silty, fine SAND, trace to some gravel; unsorted (SM). Driller notes refusal due to hard drilling. No groundwater encountered. 14 19 25 20 30 45 26 27 33 32 37 45 50/6" 44 75 60 82 50/6" Associated Earth Sciences, Inc. Exploration Boring EB-6 Hazen High School Modernization 1 Renton, WA Start Date:1/2/24 Logged By:BCY 20210251E003 Ending Date:1/2/24 Approved By:JHS Driller/Equipment:Geologic Drill / Mini Track Total Depth (ft):14.5 Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»472 Hole Diameter (in):6 Datum:NAVD 88 Groundwater Depth ATD (ft):Not encountered Groundwater Depth Post Drilling (ft) (Date): () De p t h ( f t ) Sa m p l e T y p e Sa m p l e % R e c o v e r y Gr a p h i c Sy m b o l Description Wa t e r L e v e l Bl o w s / 6 " Blows/Foot 1 0 2 0 3 0 4 0 5 0 + Ot h e r T e s t s 20 2 1 0 2 5 1 E 0 0 3 1/ 2 4 / 2 0 2 4 Sheet: 1 of 1 APPENDIX B Historical Exploration Logs (AESI 2009, 2021, 2022) Asphalt - 2 inches FillUpper 3 inches: Moist, grayish dark brown, silty, fine SAND, trace medium tocoarse sand; faint organic odor (SM).Lower 15 inches: Moist, grayish brown, silty, fine SAND to fine sandy, SILT,trace gravel; massive (SM-ML). Vashon Recessional OutwashMoist, grayish brown, silty, fine SAND, trace gravel; unsorted (SM). S-1 S-2 151010 111821 Bottom of exploration boring at 3.5 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-1 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 2020 3939 Asphalt - 2 inches FillMoist, dark brown, silty, fine SAND, some gravel; organics observed; faintorganic odor (SM). Moist, brownish gray, silty, fine SAND, some gravel; some organics; faintorganic odor; gravel in tip; poor recovery (SM). S-1 S-2 855 61114 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-2 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 1010 2525 Asphalt - 1.75 inches FillMoist, dark brown to grayish brown, fine SAND, some silt to silty, trace gravel;occasional organics; unsorted (SP-SM). Moist, dark brown, silty, fine SAND, trace medium sand; poor recovery (woodstuck in tip) (SM). S-1 S-2 755 6910 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-3 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 1010 1919 Asphalt - 1.5 inches FillMoist, dark brown to brownish gray, silty, fine SAND, some gravel; unsorted;occasional organics; faint organic odor; unsorted (SM). As above. Moist to wet, light gray, fine SAND, some silt; massive (SP-SM). S-1 S-2 S-3 645 588 91317 Bottom of exploration boring at 5 feetGroundwater encountered at 3 feet. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-4 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 99 1616 3030 Asphalt - 1.75 inches Gravel Base Course - 1 inch Vashon Recessional OutwashMoist, reddish brown, fine SAND, some silt, trace gravel; massive (SP-SM). As above. S-1 S-2 141314 121622 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-5 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 2727 3838 Asphalt - 3 inches (2 lifts) FillUpper 6 inches: Moist, dark brown, silty, fine SAND, some gravel; unsorted(SM). Vashon Recessional OutwashLower 12 inches: Moist, reddish brown, fine SAND,some silt, trace gravel;massive (SP-SM). As above. S-1 S-2 71312 111219 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-6 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 2525 3131 Asphalt - 2 inches Gravel Base Course - 3 inches FillMoist, brownish gray to dark brown, silty, fine SAND, some gravel; unsorted;organics observed; layer (~3 inches thick) of coarse gravel; faint organic odor(SM) As above. S-1 S-2 525 31116 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-7 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 77 2727 Asphalt - 1 inch FillMoist, brownish gray, silty, fine SAND, some gravel; unsorted (SM). As above; contains organics. S-1 S-2 141010 101414 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-8 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 2020 2828 Asphalt - 3 inches (2 lifts) Gravel Base Course - 2 inches FillMoist, dark brownto brownish gray, silty, fine SAND, some gravel; unsorted;faint organic odor (SM). Moist, dark brown to gray, silty, fine SAND, some gravel; unsorted; abundantorganics; organic odor (SM). S-1 S-2 191816 52228 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~465 5 10 EB-9 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 3434 5050 Asphalt - 3 inches (2 lifts) FillMoist, dark brown to grayish brown, silty, fine SAND, to fine sandy, SILT, tracegravel; organics observed; organic odor (SM-ML). As above. S-1 S-2 665 71319 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~464 5 10 EB-10 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 1111 3232 Asphalt - 3 inches (2 lifts) Gravel Base Course - 3 inches FillMoist, dark brown, silty, fine SAND, some gravel; abundant organics; organicodor; unsorted (SM). Moist, bluish gray, silty, fine SAND; massive (SM). S-1 S-2 1354 81412 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab Sample Sy m b o l 2 40 Datum Hammer Weight/Drop Sampler Type (ST): ~466 5 10 EB-11 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210251E002 3/9/22,3/9/22 Logged by: Shelby Tube Sample 140# / 30HOLT / Truck Drill Exploration Boring Water Level at time of drilling (ATD) Hazen High School Site Improvements M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 2 5 1 E 0 0 2 . G P J M a r c h 2 1 , 2 0 2 2 99 2626 Topsoil - 6 inches FillCuttings are brown GRAVEL. Very gravelly drilling 0 to 4 feet. Moist, brown, silty, fine SAND; trace gravel; blowcount likely overstateddue to oversized gravel; not representative (SM). Upper 6 inches: As above. Vashon Recessional Outwash Lower 12 inches: Moist, brown with occasional planes of oxidation, fineSAND, some silt, trace gravel; bedded with occasional thin interbeds ofsilty, fine SAND ranging to fine sandy, SILT (SP-SM). Becomes very moist to wet. Layer (.25 inches thick) of dark gray sand at tip. Pre-Olympia Glacial Till Moist, dark gray, very silty, fine SAND, some gravel; unsorted (SM) Drilling slows. Moist with wet coating from above water, brown with oxidation, silty, fineSAND, some gravel; unsorted (SM). S-1 S-2 S-3 S-4 S-5 171810 7813 81212 121617 273130 Bottom of exploration boring at 21.5 feetGroundwater encountered 8 to 12 feet. Ground Surface Elevation (ft) Grab Sample Sy m b o l 6 40 Datum Hammer Weight/Drop Sampler Type (ST): ~460 5 10 15 20 EB-1 Ring Sample No Recovery Gr a p h i c 10 Ot h e r T e s t s Hole Diameter (in) DESCRIPTION Driller/Equipment Bl o w s / 6 " JHS JG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M) Wa t e r L e v e l Project Name Water Level ()Approved by: 30 Blows/Foot Sa m p l e s De p t h ( f t ) S T Exploration Number20210397E001 10/20/21,10/20/21 Logged by: Shelby Tube Sample 140# / 30Geologic Drill Partners / Mini-Bobcat Exploration Boring Water Level at time of drilling (ATD) Hazen HS Pool Modernization M - Moisture Project Number 20 Renton, WA Date Start/Finish Co m p l e t i o n Location Sheet1 of 1 NAVD 88 We l l AE S I B O R 2 0 2 1 0 3 9 7 E 0 0 1 . G P J N o v e m b e r 5 , 2 0 2 1 2828 2121 2424 3333 61 APPENDIX C Shear Wave Velocity Results (WGS 2020) WASHINGTON 2019–2021 SCHOOL SEISMIC SAFETY PROJECT SITE CLASS ASSESSMENT See Washington Geological Survey Open File Report 2019-01 for more information. HAzEN HIGH SCHOOL Location of seismic array at the school campus. Liquefaction Very low RENTON SCHOOL DISTRICT, KING COUNTY, WA WHAT IS SITE CLASS? Site class estimates how local soils amplify earthquake- induced ground shaking, and is based on how fast seismic (shear) waves travel through the upper 30 m (100 ft) of the soil (Vs30). Site class has been approximated for the entire State of Washington, but these predictions aren’t always accurate where geology is complex. The site class measured for this project accounts for geologic complexity and is therefore more accurate. HOW DID WE MEASURE SITE CLASS? On October 22, 2020, a team from the Washington Geological Survey conducted a seismic survey at Hazen High School. We measured Vs30 by laying out 48 geophones (ground motion sensors) in a 94 m (308 ft) array. Then we conducted (1) an active survey in which a sledgehammer was struck against the ground to generate seismic waves; and (2) a passive survey where we measured ambient seismic noise. These surveys let us calculate Vs30 at the center of the array, which is then correlated to site class using the table below. It is generally accurate to assume the site class is the same under the array and the school. WHAT DID WE LEARN? □The school is built on soft rock or very dense soil, which would amplify ground shaking relative to rock. □Site class is within the predicted site class of C–D.WHAT SOILS ARE UNDER THE SCHOOL? The school is sitting on Pleistocene continental glacial drift consisting of well-sorted and fine-grained sandy units with interlayered coarser sand, gravel, and cobbles. GEOLOGIC HAzARDS AT THE SCHOOL Ground Shaking Violent MEASURED SITE CLASS Active Fault Proximity Within 5 miles of an active mapped fault Site class Description Vs30 (m/sec) Ground shaking amplification A Hard rock >1,500 Low B Rock 760–1,500 C Soft rock or very dense soil 360–760 D Stiff soil 180–360 E Soft soil <180 High C TECHNICAL OVERVIEW OF RESULTS QUESTIONS?Washington Department of Natural Resources—WA Geological Survey geology@dnr.wa.gov • 360.902.1450 • https://www.dnr.wa.gov/geology HAzEN HIGH SCHOOL—ICOS# 21350 This section provides a technical overview of the geophysical methods and results of the seismic site characterization. DISPERSION CURVE The term dispersion image refers to the image of phase velocity versus frequency of a record. Dispersion curve refers to the manually picked fundamental mode in a dispersion image. The multi-channel analysis of surface wave (MASW) dispersion images from the forward and reverse directions are poor quality so that the fundamental mode can be picked with some confidence. However, the MASW dispersion curves do not sample down to 30 m (100 ft), and there is noticeable interference from higher modes. The microtremor analysis method (MAM) dispersion image is decent quality, but does not sample the shallow layers. MAM and the forward and reverse MASW dispersion curves depict similar trends, therefore the three dispersion curves are combined into a single model. VELOCITY MODEL An initial model was generated using the 1/3 wavelength approximation and the combined dispersion curves. The initial model had an RMSE of 11.1 percent. The inversion was carried out for seven iterations and resulted in a final model with an RMSE of 4.5 percent. The final model is unconstrained in the top 1 m (3 ft), and below this shows rapidly increasing velocity to 10 m (33 ft), then a slight velocity reversal down to 17 m (56 ft), and then generally increasing velocity down to 30 m (100 ft). Our best Vs30 measurement is 376 m/sec, which places the site in the C site class near the C/D border. This is within the predicted site class of C-D. Final inverted velocity model with measured dispersion curve and modeled dispersion curve. The equation used to calculate the average shear wave velocity (Vs) for the upper 30 m is shown in the middle left of the figure. di = thickness of any layer between 0 and 30 m. Vsi = shear wave velocity in m/sec of the layer. WASHINGTON 2019–2021 SCHOOL SEISMIC SAFETY PROJECT SITE CLASS ASSESSMENT See Washington Geological Survey Open File Report 2019-01 for more information. LINdbERGH SENIOR HIGH SCHOOL Location of seismic array at the school campus. Liquefaction Very low RENTON SCHOOL dISTRICT, KING COUNTY, WA WHAT IS SITE CLASS? Site class estimates how local soils amplify earthquake- induced ground shaking, and is based on how fast seismic (shear) waves travel through the upper 30 m (100 ft) of the soil (Vs30). Site class has been approximated for the entire State of Washington, but these predictions aren’t always accurate where geology is complex. The site class measured for this project accounts for geologic complexity and is therefore more accurate. HOW dId WE MEASURE SITE CLASS? On October 22, 2020, a team from the Washington Geological Survey conducted a seismic survey at Lindbergh Senior High School. We measured Vs30 by laying out 48 geophones (ground motion sensors) in a 94 m (308 ft) array. Then we conducted (1) an active survey in which a sledgehammer was struck against the ground to generate seismic waves; and (2) a passive survey where we measured ambient seismic noise. These surveys let us calculate Vs30 at the center of the array, which is then correlated to site class using the table below. It is generally accurate to assume the site class is the same under the array and the school. WHAT dId WE LEARN? □The school is built on soft rock or very dense soil, which would amplify ground shaking relative to rock. □Site class is the same as the predicted site class of C.WHAT SOILS ARE UNdER THE SCHOOL? The school is sitting on Pleistocene continental glacial till, comprising a compact and unsorted mixture of sand, silt, clay, and gravel. GEOLOGIC HAZARdS AT THE SCHOOL Ground Shaking Violent MEASURED SITE CLASS Site class Description Vs30 (m/sec) Ground shaking amplification A Hard rock >1,500 Low B Rock 760–1,500 C Soft rock or very dense soil 360–760 D Stiff soil 180–360 E Soft soil <180 High C TECHNICAL OVERVIEW OF RESULTS QUESTIONS?Washington Department of Natural Resources—WA Geological Survey geology@dnr.wa.gov • 360.902.1450 • https://www.dnr.wa.gov/geology LINdbERGH SENIOR HIGH SCHOOL—ICOS# 21365 This section provides a technical overview of the geophysical methods and results of the seismic site characterization. dISPERSION CURVE The term dispersion image refers to the image of phase velocity versus frequency of a record. Dispersion curve refers to the manually picked fundamental mode in a dispersion image. The multi-channel analysis of surface wave (MASW) dispersion images from the forward and reverse directions are decent quality so that the fundamental mode can be picked with confidence. However, the MASW dispersion curves do not adequately sample down to 30 m (100 ft). The microtremor analysis method (MAM) dispersion image is also decent quality but does not sample the shallow layers. Overall, the MASW and MAM dispersion curves correlate well, so the MASW (forward and reverse direction) and MAM dispersion curves are combined into a single model. VELOCITY MOdEL An initial model was generated using the 1/3 wavelength approximation and the combined dispersion curves. The initial model had an RMSE of 10.4 percent. The inversion was carried out for five iterations and resulted in a final model with an RMSE of 5.6 percent. The final model is unconstrained in the top 2 m (6 ft), and below this shows rapidly increasing velocity to 10 m (30 ft), then generally increasing velocity down to 30 m (100 ft). Our best Vs30 measurement is 397 m/sec, which places the site in the C site class. Although the upper 2 m are unconstrained, adjusting them does not change the site class. All initial and final models are in the C class, so the site can be confidently classified. This is the same as the predicted site class of C. Final inverted velocity model with measured dispersion curve and modeled dispersion curve. The equation used to calculate the average shear wave velocity (Vs) for the upper 30 m is shown in the upper right corner. di = thickness of any layer between 0 and 30 m. Vsi = shear wave velocity in m/sec of the layer. WASHINGTON 2019–2021 SCHOOL SEISMIC SAFETY PROJECT SITE CLASS ASSESSMENT See Washington Geological Survey Open File Report 2019-01 for more information. RENTON HIGH SCHOOL Location of seismic array at the school campus. Liquefaction Moderate to high RENTON SCHOOL DISTRICT, KING COUNTY, WA WHAT IS SITE CLASS? Site class estimates how local soils amplify earthquake- induced ground shaking, and is based on how fast seismic (shear) waves travel through the upper 30 m (100 ft) of the soil (Vs30). Site class has been approximated for the entire State of Washington, but these predictions aren’t always accurate where geology is complex. The site class measured for this project accounts for geologic complexity and is therefore more accurate. HOW DID WE MEASURE SITE CLASS? On October 15, 2020, a team from the Washington Geological Survey conducted a seismic survey at Renton High School. We measured Vs30 by laying out 48 geophones (ground motion sensors) in a 94 m (308 ft) array. Then we conducted (1) an active survey in which a sledgehammer was struck against the ground to generate seismic waves; and (2) a passive survey where we measured ambient seismic noise. These surveys let us calculate Vs30 at the center of the array, which is then correlated to site class using the table below. It is generally accurate to assume the site class is the same under the array and the school. WHAT DID WE LEARN? □The school is built on stiff soil, which would amplify ground shaking relative to rock. □Site class is within the predicted site class of D–E.WHAT SOILS ARE UNDER THE SCHOOL? The school is sitting on urban or industrial land modified by widespread or discontinuous artificial fill. GEOLOGIC HAZARDS AT THE SCHOOL Ground Shaking Violent MEASURED SITE CLASS D Site class Description Vs30 (m/sec) Ground shaking amplification A Hard rock >1,500 Low B Rock 760–1,500 C Soft rock or very dense soil 360–760 D Stiff soil 180–360 E Soft soil <180 High TECHNICAL OVERVIEW OF RESULTS QUESTIONS?Washington Department of Natural Resources—WA Geological Survey geology@dnr.wa.gov • 360.902.1450 • https://www.dnr.wa.gov/geology RENTON HIGH SCHOOL—ICOS# 21354 This section provides a technical overview of the geophysical methods and results of the seismic site characterization. DISPERSION CURVE The term dispersion image refers to the image of phase velocity versus frequency of a record. Dispersion curve refers to the manually picked fundamental mode in a dispersion image. The multi-channel analysis of surface wave (MASW) dispersion images from the forward and reverse directions are poor quality, but the fundamental mode can be picked with some confidence. However, the microtremor analysis method (MAM) dispersion image is excellent quality, so that the fundamental mode can be picked with high confidence. MAM and the forward and reverse MASW dispersion curves correlate well, depicting similar trends. Therefore the three dispersion curves are combined into a single model. VELOCITY MODEL An initial model was generated using the 1/3 wavelength approximation and the combined dispersion curves. The initial model had an RMSE of 12.9 percent. The inversion was carried out for ten iterations and resulted in a final model with an RMSE of 4.7 percent. The final model is unconstrained in the top 1 m (3 ft), and below this shows rapidly increasing velocity to 6 m (20 ft), then generally increasing velocity down to 30 m (100 ft). Our best Vs30 measurement is 272 m/sec, which places the site solidly in the D site class. This is within the predicted site class of D–E. Final inverted velocity model with measured dispersion curve and modeled dispersion curve. The equation used to calculate the average shear wave velocity (Vs) for the upper 30 m is shown in the upper right corner. di = thickness of any layer between 0 and 30 m. Vsi = shear wave velocity in m/sec of the layer. HAZEN HIGH SCHOOL IMPROVEMENTS 18 7. OTHER PERMITS Department of Ecology Construction Stormwater General Permit City of Renton Clear & Grade Permit City of Renton Building Permit Geothermal Well Drilling Permit (provided by drilling subcontractor) Electrical Permit HAZEN HIGH SCHOOL IMPROVEMENTS 19 8. CSWPP ANALYSIS AND DESIGN This section lists the requirements that were met when designing the TESC Plan for this site. STANDARD REQUIREMENTS Erosion/Sedimentation Plan shall include the following: 1. Clearing Limits – Construction limits are delineated or noted on the project erosion control plans and shall be physically laid out on the project site. 2. Cover Measures – Contractor will use plastic sheeting, hydroseeding, and mulching to protect soils from erosion. Gravel borrow or “hog fuel” may be used in areas of excessively moist soils that will support building or traffic loads, if necessary. 3. Perimeter Protection – Temporary construction fencing will be used to delineate and protect the project clearing limits and provide a secure site. Straw wattles will be used to prevent sediment-laden water from discharging from the site. 4. Traffic Area Stabilization – The existing drive aisles and asphalt parking lot adjacent to the east side of the fields will be utilized for construction access, staging, and laydown as needed. The contractor shall coordinate with the Renton School District prior to starting construction. Additional gravel borrow or “hog fuel” may be used in areas of excessively moist soils that will support traffic loads, if necessary. 5. Sediment Retention – Filter fabric protection will also be installed in all new area drain structures and remain until the site is stabilized. 6. Surface Water Collection – Interceptor swales will be used in the appropriate areas of the site to collect stormwater runoff, if necessary. 7. Dewatering Control – Dewatering is not necessary for this site; therefore, no dewatering control measures are implemented. 8. Dust Control – Dry soils will be appropriately sprinkled with water to limit airborne dust during dry weather. 9. Flow Control – Six temporary settlement tanks will be provided on site. Discharge will be restricted and will therefore serve as a flow control measure. 10. Control Pollutants – BMPs shall be implemented to prevent or treat contamination of stormwater runoff by pH modifying sources. Carbon dioxide sparging, using dry ice or a gas diffuser as a source of CO2 will be used as needed to adjust the pH level and prevent discharge of water with elevated pH levels to the City’s Storm System. In addition, dust control will be implemented as needed to prevent fugitive dust during the treatment process. In addition, all waste materials from the site will be removed in a manner that does not cause contamination of stormwater. 11. Protect Existing and Proposed Flow Control BMPs – The native vegetation will be protected with silt fencing and perimeter construction fencing. 12. Maintain BMPs – BMPs for the project will be monitored for effectiveness on a regular basis to ensure they are repaired and replaced as necessary. 13. Manage the Project – The project will be phased to take weather and seasonal work limits into account. The BMPs will be inspected, maintained, and repaired as needed to ensure their intended performance. HAZEN HIGH SCHOOL IMPROVEMENTS 20 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT BOND QUANTITIES WORKSHEET A bond quantities worksheet is included in Appendix A. FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH A Facility Summary Sheet has been completed for each TDA and is included in Appendix D. DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND WQ FACILITIES A draft Declaration of Covenant has been included in Appendix D for City review and will be recorded prior to permit issuance. HAZEN HIGH SCHOOL IMPROVEMENTS 21 10. OPERATIONS AND MAINTENANCE MANUAL As stated in the Renton Surface Water Design Manual (RSWDM), the owner will maintain all privately owned facilities. Sections of the RSWDM outlining the operations and maintenance of these facilities have been included in this section along with maintenance manuals from proposed proprietary products. OPERATIONS AND MAINTENANCE MANUAL for Hazen High School Improvements PARTY RESPONSIBLE FOR MAINTENANCE AND OPERATIONS: Renton School District A COPY OF THE OPERATION AND MAINTENANCE MANUAL SHALL BE RETAINED ON SITE OR WITHIN REASONABLE ACCESS TO THE SITE AND SHALL BE TRANSFERRED WITH THE PROPERTY TO ANY NEW OWNER CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 A-1 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS This appendix contains the maintenance requirements for the following typical stormwater flow control and water quality facilities and on-site BMPs (ctrl/click the title to follow the link): No. 1 – Detention Ponds No. 2 – Infiltration Facilities No. 3 – Detention Tanks and Vaults No. 4 – Control Structure/Flow Restrictor No. 5 – Catch Basins and Manholes No. 6 – Conveyance Pipes and Ditches No. 7 – Debris Barriers (e.g., trash racks) No. 8 – Energy Dissipaters No. 9 – Fencing No. 10 – Gates/Bollards/Access Barriers No. 11 – Grounds (landscaping) No. 12 – Access Roads No. 13 – Basic Bioswale (grass) No. 14 – Wet Bioswale No. 15 – Filter Strip No. 16 – Wetpond No. 17 – Wetvault No. 18 – Stormwater Wetland No. 19 – Sand Filter Pond No. 20 – Sand Filter Vault No. 21 – Proprietary Facility Cartridge Filter Systems No. 22 – Baffle Oil/Water Separator No. 23 – Coalescing Plate Oil/Water Separator O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-2 No. 24 – Catch Basin Insert (not allowed in the city for oil control) No. 25 – Drywell BMP No. 26 – Gravel Filled Infiltration Trench BMP No. 27 – Gravel Filled Dispersion Trench BMP No. 28 – Native Vegetated Surface/Native Vegetated Landscape BMP No. 29 – Perforated Pipe Connections BMP No. 30 – Permeable Pavement BMP No. 31 – Bioretention BMP No. 32 – RainWater Harvesting BMP No. 33 – Rock Pad BMP No. 34 – Sheet Flow BMP No. 35 – Splash Block BMP No. 36 – Vegetated Roof BMP No. 37 – Rain Garden BMP No. 38 – Soil Amendment BMP No. 39 – Retained Trees No. 40 – Filterra System No. 41 – Compost Amended Vegetated Filter Strip (CAVFS) No. 42 – Media Filter Drain (MFD) No. 43 – Compost-Amended Biofiltration Swale O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-6 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non- floatables). No trash or debris in vault. Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged inlet/outlet pipes Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-7 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Access Manhole (cont.) Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can be opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-8 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. FROP-T Section Damaged FROP-T T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-9 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED FROP-T Section (cont.) Damaged FROP-T (cont.) Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate. Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing orifice plate Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions to overflow pipe Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip of overflow pipe Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (If applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-10 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and is structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-11 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-12 NO. 6 – CONVEYANCE PIPES AND DITCHES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/root growth in pipe Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Damaged pipes Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive vegetation growth Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Rock lining out of place or missing (If applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-15 NO. 9 – FENCING MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12-18 inches wide permitting access through an opening under a fence. No access under the fence. Wood Posts, Boards and Cross Members Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound. Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound. Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind. Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches. Post plumb to within 1½ inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards. Missing or loose tension wire. Tension wire in place and holding fabric. Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy. Structurally adequate posts or parts with a uniform protective coating. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-16 NO. 10 – GATES/BOLLARDS/ACCESS BARRIERS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Chain Link Fencing Gate Damaged or missing members Missing gate. Gates in place. Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person. Hinges intact and lubed. Gate is working freely. Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Gate is aligned and vertical. Missing stretcher bar, stretcher bands, and ties. Stretcher bar, bands, and ties in place. Locking mechanism does not lock gate Locking device missing, non-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. Bar Gate Damaged or missing cross bar Cross bar does not swing open or closed, is missing or is bent to where it does not prevent vehicle access. Cross bar swings fully open and closed and prevents vehicle access. Locking mechanism does not lock gate Locking device missing, non-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Support post damaged Support post does not hold cross bar up. Cross bar held up preventing vehicle access into facility. Bollards Damaged or missing bollards Bollard broken, missing, does not fit into support hole or hinge broken or missing. No access for motorized vehicles to get into facility. Bollards do not lock Locking assembly or lock missing or cannot be attached to lock bollard in place. No access for motorized vehicles to get into facility. Boulders Dislodged boulders Boulders not located to prevent motorized vehicle access. No access for motorized vehicles to get into facility. Evidence of vehicles circumventing boulders Motorized vehicles going around or between boulders. No access for motorized vehicles to get into facility. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-17 NO. 11 – GROUNDS (LANDSCAPING) MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged tree or shrub identified Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-47 NO. 38 – SOIL AMENDMENT BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Soil Media Unhealthy vegetation Vegetation not fully covering ground surface or vegetation health is poor. Yellowing: possible Nitrogen (N) deficiency. Poor growth: possible Phosphorous (P) deficiency. Poor flowering, spotting or curled leaves, or weak roots or stems: possible Potassium (K) deficiency. Plants are healthy and appropriate for site conditions Inadequate soil nutrients and structure In the fall, return leaf fall and shredded woody materials from the landscape to the site when possible Soil providing plant nutrients and structure Excessive vegetation growth Grass becomes excessively tall (greater than 10 inches); nuisance weeds and other vegetation start to take over. Healthy turf- “grasscycle” (mulch-mow or leave the clippings) to build turf health Weeds Preventive maintenance Avoid use of pesticides (bug and weed killers), like “weed & feed,” which damage the soil Fertilizer needed Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers or slow-release synthetic balanced fertilizers Integrated Pest Management (IPM) protocols for fertilization followed Bare spots Bare spots on soil No bare spots, area covered with vegetation or mulch mixed into the underlying soil. Compaction Poor infiltration due to soil compaction To remediate compaction, aerate soil, till to at least 8-inch depth, or further amend soil with compost and re-till If areas are turf, aerate compacted areas and top dress them with 1/4 to 1/2 inch of compost to renovate them If drainage is still slow, consider investigating alternative causes (e.g., high wet season groundwater levels, low permeability soils) Also consider site use and protection from compacting activities No soil compaction Poor infiltration Soils become waterlogged, do not appear to be infiltrating. Facility infiltrating properly Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow entering area, channelization of runoff) identified and damaged area stabilized (regrade, rock, vegetation, erosion control matting).For deep channels or cuts (over 3 inches in ponding depth), temporary erosion control measures in place until permanent repairs can be made Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is healthy with a generally good appearance. Healthy vegetation. Unhealthy plants removed/replaced. Appropriate vegetation planted in terms of exposure, soil and soil moisture. Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer to current County noxious weed list). No noxious weeds present. O&M MANUAL APPENDIX A - CITY OF RENTON SWDM STORMTRAP MAINTENANCE MANUAL 1. Introduction Regular inspections are recommended to ensure that the system is functioning as designed. Please call your Authorized StormTrap Representative if you have questions in regards to the inspection and maintenance of the StormTrap system. Prior to entry into any underground storm sewer or underground detention systems, appropriate OSHA and local safety regulations and guidelines should be followed. 2. Inspection Schedules for Municipalities StormTrap Stormwater Management Systems are recommended for inspection whenever the upstream and downstream catch basins and stormwater pipes of the stormwater collection system are inspected or maintained. This will economize the cost of the inspection if it is done at the same time the Municipal crews are visiting the area. 3. Inspection Schedules for Private Development StormTrap Stormwater Mangement Systems, for a private development, are recommended for inspection after each major storm water event. At a minimum, until a cleaning schedule can be established, an annual inspection is recommended. If inspected on an annual basis, the inspection should be conducted before the stormwater season begins to be sure that everything is functioning properly for the upcoming storm season. 4. Inspection Process Inspections should be done such that at least 2-3 days has lapsed since the most recent rain event to allow for draining. Visually inspect the system at all manhole locations. Utilizing a sediment pole, measure and document the amount of silt at each manhole location (Figure 1). Inspect each pipe opening to ensure that the silt level or any foreign objects are not blocking the pipes. Be sure to inspect the outlet pipe(s) because this is typically the smallest O&M MANUAL STORMTRAP MAINTENANCE MANUAL pipe in the system. It is common that most of the larger materials will be collected upstream of the system in catch basins, and it is therefore important at time of inspections to check these structures for large trash or blockages. Remove any blockages if you can during the inspection process only if you can do so safely from the top of the system without entering into the system. Do not go into the system under any circumstances without proper ventilation equipment and training. Pass any information requiring action onto the appropriate maintenance personnel if you cannot remove the blockages from above during the inspection process. Be sure to describe the location of each manhole and the type of material that needs to be removed. The sediment level of the system should also be measured and recorded during the inspection process. Recording the sediment level at each manhole is very important in order get a history of sediment that can be graphed over time (i.e. years) in order to estimate when the system will need to be maintained next. It is also important to keep these records to verify that the inspection process was actually performed if anyone asks for your records in the future. The sediment level in the underground detention system can be determined from the outside of the system by opening up all the manholes and using a sediment pole to measure the amount of sediment at each location. Force the stick to the bottom of the system and then remove it and measure the amount of sediment at that location. Again, do not go into the system under any circumstances without proper ventilation equipment and training. 5. When to Clean the System Any blockages should be safely removed as soon as practical so that the Stormwater detention system will fill and drain properly before the next stormwater event. The Dry Detention System should be completely cleaned whenever the sediment occupies more than 10% to 15% of the originally designed system’s volume. The Wet Detention System should be cleaned when the sediment occupies more than 30% or 1/3rd of the originally designed system’s volume. NOTE: Check with your municipality in regards to O&M MANUAL STORMTRAP MAINTENANCE MANUAL cleaning criteria, as the allowable sediment before cleaning may be more or less then described above. 6. How to Clean the StormTrap The system should be completely cleaned back to 100% of the originally designed storage volume whenever the above sediment levels have been reached. Be sure to wait at least 3 days after a stormwater event to be sure that the system is completely drained (if it is a Dry Detention System), and all of the sediments have settled to the bottom of the system (if it is a Wet Detention System). Do not enter the System unless you are properly trained, equipped, and qualified to enter a confined space as identified by local occupational safety and health regulations. There are many maintenance companies that are in business to help you clean your underground stormwater detention systems and water quality units. Please call your StormTrap representative for referrals in your area. A. Dry Detention System Cleaning Maintenance is typically performed using a vacuum truck. Sediment should be flushed towards a vacuum hose for thorough removal. For a Dry Detention System, remove the manhole cover at the top of the system and lower a vacuum hose into one of the rows of the StormTrap system. Open up the manhole at the opposite end of the StormTrap and use sewer jetting equipment to force water in the same row from one end of the StormTrap row to the opposite side. The rows of the StormTrap are completely open in one contiguous channel from one end to the other for easy cleaning. Place the vacuum hose and the sewer jetting equipment in the next row and repeat the process until all of the rows have been cleaned. When finished, replace all covers that were removed and dispose of the collected material properly. O&M MANUAL STORMTRAP MAINTENANCE MANUAL B. Wet Detention System Cleaning If the system was designed to maintain a permanent pool of water, floatables and any oil should be removed in a separate procedure prior to the removal of all sediment. The floatable trash is removed first by using a bucket strainer to capture and remove any floating debris. The floatable oils are then removed off the top of the water by using the vacuum truck to suck off any floatable fluids and liquids. The next step is to use the vacuum truck to gently remove the clarified water above the sediment layer. The final step is to clean the sediment for each row as described above in the paragraph “A. Dry Detention System Cleaning”. For smaller systems, the vacuum truck can remove all of the sediment in the basin without using the sewer jetting equipment because of the smaller space. 7. Inspection Reports Proof of these inspections is the responsibility of the property owner. All inspection reports and data should be kept on site or at a location where they will be accessible for years in the future. Some municipalities require these inspection and cleaning reports to be forwarded to the proper governmental permitting agency on an annual basis. Refer to your local and national regulations for any additional maintenance requirements and schedules not contained herein. Inspections should be a part of your standard operating procedure. O&M MANUAL STORMTRAP MAINTENANCE MANUAL Figure 1. During inspection, measure the distance from finished grade to the top of the sediment inside the system. Sample inspection and maintenance log O&M MANUAL STORMTRAP MAINTENANCE MANUAL 11 | P a g e O&M MANUAL STORMTRAP MAINTENANCE MANUAL Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 1 OF 5 StormTrap Guide Specification StormTrap 2 DoubleTrap on Stone Groundwater BELOW Invert Revised 11/21/18 This product guide specification is written according to the Construction Specifications Institute (CSI) 3-Part Format, including MasterFormat, SectionFormat, and PageFormat, contained in the CSI Manual of Practice. The section must be carefully reviewed and edited by the Engineer to meet the requirements of the project and local building code. Coordinate this section with other specification sections and the Drawings. Delete all “Specifier Notes” when editing this section. Section numbers are from MasterFormat 2016 Edition. Update section numbers to versions if required. Specifier Notes: This section covers “StormTrap®” precast concrete, modular, storm water detention. StormTrap is custom designed to meet the specific requirements of the project. Consult StormTrap for assistance in editing this section for the specific application. O&M MANUAL STORMTRAP MAINTENANCE MANUAL Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 2 OF 5 SECTION 33 46 23 – MODULAR BURIED STORMWATER STORAGE UNITS PART 1 - GENERAL 1.01 SECTION INCLUDES A. StormTrap Precast concrete, modular stormwater detention. 1.02 RELATED SECTIONS A. Section 31 00 00 – Earthwork B. Section 03 40 00 – Precast Concrete 1.03 REFERENCE STANDARDS A. AASHTO – Standard Specifications for Highway Bridges – Seventh (7th) Edition B. ACI 318 - Building Code Requirements for Structural Concrete. C. ASTM A 615/A 615M - Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement. D. ASTM C 857 - Standard Practice for Minimum Structural Design Loading for Underground Precast Concrete Utility Structures. E. ASTM C 858 - Standard Specification for Underground Precast Concrete Utility Structures. F. ASTM C 891 - Standard Practice for Installation of Underground Precast Concrete Utility Structures. G. ASTM C 990 - Standard Specification for Joints for Concrete Pipe, Manholes, and Precast Box Sections Using Preformed Flexible Joint Sealants. H. ASTM A 1064 – Standard Specification for Carbon-Steel Wire and Welded Wire Reinforcement, Plain and Deformed, for Concrete. 1.04 DESIGN REQUIREMENTS A. Precast Concrete Modular Stormwater Detention shall comply with ASTM C858. B. Underground precast concrete stormwater management system shall be sized in accordance with the design requirements provided by the Engineer of Record (EOR) and approved by the reviewing agency. C. The system shall be designed so modules are aligned and have channels that extend to the bottom of the modules allowing for relatively unrestricted fluid flow in both directions. D. Minimum Structural Design Loading: ASTM C 857. 1. Total Cover: a. Minimum: As indicated on the drawings. b. Maximum: As indicated on the drawings. 2. Concrete chamber shall be designed for AASHTO HS-20 wheel load. O&M MANUAL STORMTRAP MAINTENANCE MANUAL Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 3 OF 5 3. Minimum Soil Pressure: a. DoubleTrap Modules: As indicated on the drawings. 4. Vertical and lateral soil pressures shall be determined using: a. Groundwater: At or below invert of system. b. Lateral soil pressures to be based on Active earth pressure 1) Lateral soil pressure = 35 pcf for 120 pcf backfill unit weight c. Vertical soil pressures 1) Live load = HS-20-44 and Dead load = 120 pcf cover fill unit weight d. Engineer to verify geotechnical requirements 1.05 QUALITY ASSURANCE A. The manufacture of the concrete modules shall be performed at a precast production facility certified by the NPCA or PCI. 1.06 SUBMITTALS A. Comply with Section 01 33 00 - Submittal Procedures, except shop drawings shall be eleven inches (11”) by seventeen inches (17”). B. Product Data: Submit manufacturer’s product data and installation instructions. C. Record Documents: 1. Shop Drawings: a. Submit manufacturer’s shop drawings, including plans, elevations, sections, and details indicating layout, dimensions, foundation, cover, and joints. b. Indicate size and location of roof openings and inlet and outlet pipe openings. c. Indicate sealing of joints. D. Operation and Maintenance Data: Submit manufacturer’s operation and maintenance instructions 1.07 DELIVERY, STORAGE AND HANDLING A. Delivery of Accessories: Deliver to site in manufacturer’s original, unopened containers and packaging, with labels clearly identifying product name and manufacturer. B. Storage of Accessories: 1. Store in accordance with manufacturer’s instructions. 2. Store in clean, dry area, out of direct sunlight. C. Handling: Protect materials during handling and installation to prevent damage. 1.08 WARRANTY A. The Manufacturer shall provide a minimum five (5) year limited warranty. O&M MANUAL STORMTRAP MAINTENANCE MANUAL Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 4 OF 5 PART 2 - PRODUCTS 2.01 MANUFACTURER A. StormTrap, LLC, 1287 Windham Parkway, Romeoville, Illinois 60446. Phone (877) 867-6872. Fax (331) 318-5347. Website www.stormtrap.com. 2.02 STORMWATER DETENTION A. All material shall meet or exceed all applicable referenced standards, federal, state and local requirements, and conform to codes and ordinances of authorities having jurisdiction. B. Stormwater Detention Modules: 1. Description: Engineered, precast concrete, modular stormwater detention. 2. Module Type: StormTrap DoubleTrap 3. Size: As indicated on the drawings. 4. Concrete: Manufacturer’s Approved Mix design providing a minimum compressive strength of 6,000 psi at 28 days. 5. Reinforcing Bars: ASTM A 615, Grade 60. 6. Reinforcing Mesh: ASTM A 1064, Grade 80. 7. Cover for Reinforcing Bars: ACI 318 2.03 ACCESSORIES A. Joint Tape: 1. ASTM C 990. 2. Seven eights inch (7/8”) diameter, preformed butyl mastic joint sealer. 3. Approved by manufacturer. B. Joint Wrap: 1. Eight inch (8”) wide self-adhesive elastomeric resin bonded woven puncture resistant polymer wrap. 2. Approved by manufacturer. PART 3 - EXECUTION 3.01 EXAMINATION A. Examine area to receive stormwater detention modules. Notify Engineer if area is not acceptable. Do not begin installation until unacceptable conditions have been corrected. B. Verify in field before installation, dimensions and soils conditions, including groundwater and soil bearing capacity. O&M MANUAL STORMTRAP MAINTENANCE MANUAL Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 5 OF 5 3.02 INSTALLATION A. Install stormwater detention modules in accordance with manufacturer’s instructions and ASTM C 891. B. Install modules plumb, on line, and to proper elevation. C. Install modules with a maximum space of three quarters inch (3/4”) between adjacent modules. If the space exceeds three quarters inch (3/4”), the modules shall be reset with appropriate adjustment made to line and grade to bring the space into compliance. D. DoubleTrap: 1. Place modules on level, six-inch (6”) pad of three quarters inch (3/4”) stone that extends two feet (2’-0”) past the outside of the system as indication on the drawings. E. Joint Tape: 1. Seal perimeter horizontal joint between modules with joint tape in accordance with ASTM C 891, 8.8 and 8.12. 2. Prepare surfaces and install joint tape in accordance with manufacturer’s instructions. F. Joint Wrap: 1. Seal exterior joints between adjacent modules with joint wrap in accordance with ASTM C 891. 2. Prepare surfaces and install joint wrap in accordance with manufacturer’s instructions. G. Field Modifications to the modules is strictly prohibited without prior written consent of StormTrap. H. Excavation and fill shall be as specified in Sections 31 00 00. I. Fill: 1. Backfill material shall consist of a GW, GP, SW, or SP material as defined by the Unified Soil Classification System and that meets the gradation requirements as indicated on the drawings. 2. Native materials shall be separated from backfill materials with a geotextile filter fabric unless the drawings indicate separation is not required. 3. Deposit fill on both sides of modules at same time and to approximate same elevation. 4. Prevent wedging action against structure by stepping or serrating slopes bounding or within area to be backfilled. 5. Do not disrupt or damage joint wrap during backfilling. J. Do not use stormwater detention modules that are damaged, as determined by manufacturer. K. Contractor is responsible for installation in accordance with project plans, specifications, and all federal, state, and local regulations. END OF SECTION 33 46 23 O&M MANUAL STORMTRAP MAINTENANCE MANUAL 36 12.0 Inspection and Maintenance Looking down the Isolator Row PLUS A typical JetVac truck (This is not a StormTech product.) Examples of culvert cleaning nozzles appropriate for Isolator Row PLUS maintenance. (These are not StormTech products). 12.1 Isolator Row Plus Inspection Regular inspection and maintenance are essential to assure a properly functioning stormwater system. Inspection is easily accomplished through the manhole or optional inspection ports of an Isolator Row PLUS. Please follow local and OSHA rules for a confined space entry. Inspection ports can allow inspection to be accomplished completely from the surface without the need for a confined space entry. Inspection ports provide visual access to the system with the use of a flashlight. A stadia rod may be inserted to determine the depth of sediment. If upon visual inspection it is found that sediment has accumulated to an average depth exceeding 3” (75 mm), cleanout is required. A StormTech Isolator Row PLUS should initially be inspected immediately after completion of the site’s construction. While every effort should be made to prevent sediment from entering the system during construction, it is during this time that excess amounts of sediments are most likely to enter any stormwater system. Inspection and maintenance, if necessary, should be performed prior to passing responsibility over to the site’s owner. Once in normal service, a StormTech Isolator Row PLUS should be inspected bi-annually until an understanding of the sites characteristics is developed. The site’s maintenance manager can then revise the inspection schedule based on experience or local requirements. 12.2 Isolator Row Plus Maintenance JetVac maintenance is recommended if sediment has been collected to an average depth of 3” (75 mm) inside the Isolator Row PLUS. More frequent maintenance may be required to maintain minimum flow rates through the Isolator Row PLUS. The JetVac process utilizes a high pressure water nozzle to propel itself down the Isolator Row PLUS while scouring and suspending sediments. As the nozzle is retrieved, a wave of suspended sediments is flushed back into the manhole for vacuuming. Most sewer and pipe maintenance companies have vacuum/ JetVac combination vehicles. Fixed nozzles designed for culverts or large diameter pipe cleaning are preferable. Rear facing jets with an effective spread of at least 45” (1125 mm) are best. StormTech recommends a maximum nozzle pressure of 2000 psi be utilized during cleaning. The JetVac process shall only be performed on StormTech Rows that have ADS PLUS fabric over the foundation stone. 37 12.0 Inspection & Maintenance 12.3 Eccentric Pipe Header Inspection Theses guidelines do not supercede a pipe manufacturer’s recommended I&M procedures. Consult with the manufacturer of the pipe header system for specific I&M procedures. Inspection of the header system should be carried out quarterly. On sites which generate higher levels of sediment more frequent inspections may be necessary. Headers may be accessed through risers, access ports or manholes. Measurement of sediment may be taken with a stadia rod or similar device. Cleanout of sediment should occur when the sediment volume has reduced the storage area by 25% or the depth of sediment has reached approximately 25% of the diameter of the structure. 12.4 Eccentric Pipe Manifold Maintenance Cleanout of accumulated material should be accomplished by vacuum pumping the material from the header. Cleanout should be accomplished during dry weather. Care should be taken to avoid flushing sediments out through the outlet pipes and into the chamber rows. Eccentric Header Step-by-Step Maintenance Procedures 1. Locate manholes connected to the manifold system 2. Remove grates or covers 3. Using a stadia rod, measure the depth of sediment 4. If sediment is at a depth of about 25% pipe volume or 25% pipe diameter proceed to step 5. If not proceed to step 6. 5. Vacuum pump the sediment. Do not flush sediment out inlet pipes. 6. Replace grates and covers 7. Record depth and date and schedule next inspection StormTech Isolator Row Plus - Step-by-StepMaintenance Procedures Step 1: Inspect Isolator Row PLUS for sediment A) Inspection ports (if present) i. Remove lid from floor box frame ii. Remove cap from inspection riser iii. Using a flashlight and stadia rod, measure depth of sediment iv. If sediment is at, or above, 3” (76 mm) depth proceed to Step 2. If not proceed to Step 3. B) All Isolator Plus Rows i. Remove cover from manhole at upstream end of Isolator Row PLUS ii. Using a flashlight, inspect down Isolator Row PLUS through outlet pipe 1. Follow OSHA regulations for confined space entry if entering manhole 2. Mirrors on poles or cameras may be used to avoid a confined space entry iii. If sediment is at or above the lower row of sidewall holes [approximately 3” (76 mm)]proceed to Step 2. If not proceed to Step 3. Step 2: Clean out Isolator Row PLUS using the JetVac process A) A fixed floor cleaning nozzle with rear facing nozzle spread of 45” (1125 mm) or more is preferable B) Apply multiple passes of JetVac until backflush water is clean C) Vacuum manhole sump as required during jetting Step 3: Replace all caps, lids and covers Step 4: Inspect and clean catch basins and manholes upstream of the StormTech system following local guidelines. Figure 18 – StormTech Isolator Row Plus (not to scale) Figure 19 – Eccentric Manifold Maintenance 1, 2, 6 3, 4, 5 Please contact StormTech’s Technical Services Department at 888-892-2894 for a spreadsheet to estimate cleaning intervals. O&M MANUAL STORMTECH MAINTENANCE MANUAL ENGINEERED SOLUTIONS Modular Wetlands® Linear Operations & Maintenance Manual O&M MANUAL CONTECH MAINTENANCE MANUAL 2 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR OOPPEERRAATTIIOONN && MMAAIINNTTEENNAANNCCEE MMAANNUUAALL TTAABBLLEE OOFF CCOONNTTEENNTTSS OOvveerrvviieeww ........................................................................................................................................................................ 3 SSaaffeettyy NNoottiiccee && PPeerrssoonnaall SSaaffeettyy EEqquuiippmmeenntt ................................................................................................................. 4 MMoodduullaarr WWeettllaannddss LLiinneeaarr CCoommppoonneennttss LLiisstt ................................................................................................................. 5 IInnssppeeccttiioonn SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt ......................................................................................................................... 6 IInnssppeeccttiioonn && MMaaiinntteennaannccee NNootteess .................................................................................................................................. 7 IInnssppeeccttiioonn PPrroocceessss ......................................................................................................................................................... 7 MMaaiinntteennaannccee IInnddiiccaattoorrss ................................................................................................................................................. 9 MMaaiinntteennaannccee SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt..................................................................................................................... 9 MMaaiinntteennaannccee IInnssttrruuccttiioonnss .............................................................................................................................................11 RReeppllaacciinngg BBiiooffiillttrraattiioonn MMeeddiiaa iiff RReeqquuiirreedd ....................................................................................................................14 RReeppllaacciinngg DDrraaiinn DDoowwnn FFiilltteerr MMeeddiiaa ((OOnnllyy oonn OOllddeerr CCaalliiffoorrnniiaa MMooddeellss)) .....................................................................16 NNootteess .............................................................................................................................................................................17 IInnssppeeccttiioonn RReeppoorrtt .........................................................................................................................................................18 CClleeaanniinngg && MMaaiinntteennaannccee RReeppoorrtt ..................................................................................................................................19 O&M MANUAL CONTECH MAINTENANCE MANUAL 3 OOVVEERRVVIIEEWW This operation and maintenance (O&M) manual is for the Modular Wetlands Linear Biofilter (MWL). Please read the instructions and equipment lists closely prior to starting. It is important to follow all necessary safety procedures associated with state and local regulations. Please contact Contech for more information on pre-authorized third-party service providers who can provide inspection and maintenance services in your area. For a list of service providers in your area, please visit www.conteches.com/maintenance. PPLLAACCEEHHOOLLDDEERR FFOORR MMAARRKKEETTIINNGG PPHHOOTTOO WWAARRNNIINNGG Confined space entry may be required. Contractor to obtain all equipment and training to meet applicable local and OSHA regulations regarding confined space entry. It is the Contractor’s or entry personnel’s responsibility to always proceed safely. O&M MANUAL CONTECH MAINTENANCE MANUAL 4 SSAAFFEETTYY NNOOTTIICCEE && PPEERRSSOONNAALL SSAAFFEETTYY EEQQUUIIPPMMEENNTT Job site safety is a topic and a practice addressed comprehensively by others. The inclusions here are merely reminders to whole areas of Safety Practice that are the responsibility of the Owner(s), Manager(s), and Service Provider(s). OSHA and Canadian OSH, Federal, State/Provincial, and Local Jurisdiction Safety Standards apply on any given site or project. The knowledge and applicability of those responsibilities is the Service Provider’s responsibility and outside the scope of Contech Engineered Solutions. Safety Boots Gloves Hard Hat Eye Protection Maintenance and Protection of Traffic Plan O&M MANUAL CONTECH MAINTENANCE MANUAL 5 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR CCOOMMPPOONNEENNTTSS LLIISSTT The MWL system comes in multiple sizes and configurations, including side by side or end to end layouts, both as open planters or underground systems. See shop drawings (plans) for project specific details. The standard MWL system is comprised of the following components: O&M MANUAL CONTECH MAINTENANCE MANUAL 6 IINNSSPPEECCTTIIOONN SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT Stormwater regulations require BMPs be inspected and maintained to ensure they are operating as designed to allow for effective pollutant removal and provide protection to receiving water bodies. It is recommended that inspections be performed multiple times during the first year to assess the site-specific loading conditions. The first year of inspections can be used to set inspection and maintenance intervals for subsequent years to ensure appropriate maintenance is provided. Inspect pre-treatment, biofiltration, and discharge chambers an average of once every six to twelve months. Varies based on site specific and local conditions. Average inspection time is approximately 15 minutes. Always ensure appropriate safety protocol and procedures are followed. The following is a list of equipment required to allow for simple and effective inspection of the MWL: Modular Wetlands Linear Inspection Form Flashlight Tape Measure Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) O&M MANUAL CONTECH MAINTENANCE MANUAL 7 IINNSSPPEECCTTIIOONN && MMAAIINNTTEENNAANNCCEE NNOOTTEESS 1.Following maintenance and/or inspection, it is recommended that the maintenance operator prepare a maintenance/inspection record. The record should include any maintenance activities performed, amount and description of debris collected, and condition of the system and its various filter mechanisms. 2.The owner should keep maintenance/inspection record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspection upon request at any time. 3.Transport all debris, trash, organics, and sediments to approved facility for disposal in accordance with local and state requirements. 4.Entry into chambers may require confined space training based on state and local regulations. 5.No fertilizer shall be used in the biofiltration chamber. 6.Irrigation should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigation required is dependent on plant species. Some plants may not require irrigation after initial establishment. IINNSSPPEECCTTIIOONN PPRROOCCEESSSS 1.Prepare the inspection form by writing in the necessary information including project name, location, date & time, unit number and other information (see inspection form). 2.Observe the inside of the system through the access covers. If minimal light is available and vision into the unit is impaired, utilize a flashlight to see inside the system and all chambers. 3.Look for any out of the ordinary obstructions in the inflow pipe, pre-treatment chamber, biofiltration chamber, discharge chamber or outflow pipe. Write down any observations on the inspection form. 4.Through observation and/or digital photographs, estimate the amount of trash, debris accumulated in the pre- treatment chamber. Utilizing a tape measure or measuring stick, estimate the amount of sediment in this chamber. Record this depth on the inspection form. 5.Through visual observation, inspect the condition of the pre-filter cartridges. Look for excessive build-up of sediment on the cartridges, any build-up on the tops of the cartridges, or clogging of the holes. Record this information on the inspection form. The pre-filter cartridges can be further inspected by removing the cartridge tops and assessing the color of the BioMediaGREEN filter cubes (requires entry into pre-treatment chamber - see notes previous notes regarding confined space entry). Record the color of the material. New material is a light green color. As the media becomes clogged, it will turn darker in color, eventually becoming dark brown or black. The closer to black the media is the higher percentage that the media is exhausted and in need of replacement. O&M MANUAL CONTECH MAINTENANCE MANUAL 8 6.The biofiltration chamber is generally maintenance-free due to the system’s advanced pre-treatment chamber. For units which have open planters with vegetation, it is recommended that the vegetation be inspected. Look for any plants that are dead or showing signs of disease or other negative stressors. Record the general health of the plants on the inspection form and indicate through visual observation or digital photographs if trimming of the vegetation is required. 7.The discharge chamber houses the control riser (if applicable), drain down filter (only in California - older models), and is connected to the outflow pipe. It is important to check to ensure the orifice is in proper operating condition and free of any obstructions. It is also important to assess the condition of the drain down filter media which utilizes a block form of the BioMediaGREEN. Assess in the same manner as the cubes in the pre-filter cartridge as mentioned above. 8.Finalize the inspection report for analysis by the maintenance manager to determine if maintenance is required. O&M MANUAL CONTECH MAINTENANCE MANUAL 9 MMAAIINNTTEENNAANNCCEE IINNDDIICCAATTOORRSS Based upon the observations made during inspection, maintenance of the system may be required based on the following indicators: Missing or damaged internal components or cartridges. Obstructions in the system or its inlet and/or outlet pipes. Excessive accumulation of floatables in the pre-treatment chamber in which the length and width of the chamber is fully impacted more than 18”. Excessive accumulation of sediment in the pre-treatment chamber of more than 6” in depth. Excessive accumulation of sediment on the BioMediaGREEN media housed within the pretreatment cartridges. When media is more than 85% clogged, replacement is required. The darker the BioMediaGREEN, the more clogged it is and in need of replacement. Excessive accumulation of sediment on the BioMediaGREEN media housed within the drain down filter (California only - older models). Overgrown vegetation. MMAAIINNTTEENNAANNCCEE SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT The time has come to maintain your MWL. All necessary pre-maintenance steps must be carried out before maintenance occurs. Once traffic control has been set up per local and state regulations and access covers have been safely opened, the maintenance process can begin. It should be noted that some maintenance activities require confined space entry. All confined space requirements must be strictly followed before entry into the system. In addition, the following is recommended: Prepare the maintenance form by writing in the necessary information including project name, location, date & time, unit number and other info (see maintenance form). Set up all appropriate safety and maintenance equipment. Ensure traffic control is set up and properly positioned. Prepared pre-checks (OSHA, safety, confined space entry) are performed. o A gas meter should be used to detect the presence of any hazardous gases prior to entering the system. If hazardous gases are present, do not enter the vault. Following appropriate confined space procedures, take steps such as utilizing a venting system to address the hazard. Once it is determined to be safe, enter the system utilizing appropriate entry equipment such as a ladder and tripod with harness. O&M MANUAL CONTECH MAINTENANCE MANUAL 10 The following is a list of equipment required for maintenance of the MWL: Modular Wetlands Linear Maintenance Form Flashlight Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) Vacuum Assisted Truck with Pressure Washer Replacement BioMediaGREEN (If Required) (order BioMediaGREEN from Contech’s Maintenance Team members at https://www.conteches.com/maintenance) O&M MANUAL CONTECH MAINTENANCE MANUAL 11 MMAAIINNTTEENNAANNCCEE IINNSSTTRRUUCCTTIIOONNSS 11..AACCCCEESSSS CCOOVVEERR RREEMMOOVVAALL Upon determining that the vault is safe for entry, remove all access cover(s) and position the vacuum truck accordingly. 22..PPRREESSSSUURREE WWAASSHH SSYYSSTTEEMM CCHHAAMMBBEERRSS With the pressure washer, spray down pollutants accumulated on the walls and floors of the pre- treatment and discharge chambers. Then wash any accumulated sediment from the pre-filter cartridge(s). 33..VVAACCUUUUMM SSYYSSTTEEMM CCHHAAMMBBEERRSS Vacuum out pre-treatment and discharge chambers and remove all accumulated pollutants including trash, debris, and sediments. Be sure to vacuum the pre- treatment floor until the pervious pavers are visible and clean.((MMWWLL ssyysstteemmss oouuttssiiddee ooff CCaalliiffoorrnniiaa mmaayy oorr mmaayy nnoott hhaavvee ppeerrvviioouuss ppaavveerrss oonn tthhee fflloooorr iinn tthhee pprree-- ttrreeaattmmeenntt cchhaammbbeerr)) If pre-filter cartridges require media replacement, proceed to SStteepp 44. If not, replace the access cover(s) and proceed to SStteepp 77. O&M MANUAL CONTECH MAINTENANCE MANUAL 12 44..PPRREE--FFIILLTTEERR CCAARRTTRRIIDDGGEE LLIIDD RREEMMOOVVAALL After successfully cleaning out the pre-treatment chamber, enter the chamber and remove the lid(s) from the pre-filter cartridge(s) by removing the two thumb screws. (Older pre-filter cartridges have two bolts holding the lids on that require a 7/16” socket to remove) 55..VVAACCUUUUMM EEXXIISSTTIINNGG PPRREE--FFIILLTTEERR MMEEDDIIAA Utilize the vacuum truck hose or hose extension to remove the filter media from each of the individual media cages. Once filter media has been sucked out, use a pressure washer to spray down the inside of the cartridge and its media cages. Remove cleaned media cages and place to the side. Once removed, the vacuum hose can be inserted into the cartridge to vacuum out any remaining material near the bottom of the cartridge. 66..PPRREE--FFIILLTTEERR MMEEDDIIAA RREEPPLLAACCEEMMEENNTT Reinstall media cages and fill with new media from the manufacturer or outside supplier. Manufacturer will provide specification of media and sources to purchase. The easiest way to fill the media cages is to utilize a refilling tray that can also be sourced from the manufacturer. Place the refilling tray on top of the cartridge and fill with new bulk media shaking it down into the cages. Using your hands, lightly compact the media into each filter cage. Once the cages are full (each cartridge will hold five heaping 5gal buckets of bulk media),remove the refilling tray and replace the cartridge top, ensuring fasteners are properly tightened. O&M MANUAL CONTECH MAINTENANCE MANUAL 13 77..MMAAIINNTTAAIINNIINNGG VVEEGGEETTAATTIIOONN In general, the biofiltration chamber is maintenance-free with the exception of maintaining the vegetation. The MWL utilizes vegetation similar to surrounding landscape areas, therefore, trim vegetation to match surrounding vegetation. If any plants have died, replace them with new ones. 88..IINNSSPPEECCTT UUNNDDEERRDDRRAAIINN SSYYSSTTEEMM Each vertical under drain on the biofiltration chamber has a removable threaded cap that can be taken off to check for any blockages or root growth. Once removed, a jetting attachment to the pressure washer can be used to clean out the under drain and orifice riser if needed. 99..RREEPPLLAACCEE AACCCCEESSSS CCOOVVEERRSS Once maintenance is complete, replace all access cover(s) O&M MANUAL CONTECH MAINTENANCE MANUAL 14 RREEPPLLAACCIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA IIFF RREEQQUUIIRREEDD As with all biofilter systems, at some point the biofiltration media will need to be replaced, either due to physical clogging or sorptive exhaustion (for dissolved pollutants) of the media ion exchange capacity (to remove dissolved metals and phosphorous). The general life of this media is 10 to 20 years based on site specific conditions and pollutant loading, so replacing the biofiltration media should not be a common occurrence. In the event that the biofiltration media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new biofiltration media. The quantity of media needed can be determined by providing the model number and unit depth. Media will be provided in super sacks for easy installation. Each sack will weigh between 1,000 and 2,000 lbs. Biofiltration media replacement can be done following the steps below: 11..VVAACCUUUUMM EEXXIISSTTIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Remove the mulch and vegetation to access the biofiltration media, and then position the vacuum truck accordingly. Utilize the vacuum truck to vacuum out all the media. Once all media is removed, use the pressure washer to spray down all the netting and underdrain systems on the inside of the media containment cage. Vacuum out any remaining debris after spraying down netting. Inspect the netting for any damage or holes. If the netting is damaged, it can be repaired or replaced with guidance by the manufacturer. 22..IINNSSTTAALLLLIINNGG NNEEWW BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Ensure that the chamber is fully cleaned prior to installation of new media into the media containment cage(s). Media will be provided in super sacks for easy installation. A lifting apparatus (forklift, backhoe, boom truck, or other) is recommended to position the super sack over the biofiltration chamber. Add media in lifts to ensure that the riser pipes remain vertical. Be sure to only fill the media cage(s) up to the same level as the old media. O&M MANUAL CONTECH MAINTENANCE MANUAL 15 33..RREEPPLLAANNTT VVEEGGEETTAATTIIOONN Once the media has been replaced, replant the vegetation and cover biofiltration chamber with approved mulch (if applicable). If the existing vegetation is not being reused, and new vegetation is being planted, you will need to acquire new plant establishment media that will be installed just below the mulch layer at each plant location. (see plan drawings for details). Contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new plant establishment media. O&M MANUAL CONTECH MAINTENANCE MANUAL 16 RREEPPLLAACCIINNGG DDRRAAIINN DDOOWWNN FFIILLTTEERR MMEEDDIIAA ((OONNLLYY OONN OOLLDDEERR CCAALLIIFFOORRNNIIAA MMOODDEELLSS)) NOTE: The drain down filter is only found on units installed in California prior to 2023 If during inspection it was determined that the drain down filter media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new media. 11..RREEMMOOVVEE EEXXIISSTTIINNGG DDRRAAIINN DDOOWWNN MMEEDDIIAA Pull knob back to unlock the locking mechanism and lift the drain down filter housing to remove the used BioMediaGREEN filter block. 22..IINNSSTTAALLLL NNEEWW DDRRAAIINN DDOOWWNN MMEEDDIIAA Ensure that the chamber and housing are fully cleaned prior to installation of new media, and then insert the new BioMediaGREEN filter block. The media filter block should fit snugly between the chamber walls and be centered under the filter housing. Lower the housing over the filter block and secure the locking mechanism. O&M MANUAL CONTECH MAINTENANCE MANUAL 17 NOTES _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ O&M MANUAL CONTECH MAINTENANCE MANUAL 18 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No YesType of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. Inspection Report Modular Wetlands Linear Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging the unit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance ENGINEERED SOLUTIONS O&M MANUAL CONTECH MAINTENANCE MANUAL 19 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Site Map # Comments: Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed@ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands LinearENGINEERED SOLUTIONS O&M MANUAL CONTECH MAINTENANCE MANUAL SUPPORT DRAWINGS AND SPECIFICATIONS ARE AVAILABLE AT WWW.CONTECHES.COM © 2024 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 WWW.CONTECHES.COM ALL RIGHTS RESERVED. PRINTED IN THE USA. CONTECH ENGINEERED SOLUTIONS LLC PROVIDES SITE SOLUTIONS FOR THE CIVIL ENGINEERING INDUSTRY. CONTECH’S PORTFOLIO INCLUDES BRIDGES, DRAINAGE, SANITARY SEWER, STORMWATER AND EARTH STABILIZATION PRODUCTS. FOR INFORMATION ON OTHER CONTECH DIVISION OFFERINGS, VISIT CONTECHES.COM OR CALL 800-338-1122. ModWetLinear OM Manual 03/24 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. ENGINEERED SOLUTIONS O&M MANUAL CONTECH MAINTENANCE MANUAL CDS Guide Operation, Design, Performance and Maintenance ENGINEERED SOLUTIONS O&M MANUAL CONTECH CDS MAINTENANCE MANUAL 2 CDS® Using patented continuous deflective separation technology, the CDS system screens, separates and traps debris, sediment, and oil and grease from stormwater runoff. The indirect screening capability of the system allows for 100% removal of floatables and neutrally buoyant material without blinding. Flow and screening controls physically separate captured solids, and minimize the re-suspension and release of previously trapped pollutants. Inline units can treat up to 6 cfs, and internally bypass flows in excess of 50 cfs (1416 L/s). Available precast or cast-in- place, offline units can treat flows from 1 to 300 cfs (28.3 to 8495 L/s). The pollutant removal capacity of the CDS system has been proven in lab and field testing. Operation Overview Stormwater enters the diversion chamber where the diversion weir guides the flow into the unit’s separation chamber and pollutants are removed from the flow. All flows up to the system’s treatment design capacity enter the separation chamber and are treated. Swirl concentration and screen deflection force floatables and solids to the center of the separation chamber where 100% of floatables and neutrally buoyant debris larger than the screen apertures are trapped. Stormwater then moves through the separation screen, under the oil baffle and exits the system. The separation screen remains clog free due to continuous deflection. During the flow events exceeding the treatment design capacity, the diversion weir bypasses excessive flows around the separation chamber, so captured pollutants are retained in the separation cylinder. Design Basics There are three primary methods of sizing a CDS system. The Water Quality Flow Rate Method determines which model size provides the desired removal efficiency at a given flow rate for a defined particle size. The Rational Rainfall Method™ or the and Probabilistic Method is used when a specific removal efficiency of the net annual sediment load is required. Typically in the Unites States, CDS systems are designed to achieve an 80% annual solids load reduction based on lab generated performance curves for a gradation with an average particle size (d50) of 125 microns (μm). For some regulatory environments, CDS systems can also be designed to achieve an 80% annual solids load reduction based on an average particle size (d50) of 75 microns (μm) or 50 microns (μm). Water Quality Flow Rate Method In some cases, regulations require that a specific treatment rate, often referred to as the water quality design flow (WQQ), be treated. This WQQ represents the peak flow rate from either an event with a specific recurrence interval, e.g. the six-month storm, or a water quality depth, e.g. 1/2-inch (13 mm) of rainfall. The CDS is designed to treat all flows up to the WQQ. At influent rates higher than the WQQ, the diversion weir will direct most flow exceeding the WQQ around the separation chamber. This allows removal efficiency to remain relatively constant in the separation chamber and eliminates the risk of washout during bypass flows regardless of influent flow rates. Treatment flow rates are defined as the rate at which the CDS will remove a specific gradation of sediment at a specific removal efficiency. Therefore the treatment flow rate is variable, based on the gradation and removal efficiency specified by the design engineer. Rational Rainfall Method™ Differences in local climate, topography and scale make every site hydraulically unique. It is important to take these factors into consideration when estimating the long-term performance of any stormwater treatment system. The Rational Rainfall Method combines site-specific information with laboratory generated performance data, and local historical precipitation records to estimate removal efficiencies as accurately as possible. Short duration rain gauge records from across the United States and Canada were analyzed to determine the percent of the total annual rainfall that fell at a range of intensities. US stations’ depths were totaled every 15 minutes, or hourly, and recorded in 0.01-inch increments. Depths were recorded hourly with 1-mm resolution at Canadian stations. One trend was consistent at all sites; the vast majority of precipitation fell at low intensities and high intensity storms contributed relatively little to the total annual depth. These intensities, along with the total drainage area and runoff coefficient for each specific site, are translated into flow rates using the Rational Rainfall Method. Since most sites are relatively small and highly impervious, the Rational Rainfall Method is appropriate. Based on the runoff flow rates calculated for each intensity, operating rates within a proposed CDS system are GRATE INLET(CAST IRON HOOD FORCURB INLET OPENING) CREST OF BYPASS WEIR(ONE EACH SIDE) INLET(MULTIPLE PIPES POSSIBLE) OIL BAFFLE SUMP STORAGESEPARATION SLAB TREATMENT SCREEN OUTLET INLET FLUME SEPARATION CYLINDER CLEAN OUT(REQUIRED) DEFLECTION PAN, 3 SIDED(GRATE INLET DESIGN) O&M MANUAL CONTECH CDS MAINTENANCE MANUAL 3 determined. Performance efficiency curve determined from full scale laboratory tests on defined sediment PSDs is applied to calculate solids removal efficiency. The relative removal efficiency at each operating rate is added to produce a net annual pollutant removal efficiency estimate. Probabilistic Rational Method The Probabilistic Rational Method is a sizing program Contech developed to estimate a net annual sediment load reduction for a particular CDS model based on site size, site runoff coefficient, regional rainfall intensity distribution, and anticipated pollutant characteristics. The Probabilistic Method is an extension of the Rational Method used to estimate peak discharge rates generated by storm events of varying statistical return frequencies (e.g. 2-year storm event). Under the Rational Method, an adjustment factor is used to adjust the runoff coefficient estimated for the 10-year event, correlating a known hydrologic parameter with the target storm event. The rainfall intensities vary depending on the return frequency of the storm event under consideration. In general, these two frequency dependent parameters (rainfall intensity and runoff coefficient) increase as the return frequency increases while the drainage area remains constant. These intensities, along with the total drainage area and runoff coefficient for each specific site, are translated into flow rates using the Rational Method. Since most sites are relatively small and highly impervious, the Rational Method is appropriate. Based on the runoff flow rates calculated for each intensity, operating rates within a proposed CDS are determined. Performance efficiency curve on defined sediment PSDs is applied to calculate solids removal efficiency. The relative removal efficiency at each operating rate is added to produce a net annual pollutant removal efficiency estimate. Treatment Flow Rate The inlet throat area is sized to ensure that the WQQ passes through the separation chamber at a water surface elevation equal to the crest of the diversion weir. The diversion weir bypasses excessive flows around the separation chamber, thus preventing re-suspension or re-entrainment of previously captured particles. Hydraulic Capacity The hydraulic capacity of a CDS system is determined by the length and height of the diversion weir and by the maximum allowable head in the system. Typical configurations allow hydraulic capacities of up to ten times the treatment flow rate. The crest of the diversion weir may be lowered and the inlet throat may be widened to increase the capacity of the system at a given water surface elevation. The unit is designed to meet project specific hydraulic requirements. Performance Full-Scale Laboratory Test Results A full-scale CDS system (Model CDS2020-5B) was tested at the facility of University of Florida, Gainesville, FL. This CDS unit was evaluated under controlled laboratory conditions of influent flow rate and addition of sediment. Two different gradations of silica sand material (UF Sediment & OK-110) were used in the CDS performance evaluation. The particle size distributions (PSDs) of the test materials were analyzed using standard method “Gradation ASTM D-422 “Standard Test Method for Particle-Size Analysis of Soils” by a certified laboratory. UF Sediment is a mixture of three different products produced by the U.S. Silica Company: “Sil-Co-Sil 106”, “#1 DRY” and “20/40 Oil Frac”. Particle size distribution analysis shows that the UF Sediment has a very fine gradation (d50 = 20 to 30 μm) covering a wide size range (Coefficient of Uniformity, C averaged at 10.6). In comparison with the hypothetical TSS gradation specified in the NJDEP (New Jersey Department of Environmental Protection) and NJCAT (New Jersey Corporation for Advanced Technology) protocol for lab testing, the UF Sediment covers a similar range of particle size but with a finer d50 (d50 for NJDEP is approximately 50 μm) (NJDEP, 2003). The OK-110 silica sand is a commercial product of U.S. Silica Sand. The particle size distribution analysis of this material, also included in Figure 1, shows that 99.9% of the OK-110 sand is finer than 250 microns, with a mean particle size (d50) of 106 microns. The PSDs for the test material are shown in Figure 1. Figure 1. Particle size distributions Tests were conducted to quantify the performance of a specific CDS unit (1.1 cfs (31.3-L/s) design capacity) at various flow rates, ranging from 1% up to 125% of the treatment design capacity of the unit, using the 2400 micron screen. All tests were conducted with controlled influent concentrations of approximately 200 mg/L. Effluent samples were taken at equal time intervals across the entire duration of each test run. These samples were then processed with a Dekaport Cone sample splitter to obtain representative sub-samples for Suspended Sediment Concentration (SSC) testing using ASTM D3977-97 “Standard Test Methods for Determining Sediment Concentration in Water Samples”, and particle size distribution analysis. Results and Modeling Based on the data from the University of Florida, a performance model was developed for the CDS system. A regression analysis was used to develop a fitting curve representative of the scattered data points at various design flow rates. This model, which demonstrated good agreement with the laboratory data, can then be used to predict CDS system performance with respect O&M MANUAL CONTECH CDS MAINTENANCE MANUAL 4 to SSC removal for any particle size gradation, assuming the particles are inorganic sandy-silt. Figure 2 shows CDS predictive performance for two typical particle size gradations (NJCAT gradation and OK-110 sand) as a function of operating rate. Figure 2. CDS stormwater treatment predictive performance for various particle gradations as a function of operating rate. Many regulatory jurisdictions set a performance standard for hydrodynamic devices by stating that the devices shall be capable of achieving an 80% removal efficiency for particles having a mean particle size (d50) of 125 microns (e.g. Washington State Department of Ecology — WASDOE - 2008). The model can be used to calculate the expected performance of such a PSD (shown in Figure 3). The model indicates (Figure 4) that the CDS system with 2400 micron screen achieves approximately 80% removal at the design (100%) flow rate, for this particle size distribution (d50 = 125 μm). Figure 3. WASDOE PSD Figure 4. Modeled performance for WASDOE PSD. Maintenance The CDS system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. For example, unstable soils or heavy winter sanding will cause the grit chamber to fill more quickly but regular sweeping of paved surfaces will slow accumulation. Inspection Inspection is the key to effective maintenance and is easily performed. Pollutant transport and deposition may vary from year to year and regular inspections will help ensure that the system is cleaned out at the appropriate time. At a minimum, inspections should be performed twice per year (e.g. spring and fall) however more frequent inspections may be necessary in climates where winter sanding operations may lead to rapid accumulations, or in equipment washdown areas. Installations should also be inspected more frequently where excessive amounts of trash are expected. The visual inspection should ascertain that the system components are in working order and that there are no blockages or obstructions in the inlet and separation screen. The inspection should also quantify the accumulation of hydrocarbons, trash, and sediment in the system. Measuring pollutant accumulation can be done with a calibrated dipstick, tape measure or other measuring instrument. If absorbent material is used for enhanced removal of hydrocarbons, the level of discoloration of the sorbent material should also be identified O&M MANUAL CONTECH CDS MAINTENANCE MANUAL 5 during inspection. It is useful and often required as part of an operating permit to keep a record of each inspection. A simple form for doing so is provided. Access to the CDS unit is typically achieved through two manhole access covers. One opening allows for inspection and cleanout of the separation chamber (cylinder and screen) and isolated sump. The other allows for inspection and cleanout of sediment captured and retained outside the screen. For deep units, a single manhole access point would allows both sump cleanout and access outside the screen. The CDS system should be cleaned when the level of sediment has reached 75% of capacity in the isolated sump or when an appreciable level of hydrocarbons and trash has accumulated. If absorbent material is used, it should be replaced when significant discoloration has occurred. Performance will not be impacted until 100% of the sump capacity is exceeded however it is recommended that the system be cleaned prior to that for easier removal of sediment. The level of sediment is easily determined by measuring from finished grade down to the top of the sediment pile. To avoid underestimating the level of sediment in the chamber, the measuring device must be lowered to the top of the sediment pile carefully. Particles at the top of the pile typically offer less resistance to the end of the rod than consolidated particles toward the bottom of the pile. Once this measurement is recorded, it should be compared to the as-built drawing for the unit to determine weather the height of the sediment pile off the bottom of the sump floor exceeds 75% of the total height of isolated sump. Cleaning Cleaning of a CDS systems should be done during dry weather conditions when no flow is entering the system. The use of a vacuum truck is generally the most effective and convenient method of removing pollutants from the system. Simply remove the manhole covers and insert the vacuum hose into the sump. The system should be completely drained down and the sump fully evacuated of sediment. The area outside the screen should also be cleaned out if pollutant build-up exists in this area. In installations where the risk of petroleum spills is small, liquid contaminants may not accumulate as quickly as sediment. However, the system should be cleaned out immediately in the event of an oil or gasoline spill. Motor oil and other hydrocarbons that accumulate on a more routine basis should be removed when an appreciable layer has been captured. To remove these pollutants, it may be preferable to use absorbent pads since they are usually less expensive to dispose than the oil/water emulsion that may be created by vacuuming the oily layer. Trash and debris can be netted out to separate it from the other pollutants. The screen should be cleaned to ensure it is free of trash and debris. Manhole covers should be securely seated following cleaning activities to prevent leakage of runoff into the system from above and also to ensure that proper safety precautions have been followed. Confined space entry procedures need to be followed if physical access is required. Disposal of all material removed from the CDS system should be done in accordance with local regulations. In many jurisdictions, disposal of the sediments may be handled in the same manner as the disposal of sediments removed from catch basins or deep sump manholes. Check your local regulations for specific requirements on disposal. O&M MANUAL CONTECH CDS MAINTENANCE MANUAL 6 Note: To avoid underestimating the volume of sediment in the chamber, carefully lower the measuring device to the top of the sediment pile. Finer silty particles at the top of the pile may be more difficult to feel with a measuring stick. These finer particles typically offer less resistance to the end of the rod than larger particles toward the bottom of the pile. CDS Model Diameter Distance from Water Surface to Top of Sediment Pile Sediment Storage Capacity ft m ft m y3 m3 CDS1515 3 0.9 3.0 0.9 0.5 0.4 CDS2015 4 1.2 3.0 0.9 0.9 0.7 CDS2015 5 1.5 3.0 0.9 1.3 1.0 CDS2020 5 1.5 3.5 1.1 1.3 1.0 CDS2025 5 1.5 4.0 1.2 1.3 1.0 CDS3020 6 1.8 4.0 1.2 2.1 1.6 CDS3025 6 1.8 4.0 1.2 2.1 1.6 CDS3030 6 1.8 4.6 1.4 2.1 1.6 CDS3035 6 1.8 5.0 1.5 2.1 1.6 CDS4030 8 2.4 4.6 1.4 5.6 4.3 CDS4040 8 2.4 5.7 1.7 5.6 4.3 CDS4045 8 2.4 6.2 1.9 5.6 4.3 CDS5640 10 3.0 6.3 1.9 8.7 6.7 CDS5653 10 3.0 7.7 2.3 8.7 6.7 CDS5668 10 3.0 9.3 2.8 8.7 6.7 CDS5678 10 3.0 10.3 3.1 8.7 6.7 Table 1: CDS Maintenance Indicators and Sediment Storage Capacities O&M MANUAL CONTECH CDS MAINTENANCE MANUAL 7 CDS Inspection & Maintenance Log CDS Model: Location: Water Floatable Describe Maintenance Date depth to Layer Maintenance Personnel Comments sediment1 Thickness2 Performed —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— 1. The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the values listed in table 1 the system should be cleaned out. Note: to avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. 2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness. In the event of an oil spill, the system should be cleaned immediately.O&M MANUAL CONTECH CDS MAINTENANCE MANUAL SUPPORT • Drawings and specifications are available at www.ContechES.com. • Site-specific design support is available from our engineers. ©2017 Contech Engineered Solutions LLC, a QUIKRETE Company Contech Engineered Solutions provides site solutions for the civil engineering industry. Contech’s portfolio includes bridges, drainage, sanitary sewer, earth stabilization and stormwater treatment products. For information on other Contech division offerings, visit www.ContechES.com or call 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. The product(s) described may be protected by one or more of the following US patents: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6,406,218; 6,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038; 7,186,058; 7,296,692; 7,297,266; related foreign patents or other patents pending. 800-338-1122 www.ContechES.com cds_manual 3/17 PDF ENGINEERED SOLUTIONS O&M MANUAL CONTECH CDS MAINTENANCE MANUAL HAZEN HIGH SCHOOL IMPROVEMENTS 22 11. FIGURES FIGURE 1 – TIR WORKSHEET FIGURE 2 – VICINITY MAP FIGURE 3 – NEW + REPLACED IMPERVIOUS AREAS FIGURE 4 – EXISTING CONDITIONS FIGURE 5A – OFFSITE DRAINAGE FIGURE 5B – OFFSITE DRAINAGE FIGURE 5C – OFFSITE DRAINAGE FIGURE 6 – PROJECT MINIMUM REQUIREMENTS FLOW CHART FIGURE 7 – 100 YEAR FLOODPLAIN FIGURE 8 – SOILS MAP FIGURE 9 – DRAINAGE COMPLAINTS FIGURE 10 – EROSION HAZARDS FIGURE 11 – SENSITIVE AREAS FIGURE 12 – FLOW CONTROL BASINS FIGURE 13 – SSA SETTINGS FIGURE 14 – IDF CURVE FIGURE 15 – ISOPLUVIAL MAP Renton School District (206) 482-5253 7812 South 124th Street Seattle, WA 98178 Sascha Eastman Jacobson Consulting Engineers (206) 293-9134 Hazen High School Improvements 23N 5E 10 1101 Hoquiam Avenue NE Renton, WA 98059 Civil Construction Permit N/A 09/24/2024 (LU) 02/21/2025 (CCP) FIGURE 1: TIR WORKSHEET 11/12/2024 09/24/2024 (LU) (CCP) 11/12/2024 02/21/2025 05/16/2025(CCP)05/16/2025(CCP) 07/11/2025(CCP)07/11/2025(CCP) N/A N/A N/A May Creek N/A N/A N/A FIGURE 1: TIR WORKSHEET AgC 8% - 15%Moderate Baseball Field (TDA #1), Softball Field (TDA #2), and Misc. Improvements (TDA #3) 3 N/A TBD TBD TBD Flow Control Duration - Matching Forested Site Conditions FIGURE 1: TIR WORKSHEET Compost Amended Soil BMP T5.13 N/A N/A N/A FIGURE 1: TIR WORKSHEET StormTrap & StormTech Chambers BMP T5.13 FIGURE 1: TIR WORKSHEET Modular Wetland Vaults N/A 07/11/2025 Stormwater DOC FIGURE 1: TIR WORKSHEET FIGURE 2: VICINITY MAP SCALE: NTS PROJECT SITES PROJECT SITE FIGURE 3: NEW + REPLACED IMPERVIOUS AREAS TDA #1 Description Quantity Unit New Impervious Surface 2.36 ac TDA #2 Description Quantity Unit New Impervious Surface 1.10 ac Replaced Impervious Surface 0.01 ac TDA #3 Description Quantity Unit Replaced Impervious Surface 0.12 ac SCALE 1" = 150' 0 75 150 300 X X CO DRAINAGE BASIN #1 - WEST TO DUVALL AVE NE SEE FIGURE 5A - OFFSITE DRAINAGE DRAINAGE BASIN #2 - SOUTH TO NE 10TH ST DRAINAGE BASIN #3 - EAST TO HOQUIAM AVE NE DRAINAGE BASIN #3 - EAST TO HOQUIAM AVE NE SEE FIGURE 5B - OFFSITE DRAINAGE SEE FIGURE 5C - OFFSITE DRAINAGE SEE FIGURE 5C - OFFSITE DRAINAGE HO Q U I A M A V E N E NE 10TH ST DU V A L L A V E N E NE 12TH ST FIGURE 4: EXISTING CONDITIONS TDA #1 Description Quantity Unit Pervious Surface 2.36 ac TDA #2 Description Quantity Unit Impervious Surface 0.01 ac Pervious Surface 1.10 ac SCALE 1" = 150' 0 75 150 300 TDA #3 Description Quantity Unit Impervious Surface 0.12 ac X X CO DRAINAGE BASIN #1 - WEST TO DUVALL AVE NE SEE FIGURE 5A - OFFSITE DRAINAGE DRAINAGE BASIN #2 - SOUTH TO NE 10TH ST DRAINAGE BASIN #3 - EAST TO HOQUIAM AVE NE DRAINAGE BASIN #3 - EAST TO HOQUIAM AVE NE SEE FIGURE 5B - OFFSITE DRAINAGE SEE FIGURE 5C - OFFSITE DRAINAGE SEE FIGURE 5C - OFFSITE DRAINAGE HO Q U I A M A V E N E DU V A L L A V E N E NE 10TH ST NE 12TH ST 255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM FIGURE 5: OFFSITE DRAINAGE SCALE: NTS 206.426.2600 Project Site Regional Stormwater Facility (Cascade Park) 18"24"24" 24" FIGURE 5A: OFFSITE DRAINAGE SCALE: NTS DETENTION FACILITY: 0.35 MI DOWNSTREAM PROJECT SITE OFFSITE OUTLET #1 0.25 MI DOWNSTREAM 255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM FIGURE 5: OFFSITE DRAINAGE SCALE: NTS 206.426.2600 Project Site Regional Stormwater Facility (Cascade Park) 18"24"24" 24" FIGURE 5B: OFFSITE DRAINAGE SCALE: NTS PROJECT SITE OFFSITE OUTLET #2 SURFACE WATER FACILITY: POND 0.25 MI DOWNSTREAM 255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM FIGURE 5: OFFSITE DRAINAGE SCALE: NTS 206.426.2600 Project Site Regional Stormwater Facility (Cascade Park) 18"24"24" 24" FIGURE 5C: OFFSITE DRAINAGE SCALE: NTS SURFACE WATER FACILITY: HONEY CREEK 0.35 MI DOWNSTREAM 0.25 MILE DOWNSTREAM PROJECT SITE OFFSITE OUTLET #3.2 PROJECT SITE OFFSITE OUTLET #3.1 FIGURE 6: PROJECT MINIMIMUM REQUIREMENTS FLOW CHART PROJECT SITE FEMA FLOOD MAP # 53033C0669G FIGURE 7: 100 YR FLOODPLAIN SCALE: NTS FIGURE 8: SOILS MAP 255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM FIGURE 9: DRAINAGE COMPLAINTS SCALE: NTS 206.426.2600 PROJECT SITE 255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM PROJECT SITE FIGURE 10: EROSION HAZARDS 206.426.2600 255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM PROJECT SITE FIGURE 11: SENSITIVE AREAS 206.426.2600 ; ; CO DRAINAGE BASIN #1 - WEST TO DUVALL AVE NE SEE FIGURE 5A - OFFSITE DRAINAGE DRAINAGE BASIN #2 - SOUTH TO NE 10TH ST SEE FIGURE 5B - OFFSITE DRAINAGE SEE FIGURE 5C - OFFSITE DRAINAGE DRAINAGE BASIN #3 - EAST TO HOQUIAM AVE NE FIGURE 12: FLOW CONTROL BASINS SCALE 1" = 150' 0 75 150 300NE 12TH ST DU V A L L A V E N E NE 10TH ST HO Q U I A M A V E N E TDA #1 Description Quantity Unit Baseball Existing Flat Impervious 0.113 ac Baseball Existing Flat Pervious 0.097 ac Baseball Existing Moderate Impervious 0.016 ac Baseball Existing Moderate Pervious 0.146 ac Baseball Existing Steep Pervious 0.076 ac Baseball Field 2.360 ac TDA #2 Description Quantity Unit Softball Existing Flat Impervious 0.085 ac Softball Field 0.977 ac TDA #3 Description Quantity Unit Multipurpose Bypass Flat Paving 0.085 ac Multipurpose Bypass Roof 0.014 ac Excerpt from Storm and Sanitary Analysis 2016 User's Guide: Hydrodynamic Link Routing calculates the backwater analysis for the conveyance system. See excerpt below. FIGURE 13: SSA SETTINGS SSA: i = B / (Tc + D) E KCSWDM: IR = PR * aR * Tc-bR B = PR * aR = (3.92)(2.61) = 10.23 Where PR is 3.92 per SCDM Volume III Western Washington Isopluvial 100-year 24-hour (See Figure 15 - Isopluvial Map) and aR is 2.61 per KCSWDM Table 3.2.1.B - Coefficients for the Rational Method "iR" Equation for the 100-year 24-hour storm. Tc = Tc + D = 6.3 + 0 = 6.3 Where Tc is set to 6.3 per KCSWDM section 3.2.1 and D is a variable in SSA to show a variance in the time of concentration, which is zero for this project. E = bR = 0.63 Where bR is 0.63 per KCSWDM Table 3.2.1.B - Coefficients for the Rational Method "iR" Equation for the 100-year 24-hour storm. SSA uses the IDF curve to calculate "i" which will then be used in the Rational Method calculations during conveyance analysis. FIGURE 14: IDF CURVE PROJECT SITE P=3.92 FIGURE 15: ISOPLUVIAL MAP HAZEN HIGH SCHOOL IMPROVEMENTS 23 12. APPENDICES APPENDIX A – BOND QUANTITY WORKSHEET APPENDIX B – STORMWATER CALCULATIONS APPENDIX C – STORMWATER POLLUTION PREVENTION PLAN (SWPPP) APPENDIX D – FACILITY SUMMARY SHEET, DECLARATION OF COVENANT HAZEN HIGH SCHOOL IMPROVEMENTS 24 APPENDIX A BOND QUANTITY WORKSHEET 1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200 Date Prepared: Name: PE Registration No: Firm Name: Firm Address: Phone No. Email Address: Project Name: Project Owner: CED Plan # (LUA): Phone: CED Permit # (C):Address: Site Address: Street Intersection: Addt'l Project Owner: Parcel #(s): Phone: Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NO Water Service Provided by: If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: Roadway (Erosion Control + Transportation)D 636,408.44$ SITE IMPROVEMENT BOND QUANTITY WORKSHEET PROJECT INFORMATION CITY OF RENTON CITY OF RENTON Engineer Stamp Required (all cost estimates must have original wet stamp and signature) Clearing and Grading Utility Providers N/A Project Location and Description Project Owner Information Hazen High School Improvements Seattle, WA 98178 1023059057, 1023059072, 1023059201, 1023059278, 1023059292, 1023059084, 1023059277, & 1023059094 Mike Cato c/o Renton School District (206) 482-5253 1101 Hoquiam Ave NE, Renton WA, 98059 7812 South 124th Street Hoquiam Avenue NE and SE 144th Street 240033-0208 7/11/2025 Prepared by: FOR APPROVALProject Phase 1 alan@jacobsonengineers.com Alan Jacobson 43667 Jacobson Consulting Engineers 255 S King ST, Suite 800, Seattle, WA 98104 (206) 426-2600 15,497.15$ Abbreviated Legal Description: LOT 2 OF CITY OF RENTON LOT LINE ADJUSTMENT NO. LUA-00-148- LLA, RECORDED UNDER RECORDING NO. 20010529900002, IN KING COUNTY, WASHINGTON. Total Estimated Construction Costs A + B + C + D 1,896,727.13$ Estimated Civil Construction Permit - Construction Costs2 Stormwater (Drainage) & Misc. Utilities C 1,232,975.31$ As outlined in City Ordinance No. 4345, 50% of the plan review and inspection fees are to be paid at Permit Submittal. The balance is due at Permit Issuance. Significant changes or additional review cycles (beyond 3 cycles) during the review process may result in adjustments to the final review fees. Water A 11,846.22$ Wastewater (Sanitary Sewer)B Page 2 of 15 Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION Version 4/1/2024 Printed 7/10/2025 1 Select the current project status/phase from the following options: Page 3 of 15 Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION Version 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Unit Reference #Price Unit Quantity Cost Backfill & compaction-embankment ESC-1 7.50$ CY Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 90.00$ Each 11 990.00 Catch Basin Protection ESC-3 145.00$ Each 40 5,800.00 Crushed surfacing 1 1/4" minus ESC-4 WSDOT 9-03.9(3)110.00$ CY Ditching ESC-5 10.50$ CY Excavation-bulk ESC-6 2.30$ CY 15521 35,698.30 Fence, silt ESC-7 SWDM 5.4.3.1 5.00$ LF 1370 6,850.00 Fence, Temporary (NGPE)ESC-8 1.75$ LF Geotextile Fabric ESC-9 3.00$ SY Hay Bale Silt Trap ESC-10 0.60$ Each Hydroseeding ESC-11 SWDM 5.4.2.4 0.90$ SY Interceptor Swale / Dike ESC-12 1.15$ LF 570 655.50 Jute Mesh ESC-13 SWDM 5.4.2.2 4.00$ SY Level Spreader ESC-14 2.00$ LF Mulch, by hand, straw, 3" deep ESC-15 SWDM 5.4.2.1 2.90$ SY Mulch, by machine, straw, 2" deep ESC-16 SWDM 5.4.2.1 2.30$ SY Piping, temporary, CPP, 6"ESC-17 13.75$ LF Piping, temporary, CPP, 8"ESC-18 16.00$ LF 35 560.00 Piping, temporary, CPP, 12"ESC-19 20.50$ LF Plastic covering, 6mm thick, sandbagged ESC-20 SWDM 5.4.2.3 4.60$ SY Rip Rap, machine placed; slopes ESC-21 WSDOT 9-13.1(2)51.00$ CY Rock Construction Entrance, 50'x15'x1'ESC-22 SWDM 5.4.4.1 2,050.00$ Each Rock Construction Entrance, 100'x15'x1'ESC-23 SWDM 5.4.4.1 3,675.00$ Each Sediment pond riser assembly ESC-24 SWDM 5.4.5.2 2,525.00$ Each Sediment trap, 5' high berm ESC-25 SWDM 5.4.5.1 22.00$ LF Sed. trap, 5' high, riprapped spillway berm section ESC-26 SWDM 5.4.5.1 80.00$ LF Seeding, by hand ESC-27 SWDM 5.4.2.4 1.15$ SY Sodding, 1" deep, level ground ESC-28 SWDM 5.4.2.5 9.20$ SY Sodding, 1" deep, sloped ground ESC-29 SWDM 5.4.2.5 11.50$ SY TESC Supervisor ESC-30 125.00$ HR 200 25,000.00 Water truck, dust control ESC-31 SWDM 5.4.7 160.00$ HR 80 12,800.00 Unit Reference #Price Unit Quantity Cost SWDM D.2.1.2.5 4.00$ LF 995 3,980.00 3.90$ LF 100.00$ Each 9 900.00 EROSION/SEDIMENT SUBTOTAL:93,233.80 SALES TAX @ 10.3%9,603.08 EROSION/SEDIMENT TOTAL:102,836.88 (A) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR EROSION & SEDIMENT CONTROL Description No. (A) Tree Protection Straw Wattles Construction Fencing WRITE-IN-ITEMS Page 4 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.a EROSION_CONTROL Version: 4/01/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost GENERAL ITEMS Backfill & Compaction- embankment GI-1 7.00$ CY Backfill & Compaction- trench GI-2 10.25$ CY Clear/Remove Brush, by hand (SY)GI-3 1.15$ SY Bollards - fixed GI-4 275.00$ Each 37 10,175.00 Bollards - removable GI-5 520.00$ Each 6 3,120.00 Clearing/Grubbing/Tree Removal GI-6 11,475.00$ Acre 1 11,475.00 Excavation - bulk GI-7 2.30$ CY Excavation - Trench GI-8 5.75$ CY Fencing, cedar, 6' high GI-9 23.00$ LF Fencing, chain link, 4'GI-10 44.00$ LF Fencing, chain link, vinyl coated, 6' high GI-11 23.00$ LF Fencing, chain link, gate, vinyl coated, 20' GI-12 1,600.00$ Each Fill & compact - common barrow GI-13 28.75$ CY Fill & compact - gravel base GI-14 31.00$ CY 25 775.00 4591 142,321.00 Fill & compact - screened topsoil GI-15 44.75$ CY 160 7,160.00 1255 56,161.25 Gabion, 12" deep, stone filled mesh GI-16 74.50$ SY Gabion, 18" deep, stone filled mesh GI-17 103.25$ SY Gabion, 36" deep, stone filled mesh GI-18 172.00$ SY Grading, fine, by hand GI-19 2.90$ SY Grading, fine, with grader GI-20 2.30$ SY 320 736.00 12520 28,796.00 Monuments, 3' Long GI-21 1,025.00$ Each Sensitive Areas Sign GI-22 8.00$ Each Sodding, 1" deep, sloped ground GI-23 9.25$ SY Surveying, line & grade GI-24 975.00$ Day 3 2,925.00 Surveying, lot location/lines GI-25 2,050.00$ Acre 4 8,200.00 Topsoil Type A (imported)GI-26 32.75$ CY Traffic control crew ( 2 flaggers )GI-27 137.75$ HR Trail, 4" chipped wood GI-28 9.15$ SY Trail, 4" crushed cinder GI-29 10.25$ SY Trail, 4" top course GI-30 13.75$ SY Conduit, 2"GI-31 5.75$ LF Wall, retaining, concrete GI-32 63.00$ SF Wall, rockery GI-33 17.25$ SF SUBTOTAL THIS PAGE:8,671.00 263,173.25 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) Page 5 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) ROAD IMPROVEMENT/PAVEMENT/SURFACING AC Grinding, 4' wide machine < 1000sy RI-1 34.50$ SY AC Grinding, 4' wide machine 1000-2000sy RI-2 18.25$ SY AC Grinding, 4' wide machine > 2000sy RI-3 11.50$ SY AC Removal/Disposal RI-4 40.00$ SY 220 8,800.00 362 14,480.00 Barricade, Type III ( Permanent )RI-5 64.25$ LF Guard Rail RI-6 34.50$ LF Curb & Gutter, rolled RI-7 19.50$ LF Curb & Gutter, vertical RI-8 14.25$ LF 760 10,830.00 15 213.75 Curb and Gutter, demolition and disposal RI-9 20.50$ LF 760 15,580.00 25 512.50 Curb, extruded asphalt RI-10 6.25$ LF Curb, extruded concrete RI-11 8.00$ LF 225 1,800.00 Sawcut, asphalt, 3" depth RI-12 3.00$ LF 810 2,430.00 1300 3,900.00 Sawcut, concrete, per 1" depth RI-13 5.00$ LF 110 550.00 550 2,750.00 Sealant, asphalt RI-14 2.25$ LF Shoulder, gravel, 4" thick RI-15 17.25$ SY Sidewalk, 4" thick RI-16 43.50$ SY 400 17,400.00 390 16,965.00 Sidewalk, 4" thick, demolition and disposal RI-17 37.00$ SY 400 14,800.00 390 14,430.00 Sidewalk, 5" thick RI-18 47.00$ SY 100 4,700.00 Sidewalk, 5" thick, demolition and disposal RI-19 46.00$ SY 100 4,600.00 Sign, Handicap RI-20 97.00$ Each Striping, per stall RI-21 8.00$ Each Striping, thermoplastic, ( for crosswalk )RI-22 3.50$ SF 540 1,890.00 1305 4,567.50 Striping, 4" reflectorized line RI-23 0.55$ LF Additional 2.5" Crushed Surfacing RI-24 4.15$ SY HMA 1/2" Overlay 1.5" RI-25 16.00$ SY HMA 1/2" Overlay 2"RI-26 20.75$ SY HMA Road, 2", 4" rock, First 2500 SY RI-27 32.25$ SY HMA Road, 2", 4" rock, Qty. over 2500SY RI-28 24.00$ SY HMA Road, 4", 6" rock, First 2500 SY RI-29 51.75$ SY 410 21,217.50 363 18,785.25 HMA Road, 4", 6" rock, Qty. over 2500 SY RI-30 42.50$ SY HMA Road, 4", 4.5" ATB RI-31 43.50$ SY Gravel Road, 4" rock, First 2500 SY RI-32 17.25$ SY Gravel Road, 4" rock, Qty. over 2500 SY RI-33 11.50$ SY Thickened Edge RI-34 10.00$ LF 70 700.00 SUBTOTAL THIS PAGE:95,997.50 85,904.00 (B)(C)(D)(E) Page 6 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) PARKING LOT SURFACING No. 2" AC, 2" top course rock & 4" borrow PL-1 24.00$ SY 2" AC, 1.5" top course & 2.5" base course PL-2 32.00$ SY 4" select borrow PL-3 5.75$ SY 1.5" top course rock & 2.5" base course PL-4 16.00$ SY SUBTOTAL PARKING LOT SURFACING: (B)(C)(D)(E) LANDSCAPING & VEGETATION No. Street Trees LA-1 Median Landscaping LA-2 Right-of-Way Landscaping LA-3 Wetland Landscaping LA-4 SUBTOTAL LANDSCAPING & VEGETATION: (B)(C)(D)(E) TRAFFIC & LIGHTING No. Signs TR-1 15,000.00$ Each 2 30,000.00 Street Light System ( # of Poles)TR-2 Traffic Signal TR-3 Traffic Signal Modification TR-4 SUBTOTAL TRAFFIC & LIGHTING:30,000.00 (B)(C)(D)(E) WRITE-IN-ITEMS SUBTOTAL WRITE-IN ITEMS: STREET AND SITE IMPROVEMENTS SUBTOTAL:134,668.50 349,077.25 SALES TAX @ 10.3%13,870.86 35,954.96 STREET AND SITE IMPROVEMENTS TOTAL:148,539.36 385,032.21 (B)(C)(D)(E) Page 7 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost DRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/D D-1 30.00$ SY * (CBs include frame and lid) Beehive D-2 103.00$ Each Through-curb Inlet Framework D-3 460.00$ Each CB Type I D-4 1,725.00$ Each 2 3,450.00 3 5,175.00 CB Type IL D-5 2,000.00$ Each CB Type II, 48" diameter D-6 3,500.00$ Each 2 7,000.00 for additional depth over 4' D-7 550.00$ FT 12 6,600.00 CB Type II, 54" diameter D-8 4,075.00$ Each 2 8,150.00 for additional depth over 4'D-9 570.00$ FT 10 5,700.00 CB Type II, 60" diameter D-10 4,225.00$ Each for additional depth over 4'D-11 690.00$ FT CB Type II, 72" diameter D-12 6,900.00$ Each for additional depth over 4'D-13 975.00$ FT CB Type II, 96" diameter D-14 16,000.00$ Each for additional depth over 4'D-15 1,050.00$ FT Trash Rack, 12"D-16 400.00$ Each Trash Rack, 15"D-17 470.00$ Each Trash Rack, 18"D-18 550.00$ Each Trash Rack, 21"D-19 630.00$ Each Cleanout, PVC, 4"D-20 170.00$ Each Cleanout, PVC, 6"D-21 195.00$ Each Cleanout, PVC, 8"D-22 230.00$ Each Culvert, PVC, 4" D-23 11.50$ LF Culvert, PVC, 6" D-24 15.00$ LF 65 975.00 Culvert, PVC, 8" D-25 17.00$ LF Culvert, PVC, 12" D-26 26.00$ LF 45 1,170.00 362 9,412.00 Culvert, PVC, 15" D-27 40.00$ LF Culvert, PVC, 18" D-28 47.00$ LF Culvert, PVC, 24"D-29 65.00$ LF Culvert, PVC, 30" D-30 90.00$ LF Culvert, PVC, 36" D-31 150.00$ LF Culvert, CMP, 8"D-32 22.00$ LF Culvert, CMP, 12"D-33 33.00$ LF SUBTOTAL THIS PAGE:4,620.00 43,012.00 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Page 8 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued) Culvert, CMP, 15"D-34 40.00$ LF Culvert, CMP, 18"D-35 47.00$ LF Culvert, CMP, 24"D-36 64.00$ LF Culvert, CMP, 30"D-37 90.00$ LF Culvert, CMP, 36"D-38 150.00$ LF Culvert, CMP, 48"D-39 218.00$ LF Culvert, CMP, 60"D-40 310.00$ LF Culvert, CMP, 72"D-41 400.00$ LF Culvert, Concrete, 8"D-42 48.00$ LF Culvert, Concrete, 12"D-43 55.00$ LF Culvert, Concrete, 15"D-44 89.00$ LF Culvert, Concrete, 18"D-45 100.00$ LF Culvert, Concrete, 24"D-46 120.00$ LF Culvert, Concrete, 30"D-47 145.00$ LF Culvert, Concrete, 36"D-48 175.00$ LF Culvert, Concrete, 42"D-49 200.00$ LF Culvert, Concrete, 48"D-50 235.00$ LF Culvert, CPE Triple Wall, 6" D-51 16.00$ LF Culvert, CPE Triple Wall, 8" D-52 18.00$ LF Culvert, CPE Triple Wall, 12" D-53 27.00$ LF Culvert, CPE Triple Wall, 15" D-54 40.00$ LF Culvert, CPE Triple Wall, 18" D-55 47.00$ LF Culvert, CPE Triple Wall, 24" D-56 64.00$ LF Culvert, CPE Triple Wall, 30" D-57 90.00$ LF Culvert, CPE Triple Wall, 36" D-58 149.00$ LF Culvert, LCPE, 6"D-59 69.00$ LF Culvert, LCPE, 8"D-60 83.00$ LF Culvert, LCPE, 12"D-61 96.00$ LF Culvert, LCPE, 15"D-62 110.00$ LF Culvert, LCPE, 18"D-63 124.00$ LF Culvert, LCPE, 24"D-64 138.00$ LF Culvert, LCPE, 30"D-65 151.00$ LF Culvert, LCPE, 36"D-66 165.00$ LF Culvert, LCPE, 48"D-67 179.00$ LF Culvert, LCPE, 54"D-68 193.00$ LF SUBTOTAL THIS PAGE: (B)(C)(D)(E) Page 9 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued) Culvert, LCPE, 60"D-69 206.00$ LF Culvert, LCPE, 72"D-70 220.00$ LF Culvert, HDPE, 6"D-71 48.00$ LF Culvert, HDPE, 8"D-72 60.00$ LF Culvert, HDPE, 12"D-73 85.00$ LF Culvert, HDPE, 15"D-74 122.00$ LF Culvert, HDPE, 18"D-75 158.00$ LF Culvert, HDPE, 24"D-76 254.00$ LF Culvert, HDPE, 30"D-77 317.00$ LF Culvert, HDPE, 36"D-78 380.00$ LF Culvert, HDPE, 48"D-79 443.00$ LF Culvert, HDPE, 54"D-80 506.00$ LF Culvert, HDPE, 60"D-81 570.00$ LF Culvert, HDPE, 72"D-82 632.00$ LF Pipe, Polypropylene, 6"D-83 96.00$ LF Pipe, Polypropylene, 8"D-84 100.00$ LF Pipe, Polypropylene, 12"D-85 100.00$ LF Pipe, Polypropylene, 15"D-86 103.00$ LF Pipe, Polypropylene, 18"D-87 106.00$ LF Pipe, Polypropylene, 24"D-88 119.00$ LF Pipe, Polypropylene, 30"D-89 136.00$ LF Pipe, Polypropylene, 36"D-90 185.00$ LF Pipe, Polypropylene, 48"D-91 260.00$ LF Pipe, Polypropylene, 54"D-92 381.00$ LF Pipe, Polypropylene, 60"D-93 504.00$ LF Pipe, Polypropylene, 72"D-94 625.00$ LF Culvert, DI, 6"D-95 70.00$ LF Culvert, DI, 8"D-96 101.00$ LF Culvert, DI, 12"D-97 121.00$ LF Culvert, DI, 15"D-98 148.00$ LF Culvert, DI, 18"D-99 175.00$ LF Culvert, DI, 24"D-100 200.00$ LF Culvert, DI, 30"D-101 227.00$ LF Culvert, DI, 36"D-102 252.00$ LF Culvert, DI, 48"D-103 279.00$ LF Culvert, DI, 54"D-104 305.00$ LF Culvert, DI, 60"D-105 331.00$ LF Culvert, DI, 72"D-106 357.00$ LF SUBTOTAL THIS PAGE: (B)(C)(D)(E) Page 10 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Specialty Drainage Items Ditching SD-1 10.90$ CY Flow Dispersal Trench (1,436 base+)SD-3 32.00$ LF French Drain (3' depth)SD-4 30.00$ LF Geotextile, laid in trench, polypropylene SD-5 3.40$ SY Mid-tank Access Riser, 48" dia, 6' deep SD-6 2,300.00$ Each Pond Overflow Spillway SD-7 18.25$ SY Restrictor/Oil Separator, 12"SD-8 1,320.00$ Each Restrictor/Oil Separator, 15"SD-9 1,550.00$ Each Restrictor/Oil Separator, 18"SD-10 1,950.00$ Each Riprap, placed SD-11 48.20$ CY Tank End Reducer (36" diameter)SD-12 1,375.00$ Each Infiltration pond testing SD-13 143.00$ HR Permeable Pavement SD-14 Permeable Concrete Sidewalk SD-15 10.50$ SF Culvert, Box __ ft x __ ft SD-16 SUBTOTAL SPECIALTY DRAINAGE ITEMS: (B)(C)(D)(E) STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch) Detention Pond SF-1 Each Detention Tank SF-2 Each Detention Vault SF-3 Each Infiltration Pond SF-4 Each Infiltration Tank SF-5 Each Infiltration Vault SF-6 Each Infiltration Trenches SF-7 Each Basic Biofiltration Swale SF-8 Each Wet Biofiltration Swale SF-9 Each Wetpond SF-10 Each Wetvault SF-11 Each Sand Filter SF-12 Each Sand Filter Vault SF-13 Each Linear Sand Filter SF-14 Each Proprietary Facility SF-15 Each Bioretention Facility SF-16 Each SUBTOTAL STORMWATER FACILITIES: (B)(C)(D)(E) Page 11 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs) WI-1 Round Solid Locking Cover WI-2 400.00$ Each 4 1,600.00 Control Structure WI-3 3,600.00$ Each 2 7,200.00 Connect to Existing System WI-4 3,600.00$ Each 2 7,200.00 WI-5 WI-6 StormTech Chamber Detention System (Softball)WI-7 404,430.00$ LS 1 404,430.00 StormTrap Detention System WI-8 571,776.00$ LS 1 571,776.00 StormTech Chamber Detention System (Multi)WI-9 418,770.00$ LS WI-10 Modular Wetland - 4'x4'WI-11 27,500.00$ Each Modular Wetland - 4'x6'WI-12 34,000.00$ Each 2 68,000.00 WI-13 Contech CDS Solids Separator WI-14 10,000.00$ Each 1 10,000.00 WI-15 SUBTOTAL WRITE-IN ITEMS:7,200.00 1,063,006.00 DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:11,820.00 1,106,018.00 SALES TAX @ 10.3%1,217.46 113,919.85 DRAINAGE AND STORMWATER FACILITIES TOTAL:13,037.46 1,219,937.85 (B) (C) (D) (E) Page 12 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Connection to Existing Watermain W-1 3,400.00$ Each 1 3,400.00 Ductile Iron Watermain, CL 52, 4 Inch Diameter W-2 58.00$ LF Ductile Iron Watermain, CL 52, 6 Inch Diameter W-3 65.00$ LF 36 2,340.00 Ductile Iron Watermain, CL 52, 8 Inch Diameter W-4 75.00$ LF Ductile Iron Watermain, CL 52, 10 Inch Diameter W-5 80.00$ LF Ductile Iron Watermain, CL 52, 12 Inch Diameter W-6 145.00$ LF Gate Valve, 4 inch Diameter W-7 1,225.00$ Each Gate Valve, 6 inch Diameter W-8 1,350.00$ Each Gate Valve, 8 Inch Diameter W-9 1,550.00$ Each Gate Valve, 10 Inch Diameter W-10 2,100.00$ Each Gate Valve, 12 Inch Diameter W-11 2,500.00$ Each Fire Hydrant Assembly W-12 5,000.00$ Each 1 5,000.00 Permanent Blow-Off Assembly W-13 1,950.00$ Each Air-Vac Assembly, 2-Inch Diameter W-14 3,050.00$ Each Air-Vac Assembly, 1-Inch Diameter W-15 1,725.00$ Each Compound Meter Assembly 3-inch Diameter W-16 9,200.00$ Each Compound Meter Assembly 4-inch Diameter W-17 10,500.00$ Each Compound Meter Assembly 6-inch Diameter W-18 11,500.00$ Each Pressure Reducing Valve Station 8-inch to 10-inch W-19 23,000.00$ Each WATER SUBTOTAL:10,740.00 SALES TAX @ 10.3%1,106.22 WATER TOTAL:11,846.22 (B) (C) (D) (E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR WATER Quantity Remaining (Bond Reduction) (B)(C) Page 13 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.d WATER Version: 4/1/2024 Printed 7/10/2025 CED Permit #:240033-0208 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Clean Outs SS-1 1,150.00$ Each 1 1,150.00 Grease Interceptor, 500 gallon SS-2 9,200.00$ Each Grease Interceptor, 1000 gallon SS-3 11,500.00$ Each Grease Interceptor, 1500 gallon SS-4 17,200.00$ Each Side Sewer Pipe, PVC. 4 Inch Diameter SS-5 92.00$ LF Side Sewer Pipe, PP. 6 Inch Diameter SS-6 150.00$ LF 86 12,900.00 Sewer Pipe, PVC, 8 inch Diameter SS-7 120.00$ LF Sewer Pipe, PVC, 12 Inch Diameter SS-8 144.00$ LF Sewer Pipe, DI, 8 inch Diameter SS-9 130.00$ LF Sewer Pipe, DI, 12 Inch Diameter SS-10 150.00$ LF Manhole, 48 Inch Diameter SS-11 6,900.00$ Each Manhole, 54 Inch Diameter SS-13 6,800.00$ Each Manhole, 60 Inch Diameter SS-15 7,600.00$ Each Manhole, 72 Inch Diameter SS-17 10,600.00$ Each Manhole, 96 Inch Diameter SS-19 16,000.00$ Each Pipe, C-900, 12 Inch Diameter SS-21 205.00$ LF Outside Drop SS-24 1,700.00$ LS Inside Drop SS-25 1,150.00$ LS Sewer Pipe, PVC, ____ Inch Diameter SS-26 Lift Station (Entire System)SS-27 LS SANITARY SEWER SUBTOTAL:14,050.00 SALES TAX @ 10.3%1,447.15 SANITARY SEWER TOTAL:15,497.15 (B) (C) (D) (E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR SANITARY SEWER Quantity Remaining (Bond Reduction) (B)(C) Page 14 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.e SANITARY SEWER Version: 4/1/2024 Printed 7/10/2025 1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200 Date: Name: Project Name: PE Registration No: CED Plan # (LUA): Firm Name:CED Permit # (C): Firm Address: Site Address: Phone No. Parcel #(s): Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a) Existing Right-of-Way Improvements Subtotal (b) (b)148,539.36$ Future Public Improvements Subtotal (c)-$ Stormwater & Drainage Facilities (Public & Private) Subtotal (d) (d)1,232,975.31$ (e) (f) Site Restoration Existing Right-of-Way and Storm Drainage Improvements Maintenance Bond 276,302.93$ Bond Reduction 2 Construction Permit Bond Amount 3 Minimum Bond Amount is $10,000.00 1 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering. 2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% will cover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering. * Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton. ** Note: All prices include labor, equipment, materials, overhead, profit, and taxes. (206) 426-2600 alan@jacobsonengineers.com Hazen High School Improvements 1101 Hoquiam Ave NE, Renton WA, 98059 1023059057, 1023059072, 1023059201, 1023059278, 1023059292, 1023059084, 1023059277, & 1023059094 FOR APPROVAL 240033-0208 255 S King ST, Suite 800, Seattle, WA 98104 1,558,621.23$ P (a) x 100% SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS 7/11/2025 Alan Jacobson 43667 Jacobson Consulting Engineers R ((b x 150%) + (d x 100%)) S (e) x 150% + (f) x 100% Bond Reduction: Existing Right-of-Way Improvements (Quantity Remaining)2 Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2 T (P +R - S) Prepared by: Project Information CONSTRUCTION BOND AMOUNT */** (prior to permit issuance) EST1 ((b) + (c) + (d)) x 20% -$ MAINTENANCE BOND */** (after final acceptance of construction) 102,836.88$ 148,539.36$ 1,455,784.35$ 102,836.88$ -$ 1,232,975.31$ -$ Page 15 of 15 Ref 8-H Bond Quantity Worksheet SECTION III. BOND WORKSHEET Version: 4/1/2024 Printed 7/10/2025 HAZEN HIGH SCHOOL IMPROVEMENTS 25 APPENDIX B STORMWATER CALCULATIONS ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 02/13/2025 1:45 PM Report Generation Date: 02/13/2025 1:45 PM ————————————————————————————————— Input File Name: 2024-08-19 Hazen HS Baseball TESC Sizing.fld Project Name: Hazen HS Analysis Title: TESC Sizing Comments: Baseball Basin ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 16 Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 3.750 3.750 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 3.750 3.750 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Forest, Flat 3.750 ---------------------------------------------- EROSION CONTROL SIZING - BASEBALL BASIN Subbasin Total 3.750 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Lawn, Flat 0.650 SIDEWALKS/FLAT 3.100 ---------------------------------------------- Subbasin Total 3.750 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 713.650 _____________________________________ Total: 713.650 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 83.780 _____________________________________ Total: 83.780 EROSION CONTROL SIZING - BASEBALL BASIN Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 4.517 ac-ft/year, Post Developed: 0.530 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 9.442E-02 2-Year 1.340 5-Year 0.149 5-Year 1.753 10-Year 0.185 10-Year 2.098 25-Year 0.255 25-Year 2.550 50-Year 0.280 50-Year 3.161 100-Year 0.303 100-Year 3.932 200-Year 0.449 200-Year 4.153 500-Year 0.645 500-Year 4.433 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals EROSION CONTROL SIZING - BASEBALL BASIN TESC Sediment Trap Sizing (BMP C240) - Baseball Field Total Site: Pervious Area Impervious Area Total Area 0.65 ac 3.10 ac 3.75 ac SA = FS (Q2 / VS ) SA = Surface Area (ft2) FS = Factor of Safety = 2 Q2 = 2-year, 24-hour storm flow rate (ft3/s) VS = Settling Velocity = 0.00096 ft/s Per MGS TESC Sizing Report: 2-year, 24-hour storm event Q2 = 1.34 ft3/s Surface Area Calculation: SA = 2 (1.34/ 0.00096) SA = 2,791 ft2 VR = SA * 3.5 ft minimum storage depth VR = 2,791 * 3.5 VR = 9,768 ft3 Storage Volume Required VR = 9,768 ft3 * (7.48 gal/ 1 ft3) VR = 73,067 Gallons Required Volume Provided: (4) 18,900 Gallon sediment storage tanks V = 4 * 18,900 V = 75,600 Gallons Provided ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.62 Program License Number: 201910001 Project Simulation Performed on: 08/19/2024 11:17 AM Report Generation Date: 08/19/2024 11:17 AM ————————————————————————————————— Input File Name: 2024-08-19 Hazen HS Softball TESC Sizing.fld Project Name: Hazen HS Analysis Title: TESC Sizing Comments: Softball Basin ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 16 Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.000 1.000 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.000 1.000 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Forest, Flat 1.000 ---------------------------------------------- EROSION CONTROL SIZING - SOFTBALL BASIN Subbasin Total 1.000 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 1.000 ---------------------------------------------- Subbasin Total 1.000 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 190.307 _____________________________________ Total: 190.307 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed EROSION CONTROL SIZING - SOFTBALL BASIN Average Recharge Per Year, (Number of Years= 158) Predeveloped: 1.204 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 2.518E-02 2-Year 0.410 5-Year 3.967E-02 5-Year 0.529 10-Year 4.935E-02 10-Year 0.623 25-Year 6.799E-02 25-Year 0.781 50-Year 7.465E-02 50-Year 0.935 100-Year 8.092E-02 100-Year 1.165 200-Year 0.120 200-Year 1.241 500-Year 0.172 500-Year 1.339 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals EROSION CONTROL SIZING - SOFTBALL BASIN TESC Sediment Trap Sizing (BMP C240) - Softball Field Total Site: Pervious Area Impervious Area Total Area 0 ac 1.0 ac 1.0 ac SA = FS (Q2 / VS ) SA = Surface Area (ft2) FS = Factor of Safety = 2 Q2 = 2-year, 24-hour storm flow rate (ft3/s) VS = Settling Velocity = 0.00096 ft/s Per MGS TESC Sizing Report: 2-year, 24-hour storm event Q2 = 0.41 ft3/s Surface Area Calculation: SA = 2 (0.41 / 0.00096) SA = 854 ft2 VR = SA * 3.5 ft minimum storage depth VR = 854 * 3.5 VR = 2,989 ft3 Storage Volume Required VR = 2,989 ft3 * (7.48 gal/ 1 ft3) VR = 22,362 Gallons Required Volume Provided: (2) 18,900 Gallon sediment storage tanks V = 2 * 18,900 V = 37,800 Gallons Provided ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 02/20/2025 3:13 PM Report Generation Date: 02/20/2025 5:50 PM ————————————————————————————————— Input File Name: 2025-02-20 Hazen Detention Sizing Baseball Modular Vault.fld Project Name: Hazen HS Analysis Title: Detention Sizing - Baseball Comments: StormTrap Precast Vault ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 16 Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 2.808 2.808 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.808 2.808 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- C, Forest, Flat 2.360 ---------------------------------------------- DETENTION SIZING - BASEBALL FIELD Subbasin Total 2.360 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- C, Lawn, Flat 0.097 C, Lawn, Mod 0.146 C, Lawn, Steep 0.076 SIDEWALKS/FLAT 0.113 SIDEWALKS/MOD 0.016 ---------------------------------------------- Subbasin Total 0.448 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 2.360 ---------------------------------------------- Subbasin Total 2.360 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- C, Lawn, Flat 0.097 C, Lawn, Mod 0.146 C, Lawn, Steep 0.076 SIDEWALKS/FLAT 0.113 SIDEWALKS/MOD 0.016 ---------------------------------------------- Subbasin Total 0.448 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: StormTrap Vault DETENTION SIZING - BASEBALL FIELD Link Type: Structure Downstream Link: None Prismatic Pond Option Used Pond Floor Elevation (ft) : 443.50 Riser Crest Elevation (ft) : 453.00 Max Pond Elevation (ft) : 453.50 Storage Depth (ft) : 9.50 Pond Bottom Length (ft) : 61.5 Pond Bottom Width (ft) : 77.0 Pond Side Slopes (ft/ft) : Z1= 0.00 Z2= 0.00 Z3= 0.00 Z4= 0.00 Bottom Area (sq-ft) : 4740. Area at Riser Crest El (sq-ft) : 4,740. (acres) : 0.109 Volume at Riser Crest (cu-ft) : 45,028. (ac-ft) : 1.034 Area at Max Elevation (sq-ft) : 4740. (acres) : 0.109 Vol at Max Elevation (cu-ft) : 47,398. (ac-ft) : 1.088 Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.040 Riser Crest Elevation : 453.00 ft Hydraulic Structure Geometry Number of Devices: 4 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 444.00 Diameter (in) : 1.00 Orientation : Horizontal Elbow : No ---Device Number 2 --- Device Type : Circular Orifice Control Elevation (ft) : 449.40 Diameter (in) : 0.87 Orientation : Horizontal Elbow : Yes ---Device Number 3 --- Device Type : Circular Orifice Control Elevation (ft) : 450.70 Diameter (in) : 0.75 Orientation : Horizontal DETENTION SIZING - BASEBALL FIELD Elbow : Yes --- Device Number 4 --- Device Type : Rectangular Weir that Intersects the Riser Top Invert Elevation (ft) : 451.70 Length (ft) : 0.040 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 Number of Links: 1 ********** Link: StormTrap Vault ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 446.650 1.11-Year 447.026 1.25-Year 447.409 2.00-Year 448.476 3.33-Year 449.311 5-Year 450.105 10-Year 451.501 25-Year 452.207 50-Year 452.575 100-Year 452.801 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Target Surfaces 449.123 Subbasin: Flow Through 40.752 Link: New Copy Lnk1 0.000 _____________________________________ Total: 489.876 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Target Surfaces 0.000 Subbasin: Flow Through 40.752 DETENTION SIZING - BASEBALL FIELD Link: StormTrap Vault 0.000 _____________________________________ Total: 40.752 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 3.100 ac-ft/year, Post Developed: 0.258 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** 2-Year Discharge Rate : 0.124 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.06 cfs Off-line Design Discharge Rate (91% Exceedance): 0.03 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 431.38 Inflow Volume Including PPT-Evap (ac-ft): 431.38 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 431.38 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: StormTrap Vault ********** Basic Wet Pond Volume (91% Exceedance): 12353. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 18529. cu-ft 2-Year Discharge Rate : 0.056 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.40 cfs Off-line Design Discharge Rate (91% Exceedance): 0.22 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1326.32 Inflow Volume Including PPT-Evap (ac-ft): 1326.32 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% DETENTION SIZING - BASEBALL FIELD Primary Outflow To Downstream System (ac-ft): 1326.15 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Copy Lnk1 Scenario Postdeveloped Compliance Link: StormTrap Vault *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.124 2-Year 5.646E-02 5-Year 0.190 5-Year 8.222E-02 10-Year 0.241 10-Year 0.114 25-Year 0.353 25-Year 0.165 50-Year 0.397 50-Year 0.220 100-Year 0.431 100-Year 0.259 200-Year 0.555 200-Year 0.377 500-Year 0.720 500-Year 0.536 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -38.9% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -24.7% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 1.1% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- DETENTION SIZING - BASEBALL FIELD WATER QUALITY DESIGN FLOW RATE ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 11/11/2024 6:00 PM Report Generation Date: 11/11/2024 6:00 PM ————————————————————————————————— Input File Name: 2024-11-04 Hazen Softball Detention Sizing MC3500.fld Project Name: Hazen HS Analysis Title: Detention Sizing - Softball Comments: MC3500 Chambers ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 16 Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.201 1.201 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.201 1.201 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- C, Forest, Flat 1.101 ---------------------------------------------- DETENTION SIZING - SOFTBALL FIELD Subbasin Total 1.101 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- C, Lawn, Flat 0.014 C, Lawn, Mod 0.001 SIDEWALKS/FLAT 0.085 ---------------------------------------------- Subbasin Total 0.100 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 1.101 ---------------------------------------------- Subbasin Total 1.101 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- C, Lawn, Flat 0.014 C, Lawn, Mod 0.001 SIDEWALKS/FLAT 0.085 ---------------------------------------------- Subbasin Total 0.100 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: MC 3500 Chambers Link Type: Structure Downstream Link: None User Specified Elevation Volume Table Used DETENTION SIZING - SOFTBALL FIELD Elevation (ft) Pond Volume (cu-ft) 470.50 0. 470.58 256. 470.67 511. 470.75 767. 470.83 1022. 470.92 1278. 471.00 1533. 471.08 1789. 471.17 2044. 471.25 2300. 471.33 2878. 471.42 3453. 471.50 4026. 471.58 4598. 471.67 5168. 471.75 5735. 471.83 6300. 471.92 6863. 472.00 7424. 472.08 7982. 472.17 8537. 472.25 9089. 472.33 9639. 472.42 10185. 472.50 10729. 472.58 11268. 472.67 11804. 472.75 12337. 472.83 12865. 472.92 13389. 473.00 13909. 473.08 14423. 473.17 14933. 473.25 15438. 473.33 15938. 473.42 16431. 473.50 16919. 473.58 17400. 473.67 17874. 473.75 18341. 473.83 18801. 473.92 19252. 474.00 19695. 474.08 20128. 474.17 20551. 474.25 20963. 474.33 21363. 474.42 21749. 474.50 22119. 474.58 22468. 474.67 22787. 474.75 23079. 474.83 23362. 474.92 23635. 475.00 23896. DETENTION SIZING - SOFTBALL FIELD 475.08 24152. 475.17 24407. 475.25 24663. 475.33 24918. 475.42 25174. 475.50 25429. 475.58 25685. 475.67 25940. 475.75 26196. 475.83 26451. 475.92 26707. 476.00 26962. Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.020 Riser Crest Elevation : 475.00 ft Hydraulic Structure Geometry Number of Devices: 3 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 471.36 Diameter (in) : 0.87 Orientation : Horizontal Elbow : No ---Device Number 2 --- Device Type : Circular Orifice Control Elevation (ft) : 472.98 Diameter (in) : 0.50 Orientation : Horizontal Elbow : Yes --- Device Number 3 --- Device Type : Rectangular Weir that Intersects the Riser Top Invert Elevation (ft) : 474.05 Length (ft) : 0.020 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 Number of Links: 1 DETENTION SIZING - SOFTBALL FIELD ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 Number of Links: 1 ********** Link: MC 3500 Chambers ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 472.248 1.11-Year 472.367 1.25-Year 472.493 2.00-Year 472.847 3.33-Year 473.147 5-Year 473.437 10-Year 474.026 25-Year 474.476 50-Year 474.645 100-Year 474.690 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Target Surfaces 209.528 Subbasin: Flow Through 1.933 Link: New Copy Lnk1 0.000 _____________________________________ Total: 211.461 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Target Surfaces 0.000 Subbasin: Flow Through 1.933 Link: MC 3500 Chambers 0.000 _____________________________________ Total: 1.933 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 1.338 ac-ft/year, Post Developed: 0.012 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 DETENTION SIZING - SOFTBALL FIELD ********** Link: New Copy Lnk1 ********** 2-Year Discharge Rate : 0.051 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.03 cfs Off-line Design Discharge Rate (91% Exceedance): 0.01 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 180.31 Inflow Volume Including PPT-Evap (ac-ft): 180.31 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 180.31 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: MC 3500 Chambers ********** Basic Wet Pond Volume (91% Exceedance): 5722. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 8583. cu-ft 2-Year Discharge Rate : 0.025 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.19 cfs Off-line Design Discharge Rate (91% Exceedance): 0.11 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 597.82 Inflow Volume Including PPT-Evap (ac-ft): 597.82 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 597.70 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Copy Lnk1 Scenario Postdeveloped Compliance Link: MC 3500 Chambers *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff DETENTION SIZING - SOFTBALL FIELD Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 5.128E-02 2-Year 2.491E-02 5-Year 7.617E-02 5-Year 3.372E-02 10-Year 9.624E-02 10-Year 3.984E-02 25-Year 0.126 25-Year 5.868E-02 50-Year 0.142 50-Year 6.967E-02 100-Year 0.156 100-Year 7.284E-02 200-Year 0.208 200-Year 0.116 500-Year 0.279 500-Year 0.173 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -0.1% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -0.1% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -53.8% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- DETENTION SIZING - SOFTBALL FIELD WATER QUALITY DESIGN FLOW RATE Project: Chamber Model - MC-3500 Units -Imperial Number of Chambers -152 Number of End Caps - 8 Voids in the stone (porosity) - 40 % Base of Stone Elevation - 469.50 ft Amount of Stone Above Chambers - 12 in Amount of Stone Below Chambers - 9 in Area of system - 8111 sf Min. Area - Height of System Incremental Single Chamber Incremental Single End Cap Incremental Chambers Incremental End Cap Incremental Stone Incremental Ch, EC and Stone Cumulative System Elevation (inches)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(feet) 66 0.00 0.00 0.00 0.00 270.37 270.37 27943.17 475.00 65 0.00 0.00 0.00 0.00 270.37 270.37 27672.80 474.92 64 0.00 0.00 0.00 0.00 270.37 270.37 27402.44 474.83 63 0.00 0.00 0.00 0.00 270.37 270.37 27132.07 474.75 62 0.00 0.00 0.00 0.00 270.37 270.37 26861.70 474.67 61 0.00 0.00 0.00 0.00 270.37 270.37 26591.34 474.58 60 0.00 0.00 0.00 0.00 270.37 270.37 26320.97 474.50 59 0.00 0.00 0.00 0.00 270.37 270.37 26050.60 474.42 58 0.00 0.00 0.00 0.00 270.37 270.37 25780.24 474.33 57 0.00 0.00 0.00 0.00 270.37 270.37 25509.87 474.25 56 0.00 0.00 0.00 0.00 270.37 270.37 25239.50 474.17 55 0.00 0.00 0.00 0.00 270.37 270.37 24969.14 474.08 54 0.06 0.00 8.83 0.00 266.84 275.66 24698.77 474.00 53 0.19 0.02 29.50 0.19 258.49 288.18 24423.11 473.92 52 0.29 0.04 44.68 0.30 252.37 297.36 24134.92 473.83 51 0.40 0.05 61.35 0.41 245.66 307.43 23837.57 473.75 50 0.69 0.07 104.45 0.54 228.37 333.36 23530.14 473.67 49 1.03 0.09 156.30 0.71 207.56 364.57 23196.78 473.58 48 1.25 0.11 189.93 0.86 194.05 384.84 22832.21 473.50 47 1.42 0.13 216.18 1.01 183.49 400.68 22447.37 473.42 46 1.57 0.14 239.12 1.16 174.26 414.53 22046.69 473.33 45 1.71 0.16 259.49 1.30 166.05 426.84 21632.16 473.25 44 1.83 0.18 277.93 1.45 158.61 438.00 21205.32 473.17 43 1.94 0.20 294.54 1.60 151.91 448.05 20767.32 473.08 42 2.04 0.22 310.21 1.75 145.59 457.54 20319.27 473.00 41 2.13 0.23 324.47 1.88 139.83 466.18 19861.73 472.92 40 2.22 0.25 338.08 2.00 134.33 474.42 19395.55 472.83 39 2.31 0.27 350.63 2.12 129.26 482.02 18921.13 472.75 38 2.38 0.28 362.49 2.24 124.48 489.20 18439.11 472.67 37 2.46 0.29 373.78 2.35 119.91 496.05 17949.91 472.58 36 2.53 0.31 384.28 2.46 115.67 502.41 17453.87 472.50 35 2.59 0.32 394.25 2.57 111.64 508.46 16951.45 472.42 34 2.66 0.33 403.72 2.68 107.81 514.20 16442.99 472.33 33 2.72 0.35 412.70 2.78 104.18 519.65 15928.79 472.25 32 2.77 0.36 421.24 2.88 100.72 524.84 15409.14 472.17 31 2.82 0.37 429.35 2.98 97.44 529.76 14884.30 472.08 30 2.88 0.38 437.07 3.07 94.31 534.45 14354.54 472.00 29 2.92 0.40 444.47 3.17 91.31 538.95 13820.09 471.92 28 2.97 0.41 451.42 3.26 88.49 543.18 13281.14 471.83 27 3.01 0.42 457.89 3.35 85.87 547.11 12737.96 471.75 26 3.05 0.43 464.10 3.44 83.35 550.89 12190.85 471.67 25 3.09 0.44 470.33 3.52 80.83 554.68 11639.96 471.58 24 3.13 0.45 475.84 3.61 78.59 558.04 11085.29 471.50 23 3.17 0.46 481.18 3.69 76.42 561.29 10527.25 471.42 22 3.20 0.47 486.32 3.77 74.33 564.42 9965.96 471.33 21 3.23 0.48 491.13 3.84 72.38 567.35 9401.55 471.25 20 3.26 0.49 495.73 3.91 70.51 570.16 8834.20 471.17 19 3.29 0.50 500.12 3.98 68.73 572.83 8264.04 471.08 18 3.32 0.51 504.33 4.05 67.01 575.40 7691.21 471.00 17 3.34 0.51 508.31 4.12 65.40 577.82 7115.82 470.92 16 3.37 0.52 512.03 4.18 63.88 580.09 6538.00 470.83 15 3.39 0.53 515.66 4.24 62.41 582.30 5957.91 470.75 14 3.41 0.54 519.01 4.29 61.05 584.35 5375.60 470.67 13 3.44 0.54 522.43 4.35 59.66 586.43 4791.25 470.58 12 3.46 0.55 525.57 4.40 58.38 588.35 4204.82 470.50 11 3.48 0.56 528.76 4.44 57.09 590.29 3616.48 470.42 10 3.51 0.59 532.77 4.76 55.35 592.89 3026.19 470.33 9 0.00 0.00 0.00 0.00 270.37 270.37 2433.30 470.25 8 0.00 0.00 0.00 0.00 270.37 270.37 2162.93 470.17 7 0.00 0.00 0.00 0.00 270.37 270.37 1892.57 470.08 6 0.00 0.00 0.00 0.00 270.37 270.37 1622.20 470.00 5 0.00 0.00 0.00 0.00 270.37 270.37 1351.83 469.92 4 0.00 0.00 0.00 0.00 270.37 270.37 1081.47 469.83 3 0.00 0.00 0.00 0.00 270.37 270.37 811.10 469.75 2 0.00 0.00 0.00 0.00 270.37 270.37 540.73 469.67 1 0.00 0.00 0.00 0.00 270.37 270.37 270.37 469.58 HAZEN HS - SOFTBALL 7665 sf min. area StormTech MC-3500 Cumulative Storage Volumes TOP OF LIVE STORAGE BOTTOM OF LIVE STORAGE Element From (Inlet) To (Outlet) Length Inlet Outlet Total Average Pipe Manning's Entrance Exit/Bend Peak Time of Max Travel Design Max Flow / Total Max Reported ID Node Node Invert Invert Drop Slope Diameter Roughness Losses Losses Flow Peak Flow Time Flow Design Flow Time Flow Condition Elevation Elevation or Height Flow Velocity Capacity Ratio Surcharged Depth Occurrence (ft) (ft) (ft) (ft) (%) (inches) (cfs) (days hh:mm) (ft/sec)(min) (cfs) (min) (ft) Pipe - (12) SD B1 SD B2 31.90 453.00 452.25 0.75 2.34 12 0.015 0.80 0.50 4.26 0 00:15 5.29 0.10 4.88 0.87 6.00 1.01 SURCHARGED Pipe - (12) (1) SD B2 Out-1Pipe - (12) (1) 10.86 452.25 452.00 0.25 2.34 12 0.015 0.50 0.50 4.26 0 00:15 5.30 0.03 4.88 0.87 0.00 1.01 Calculated Pipe - (13) Structure - (17) SD A1 20.09 444.00 444.00 0.00 0.00 12 0.015 0.50 0.60 0.42 0 00:00 1.76 0.19 1.43 0.29 0.00 0.34 Calculated Pipe - (14) SD A1 SD A2 11.83 444.00 443.76 0.24 2.04 12 0.015 0.60 0.50 0.93 0 00:00 3.25 0.06 4.56 0.20 0.00 0.51 Calculated Pipe - (14) (1) SD A2 SD A3 124.72 442.26 440.39 1.87 1.50 12 0.015 0.50 0.60 3.69 0 00:00 6.67 0.31 3.91 0.94 0.00 0.74 Calculated Pipe - (17) SD A4 Out-1Pipe - (17) 15.66 430.11 428.54 1.57 10.00 12 0.015 0.50 0.60 3.10 0 00:00 8.73 0.03 10.09 0.31 0.00 0.46 Calculated Pipe - (18) SD A3 SD A4 123.92 440.39 430.11 10.28 8.30 12 0.015 0.60 0.60 3.61 0 00:00 10.22 0.20 9.19 0.39 0.00 0.48 Calculated Pipe - (20) SD C3 SD C4 31.10 466.53 465.62 0.91 2.93 12 0.015 0.70 0.50 4.26 0 00:00 7.83 0.07 5.47 0.78 0.00 0.71 Calculated Pipe - (21) SD C4 Out-1Pipe - (21) 14.42 465.62 465.20 0.41 2.87 12 0.015 0.50 0.50 3.26 0 00:00 5.87 0.04 5.40 0.60 0.00 0.67 Calculated Pipe - (22) SDCO SD B1 444.39 459.60 453.34 6.26 1.41 8 0.015 0.50 0.80 0.35 0 00:15 2.51 2.95 1.25 0.28 0.00 0.45 Calculated Pipe - (7) Structure - (8) SD C1 30.39 470.36 470.36 0.00 0.00 12 0.015 0.50 0.60 0.07 0 01:08 1.08 0.47 1.43 0.05 0.00 0.14 Calculated Pipe - (8) SD C1 SD C2 9.86 470.36 469.87 0.49 4.99 12 0.015 0.60 0.50 0.25 0 00:00 2.70 0.06 7.13 0.03 0.00 0.07 Calculated Pipe - (8) (2) SD C2 SD C3 31.81 468.37 466.53 1.84 5.78 12 0.015 0.50 0.70 5.86 0 00:00 8.47 0.06 7.67 0.76 0.00 0.92 Calculated TABLE 4 - PIPE ANALYSISCONVEYANCE ANALYSIS Element Invert Boundary Flap Fixed Peak Peak Maximum Maximum ID Elevation Type Gate Water Inflow Lateral HGL Depth HGL Elevation Elevation Inflow Attained Attained (ft) (ft) (cfs) (cfs) (ft) (ft) Out-1Pipe - (12) (1) 452.00 FIXED NO 453.00 4.26 0.00 1.00 453.00 Out-1Pipe - (17) 428.54 FIXED NO 428.54 3.10 0.00 0.39 428.93 Out-1Pipe - (21) 465.20 FIXED NO 465.20 3.26 0.00 0.57 465.77 TABLE 5 - SITE OUTFALLSCONVEYANCE ANALYSIS Element Invert Ground/Rim Ground/Rim Initial Initial Surcharge Minimum Peak Peak Maximum Maximum Minimum Average Average Time of Time of Total Total ID Elevation (Max) (Max) Water Water Elevation Pipe Cover Inflow Lateral HGL HGL Freeboard HGL HGL Maximum Peak Flooded Time Elevation Offset Elevation Depth Inflow Elevation Depth Attained Elevation Depth HGL Flooding Volume Flooded Attained Attained Attained Attained Occurrence Occurrence (ft) (ft) (ft) (ft) (ft) (ft) (inches) (cfs) (cfs) (ft) (ft) (ft) (ft) (ft) (days hh:mm) (days hh:mm) (ac-inches) (minutes) SD A1 444.00 455.09 11.09 444.00 0.00 455.09 120.88 0.93 0.00 444.35 0.35 10.74 444.19 0.19 0 00:00 0 00:00 0.00 0.00 SD A2 442.26 455.54 13.28 444.86 2.60 455.54 129.25 0.44 0.00 444.80 2.54 10.75 442.45 0.19 0 00:00 0 00:00 0.00 0.00 SD A3 440.39 455.51 15.13 440.39 0.00 455.51 169.36 3.69 0.00 440.86 0.47 14.65 440.50 0.11 0 00:00 0 00:00 0.00 0.00 SD A4 430.11 434.84 4.73 430.11 0.00 434.84 44.66 3.61 0.00 430.65 0.54 4.19 430.23 0.12 0 00:00 0 00:00 0.00 0.00 SD B1 453.00 456.06 3.06 453.00 0.00 456.06 24.61 4.26 3.92 455.46 2.46 0.60 453.02 0.02 0 00:13 0 00:00 0.00 0.00 SD B2 452.25 456.03 3.78 452.25 0.00 456.03 33.17 4.26 0.00 453.77 1.52 2.26 453.01 0.76 0 00:13 0 00:00 0.00 0.00 SD C1 470.36 476.84 6.48 470.36 0.00 476.84 65.61 0.25 0.00 470.44 0.08 6.40 470.44 0.08 0 01:01 0 00:00 0.00 0.00 SD C2 468.37 476.56 8.19 470.97 2.60 476.56 68.14 0.07 0.00 470.92 2.55 5.64 468.44 0.07 0 00:00 0 00:00 0.00 0.00 SD C3 466.53 471.37 4.84 466.53 0.00 471.37 45.94 5.86 0.00 471.11 4.58 0.26 466.61 0.08 0 00:00 0 00:00 0.00 0.00 SD C4 465.62 468.61 2.99 465.62 0.00 468.61 23.76 4.26 0.00 466.44 0.82 2.17 465.70 0.08 0 00:00 0 00:00 0.00 0.00 SDCO 459.60 461.26 1.66 459.60 0.00 461.26 11.92 0.37 0.37 459.84 0.24 1.42 459.61 0.01 0 00:15 0 00:00 0.00 0.00 Structure - (17) 444.00 455.39 11.39 444.00 0.00 445.17 124.53 0.51 0.26 444.45 0.45 10.94 444.33 0.33 0 00:00 0 00:00 0.00 0.00 Structure - (8) 470.36 471.53 1.17 470.36 0.00 471.53 1.86 0.07 0.07 470.57 0.21 0.96 470.57 0.21 0 00:23 0 00:00 0.00 0.00 TABLE 6 - STRUCTURE ANALYSIS CONVEYANCE ANALYSIS Element Area Drainage Weighted Accumulated Total Peak Rainfall Time ID Node ID Runoff Precipitation Runoff Runoff Intensity of Coefficient Concentration (acres) (inches) (inches) (cfs) (inches/hr) (days hh:mm:ss) BASEBALL 0.45 SDCO 0.44 0.46 0.20 0.37 1.858 0 00:15:00 SDB1 2.34 SD B1 0.90 0.46 0.42 3.92 1.858 0 00:15:00 TABLE 7 - SUBBASIN SUMMARYCONVEYANCE ANALYSIS CONVEYANCE - DOWNSTREAM OF STORMTRAP VAULT CONVEYANCE - UPSTREAM OF STORMTRAP VAULT CONVEYANCE - DOWNSTREAM OF MC-3500 HAZEN HIGH SCHOOL IMPROVEMENTS 26 APPENDIX C STORMWATER POLLUTION PREVENTION PLAN (SWPPP) Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan (SWPPP) for Hazen High School Improvements Prepared for: Renton School District and Forma Construction Permittee / Owner Developer Operator / Contractor Renton School District Renton School District Forma Construction 1101 Hoquiam Avenue NE, Renton, WA, 98059 Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number Charlie Blankenship Forma Construction Cell: (206) 261-9124 SWPPP Prepared By Name Organization Contact Phone Number Sascha Eastman Jacobson Consulting Engineers Cell: (206) 293-9134 SWPPP Preparation Date 05 / 16 / 2025 Project Construction Dates Activity / Phase Start Date End Date Sitework and Building Construction April 2025 January 2029 Page | 1 Table of Contents 1.0 Project Information .......................................................................................................................... 4 1.1 Existing Conditions ......................................................................................................................... 4 1.2 Proposed Construction Activities .................................................................................................... 6 2.0 Construction Stormwater Best Management Practices (BMPs) ..................................................... 7 2.1 The 13 Elements ............................................................................................................................. 7 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits ........................................................... 7 2.1.2 Element 2: Establish Construction Access ............................................................................... 8 2.1.3 Element 3: Control Flow Rates ................................................................................................. 9 2.1.4 Element 4: Install Sediment Controls ...................................................................................... 10 2.1.5 Element 5: Stabilize Soils ........................................................................................................11 2.1.6 Element 6: Protect Slopes........................................................................................................12 2.1.7 Element 7: Protect Drain Inlets ................................................................................................13 2.1.8 Element 8: Stabilize Channels and Outlets .............................................................................14 2.1.9 Element 9: Control Pollutants ..................................................................................................15 2.1.10 Element 10: Control Dewatering .............................................................................................19 2.1.11 Element 11: Maintain BMPs ....................................................................................................20 2.1.12 Element 12: Manage the Project .............................................................................................21 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs ....................................................25 3.0 Pollution Prevention Team .............................................................................................................26 4.0 Monitoring and Sampling Requirements ........................................................................................27 4.1 Site Inspection ...............................................................................................................................27 4.2 Stormwater Quality Sampling ........................................................................................................27 4.2.1 Turbidity Sampling ..................................................................................................................27 4.2.2 pH Sampling ...........................................................................................................................29 5.0 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies ....................................30 5.1 303(d) Listed Waterbodies .............................................................................................................30 5.2 TMDL Waterbodies .......................................................................................................................30 6.0 Reporting and Record Keeping ......................................................................................................31 6.1 Record Keeping .............................................................................................................................31 6.1.1 Site Logbook ...........................................................................................................................31 6.1.2 Records Retention ..................................................................................................................31 6.1.3 Updating the SWPPP ..............................................................................................................31 6.2 Reporting .......................................................................................................................................32 6.2.1 Discharge Monitoring Reports .................................................................................................32 6.2.2 Notification of Noncompliance .................................................................................................32 Page | 2 List of Tables Table 1 – Summary of Site Pollutant Constituents ....................................................................... 5 Table 2 – Pollutants .....................................................................................................................15 Table 3 – pH-Modifying Sources .................................................................................................17 Table 4 – Dewatering BMPs ........................................................................................................19 Table 5 – Management ................................................................................................................21 Table 6 – BMP Implementation Schedule ....................................................................................23 Table 7 – Team Information .........................................................................................................26 Table 8 – Turbidity Sampling Method ..........................................................................................27 Table 9 – pH Sampling Method ...................................................................................................29 List of Appendices A. Site Map B. BMP Detail C. Correspondence – N/A D. Site Inspection Form E. Construction Stormwater General Permit (CSWGP) F. 303(d) List Waterbodies / TMDL Waterbodies Information – N/A G. Contaminated Site Information H. Engineering Calculations Page | 3 List of Acronyms and Abbreviations Acronym / Abbreviation Explanation 303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies BFO Bellingham Field Office of the Department of Ecology BMP(s) Best Management Practice(s) CESCL CMMP Certified Erosion and Sediment Control Lead Contaminated Media Management Plan CO2 Carbon Dioxide CRO Central Regional Office of the Department of Ecology CSWGP Construction Stormwater General Permit CWA Clean Water Act DMR Discharge Monitoring Report DO Dissolved Oxygen Ecology Washington State Department of Ecology EPA United States Environmental Protection Agency ERO Eastern Regional Office of the Department of Ecology ERTS Environmental Report Tracking System ESC Erosion and Sediment Control GULD General Use Level Designation NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Units NWRO Northwest Regional Office of the Department of Ecology pH Power of Hydrogen RCW Revised Code of Washington SPCC Spill Prevention, Control, and Countermeasure su Standard Units SWMMEW Stormwater Management Manual for Eastern Washington SWMMWW Stormwater Management Manual for Western Washington SWPPP Stormwater Pollution Prevention Plan TESC Temporary Erosion and Sediment Control SWRO Southwest Regional Office of the Department of Ecology TMDL Total Maximum Daily Load VFO Vancouver Field Office of the Department of Ecology WAC Washington Administrative Code WSDOT Washington Department of Transportation WWHM Western Washington Hydrology Model Page | 4 1.0 Project Information Project/Site Name: Hazen High School Street/Location: 1101 Hoquiam Ave NE City: Renton State: WA Zip code: 98059 Subdivision: N/A Receiving waterbody: Lower Cedar River 1.1 Existing Conditions Hazen High School is a developed campus that is polygon-shaped and consists of 29.28 acres. The area within the district’s property boundary includes eight parcels: parcel 1 (1023059057) 0.78 acres, parcel 2 (1023059072) 3.66 acres, parcel 3 (1023059201) 14.93 acres, parcel 4 (1023059278) 4.10 acres, parcel 5 (1023059292) 0.45 acres, parcel 6 (1023059084) 0.45 acres, parcel 7 (1023059277) 2.54 acres, parcel 8 (1023059094) 2.37 acres. The school consists of a single primary school building on the east side of the campus, parking and drive areas on all sides of the building, a baseball field to the west, a track and field to the southwest, a softball field and tennis courts directly south, and landscaping around the property perimeter and in the parking lots. The main building is surrounded by low landscaping and concrete sidewalks. Total acreage: 29.28-acres Disturbed acreage: 4.09-acres Landscape topography: In general, the site topography of Hazen High School around the proposed project work scope is relatively flat at roughly 1%-2% for the existing baseball and softball fields located on the west and south sides of the school’s campus. Drainage patterns: The school site consists of (3) three Threshold Discharge Areas. Proposed drainage from each TDA will continue to discharge to the same point of connection in the final condition. TDA #1 includes the existing baseball field, assumed to be underdrained and routed to a pond southwest of the field, which discharges via a dispersion trench toward Duvall Ave NE through native vegetation. Recent improvements to Duvall Ave NE include curb, gutter, sidewalk, water quality treatment, and a new 12” storm main. Proposed improvements will discharge stormwater runoff from the redeveloped areas, including a new underdrained synthetic turf baseball field (that is considered 100% impervious), into a new StormTrap detention system. Flow will then pass through a 54” Type II SDMH flow control structure, a Modular Wetland Water Quality system, and a 12” storm pipe before connecting to the existing storm main in Duvall Ave NE. TDA #2 Page | 5 covers the central site, including the grass play field north of the baseball field, parking lots to the west and south of the school, the rubberized track and grass field, and the grass softball field. Runoff flows south via a 12” storm pipe to the existing system in NE 10th St. The proposed synthetic softball field will have an underdrain system routed to a new StormTech detention system, then flow west to a 54” Type II SDMH flow control structure, a Modular Wetland Water Quality system, and a 12” storm pipe connecting to the existing 12” storm pipe leading to NE 10th St. TDA #3 includes parking areas north, east, and south of the school, the grass multipurpose field, and tennis courts, all connecting to the existing storm system in Hoquiam Ave NE at multiple locations. Redeveloped areas will use an existing connection to Hoquiam Ave NE for the new security vestibule and bollard installation. Existing Vegetation: The site is fully developed with a small pocket of native vegetation west of the existing baseball field. Critical Areas: No critical areas exist on the project parcel. List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: The project eventually discharges to the Duwamish River which is 303d listed impaired for water, sediment, and fish tissue. Table 1 below includes a list of suspected and/or known contaminants associated with the construction activity. Table 1 – Summary of Site Pollutant Constituents Constituent (Pollutant) Location Depth Concentration Oil and Grease Parking Lot Surface Typical concentration from parking lots Diesel Fuel Oil Near SE corner of Building east of parking lot 17-ft + below grade Below contamination limits for contamination from UST removed in August 2011 after site was retested in November 2011 Total Suspended Solids Buildings and Parking Lots Surface N/A pH Newly installed concrete areas Surface N/A Page | 6 1.2 Proposed Construction Activities Description of site development: Campus Improvements are proposed and will consist of replacing the existing baseball and softball fields with turf fields, installing detention systems with subdrainage to support the turf fields, installing a security vestibule at the main entrance to the school building, and installing geothermal wells at the location of the baseball field. The proposed improvements will include storm and electrical services. Description of construction activities (example: site preparation, demolition, excavation): The project will consist of site preparation, demolition, excavation for detention systems, and replacement paving. Description of site drainage including flow from and onto adjacent properties. Must be consistent with the Site Map in Appendix A: Stormwater will be discharged to three locations on site: The first along the west property line to Duvall Ave NE, the second at the south property line within NE 10th St, and the last along the east property line to Hoquiam Ave SE. Water will flow into a detention system, onsite flow control systems, and water quality treatment prior to connections to the existing municipal systems. The existing school is surrounded by single-family residences and established public right-of- way with drainage systems. Generally, the residences surrounding the site flow away from the school property, Therefore, there are no substantial areas of offsite flow entering the existing parcel. Description of final stabilization (example: extent of revegetation, paving, landscaping): At final stabilization, the project area located on the west, east, and south sides of the school’s campus will include new turf fields, new geothermal wells, a new security vestibule, and associated replaced paving. Contaminated Site Information: Proposed activities regarding contaminated soils or groundwater (example: on-site treatment system, authorized sanitary sewer discharge) - Contaminated soils were discovered in 2011 upon removal of a 12,000 gallon standard heating fuel oil UST located near the southeast corner of the site east of the parking lot and south of the boiler room; See Site Map in Appendix A. The area of suspected contamination was excavated and tested with lab results indicated no threshold contamination limits were reached (1,000 mg/kg of soil with 2,000 mg/kg being the threshold). Groundwater contamination was discovered at the time with samples being above the 500 ug/L level for MTCA Method A Cleanout. That said, approximately 442.66 tons of contaminated soil and 1,268 gallons of groundwater were removed from the site and properly disposed of off-site at a legal disposal facility (Waste Management). Reference “Hazen High School – Impacted Soil and Groundwater Technical Memorandum” in Appendix G. Page | 7 2.0 Construction Stormwater Best Management Practices (BMPs) The SWPPP is a living document reflecting current conditions and changes throughout the life of the project. These changes may be informal (i.e. handwritten notes and deletions). Update the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design. 2.1 The 13 Elements 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Trees that are to be preserved, as well as all sensitive areas and their buffers, if any, shall be clearly delineated, both in the field and on the plans. In general, natural vegetation and native topsoil shall be retained in an undisturbed state to the maximum extent possible. The BMPs relevant to marking the clearing limits that will be applied for this project include: List and describe BMPs: · Preserving Natural Vegetation (BMP C101) · High-Visibility Fence (BMP C103) Installation Schedules: BMP’s will be installed at the beginning of construction and be inspected and maintained throughout construction. Page | 8 2.1.2 Element 2: Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering state waters. All wash wastewater shall be controlled on site. The specific BMPs related to establishing construction access that will be used on this project include: List and describe BMPs: · Stabilized Construction Access (BMP C105) Installation Schedules: BMP’s will be installed at the beginning of construction and be inspected and maintained throughout construction. Page | 9 2.1.3 Element 3: Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. The specific BMPs for flow control that shall be used on this project include: Will you construct stormwater retention and/or detention facilities? Yes No Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? Yes No In order to protect the properties and waterways downstream of the project site, stormwater discharge from the site will be controlled. The specific BMPs for flow control that shall be used on this project include: · Project will install Straw Wattles and Catch Basin Filter Socks to slow down and control any construction stormwater from entering the existing downstream storm system: o Interceptor Dike and Swale (BMP C200) o Check Dams (BMP C207) o Storm Drain Inlet Protection (BMP C220) o Silt Fence (BMP C233) o Straw Wattles (BMP C235) o Temporary Water Storage Tanks for Sedimentation Installation Schedules: BMP’s will be installed at the beginning of construction and be inspected and maintained throughout construction until the site is fully stabilized, and permanent flow control facilities are functioning. Page | 10 2.1.4 Element 4: Install Sediment Controls All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged to an infiltration facility. Specific BMPs to be used for controlling sediment on this project include: List and describe BMPs: · Inlet Protection (BMP C220) · Silt Fence (BMP C233) · Straw Wattles (BMP C235) · Temporary Water Storage Tanks for Sedimentation See Appendix B – Construction BMPs for BMP details. In addition, sediment will be removed from paved areas in and adjacent to construction work areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on vehicle tires away from the site and to minimize wash-off of sediments from adjacent streets in runoff. Whenever possible, sediment laden water shall be discharged into on-site, level, vegetated areas. The following BMPs will be implemented as end-of-pipe sediment controls as required to meet permitted turbidity limits in the site discharge(s). Prior to the implementation of these technologies, sediment sources and erosion control, and soil stabilization BMP efforts will be maximized to reduce the need for end-of-pipe sedimentation controls. · Construction Stormwater Chemical Treatment (BMP C 250) (implemented only with prior written approval from Ecology) · Construction Stormwater Filtration (BMP C251) The above BMPs will ensure that the construction activities will not interfere with the movement of juvenile Salmonids attempting to enter off-channel areas or drainages. The above BMPs shall be installed at the beginning of construction and must be functional before other land disturbing activities – especially grading and filling – take place. Inspection and Maintenance Plan to be prepared by contractor in accordance with the BMP details from Volume II of the State of Washington Department of Ecology’s 2019 Stormwater Management Manual for Western Washington, found in Appendix B. The Responsible Staff for inspection and maintenance will be the operator/contractor. Page | 11 2.1.5 Element 5: Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project are listed below: List and describe BMPs: · Temporary and Permanent Seeding (BMP C120) · Mulching (BMP C121) · Plastic Covering (BMP C123) · Dust Control (BMP C140) West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Anticipated project dates: Start date: April 2025 End date: January 2029 Will you construct during the wet season? Yes No Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project include: · Plastic Covering (BMP C123) See Appendix B – Construction BMPs for BMP details. The project site is located west of the Cascade Mountain Crest. As such, no soil shall remain exposed and unworked for more than 7 days during the dry season (May 1 to September 30) and 2 days during the wet season (October 1 to April 30). Regardless of the time of year, all soil shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather forecasts. All stockpiled soil shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. Construction activities shall be scheduled in a way that limits the amount of time soil is exposed throughout the duration of the project. Page | 12 2.1.6 Element 6: Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion during construction. Will steep slopes be present at the site during construction? Yes No All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion. The following specific BMPs will be used to protect slopes for this project: · N/A; construction will not be occurring within sloped portions of the property. Page | 13 2.1.7 Element 7: Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment-laden runoff on and near the project site. All inlets will be inspected weekly at a minimum and daily during storm events. Inlet protection devices will be cleaned or replaced when sediment has reached 1/3 capacity or as specified by the product manufacturer. List and describe BMPs: · Interceptor Dike and Swale (BMP C200) · Check Dams (BMP C207) · Inlet Protection (BMP C220) · Silt Fence (BMP C233) · Straw Wattles (BMP C235) · Temporary Water Storage Tanks for Sedimentation Installation Schedules: BMP’s will be installed at the beginning of construction and be inspected and maintained throughout construction until the site is fully stabilized, and permanent flow control facilities are functioning. Inspection and Maintenance Plan to be prepared by contractor in accordance with the BMP details from Volume II of the State of Washington Department of Ecology’s 2019 Stormwater Management Manual for Western Washington, found in Appendix B. The Responsible Staff for inspection and maintenance will be the operator/contractor. Page | 14 2.1.8 Element 8: Stabilize Channels and Outlets Where site runoff is to be conveyed in channels or discharged to a stream or some other natural discharge point, efforts will be taken to prevent downstream erosion. There are no existing downstream channels or streams that the site will directly discharge stormwater runoff to, therefore no BMPs are proposed for Element 8. Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches, will be installed at the outlets of all conveyance systems. List and describe BMPs: · Inlet Protection (BMP C220) · Silt Fence (BMP C233) · Straw Wattles (BMP C235) Installation Schedules: BMP’s will be installed at the beginning of construction and be inspected and maintained throughout construction until site is fully stabilized, and permanent flow control facilities are functioning. Page | 15 2.1.9 Element 9: Control Pollutants The following pollutants are anticipated to be present on-site: Table 2 – Pollutants Pollutant (and source, if applicable) Vehicles and construction equipment Excavation: Excess Soil Demolition: Dust, Soil, Debris Concrete and grout Sanitary wastewater Solid Waste Ground Source Well Field Drilling: review for potential groundwater or soil contamination; follow CMMP if encountered All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. Vehicles, construction equipment, and/or petroleum product storage/dispensing: · All vehicles, equipment, and petroleum product storage/dispensing areas will be inspected regularly to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills. · On-site fueling tanks and petroleum product storage containers shall include secondary containment. · Spill prevention measures, such as drip pans, will be used when conducting maintenance and repair of vehicles or equipment. · In order to perform emergency repairs on site, temporary plastic will be placed beneath and additionally, if it is raining, over the vehicle. · Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Demolition: · Dust released from demolished sidewalks, buildings, or structures will be controlled using Dust Control measures (BMP C140). · Storm drain inlets vulnerable to stormwater discharge carrying dust, soil, or debris will be protected using Storm Drain Inlet Protection (BMP C220 as described above for Element 7). Page | 16 · Process water and slurry resulting from sawcutting and surfacing operations will be prevented from entering the waters of the State by implementing Sawcutting and Surfacing Pollution Prevention measures (BMP C152). Concrete and grout: · Process water and slurry resulting from concrete work will be prevented from entering the waters of the State by implementing Concrete Handling measures (BMP C151). Sanitary wastewater: · Portable sanitation facilities will be firmly secured, regularly maintained, and emptied when necessary. Solid Waste: · Solid waste will be stored in secure, clearly marked containers. Other: · A contingency plan, including dewatering if required, will be developed for inadvertent discovery of additional contaminated soil and/or groundwater on the site related to the contaminated soil and groundwater cleanup that required removal for a leaking 12,000 (1” hole on bottom) gallon fuel oil UST located in the SE corner of the south of the boiler room. Contingency plan or Contaminated Media Management Plan (CMMP) will be provided for the project by PBS Environmental as a standalone document that the contractor shall manage and keep on-site during construction to be administered as necessary to address any additional pollutant sources on site. Reference CMMP in Appendix G. List and describe BMPs: · Dust Control (BMP C140) · Materials on Hand (BMP C150) · Concrete Handling (BMP C151) · Sawcutting and Surfacing Pollution Prevention (BMP C152) · Material Delivery, Storage, and Containment (BMP C153) · Concrete Washout Area (BMP C154) Installation Schedules: BMP’s will be implemented at the beginning of construction and be inspected and maintained throughout construction until site is fully stabilized. Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? Yes No Page | 17 Will wheel wash or tire bath system BMPs be used during construction? Yes No List and describe BMPs: N/A; refer to CMMP in Appendix G for fuel oil contaminated soils or groundwater discovered in area of work. Installation Schedules: BMP’s will be installed at the beginning of construction and be inspected and maintained throughout construction until site is fully stabilized, and wheel wash is no longer needed. Will pH-modifying sources be present on-site? Yes No Table 3 – pH-Modifying Sources None X Bulk cement Cement kiln dust Fly ash X Other cementitious materials X New concrete washing or curing waters X Waste streams generated from concrete grinding and sawing Exposed aggregate processes Dewatering concrete vaults X Concrete pumping and mixer washout waters Recycled concrete Other (i.e. calcium lignosulfate) [please describe] Where pH-modifying sources may be encountered, steps must be taken to prevent pollutants from contaminating stormwater and raising the pH level above 8.5. The acceptable pH range for stormwater is between 6.5 and 8.5, beyond that, pH neutralization must occur. The specific BMPs for pH modification that shall be used in this project include: · High pH Neutralization Using CO2 (BMP C252). This BMP must be utilized as soon as a stormwater pH reaches higher than 8.5, which typically occurs when the aforementioned pH-modifying sources come into contact with stormwater. Inspection and Maintenance Plan to be prepared by contractor in accordance with the BMP details from Volume II of the State of Washington Department of Ecology’s 2019 Stormwater Management Manual for Western Washington, found in Appendix B. Page | 18 The Responsible Staff for inspection and maintenance will be the operator/contractor. Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas with appropriate BMPs installed. Will uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters? Yes No Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas with appropriate BMPs installed. · Materials on Hand (BMP C150) · Concrete Handling (BMP C151) · Sawcutting and Surfacing Pollution Prevention (BMP C152) · Material Delivery, Storage and Containment (BMP C153) · Concrete Washout Area (BMP C154) · Treating and Disposing of High pH Water (BMP C252) Installation Schedules: BMP’s will be implemented at the beginning of construction and be inspected and maintained throughout construction as required. Page | 19 2.1.10 Element 10: Control Dewatering This project does not propose dewatering and therefore will not be implementing any dewatering BMPs associated with Element 10, as groundwater discovering during construction is not anticipated. However, if groundwater is discovered and is contaminated with fuel oil, the contractor shall follow the CMMP for containment and cleanup procedures. Reference CMMP located in Appendix G. Table 4 – Dewatering BMPs Infiltration Transport off-site in a vehicle (vacuum truck for legal disposal) Ecology-approved on-site chemical treatment or other suitable treatment technologies Sanitary or combined sewer discharge with local sewer district approval (last resort) Use of sedimentation bag with discharge to ditch or swale (small volumes of localized dewatering) Follow CMMP if groundwater is discovered on-site and is contaminated with fuel oil List and describe BMPs: N/A Page | 20 2.1.11 Element 11: Maintain BMPs All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP specification (see Volume II of the SWMMWW or Chapter 7 of the SWMMEW). Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to once every calendar month. All temporary ESC BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal of either BMPs or vegetation shall be permanently stabilized. Additionally, protection must be provided for all BMPs installed for the permanent control of stormwater from sediment and compaction. BMPs that are to remain in place following completion of construction shall be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed, and the facility shall be returned to conditions specified in the construction documents. Page | 21 2.1.12 Element 12: Manage the Project The project will be managed based on the following principles: · Projects will be phased to the maximum extent practicable and seasonal work limitations will be taken into account. · Inspection and monitoring: o Inspection, maintenance and repair of all BMPs will occur as needed to ensure performance of their intended function. o Site inspections and monitoring will be conducted in accordance with Special Condition S4 of the CSWGP. Sampling locations are indicated on the Site Map. Sampling station(s) are located in accordance with applicable requirements of the CSWGP. · Maintain an updated SWPPP. o The SWPPP will be updated, maintained, and implemented in accordance with Special Conditions S3, S4, and S9 of the CSWGP. As site work progresses the SWPPP will be modified routinely to reflect changing site conditions. The SWPPP will be reviewed monthly to ensure the content is current. Table 5 – Management X Design the project to fit the existing topography, soils, and drainage patterns X Emphasize erosion control rather than sediment control X Minimize the extent and duration of the area exposed X Keep runoff velocities low X Retain sediment on-site X Thoroughly monitor site and maintain all ESC measures X Schedule major earthwork during the dry season X Follow CMMP for any soils or groundwater contaminated with fuel oil or other sources discovered onsite; reference CMMP in Appendix G. Other (please describe) As this project site is located west of the Cascade Mountain Crest, the project will be managed according to the following key project components: Phasing of Construction · The construction project is being phased to the extent practicable in order to prevent soil erosion, and, to the maximum extent possible, the transport of sediment from the site during construction. · Revegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities during each phase of construction, per the Scheduling BMP (C162). Page | 22 Seasonal Work Limitations · From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt-laden runoff will be prevented from leaving the site through a combination of the following: o Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters; and o Limitations on activities and the extent of disturbed areas; and o Proposed erosion and sediment control measures. · Based on the information provided and/or local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance. · The following activities are exempt from the seasonal clearing and grading limitations: o Routine maintenance and necessary repair of erosion and sediment control BMPs; o Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil; and Inspection and Monitoring · All BMPs shall be inspected, maintained, and repaired as needed to ensure continued performance of their intended function. Site inspections shall be conducted by a person who is knowledgeable in the principles and practices of erosion and sediment control. This person has the necessary skills to: o Assess the site conditions and construction activities that could impact the quality of stormwater, and o Assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. · A Certified Erosion and Sediment Control Lead shall be on-site or on-call at all times. · Whenever inspection and/or monitoring reveals that the BMPs identified in this SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or design changes shall be implemented as soon as possible; adhere to guidelines outlined in the CMMP for any soils or groundwater found to be contaminated with fuel oil or other pollutant sources discovered onsite. See Appendix B – Construction BMPs for BMP details. Inspection and Maintenance Plan to be prepared by contractor in accordance with the BMP details from Volume II of the State of Washington Department of Ecology’s 2019 Stormwater Management Manual for Western Washington, found in Appendix B. The Responsible Staff for inspection and maintenance will be the operator/contractor. Page | 23 Table 6 – BMP Implementation Schedule Phase of Construction Project Stormwater BMPs Date Wet/Dry Season [Insert construction activity] [Insert BMP] [MM/DD/YYYY] [Insert Season] Page | 24 Phase of Construction Project Stormwater BMPs Date Wet/Dry Season [Insert construction activity] [Insert BMP] [MM/DD/YYYY] [Insert Season] Page | 25 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs The project will be implementing BMP T5.13 for Post-Construction Soil Quality and Depth. To comply with the requirements of this BMP, the duff layer and native topsoil will be stockpiled and retained on site during grading activities to be reapplied for use in post-construction soils prior to planting. Existing vegetation or landscaped areas will be protected during construction (BMP C101 and C233). Topsoil will be imported as needed to meet BMP T5.13 requirements. Soil quality and depth will be established at the end of construction to prevent compaction from heavy machinery. Page | 26 3.0 Pollution Prevention Team Table 7 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) Charlie Blankenship Forma Construction CESCL #8052413 charlieb@formacc.com (206) 261-9124 Resident Engineer TBD Emergency Ecology Contact TBD Emergency Permittee/ Owner Contact Mike Cato Facilities Project Manager – Capital Planning & Construction Renton School District No. 403 michael.cato@rentonschools.us (425) 204-4473 (Office) (206) 643-2887 (Cell) Non-Emergency Owner Contact Mike Cato Facilities Project Manager – Capital Planning & Construction Renton School District No. 403 michael.cato@rentonschools.us (425) 204-4473 (Office) (206) 643-2887 (Cell) Monitoring Personnel TBD Ecology Regional Office Northwest Regional Office in Shoreline Contact: Amy Jankowiak amy.jankowiak@ecy.wa.gov (425) 429-4529 Page | 27 4.0 Monitoring and Sampling Requirements Monitoring includes visual inspection, sampling for water quality parameters of concern, and documentation of the inspection and sampling findings in a site logbook. A site logbook will be maintained for all on-site construction activities and will include: · A record of the implementation of the SWPPP and other permit requirements · Site inspections · Stormwater sampling data File a blank form under Appendix D. The site logbook must be maintained on-site within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See CSWGP Special Condition S8 and Section 5 of this template. Complete the following paragraph for sites that discharge to impaired waterbodies for fine sediment, turbidity, phosphorus, or pH: 4.1 Site Inspection Site inspections will be conducted at least once every calendar week and within 24 hours following any discharge from the site. For sites that are temporarily stabilized and inactive, the required frequency is reduced to once per calendar month. The discharge point(s) are indicated on the Site Map (see Appendix A) and in accordance with the applicable requirements of the CSWGP. 4.2 Stormwater Quality Sampling 4.2.1 Turbidity Sampling Requirements include a calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: Table 8 – Turbidity Sampling Method X Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size) The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency of less than 33 centimeters. Page | 28 If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater than 6 cm, the following steps will be conducted: 1. Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site logbook. If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will be conducted: 1. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) within 24 hours. https://www.ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue · Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima): (509) 575-2490 · Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400 · Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 · Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site logbook. 4. Continue to sample discharges daily until one of the following is true: · Turbidity is 25 NTU (or lower). · Transparency is 33 cm (or greater). · Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater. · The discharge stops or is eliminated. Page | 29 4.2.2 pH Sampling pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards poured concrete or recycled concrete over the life of the project). The use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD] or fly ash) also requires pH monitoring. For significant concrete work, pH sampling will start the first day concrete is poured and continue until it is cured, typically three (3) weeks after the last pour. For engineered soils and recycled concrete, pH sampling begins when engineered soils or recycled concrete are first exposed to precipitation and continues until the area is fully stabilized. If the measured pH is 8.5 or greater, the following measures will be taken: 1. Prevent high pH water from entering storm sewer systems or surface water. 2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate technology such as carbon dioxide (CO2) sparging (liquid or dry ice). 3. Written approval will be obtained from Ecology prior to the use of chemical treatment other than CO2 sparging or dry ice. Method for sampling pH: Table 9 – pH Sampling Method X pH meter pH test kit Wide range pH indicator paper Page | 30 5.0 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies 5.1 303(d) Listed Waterbodies Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? Yes No List the impairment(s): N/A List and describe BMPs: N/A 5.2 TMDL Waterbodies In order to protect the properties and waterways downstream of the project site and remain TMDL compliant, stormwater discharges from the site will be controlled. The specific BMPs for flow control that shall be used on this project include: · Storm Drain Inlet Protection (BMP C220) · Straw Wattles (BMP C235) In general, discharge rates of stormwater from the site will be controlled where increases in impervious area or soil compaction during construction could lead to downstream erosion, or where necessary to meet local agency stormwater discharge requirements. The Straw Wattles and Catch Basin Filter Socks shall be installed at the beginning of construction activities prior to significant excavation and grading work to ensure the protection of properties downstream to the maximum extent possible. These BMPs shall be inspected to ensure they are functioning properly before constructing site improvements. Inspection and Maintenance Plan to be prepared by contractor in accordance with Volume II of the State of Washington Department of Ecology’s 2019 Stormwater Management Manual for Western Washington, found in Appendix B. The Responsible Staff for inspection and maintenance will be the operator/contractor. Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point of discharge. NOTE: A Construction Stormwater General Permit (CSWGP) is required for this project as it will disturb more than 1.0 acres of land and will be included in Appendix F. Page | 31 6.0 Reporting and Record Keeping 6.1 Record Keeping 6.1.1 Site Logbook A site logbook will be maintained for all on-site construction activities and will include: · A record of the implementation of the SWPPP and other permit requirements · Site inspections · Sample logs 6.1.2 Records Retention Records will be retained during the life of the project and for a minimum of three (3) years following the termination of permit coverage in accordance with Special Condition S5.C of the CSWGP. Permit documentation to be retained on-site: · CSWGP · Permit Coverage Letter · SWPPP · Site Logbook Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP. 6.1.3 Updating the SWPPP The SWPPP will be modified if: · Found ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. · There is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine additional or modified BMPs are necessary for compliance. An updated timeline for BMP implementation will be prepared. Page | 32 6.2 Reporting 6.2.1 Discharge Monitoring Reports Cumulative soil disturbance is one (1) acre or larger; therefore, Discharge Monitoring Reports (DMRs) will be submitted to Ecology monthly. If there was no discharge during a given monitoring period the DMR will be submitted as required, reporting “No Discharge”. The DMR due date is fifteen (15) days following the end of each calendar month. DMRs will be reported online through Ecology’s WQWebDMR System. 6.2.2 Notification of Noncompliance If any of the terms and conditions of the permit are not met, and the resulting noncompliance may cause a threat to human health or the environment, the following actions will be taken: 1. Ecology will be notified within 24-hours of the failure to comply by calling the applicable regional office ERTS phone number (Regional office numbers listed below). 2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or correct the noncompliance. If applicable, sampling and analysis of any noncompliance will be repeated immediately, and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3. A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days unless requested earlier by Ecology. Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6 cm or less, the Ecology Regional office will be notified by phone within 24 hours of analysis as required by Special Condition S5.A of the CSWGP. · Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit, Snohomish, or Whatcom County Include the following information: 1. Your name and / Phone number 2. Permit number 3. City / County of project 4. Sample results 5. Date / Time of call 6. Date / Time of sample 7. Project name In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH water. Page | 33 Appendix/Glossary A. Site Map B. BMP Detail C. Correspondence – N/A D. Site Inspection Form E. Construction Stormwater General Permit (CSWGP) F. 303(d) List Waterbodies / TMDL Waterbodies Information – N/A G. Contaminated Site Information H. Engineering Calculations Page | 34 Appendix A – Site Map Vicinity Map Temporary Erosion and Sediment Control (TESC) Plans TESC Details Forma Construction Site Logistics Plans APPENDIX A - VICINITY MAP SCALE: NTS PROJECT SITES PROJECT SITE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE ORIGINAL FUEL OIL UST REPLACED WITH NEW DIESEL FUEL UST IN 2011 AFTER LEAK DETECTED AND SOILS AND GROUNDWATER CONTAMINATION DETECTED IN AREA AROUND UST LOCATION OF STORMWATER DISCHARGE OFF-SITE AND CONSTRUCTION SITE RUNOFF WATER QUALITY SAMPLING STATION LOCATION OF STORMWATER DISCHARGE OFF-SITE AND CONSTRUCTION SITE RUNOFF WATER QUALITY SAMPLING STATION APPROXIMATE LOCATION OF DEWATERING TANKS APPROXIMATE LOCATION OF DEWATERING TANKS NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE B-3 B-2 WSW1-8 B-1 SP-2 SP-1 NSW1-8 ESW1-8 SSW1-8 BOT-10 SEPT 2011 SAMPLE LOCATION xxx1-8 NOV 2011 BORING LOCATION UST LOCATION B-x B-3 B-2 WSW1-8 B-1 SP-2 SP-1 NSW1-8 ESW1-8 SSW1-8 BOT-10 NOT TO SCALE Note: Sample/Boring locations are approximated from PBS Environmental "Hazen High School - Impacted Soil and Groundwater Technical Memorandum" dated April 1, 2025. NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE NOTE: SHEET HAS BEEN PRINTED TO BE 11X17 AND NOT TO SCALE Page | 35 Appendix B – BMP Details Preserving Natural Vegetation (BMP C101) High-Visibility Fence (BMP C103) Stabilized Construction Access (BMP C105) Temporary and Permanent Seeding (BMP C120) Mulching (BMP C121) Plastic Covering (BMP C123) Dust Control (BMP C140) Materials on Hand (BMP C150) Concrete Handling (BMP C151) Sawcutting and Surfacing Pollution Prevention (BMP C152) Material Delivery, Storage and Containment (BMP C153) Concrete Washout Area (BMP C154) Certified Erosion and Sediment Control Lead (BMP C160) Scheduling (BMP C162) Storm Drain Inlet Protection (BMP C220) Silt Fence (BMP C233) Straw Wattles (BMP C235) Construction Stormwater Chemical Treatment (BMP C250) Construction Stormwater Filtration (BMP C251) High pH Neutralization Using CO2 (BMP C252) BMP C101: Preserving Natural Vegetation Purpose The purpose of preserving natural vegetation is to reduce erosion wherever practicable. Limiting site disturbance is the single most effective method for reducing erosion. For example, conifers can hold up to about 50 percent of all rain that falls during a storm. Up to 20-30 percent of this rain may never reach the ground but is taken up by the tree or evaporates. Another benefit is that the rain held in the tree can be released slowly to the ground after the storm. Conditions of Use Natural vegetation should be preserved on steep slopes, near perennial and intermittent water- courses or swales, and on building sites in wooded areas. l As required by local governments. l Phase construction to preserve natural vegetation on the project site for as long as possible during the construction period. Design and Installation Specifications Natural vegetation can be preserved in natural clumps or as individual trees, shrubs and vines. The preservation of individual plants is more difficult because heavy equipment is generally used to remove unwanted vegetation. The points to remember when attempting to save individual plants are: l Is the plant worth saving? Consider the location, species, size, age, vigor, and the work involved. Local governments may also have ordinances to save natural vegetation and trees. l Fence or clearly mark areas around trees that are to be saved. It is preferable to keep ground disturbance away from the trees at least as far out as the dripline. Plants need protection from three kinds of injuries: l Construction Equipment - This injury can be above or below the ground level. Damage results from scarring, cutting of roots, and compaction of the soil. Placing a fenced buffer zone around plants to be saved prior to construction can prevent construction equipment injuries. l Grade Changes - Changing the natural ground level will alter grades, which affects the plant's ability to obtain the necessary air, water, and minerals. Minor fills usually do not cause prob- lems although sensitivity between species does vary and should be checked. Trees can typ- ically tolerate fill of 6 inches or less. For shrubs and other plants, the fill should be less. When there are major changes in grade, it may become necessary to supply air to the roots of plants. This can be done by placing a layer of gravel and a tile system over the roots before the fill is made. The tile system should be laid out on the original grade leading from a dry well 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 271 around the tree trunk. The system should then be covered with small stones to allow air to cir- culate over the root area. Lowering the natural ground level can seriously damage trees and shrubs. The highest per- centage of the plant roots are in the upper 12 inches of the soil and cuts of only 2-3 inches can cause serious injury. To protect the roots it may be necessary to terrace the immediate area around the plants to be saved. If roots are exposed, construction of retaining walls may be needed to keep the soil in place. Plants can also be preserved by leaving them on an undis- turbed, gently sloping mound. To increase the chances for survival, it is best to limit grade changes and other soil disturbances to areas outside the dripline of the plant. l Excavations - Protect trees and other plants when excavating for drainfields, power, water, and sewer lines. Where possible, the trenches should be routed around trees and large shrubs. When this is not possible, it is best to tunnel under them. This can be done with hand tools or with power augers. If it is not possible to route the trench around plants to be saved, then the following should be observed: o Cut as few roots as possible. When you have to cut, cut clean. Paint cut root ends with a wood dressing like asphalt base paint if roots will be exposed for more than 24-hours. o Backfill the trench as soon as possible. o Tunnel beneath root systems as close to the center of the main trunk to preserve most of the important feeder roots. Some problems that can be encountered with a few specific trees are: l Maple, Dogwood, Red alder, Western hemlock, Western red cedar, and Douglas fir do not readily adjust to changes in environment and special care should be taken to protect these trees. l The windthrow hazard of Pacific silver fir and madrona is high, while that of Western hemlock is moderate. The danger of windthrow increases where dense stands have been thinned. Other species (unless they are on shallow, wet soils less than 20 inches deep) have a low windthrow hazard. l Cottonwoods, maples, and willows have water-seeking roots. These can cause trouble in sewer lines and infiltration fields. On the other hand, they thrive in high moisture conditions that other trees would not. l Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, Sitka spruce, Western red cedar, Western hemlock, Pacific dogwood, and Red alder can cause ser- ious disease problems. Disease can become established through damaged limbs, trunks, roots, and freshly cut stumps. Diseased and weakened trees are also susceptible to insect attack. Maintenance Standards Inspect flagged and/or fenced areas regularly to make sure flagging or fencing has not been removed or damaged. If the flagging or fencing has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 272 If tree roots have been exposed or injured, “prune” cleanly with an appropriate pruning saw or lop- pers directly above the damaged roots and recover with native soils. Treatment of sap flowing trees (fir, hemlock, pine, soft maples) is not advised as sap forms a natural healing barrier. BMP C102: Buffer Zones Purpose Creation of an undisturbed area or strip of natural vegetation or an established suitable planting that will provide a living filter to reduce soil erosion and stormwater runoff velocities. Conditions of Use Buffer zones are used along streams, wetlands and other bodies of water that need protection from erosion and sedimentation. Contractors can use vegetative buffer zone BMPs to protect natural swales and they can incorporate them into the natural landscaping of an area. Do not use critical-areas buffer zones as sediment treatment areas. These areas shall remain com- pletely undisturbed. The local permitting authority may expand the buffer widths temporarily to allow the use of the expanded area for removal of sediment. The types of buffer zones can change the level of protection required as shown below: Designated Critical Area Buffers - buffers that protect Critical Areas, as defined by the Washington State Growth Management Act, and are established and managed by the local permitting authority. These should not be disturbed and must protected with sediment control BMPs to prevent impacts. The local permitting authority may expand the buffer widths temporarily to allow the use of the expan- ded area for removal of sediment. Vegetative Buffer Zones - areas that may be identified in undisturbed vegetation areas or managed vegetation areas that are outside any Designated Critical Area Buffer. They may be utilized to provide an additional sediment control area and/or reduce runoff velocities. If being used for pre- servation of natural vegetation, they should be arranged in clumps or strips. They can be used to pro- tect natural swales and incorporated into the natural landscaping area. Design and Installation Specifications l Preserving natural vegetation or plantings in clumps, blocks, or strips is generally the easiest and most successful method. l Leave all unstable steep slopes in natural vegetation. l Mark clearing limits and keep all equipment and construction debris out of the natural areas and buffer zones. Steel construction fencing is the most effective method to protect sensitive areas and buffers. Alternatively, wire-backed silt fence on steel posts is marginally effective. Flagging alone is typically not effective. l Keep all excavations outside the dripline of trees and shrubs. l Do not push debris or extra soil into the buffer zone area because it will cause damage by 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 273 N/A burying and smothering vegetation. l Vegetative buffer zones for streams, lakes or other waterways shall be established by the local permitting authority or other state or federal permits or approvals. Maintenance Standards Inspect the area frequently to make sure flagging remains in place and the area remains undis- turbed. Replace all damaged flagging immediately. Remove all materials located in the buffer area that may impede the ability of the vegetation to act as a filter. BMP C103: High-Visibility Fence Purpose High-visibility fencing is intended to: l Restrict clearing to approved limits. l Prevent disturbance of sensitive areas, their buffers, and other areas required to be left undis- turbed. l Limit construction traffic to designated construction entrances, exits, or internal roads. l Protect areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits plastic, fabric, or metal fence may be used: l At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared. l As necessary to control vehicle access to and on the site. Design and Installation Specifications High-visibility plastic fence shall be composed of a high-density polyethylene material and shall be at least four feet in height. Posts for the fencing shall be steel or wood and placed every 6 feet on center (maximum) or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope shall be used as a top stringer to prevent sagging between posts. The fence color shall be high-visibility orange. The fence tensile strength shall be 360 lbs/ft using the ASTM D4595 testing method. If appropriate install fabric silt fence in accordance with BMP C233: Silt Fence to act as high-visibility fence. Silt fence shall be at least 3 feet high and must be highly visible to meet the requirements of this BMP. Metal fences shall be designed and installed according to the manufacturer's specifications. Metal fences shall be at least 3 feet high and must be highly visible. Fences shall not be wired or stapled to trees. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 274 Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. BMP C105: Stabilized Construction Access Purpose Stabilized construction accesses are established to reduce the amount of sediment transported onto paved roads outside the project site by vehicles or equipment. This is done by constructing a sta- bilized pad of quarry spalls at entrances and exits for project sites. Conditions of Use Construction accesses shall be stabilized wherever traffic will be entering or leaving a construction site if paved roads or other paved areas are within 1,000 feet of the site. For residential subdivision construction sites, provide a stabilized construction access for each res- idence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient length/width to provide vehicle access/parking, based on lot size and configuration. On large commercial, highway, and road projects, the designer should include enough extra mater- ials in the contract to allow for additional stabilized accesses not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and Installation Specifications See Figure II-3.1: Stabilized Construction Access for details. Note: the 100’ minimum length of the access shall be reduced to the maximum practicable size when the size or configuration of the site does not allow the full length (100’). Construct stabilized construction accesses with a 12-inch thick pad of 4-inch to 8-inch quarry spalls, a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed con- crete, cement, or calcium chloride for construction access stabilization because these products raise pH levels in stormwater and concrete discharge to waters of the State is prohibited. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the standards listed in Table II-3.2: Stabilized Con- struction Access Geotextile Standards. Geotextile Property Required Value Grab Tensile Strength (ASTM D4751)200 psi min. Table II-3.2: Stabilized Construction Access Geotextile Standards 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 275 Geotextile Property Required Value Grab Tensile Elongation (ASTM D4632)30% max. Mullen Burst Strength (ASTM D3786-80a)400 psi min. AOS (ASTM D4751)20-45 (U.S. standard sieve size) Table II-3.2: Stabilized Construction Access Geotextile Standards (continued) l Consider early installation of the first lift of asphalt in areas that will be paved; this can be used as a stabilized access. Also consider the installation of excess concrete as a stabilized access. During large concrete pours, excess concrete is often available for this purpose. l Fencing (see BMP C103: High-Visibility Fence) shall be installed as necessary to restrict traffic to the construction access. l Whenever possible, the access shall be constructed on a firm, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. l Construction accesses should avoid crossing existing sidewalks and back of walk drains if at all possible. If a construction access must cross a sidewalk or back of walk drain, the full length of the sidewalk and back of walk drain must be covered and protected from sediment leaving the site. Alternative Material Specification WSDOT has raised safety concerns about the Quarry Spall rock specified above. WSDOT observes that the 4-inch to 8-inch rock sizes can become trapped between Dually truck tires, and then released off-site at highway speeds. WSDOT has chosen to use a modified specification for the rock while continuously verifying that the Stabilized Construction Access remains effective. To remain effective, the BMP must prevent sediment from migrating off site. To date, there has been no per- formance testing to verify operation of this new specification. Jurisdictions may use the alternative specification, but must perform increased off-site inspection if they use, or allow others to use, it. Stabilized Construction Accesses may use material that meets the requirements of WSDOT's Stand- ard Specifications for Road, Bridge, and Municipal Construction Section 9-03.9(1) (WSDOT, 2016) for ballast except for the following special requirements. The grading and quality requirements are listed in Table II-3.3: Stabilized Construction Access Alternative Material Requirements. Sieve Size Percent Passing 2½″99-100 Table II-3.3: Stabilized Construction Access Alternative Material Requirements 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 276 Sieve Size Percent Passing 2″65-100 ¾″40-80 No. 4 5 max. No. 100 0-2 % Fracture 75 min. Table II-3.3: Stabilized Construction Access Alternative Material Requirements (continued) l All percentages are by weight. l The sand equivalent value and dust ratio requirements do not apply. l The fracture requirement shall be at least one fractured face and will apply the combined aggregate retained on the No. 4 sieve in accordance with FOP for AASHTO T 335. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the specifications. l If the access is not preventing sediment from being tracked onto pavement, then alternative measures to keep the streets free of sediment shall be used. This may include replace- ment/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of the access, or the installation of BMP C106: Wheel Wash. l Any sediment that is tracked onto pavement shall be removed by shoveling or street sweep- ing. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is inef- fective and there is a threat to public safety. If it is necessary to wash the streets, the con- struction of a small sump to contain the wash water shall be considered. The sediment would then be washed into the sump where it can be controlled. l Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high effi- ciency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches. l Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. l If vehicles are entering or exiting the site at points other than the construction access(es), BMP C103: High-Visibility Fence shall be installed to control traffic. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 277 l Upon project completion and site stabilization, all construction accesses intended as per- manent access for maintenance shall be permanently stabilized. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 278 Figure II-3.1: Stabilized Construction Access 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 279 Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. Following construction, these areas shall be restored to pre-construction condition or better to pre- vent future erosion. Perform street cleaning at the end of each day or more often if necessary. BMP C120: Temporary and Permanent Seeding Purpose Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1. Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. Between October 1 and March 30 seeding requires a cover of mulch or an erosion control blanket until 75 percent grass cover is established. Review all disturbed areas in late August to early September and complete all seeding by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average pro- tection. Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding. See BMP C121: Mulching for specifications. Seed and mulch all disturbed areas not otherwise vegetated at final site stabilization. Final sta- bilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent erosion. See BMP T5.13: Post-Construction Soil Quality and Depth. Design and Installation Specifications General l Install channels intended for vegetation before starting major earthwork and hydroseed with a Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control blankets over the top of hydroseed. Before allowing water to flow in vegetated channels, establish 75 percent vegetation cover. If vegetated channels cannot be established by seed 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 284 before water flow; install sod in the channel bottom — over top of hydromulch and erosion con- trol blankets. l Confirm the installation of all required surface water control measures to prevent seed from washing away. l Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 per- cent tackifier. See BMP C121: Mulching for specifications. l Areas that will have seeding only and not landscaping may need compost or meal-based mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on the disturbed soil surface before application. See BMP T5.13: Post-Construction Soil Quality and Depth. l When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up in contact with the soil surface. This reduces the ability to establish a good stand of grass quickly. To overcome this, consider increasing seed quantities by up to 50 percent. l Enhance vegetation establishment by dividing the hydromulch operation into two phases: o Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in the first lift. o Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by: o Installing the mulch, seed, fertilizer, and tackifier in one lift. o Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per acre. o Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance vegetative establishment. The increased cost may be offset by the reduced need for: o Irrigation. o Reapplication of mulch. o Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and Bon- ded Fiber Matrix/ Mechanically Bonded Fiber Matrix (BFM/MBFMs) (3,000 pounds per acre minimum). l Seed may be installed by hand if: o Temporary and covered by straw, mulch, or topsoil. o Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or erosion blankets. l The seed mixes listed in Table II-3.4: Temporary and Permanent Seed Mixes include 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 285 recommended mixes for both temporary and permanent seeding. l Apply these mixes, with the exception of the wet area seed mix, at a rate of 120 pounds per acre. This rate can be reduced if soil amendments or slow-release fertilizers are used. Apply the wet area seed mix at a rate of 60 pounds per acre. l Consult the local suppliers or the local conservation district for their recommendations. The appropriate mix depends on a variety of factors, including location, exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by the local authority may be used, depending on the soil type and hydrology of the area. Common Name Latin Name % Weight % Purity % Germination Temporary Erosion Control Seed Mix A standard mix for areas requiring a temporary vegetative cover. Chewings or annual blue grass Festuca rubra var. commutata or Poa anna 40 98 90 Perennial rye Lolium perenne 50 98 90 Redtop or colonial bentgrass Agrostis alba or Agrostis tenuis 5 92 85 White dutch clover Trifolium repens 5 98 90 Landscaping Seed Mix A recommended mix for landscaping seed. Perennial rye blend Lolium perenne 70 98 90 Chewings and red fescue blend Festuca rubra var. commutata or Fes- tuca rubra 30 98 90 Low-Growing Turf Seed Mix A turf seed mix for dry situations where there is no need for watering. This mix requires very little main- tenance. Dwarf tall fescue (several varieties) Festuca arundin- acea var. 45 98 90 Dwarf perennial rye (Barclay) Lolium perenne var. barclay 30 98 90 Red fescue Festuca rubra 20 98 90 Colonial bentgrass Agrostis tenuis 5 98 90 Bioswale Seed Mix A seed mix for bioswales and other intermittently wet areas. Tall or meadow fes-Festuca arundin-75-80 98 90 Table II-3.4: Temporary and Permanent Seed Mixes 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 286 Common Name Latin Name % Weight % Purity % Germination cue acea or Festuca elatior Seaside/Creeping bentgrass Agrostis palustris 10-15 92 85 Redtop bentgrass Agrostis alba or Agrostis gigantea 5-10 90 80 Wet Area Seed Mix A low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wet- lands. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable. Tall or meadow fes- cue Festuca arundin- acea or Festuca elatior 60-70 98 90 Seaside/Creeping bentgrass Agrostis palustris 10-15 98 85 Meadow foxtail Alepocurus praten- sis 10-15 90 80 Alsike clover Trifolium hybridum 1-6 98 90 Redtop bentgrass Agrostis alba 1-6 92 85 Meadow Seed Mix A recommended meadow seed mix for infrequently maintained areas or non-maintained areas where col- onization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seed- ing should take place in September or very early October in order to obtain adequate establishment prior to the winter months. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending the soil can reduce the need for clover. Redtop or Oregon bentgrass Agrostis alba or Agrostis ore- gonensis 20 92 85 Red fescue Festuca rubra 70 98 90 White dutch clover Trifolium repens 10 98 90 Table II-3.4: Temporary and Permanent Seed Mixes (continued) Roughening and Rototilling l The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk slopes before seeding if engineering purposes require compaction. Backblading or smoothing of slopes greater than 4H:1V is not allowed if they are to be seeded. l Restoration-based landscape practices require deeper incorporation than that provided by a simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to improve long-term permeability, infiltration, and water inflow qualities. At a minimum, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 287 permanent areas shall use soil amendments to achieve organic matter and permeability per- formance defined in engineered soil/landscape systems. For systems that are deeper than 8 inches complete the rototilling process in multiple lifts, or prepare the engineered soil system per specifications and place to achieve the specified depth. Fertilizers l Conducting soil tests to determine the exact type and quantity of fertilizer is recommended. This will prevent the over-application of fertilizer. l Organic matter is the most appropriate form of fertilizer because it provides nutrients (includ- ing nitrogen, phosphorus, and potassium) in the least water-soluble form. l In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer at a rate of 90 pounds per acre. Always use slow-release fertilizers because they are more efficient and have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agit- ate, more than 20 minutes before use. Too much agitation destroys the slow-release coating. l There are numerous products available that take the place of chemical fertilizers. These include several with seaweed extracts that are beneficial to soil microbes and organisms. If 100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be necessary. Cottonseed meal provides a good source of long-term, slow-release, available nitrogen. Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix l On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application. Numerous products are available commercially. Most products require 24-36 hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally, products come in 40-50 pound bags and include all necessary ingredients except for seed and fertilizer. l Install products per manufacturer's instructions. l BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation establishment. Advantages over blankets include: o BFM and MBFMs do not require surface preparation. o Helicopters can assist in installing BFM and MBFMs in remote areas. o On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses for safety. o Installing BFM and MBFMs can save at least $1,000 per acre compared to blankets. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 288 Maintenance Standards Reseed any seeded areas that fail to establish at least 75 percent cover (100 percent cover for areas that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such as sodding, mulching, nets, or blankets. l Reseed and protect by mulch any areas that experience erosion after achieving adequate cover. Reseed and protect by mulch any eroded area. l Supply seeded areas with adequate moisture, but do not water to the extent that it causes run- off. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C121: Mulching Purpose Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating soil temperatures. There are a variety of mulches that can be used. This section discusses only the most common types of mulch. Conditions of Use As a temporary cover measure, mulch should be used: l For less than 30 days on disturbed areas that require cover. l At all times for seeded areas, especially during the wet season and during the hot summer months. l During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief. Mulch may be applied at any time of the year and must be refreshed periodically. For seeded areas, mulch may be made up of 100 percent: l cottonseed meal; l fibers made of wood, recycled cellulose, hemp, or kenaf; 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 289 l compost; l or blends of these. Tackifier shall be plant-based, such as guar or alpha plantago, or chemical-based such as poly- acrylamide or polymers. Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application. Recycled cellulose may contain polychlorinated biphenyl (PCBs). Ecology recommends that products should be evaluated for PCBs prior to use. Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use. PAM shall not be directly applied to water or allowed to enter a water body. Any mulch or tackifier product used shall be installed per the manufacturer’s instructions. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table II-3.6: Mulch Standards and Guidelines. Consult with the local supplier or the local conservation district for their recom- mendations. Increase the application rate until the ground is 95% covered (i.e. not visible under the mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or other areas highly susceptible to erosion. Where the option of “Compost” is selected, it should be a coarse compost that meets the size grad- ations listed in Table II-3.5: Size Gradations of Compost as Mulch Material when tested in accord- ance with Test Method 02.02-B found in Test Methods for the Examination of Composting and Compost (Thompson, 2001). Sieve Size Percent Passing 3"100% 1"90% - 100% 3/4"70% - 100% 1/4"40% - 100% Table II-3.5: Size Gradations of Compost as Mulch Material Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter. Composted organic materials have higher specific gravities (densities) than straw, wood, or chipped material. Consult the Hydraulic Permit Authority (HPA) for mulch mixes if applicable. Maintenance Standards The thickness of the mulch cover must be maintained. Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 290 Mulch Mater- ial Guideline Description Straw Quality Standards Air-dried; free from undesirable seed and coarse material. Application Rates 2"-3" thick; 5 bales per 1,000 sf or 2-3 tons per acre Remarks Cost-effective protection when applied with adequate thickness. Hand- application generally requires greater thickness than blown straw. The thickness of straw may be reduced by half when used in conjunction with seeding. In windy areas straw must be held in place by crimping, using a tackifier, or covering with netting. Blown straw always has to be held in place with a tackifier as even light winds will blow it away. Straw, however, has several deficiencies that should be considered when selecting mulch materials. It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits It should also not be used within the ordinary high-water elevation of surface waters (due to flot- ation). Hydromulch Quality Standards No growth inhibiting factors. Application Rates Approx. 35-45 lbs per 1,000 sf or 1,500 - 2,000 lbs per acre Remarks Shall be applied with hydromulcher. Shall not be used without seed and tackifier unless the application rate is at least doubled. Fibers longer than about 3/4 - 1 inch clog hydromulch equipment. Fibers should be kept to less than 3/4 inch. Compost Quality Standards No visible water or dust during handling. Must be produced per WAC 173- 350, Solid Waste Handling Standards, but may have up to 35% biosolids. Application Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs per cubic yard) Remarks More effective control can be obtained by increasing thickness to 3". Excel- lent mulch for protecting final grades until landscaping because it can be dir- ectly seeded or tilled into soil as an amendment. Compost used for mulch has a coarser size gradation than compost used for BMP C125: Topsoiling / Composting or BMP T5.13: Post-Construction Soil Quality and Depth. It is more stable and practical to use in wet areas and during rainy weather conditions. Do not use near wetlands or near phosphorous impaired water bodies. Chipped Site Veget- ation Quality Standards Gradations from fines to 6 inches in length for texture, variation, and inter- locking properties. Include a mix of various sizes so that the average size is between 2- and 4- inches. Application Rates 2" thick min.; Table II-3.6: Mulch Standards and Guidelines 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 291 Mulch Mater- ial Guideline Description Remarks This is a cost-effective way to dispose of debris from clearing and grub- bing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above approx. 10% because of its tendency to be transported by runoff. It is not recommended within 200 feet of sur- face waters. If permanent seeding or planting is expected shortly after mulch, the decomposition of the chipped vegetation may tie up nutrients important to grass establishment. Note: thick application of this material over existing grass, herbaceous spe- cies, and some groundcovers could smother and kill vegetation. Wood- Based Mulch Quality Standards No visible water or dust during handling. Must be purchased from a supplier with a Solid Waste Handling Permit or one exempt from solid waste reg- ulations. Application Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs. per cubic yard) Remarks This material is often called "wood straw" or "hog fuel". The use of mulch ultimately improves the organic matter in the soil. Special caution is advised regarding the source and composition of wood-based mulches. Its preparation typically does not provide any weed seed control, so evidence of residual vegetation in its composition or known inclusion of weed plants or seeds should be monitored and prevented (or minimized). Wood Strand Mulch Quality Standards A blend of loose, long, thin wood pieces derived from native conifer or deciduous trees with high length-to-width ratio. Application Rates 2" thick min. Remarks Cost-effective protection when applied with adequate thickness. A min- imum of 95-percent of the wood strand shall have lengths between 2 and 10-inches, with a width and thickness between 1/16 and 1/2-inches. The mulch shall not contain resin, tannin, or other compounds in quantities that would be detrimental to plant life. Sawdust or wood shavings shall not be used as mulch. [Specification 9-14.4(4) from the Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT, 2016) Table II-3.6: Mulch Standards and Guidelines (continued) BMP C122: Nets and Blankets Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 292 BMP C123: Plastic Covering Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. Conditions of Use Plastic covering may be used on disturbed areas that require cover measures for less than 30 days, except as stated below. l Plastic is particularly useful for protecting cut and fill slopes and stockpiles. However, the rel- atively rapid breakdown of most polyethylene sheeting makes it unsuitable for applications greater than six months. l Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. l Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on- site measures to counteract the increases. Creating a trough with wattles or other material can convey clean water away from these areas. l To prevent undercutting, trench and backfill rolled plastic covering products. l Although the plastic material is inexpensive to purchase, the cost of installation, maintenance, removal, and disposal add to the total costs of this BMP. l Whenever plastic is used to protect slopes, install water collection measures at the base of the slope. These measures include plastic-covered berms, channels, and pipes used to convey clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a plastic covered slope with dirty runoff from a project. l Other uses for plastic include: o Temporary ditch liner. o Pond liner in temporary sediment pond. o Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored. o Emergency slope protection during heavy rains. o Temporary drainpipe (“elephant trunk”) used to direct water. Design and Installation Specifications l Plastic slope cover must be installed as follows: 1. Run plastic up and down the slope, not across the slope. 2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 298 3. Provide a minimum of 8-inch overlap at the seams. 4. On long or wide slopes, or slopes subject to wind, tape all seams. 5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope and backfill with soil to keep water from flowing underneath. 6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them together with twine to hold them in place. 7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This prevents high velocity runoff from contacting bare soil, which causes extreme erosion. 8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be staked in place. l Plastic sheeting shall have a minimum thickness of 0.06 millimeters. l If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be installed at the toe of the slope in order to reduce the velocity of runoff. Maintenance Standards l Torn sheets must be replaced and open seams repaired. l Completely remove and replace the plastic if it begins to deteriorate due to ultraviolet radi- ation. l Completely remove plastic when no longer needed. l Dispose of old tires used to weight down plastic sheeting appropriately. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C124: Sodding Purpose The purpose of sodding is to establish turf for immediate erosion protection and to stabilize drainage paths where concentrated overland flow will occur. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 299 BMP C140: Dust Control Purpose Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage ways, and surface waters. Conditions of Use Use dust control in areas (including roadways) subject to surface and air movement of dust where on-site or off-site impacts to roadways, drainage ways, or surface waters are likely. Design and Installation Specifications l Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching, or paving is impractical, apply gravel or landscaping rock. l Limit dust generation by clearing only those areas where immediate activity will take place, leaving the remaining area(s) in the original condition. Maintain the original ground cover as long as practical. l Construct natural or artificial windbreaks or windscreens. These may be designed as enclos- ures for small dust sources. l Sprinkle the site with water until the surface is wet. Repeat as needed. To prevent carryout of mud onto the street, refer to BMP C105: Stabilized Construction Access and BMP C106: Wheel Wash. l Irrigation water can be used for dust control. Irrigation systems should be installed as a first step on sites where dust control is a concern. l Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and cautions regarding handling and application. Used oil is prohibited from use as a dust sup- pressant. Local governments may approve other dust palliatives such as calcium chloride or PAM. l PAM (BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection) added to water at a rate of 0.5 pounds per 1,000 gallons of water per acre and applied from a water truck is more effect- ive than water alone. This is due to increased infiltration of water into the soil and reduced evaporation. In addition, small soil particles are bonded together and are not as easily trans- ported by wind. Adding PAM may reduce the quantity of water needed for dust control. Note that the application rate specified here applies to this BMP, and is not the same application rate that is specified in BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection, but the downstream protections still apply. Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use. PAM shall not be directly applied to water or allowed to enter a water body. l Contact your local Air Pollution Control Authority for guidance and training on other dust con- trol measures. Compliance with the local Air Pollution Control Authority constitutes 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 313 compliance with this BMP. l Use vacuum street sweepers. l Remove mud and other dirt promptly so it does not dry and then turn into dust. l Techniques that can be used for unpaved roads and lots include: o Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. o Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials. o Add surface gravel to reduce the source of dust emission. Limit the amount of fine particles (those smaller than .075 mm) to 10 to 20 percent. o Use geotextile fabrics to increase the strength of new roads or roads undergoing recon- struction. o Encourage the use of alternate, paved routes, if available. o Apply chemical dust suppressants using the admix method, blending the product with the top few inches of surface material. Suppressants may also be applied as surface treatments. o Limit dust-causing work on windy days. o Pave unpaved permanent roads and other trafficked areas. Maintenance Standards Respray area as necessary to keep dust to a minimum. BMP C150: Materials on Hand Purpose Keep quantities of erosion prevention and sediment control materials on the project site at all times to be used for regular maintenance and emergency situations such as unexpected heavy rains. Hav- ing these materials on-site reduces the time needed to replace existing or implement new BMPs when inspections indicate that existing BMPs are not meeting the Construction SWPPP require- ments. In addition, contractors can save money by buying some materials in bulk and storing them at their office or yard. Conditions of Use l Construction projects of any size or type can benefit from having materials on hand. A small commercial development project could have a roll of plastic and some gravel available for immediate protection of bare soil and temporary berm construction. A large earthwork project, such as highway construction, might have several tons of straw, several rolls of plastic, flexible 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 314 pipe, sandbags, geotextile fabric and steel “T” posts. l Materials should be stockpiled and readily available before any site clearing, grubbing, or earthwork begins. A large contractor or project proponent could keep a stockpile of materials that are available for use on several projects. l If storage space at the project site is at a premium, the contractor could maintain the materials at their office or yard. The office or yard must be less than an hour from the project site. Design and Installation Specifications Depending on project type, size, complexity, and length, materials and quantities will vary. A good minimum list of items that will cover numerous situations includes: l Clear Plastic, 6 mil l Drainpipe, 6 or 8 inch diameter l Sandbags, filled l Straw Bales for mulching l Quarry Spalls l Washed Gravel l Geotextile Fabric l Catch Basin Inserts l Steel "T" Posts l Silt fence material l Straw Wattles Maintenance Standards l All materials with the exception of the quarry spalls, steel “T” posts, and gravel should be kept covered and out of both sun and rain. l Re-stock materials as needed. BMP C151: Concrete Handling Purpose Concrete work can generate process water and slurry that contain fine particles and high pH, both of which can violate water quality standards in the receiving water. Concrete spillage or concrete dis- charge to waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, con- crete process water, and concrete slurry from entering waters of the State. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 315 Conditions of Use Any time concrete is used, utilize these management practices. Concrete construction project com- ponents include, but are not limited to: l Curbs l Sidewalks l Roads l Bridges l Foundations l Floors l Runways Disposal options for concrete, in order of preference are: 1. Off-site disposal 2. Concrete wash-out areas (see BMP C154: Concrete Washout Area) 3. De minimus washout to formed areas awaiting concrete Design and Installation Specifications l Wash concrete truck drums at an approved off-site location or in designated concrete washout areas only. Do not wash out concrete trucks onto the ground (including formed areas awaiting concrete), or into storm drains, open ditches, streets, or streams. Refer to BMP C154: Concrete Washout Area for information on concrete washout areas. o Return unused concrete remaining in the truck and pump to the originating batch plant for recycling. Do not dump excess concrete on site, except in designated concrete washout areas as allowed in BMP C154: Concrete Washout Area. l Wash small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheelbarrows) into designated concrete washout areas or into formed areas awaiting concrete pour. l At no time shall concrete be washed off into the footprint of an area where an infiltration fea- ture will be installed. l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas. l Do not allow washwater from areas, such as concrete aggregate driveways, to drain directly (without detention or treatment) to natural or constructed stormwater conveyances. l Contain washwater and leftover product in a lined container when no designated concrete washout areas (or formed areas, allowed as described above) are available. Dispose of con- tained concrete and concrete washwater (process water) properly. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 316 l Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface waters. l Refer to BMP C252: Treating and Disposing of High pH Water for pH adjustment require- ments. l Refer to the Construction Stormwater General Permit (CSWGP) for pH monitoring require- ments if the project involves one of the following activities: o Significant concrete work (as defined in the CSWGP). o The use of soils amended with (but not limited to) Portland cement-treated base, cement kiln dust or fly ash. o Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for high pH. Maintenance Standards Check containers for holes in the liner daily during concrete pours and repair the same day. BMP C152: Sawcutting and Surfacing Pollution Prevention Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high pH (concrete cutting), both of which can violate the water quality standards in the receiving water. Concrete spillage or concrete discharge to waters of the State is prohibited. Use this BMP to minimize and eliminate process water and slurry created through sawcutting or surfacing from enter- ing waters of the State. Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Saw- cutting and surfacing operations include, but are not limited to: l Sawing l Coring l Grinding l Roughening l Hydro-demolition l Bridge and road surfacing 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 317 Design and Installation Specifications l Vacuum slurry and cuttings during cutting and surfacing operations. l Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight. l Slurry and cuttings shall not drain to any natural or constructed drainage conveyance includ- ing stormwater systems. This may require temporarily blocking catch basins. l Dispose of collected slurry and cuttings in a manner that does not violate ground water or sur- face water quality standards. l Do not allow process water generated during hydro-demolition, surface roughening or similar operations to drain to any natural or constructed drainage conveyance including stormwater systems. Dispose of process water in a manner that does not violate ground water or surface water quality standards. l Handle and dispose of cleaning waste material and demolition debris in a manner that does not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an appropriate disposal site. Maintenance Standards Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters of the state. If inspections show that a violation of water quality standards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and/or vacuum trucks. BMP C153: Material Delivery, Storage, and Containment Purpose Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from material delivery and storage. Minimize the storage of hazardous materials on-site, store mater- ials in a designated area, and install secondary containment. Conditions of Use Use at construction sites with delivery and storage of the following materials: l Petroleum products such as fuel, oil and grease l Soil stabilizers and binders (e.g., Polyacrylamide) l Fertilizers, pesticides and herbicides l Detergents l Asphalt and concrete compounds 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 318 l Hazardous chemicals such as acids, lime, adhesives, paints, solvents, and curing compounds l Any other material that may be detrimental if released to the environment Design and Installation Specifications l The temporary storage area should be located away from vehicular traffic, near the con- struction entrance(s), and away from waterways or storm drains. l Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. l Hazardous material storage on-site should be minimized. l Hazardous materials should be handled as infrequently as possible. l During the wet weather season (Oct 1 – April 30), consider storing materials in a covered area. l Materials should be stored in secondary containments, such as an earthen dike, horse trough, or even a children’s wading pool for non-reactive materials such as detergents, oil, grease, and paints. Small amounts of material may be secondarily contained in “bus boy” trays or con- crete mixing trays. l Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, within secondary containment. l If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums, preventing water from collecting. l Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in approved containers and drums and shall not be overfilled. Containers and drums shall be stored in temporary secondary containment facilities. l Temporary secondary containment facilities shall provide for a spill containment volume able to contain 10% of the total enclosed container volume of all containers, or 110% of the capa- city of the largest container within its boundary, whichever is greater. l Secondary containment facilities shall be impervious to the materials stored therein for a min- imum contact time of 72 hours. l Sufficient separation should be provided between stored containers to allow for spill cleanup and emergency response access. l During the wet weather season (Oct 1 – April 30), each secondary containment facility shall be covered during non-working days, prior to and during rain events. l Keep material storage areas clean, organized and equipped with an ample supply of appro- priate spill clean-up material (spill kit). l The spill kit should include, at a minimum: 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 319 o 1-Water Resistant Nylon Bag o 3-Oil Absorbent Socks 3”x 4’ o 2-Oil Absorbent Socks 3”x 10’ o 12-Oil Absorbent Pads 17”x19” o 1-Pair Splash Resistant Goggles o 3-Pair Nitrile Gloves o 10-Disposable Bags with Ties o Instructions Maintenance Standards l Secondary containment facilities shall be maintained free of accumulated rainwater and spills. In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums. These liquids shall be handled as hazardous waste unless testing determines them to be non-hazardous. l Re-stock spill kit materials as needed. BMP C154: Concrete Washout Area Purpose Prevent or reduce the discharge of pollutants from concrete waste to stormwater by conducting washout off-site, or performing on-site washout in a designated area. Conditions of Use Concrete washout areas are implemented on construction projects where: l Concrete is used as a construction material l It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant, etc.). l Concrete truck drums are washed on-site. Note that auxiliary concrete truck components (e.g. chutes and hoses) and small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheel- barrows) may be washed into formed areas awaiting concrete pour. At no time shall concrete be washed off into the footprint of an area where an infiltration feature will be installed. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 320 Design and Installation Specifications Implementation l Perform washout of concrete truck drums at an approved off-site location or in designated con- crete washout areas only. l Do not wash out concrete onto non-formed areas, or into storm drains, open ditches, streets, or streams. l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas. l Do not allow excess concrete to be dumped on-site, except in designated concrete washout areas as allowed above. l Concrete washout areas may be prefabricated concrete washout containers, or self-installed structures (above-grade or below-grade). l Prefabricated containers are most resistant to damage and protect against spills and leaks. Companies may offer delivery service and provide regular maintenance and disposal of solid and liquid waste. l If self-installed concrete washout areas are used, below-grade structures are preferred over above-grade structures because they are less prone to spills and leaks. l Self-installed above-grade structures should only be used if excavation is not practical. l Concrete washout areas shall be constructed and maintained in sufficient quantity and size to contain all liquid and concrete waste generated by washout operations. Education l Discuss the concrete management techniques described in this BMP with the ready-mix con- crete supplier before any deliveries are made. l Educate employees and subcontractors on the concrete waste management techniques described in this BMP. l Arrange for the contractor’s superintendent or Certified Erosion and Sediment Control Lead (CESCL) to oversee and enforce concrete waste management procedures. l A sign should be installed adjacent to each concrete washout area to inform concrete equip- ment operators to utilize the proper facilities. Contracts Incorporate requirements for concrete waste management into concrete supplier and subcontractor agreements. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 321 Location and Placement l Locate concrete washout areas at least 50 feet from sensitive areas such as storm drains, open ditches, water bodies, or wetlands. l Allow convenient access to the concrete washout area for concrete trucks, preferably near the area where the concrete is being poured. l If trucks need to leave a paved area to access the concrete washout area, prevent track-out with a pad of rock or quarry spalls (see BMP C105: Stabilized Construction Access). These areas should be far enough away from other construction traffic to reduce the likelihood of acci- dental damage and spills. l The number of concrete washout areas you install should depend on the expected demand for storage capacity. l On large sites with extensive concrete work, concrete washout areas should be placed in mul- tiple locations for ease of use by concrete truck drivers. Concrete Truck Washout Procedures l Washout of concrete truck drums shall be performed in designated concrete washout areas only. l Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and discharged into designated concrete washout areas or properly disposed of off-site. Concrete Washout Area Installation l Concrete washout areas should be constructed as shown in the figures below, with a recom- mended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to contain all liquid and concrete waste generated by washout operations. l Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free of holes, tears, or other defects that compromise the impermeability of the material. l Lath and flagging should be commercial type. l Liner seams shall be installed in accordance with manufacturers’ recommendations. l Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic lining material. Maintenance Standards Inspection and Maintenance l Inspect and verify that concrete washout areas are in place prior to the commencement of con- crete work. l Once concrete wastes are washed into the designated washout area and allowed to harden, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 322 the concrete should be broken up, removed, and disposed of per applicable solid waste reg- ulations. Dispose of hardened concrete on a regular basis. l During periods of concrete work, inspect the concrete washout areas daily to verify continued performance. o Check overall condition and performance. o Check remaining capacity (% full). o If using self-installed concrete washout areas, verify plastic liners are intact and side- walls are not damaged. o If using prefabricated containers, check for leaks. l Maintain the concrete washout areas to provide adequate holding capacity with a minimum freeboard of 12 inches. l Concrete washout areas must be cleaned, or new concrete washout areas must be con- structed and ready for use once the concrete washout area is 75% full. l If the concrete washout area is nearing capacity, vacuum and dispose of the waste material in an approved manner. l Do not discharge liquid or slurry to waterways, storm drains or directly onto ground. l Do not discharge to the sanitary sewer without local approval. l Place a secure, non-collapsing, non-water collecting cover over the concrete washout area prior to predicted wet weather to prevent accumulation and overflow of pre- cipitation. l Remove and dispose of hardened concrete and return the structure to a functional con- dition. Concrete may be reused on-site or hauled away for disposal or recycling. l When you remove materials from a self-installed concrete washout area, build a new struc- ture; or, if the previous structure is still intact, inspect for signs of weakening or damage, and make any necessary repairs. Re-line the structure with new plastic after each cleaning. Removal of Concrete Washout Areas l When concrete washout areas are no longer required for the work, the hardened concrete, slurries and liquids shall be removed and properly disposed of. l Materials used to construct concrete washout areas shall be removed from the site of the work and disposed of or recycled. l Holes, depressions or other ground disturbance caused by the removal of the concrete washout areas shall be backfilled, repaired, and stabilized to prevent erosion. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 323 Figure II-3.7: Concrete Washout Area with Wood Planks 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 324 3m Minimum -e- -e-Lath and flagging on 3 sides Sandbag0□ CD □ '>TI SandbagBermc> 10 mil plastic lining□Varies A iAf 'Xo-o-1 m •x Q —I Berm 10 CD CD Section A-A6 10 mil plastic liningPlan Notes: 1.Actual layout determined in the field. A concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. Type "Below Grade ii 2. 3m Minimum JSL JHL T8T Wood frame securely fastened around entire perimeter with two stakes B BtI■s-a ■s-a Varies 10 mil plastic lining S 3 E VStake (typ.) M Section B-Bw 10 mil plastic lining Two-stacked 2x12 rough wood frame Plan Type "Above Grade" with Wood Planks NOT TO SCALE Concrete Washout Area with Wood Planks Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Figure II-3.8: Concrete Washout Area with Straw Bales 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 325 Straw bale 10 mil plastic lining Binding wire Staples (2 per bale)Native material (optional) Wood or metal stakes (2 per bale) Plywood 1200 mm x 610 mm painted white Wood post (89 mm x 89 mm x 2.4 m)Lag screws (12.5 mm)Section B-B Black letters 150 mm heightILCONCRETE WASHOUT' U915 mm f 915 mm T3m Minimum Concrete Washout Sign Detail (or equivalent)Stake (typ)A B Bt1 i 50 mm 3.05 mm dia. steel wire Varies 200 mm f Staple Detail 10 mil plastic lining Notes:Straw bale (typ)1. Actual layout determined in the field. The concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. Plan 2. Type "Above Grade" with Straw Bales NOT TO SCALE Concrete Washout Area with Straw Bales Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Figure II-3.9: Prefabricated Concrete Washout Container w/Ramp 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 326 ■•-0 \riy l-j X - NOT TO SCALE Prefabricated Concrete Washout Container w/Ramp Revised June 2016DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyright.htmMor copyright notice including permissions, limitation of liability, and disclaimer.State of Washington BMP C160: Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of erosion and sediment control (ESC), and water quality protection. The designated person shall be responsible for ensuring compliance with all local, state, and federal erosion and sediment control and water quality requirements. Construction sites one acre or larger that discharge to waters of the State must designate a Certified Erosion and Sediment Control Lead (CESCL) as the responsible representative. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge stormwater to sur- face waters of the state. Sites less than one acre may have a person without CESCL certification conduct inspections. The CESCL shall: l Have a current certificate proving attendance in an erosion and sediment control training course that meets the minimum ESC training and certification requirements established by Ecology. Ecology has provided the minimum requirements for CESCL course training, as well as a list of ESC training and certification providers at: https://ecology.wa.gov/Regulations-Permits/Permits-certifications/Certified-erosion-sed- iment-control OR l Be a Certified Professional in Erosion and Sediment Control (CPESC). For additional inform- ation go to: http://www.envirocertintl.org/cpesc/ Specifications l CESCL certification shall remain valid for three years. l The CESCL shall have authority to act on behalf of the contractor or project proponent and shall be available, or on-call, 24 hours per day throughout the period of construction. l The Construction SWPPP shall include the name, telephone number, fax number, and address of the designated CESCL. See II-2 Construction Stormwater Pollution Prevention Plans (Construction SWPPPs). l A CESCL may provide inspection and compliance services for multiple construction projects in the same geographic region, but must be on site whenever earthwork activities are 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 327 occurring that could generate release of turbid water. l Duties and responsibilities of the CESCL shall include, but are not limited to the following: o Maintaining a permit file on site at all times which includes the Construction SWPPP and any associated permits and plans. o Directing BMP installation, inspection, maintenance, modification, and removal. o Updating all project drawings and the Construction SWPPP with changes made. o Completing any sampling requirements including reporting results using electronic Dis- charge Monitoring Reports (WebDMR). o Facilitate, participate in, and take corrective actions resulting from inspections per- formed by outside agencies or the owner. o Keeping daily logs, and inspection reports. Inspection reports should include: n Inspection date/time. n Weather information; general conditions during inspection and approximate amount of precipitation since the last inspection. n Visual monitoring results, including a description of discharged stormwater. The presence of suspended sediment, turbid water, discoloration, and oil sheen shall be noted, as applicable. n Any water quality monitoring performed during inspection. n General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. n A summary or list of all BMPs implemented, including observations of all erosion/sediment control structures or practices. The following shall be noted: 1. Locations of BMPs inspected. 2. Locations of BMPs that need maintenance. 3. Locations of BMPs that failed to operate as designed or intended. 4. Locations of where additional or different BMPs are required. BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by wind, rain, runoff, and vehicle tracking. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 328 Conditions of Use The construction sequence schedule is an orderly listing of all major land-disturbing activities together with the necessary erosion and sedimentation control measures planned for the project. This type of schedule guides the contractor on work to be done before other work is started so that serious erosion and sedimentation problems can be avoided. Following a specified work schedule that coordinates the timing of land-disturbing activities and the installation of control measures is perhaps the most cost-effective way of controlling erosion during construction. The removal of ground cover leaves a site vulnerable to erosion. Construction sequen- cing that limits land clearing, provides timely installation of erosion and sedimentation controls, and restores protective cover quickly can significantly reduce the erosion potential of a site. Design Considerations l Minimize construction during rainy periods. l Schedule projects to disturb only small portions of the site at any one time. Complete grading as soon as possible. Immediately stabilize the disturbed portion before grading the next por- tion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses. II-3.3 Construction Runoff BMPs BMP C200: Interceptor Dike and Swale Purpose Provide a dike of compacted soil or a swale at the top or base of a disturbed slope or along the peri- meter of a disturbed construction area to convey stormwater. Use the dike and/or swale to intercept the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can prevent storm runoff from entering the work area or sediment-laden runoff from leaving the con- struction site. Conditions of Use Use an interceptor dike or swale where runoff from an exposed site or disturbed slope must be con- veyed to an erosion control BMP which can safely convey the stormwater. l Locate upslope of a construction site to prevent runoff from entering the disturbed area. l When placed horizontally across a disturbed slope, it reduces the amount and velocity of run- off flowing down the slope. l Locate downslope to collect runoff from a disturbed area and direct it to a sediment BMP (e.g. BMP C240: Sediment Trap or BMP C241: Sediment Pond (Temporary)). 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 329 thickness is 2 feet. o For outlets at the base of steep slope pipes (pipe slope greater than 10 percent), use an engineered energy dissipator. o Filter fabric or erosion control blankets should always be used under riprap to prevent scour and channel erosion. See BMP C122: Nets and Blankets. l Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. This work may require a Hydraulic Project Approval (HPA) from the Washington State Depart- ment of Fish and Wildlife. See I-2.11 Hydraulic Project Approvals. Maintenance Standards l Inspect and repair as needed. l Add rock as needed to maintain the intended function. l Clean energy dissipator if sediment builds up. BMP C220: Inlet Protection Purpose Inlet protection prevents coarse sediment from entering drainage systems prior to permanent sta- bilization of the disturbed area. Conditions of Use Use inlet protection at inlets that are operational before permanent stabilization of the disturbed areas that contribute runoff to the inlet. Provide protection for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless those inlets are preceded by a sediment trapping BMP. Also consider inlet protection for lawn and yard drains on new home construction. These small and numerous drains coupled with lack of gutters can add significant amounts of sediment into the roof drain system. If possible, delay installing lawn and yard drains until just before landscaping, or cap these drains to prevent sediment from entering the system until completion of landscaping. Provide 18-inches of sod around each finished lawn and yard drain. Table II-3.10: Storm Drain Inlet Protection lists several options for inlet protection. All of the methods for inlet protection tend to plug and require a high frequency of maintenance. Limit contributing drain- age areas for an individual inlet to one acre or less. If possible, provide emergency overflows with additional end-of-pipe treatment where stormwater ponding would cause a hazard. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 356 Type of Inlet Pro- tection Emergency Overflow Applicable for Paved/ Earthen Sur- faces Conditions of Use Drop Inlet Protection Excavated drop inlet protection Yes, temporary flooding may occur Earthen Applicable for heavy flows. Easy to maintain. Large area requirement: 30'x30'/acre Block and gravel drop inlet pro- tection Yes Paved or Earthen Applicable for heavy concentrated flows. Will not pond. Gravel and wire drop inlet pro- tection No Paved or Earthen Applicable for heavy concentrated flows. Will pond. Can withstand traffic. Catch basin filters Yes Paved or Earthen Frequent maintenance required. Curb Inlet Protection Curb inlet pro- tection with wooden weir Small capacity overflow Paved Used for sturdy, more compact install- ation. Block and gravel curb inlet pro- tection Yes Paved Sturdy, but limited filtration. Culvert Inlet Protection Culvert inlet sed- iment trap N/A N/A 18 month expected life. Table II-3.10: Storm Drain Inlet Protection Design and Installation Specifications Excavated Drop Inlet Protection Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet. Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe- cifications for excavated drop inlet protection include: l Provide a depth of 1-2 ft as measured from the crest of the inlet structure. l Slope sides of excavation should be no steeper than 2H:1V. l Minimum volume of excavation is 35 cubic yards. l Shape the excavation to fit the site, with the longest dimension oriented toward the longest inflow area. l Install provisions for draining to prevent standing water. l Clear the area of all debris. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 357 l Grade the approach to the inlet uniformly. l Drill weep holes into the side of the inlet. l Protect weep holes with screen wire and washed aggregate. l Seal weep holes when removing structure and stabilizing area. l Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass flow. Block and Gravel Filter A block and gravel filter is a barrier formed around the inlet with standard concrete blocks and gravel. See Figure II-3.17: Block and Gravel Filter. Design and installation specifications for block gravel fil- ters include: l Provide a height of 1 to 2 feet above the inlet. l Recess the first row of blocks 2-inches into the ground for stability. l Support subsequent courses by placing a pressure treated wood 2x4 through the block open- ing. l Do not use mortar. l Lay some blocks in the bottom row on their side to allow for dewatering the pool. l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings. l Place gravel to just below the top of blocks on slopes of 2H:1V or flatter. l An alternative design is a gravel berm surrounding the inlet, as follows: o Provide a slope of 3H:1V on the upstream side of the berm. o Provide a slope of 2H:1V on the downstream side of the berm. o Provide a 1-foot wide level stone area between the gravel berm and the inlet. o Use stones 3 inches in diameter or larger on the upstream slope of the berm. o Use gravel ½- to ¾-inch at a minimum thickness of 1-foot on the downstream slope of the berm. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 358 Figure II-3.17: Block and Gravel Filter 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 359 A Drain grate r>Aft> QS, SSL ogjfe Q. ~ _ ?rygioSOso^cy.;Concrete block Sfei A* o• o>cr> °i?o ^•Pa- ■sPc^I? 4 STTO <&', Gravel backfill■osVf\ A-°i ° _?o “■'frvSPP^ •§?° to. gdp> §0-^<S> q® v«r.^4y A Plan View Concrete block Wire screen or filter fabric Overflow water Gravel backfill Ponding height |5»S Water'^n iplllpfls^Drop inlet Section A-A Notes: 1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas, (less than 5%) 2. Excavate a basin of sufficient size adjacent to the drop inlet. 3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent runoff from bypassing the inlet. A temporary dike may be necessary on the downslope side of the structure. NOT TO SCALE Block and Gravel Filter Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Gravel and Wire Mesh Filter Gravel and wire mesh filters are gravel barriers placed over the top of the inlet. This method does not provide an overflow. Design and installation specifications for gravel and wire mesh filters include: l Use a hardware cloth or comparable wire mesh with ½-inch openings. o Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot bey- ond each side of the inlet structure. o Overlap the strips if more than one strip of mesh is necessary. l Place coarse aggregate over the wire mesh. o Provide at least a 12-inch depth of aggregate over the entire inlet opening and extend at least 18-inches on all sides. Catch Basin Filters Catch basin filters are designed by manufacturers for construction sites. The limited sediment stor- age capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. To reduce maintenance requirements, combine a catch basin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights-of-way. Design and install- ation specifications for catch basin filters include: l Provides 5 cubic feet of storage. l Requires dewatering provisions. l Provides a high-flow bypass that will not clog under normal use at a construction site. l Insert the catch basin filter in the catch basin just below the grating. Curb Inlet Protection with Wooden Weir Curb inlet protection with wooden weir is an option that consists of a barrier formed around a curb inlet with a wooden frame and gravel. Design and installation specifications for curb inlet protection with wooden weirs include: l Use wire mesh with ½-inch openings. l Use extra strength filter cloth. l Construct a frame. l Attach the wire and filter fabric to the frame. l Pile coarse washed aggregate against the wire and fabric. l Place weight on the frame anchors. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 360 Block and Gravel Curb Inlet Protection Block and gravel curb inlet protection is a barrier formed around a curb inlet with concrete blocks and gravel. See Figure II-3.18: Block and Gravel Curb Inlet Protection. Design and installation spe- cifications for block and gravel curb inlet protection include: l Use wire mesh with ½-inch openings. l Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks. l Place a 2x4 stud through the outer holes of each spacer block to align the front blocks. l Place blocks on their sides across the front of the inlet and abutting the spacer blocks. l Place wire mesh over the outside vertical face. l Pile coarse aggregate against the wire to the top of the barrier. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 361 Figure II-3.18: Block and Gravel Curb Inlet Protection 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 362 A Catch basin Back of sidewalk 2x4 Wood stud Curb inletBack of curb Concrete block pt < 1'[ ]o a & Wire screen or filter fabric 3c§ i?$C5 3Ko..om,o jOjsQi 0»Wm JS SS A Concrete block% inch (20 mm) Drain gravel Plan View Ponding height % inch (20 mm) Drain gravel Overflow w I□Curb inlet Wire screen or filter fabric r2x4 Wood stud (100x50 Timber stud)/iCatch basin Concrete block Section A-A Notes: 1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff. 2. Barrier shall allow for overflow from severe storm event. 3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately.NOT TO SCALE Block and Gravel Curb Inlet Protection Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Curb and Gutter Sediment Barrier Curb and gutter sediment barrier is a sandbag or rock berm (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure II-3.19: Curb and Gutter Barrier. Design and installation specifications for curb and gutter sediment barrier include: l Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet. l Construct a horseshoe shaped sedimentation trap on the upstream side of the berm. Size the trap to sediment trap standards for protecting a culvert inlet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 363 Figure II-3.19: Curb and Gutter Barrier 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 364 Back of sidewalk Burlap sacks to overlap onto curb Back of curb Curb inletRunoff SpillwayRunoff Catch basin Plan View Gravel filled sandbags stacked tightly Notes: 1. Place curb type sediment barriers on gently sloping street segments, where water can pond and allow sediment to separate from runoff. 2. Sandbags of either burlap or woven 'geotextile' fabric, are filled with gravel, layered and packed tightly. 3. Leave a one sandbag gap in the top row to provide a spillway for overflow. 4. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately.NOT TO SCALE Curb and Gutter Barrier Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Maintenance Standards l Inspect all forms of inlet protection frequently, especially after storm events. Clean and replace clogged catch basin filters. For rock and gravel filters, pull away the rocks from the inlet and clean or replace. An alternative approach would be to use the clogged rock as fill and put fresh rock around the inlet. l Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appropriate. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C231: Brush Barrier Purpose The purpose of brush barriers is to reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use l Brush barriers may be used downslope of disturbed areas that are less than one-quarter acre. l Brush barriers are not intended to treat concentrated flows, nor are they intended to treat sub- stantial amounts of overland flow. Any concentrated flows must be directed to a sediment trap- ping BMP. The only circumstance in which overland flow can be treated solely by a brush barrier, rather than by a sediment trapping BMP, is when the area draining to the barrier is small. l Brush barriers should only be installed on contours. Design and Installation Specifications l Height: 2 feet (minimum) to 5 feet (maximum). l Width: 5 feet at base (minimum) to 15 feet (maximum). l Filter fabric (geotextile) may be anchored over the brush berm to enhance the filtration ability of the barrier. Ten-ounce burlap is an adequate alternative to filter fabric. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 365 N/A BMP C233: Silt Fence Purpose Silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use Silt fence may be used downslope of all disturbed areas. l Silt fence shall prevent sediment carried by runoff from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence. l Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow. Convey any concentrated flows through the drainage system to a sediment trapping BMP. l Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide an adequate method of silt control for anything deeper than sheet or overland flow. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 370 Figure II-3.22: Silt Fence 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 371 Joints in geotextile fabric shall be spliced at posts. Use staples, wire rings or equivalent to attach fabric to posts 2"x2" by 14 Ga. wire or equivalent, if standard strength fabric used x x X VX' XX>0<A xoi Rx Xxx>-X>:X XXXX’1 I EEj-X X I I: ;■;<>'_ >' *X xvwy !>x x ■,x' _n------ i ii i 6' max IMinimum 4''x4'' trench I II Post spacing may be increased to 8' if wire backing is used 2"x2" wood posts, steel fence posts, or equivalent 2''x2" by 14 Ga. wire or equivalent, if standard strength fabric used Geotextile fabric 2' min 7 Backfill trench with native soil or %" - 1.5" washed gravel r 'ToplE -T.\\ Minimum 4''x4'' trench . V 2"x2" wood posts, steel fence posts, or equivalent NOT TO SCALE Silt Fence Revised July 2017 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Design and Installation Specifications l Use in combination with other construction stormwater BMPs. l Maximum slope steepness (perpendicular to the silt fence line) 1H:1V. l Maximum sheet or overland flow path length to the silt fence of 100 feet. l Do not allow flows greater than 0.5 cfs. l Use geotextile fabric that meets the following standards. All geotextile properties listed below are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or exceed the values shown in Table II-3.11: Geotextile Fabric Standards for Silt Fence): Geotextile Property Minimum Average Roll Value Polymeric Mesh AOS (ASTM D4751) 0.60 mm maximum for slit film woven (#30 sieve). 0.30 mm maximum for all other geotextile types (#50 sieve). 0.15 mm minimum for all fabric types (#100 sieve). Water Permittivity (ASTM D4491) 0.02 sec-1 minimum Grab Tensile Strength (ASTM D4632) 180 lbs. Minimum for extra strength fabric. 100 lbs minimum for standard strength fabric. Grab Tensile Strength (ASTM D4632) 30% maximum Ultraviolet Resistance (ASTM D4355) 70% minimum Table II-3.11: Geotextile Fabric Standards for Silt Fence l Support standard strength geotextiles with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the geotextile. Silt fence materials are available that have synthetic mesh backing attached. l Silt fence material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of 0°F to 120°F. l One-hundred percent biodegradable silt fence is available that is strong, long lasting, and can be left in place after the project is completed, if permitted by the local jurisdiction. l Refer to Figure II-3.22: Silt Fence for standard silt fence details. Include the following Stand- ard Notes for silt fence on construction plans and specifications: 1. The Contractor shall install and maintain temporary silt fences at the locations shown in the Plans. 2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those activities. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 372 3. The silt fence shall have a 2-feet min. and a 2½-feet max. height above the original ground surface. 4. The geotextile fabric shall be sewn together at the point of manufacture to form fabric lengths as required. Locate all sewn seams at support posts. Alternatively, two sections of silt fence can be overlapped, provided that the overlap is long enough and that the adjacent silt fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. 5. Attach the geotextile fabric on the up-slope side of the posts and secure with staples, wire, or in accordance with the manufacturer's recommendations. Attach the geotextile fabric to the posts in a manner that reduces the potential for tearing. 6. Support the geotextile fabric with wire or plastic mesh, dependent on the properties of the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely to the up-slope side of the posts with the geotextile fabric up-slope of the mesh. 7. Mesh support, if used, shall consist of steel wire with a maximum mesh spacing of 2- inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh must be as resistant to the same level of ultraviolet radiation as the geotextile fabric it supports. 8. Bury the bottom of the geotextile fabric 4-inches min. below the ground surface. Backfill and tamp soil in place over the buried portion of the geotextile fabric, so that no flow can pass beneath the silt fence and scouring cannot occur. When wire or polymeric back-up support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches min. 9. Drive or place the silt fence posts into the ground 18-inches min. A 12–inch min. depth is allowed if topsoil or other soft subgrade soil is not present and 18-inches cannot be reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of 3H:1V or steeper and the slope is perpendicular to the fence. If required post depths cannot be obtained, the posts shall be adequately secured by bracing or guying to pre- vent overturning of the fence due to sediment loading. 10. Use wood, steel or equivalent posts. The spacing of the support posts shall be a max- imum of 6-feet. Posts shall consist of either: l Wood with minimum dimensions of 2 inches by 2 inches by 3 feet. Wood shall be free of defects such as knots, splits, or gouges. l No. 6 steel rebar or larger. l ASTM A 120 steel pipe with a minimum diameter of 1-inch. l U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft. l Other steel posts having equivalent strength and bending resistance to the post sizes listed above. 11. Locate silt fences on contour as much as possible, except at the ends of the fence, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 373 where the fence shall be turned uphill such that the silt fence captures the runoff water and prevents water from flowing around the end of the fence. 12. If the fence must cross contours, with the exception of the ends of the fence, place check dams perpendicular to the back of the fence to minimize concentrated flow and erosion. The slope of the fence line where contours must be crossed shall not be steeper than 3H:1V. l Check dams shall be approximately 1-foot deep at the back of the fence. Check dams shall be continued perpendicular to the fence at the same elevation until the top of the check dam intercepts the ground surface behind the fence. l Check dams shall consist of crushed surfacing base course, gravel backfill for walls, or shoulder ballast. Check dams shall be located every 10 feet along the fence where the fence must cross contours. l Refer to Figure II-3.23: Silt Fence Installation by Slicing Method for slicing method details. The following are specifications for silt fence installation using the slicing method: 1. The base of both end posts must be at least 2- to 4-inches above the top of the geo- textile fabric on the middle posts for ditch checks to drain properly. Use a hand level or string level, if necessary, to mark base points before installation. 2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard applications. 3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as possible to the geotextile fabric, enabling posts to support the geotextile fabric from upstream water pressure. 4. Install posts with the nipples facing away from the geotextile fabric. 5. Attach the geotextile fabric to each post with three ties, all spaced within the top 8- inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post nipple when tightening to prevent sagging. 6. Wrap approximately 6-inches of the geotextile fabric around the end posts and secure with 3 ties. 7. No more than 24-inches of a 36-inch geotextile fabric is allowed above ground level. 8. Compact the soil immediately next to the geotextile fabric with the front wheel of the tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the upstream side first and then each side twice for a total of four trips. Check and correct the silt fence installation for any deviation before compaction. Use a flat-bladed shovel to tuck the fabric deeper into the ground if necessary. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 374 Figure II-3.23: Silt Fence Installation by Slicing Method 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 375 Ponding height max. 24" \v 3: 3:POST SPACING: 7 max. on open runs 4' max. on pooling areasAttach fabric to upstream side of post Top of Fabric I'////A E'////// Belt * FLOW POST DEPTH: As much below ground as fabric above ground top 8" Drive over each side of silt fence 2 to 4 times with device exerting 60 p.s.i. or greater i Diagonal attachment doubles strength100% compaction100% compaction r33n TT~ J]=I iLE inWo Q.ILEt Attachment Details: • Gather fabric at posts, if needed. • Utilize three ties per post, all within top 8" of fabric. • Position each tie diagonally, puncturing holes vertically a minimum of 1" apart. • Hang each tie on a post nipple and tighten securely. Use cable ties (50 lbs) or soft wire. oQ. Q.31HM1I meii=iii=iii i=in No more than 24" of a 36" fabric is allowed above ground Roll of silt fenceOperation Post installed after compaction Fabric above groundPIo Silt Fence ifJC il==U 200 - jj=ji 300mmIrmssrSlicing blade (18 mm width) Horizontal chisel point (76 mm width) Completed Installation Vibratory plow is not acceptable because of horizontal compaction NOT TO SCALE Silt Fence Installation by Slicing Method Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Maintenance Standards l Repair any damage immediately. l Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment trap- ping BMP. l Check the uphill side of the silt fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence and remove the trapped sediment. l Remove sediment deposits when the deposit reaches approximately one-third the height of the silt fence, or install a second silt fence. l Replace geotextile fabric that has deteriorated due to ultraviolet breakdown. BMP C234: Vegetated Strip Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use l Vegetated strips may be used downslope of all disturbed areas. l Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to BMP C241: Sediment Pond (Temporary) or other sediment trapping BMP. The only circumstance in which overland flow can be treated solely by a vegetated strip, rather than by a sediment trapping BMP, is when the following criteria are met (see Table II- 3.12: Contributing Drainage Area for Vegetated Strips): Average Contributing Area Slope Average Contributing Area Per- cent Slope Max Contributing area Flowpath Length 1.5H : 1V or flatter 67% or flatter 100 feet 2H : 1V or flatter 50% or flatter 115 feet 4H : 1V or flatter 25% or flatter 150 feet 6H : 1V or flatter 16.7% or flatter 200 feet 10H : 1V or flatter 10% or flatter 250 feet Table II-3.12: Contributing Drainage Area for Vegetated Strips 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 376 Design and Installation Specifications l The vegetated strip shall consist of a continuous strip of dense vegetation with topsoil for a min- imum of a 25-foot length along the flowpath. Grass-covered, landscaped areas are generally not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips shall consist of undisturbed native growth with a well-developed soil that allows for infiltration of runoff. l The slope within the vegetated strip shall not exceed 4H:1V. l The uphill boundary of the vegetated strip shall be delineated with clearing limits. Maintenance Standards l Any areas damaged by erosion or construction activity shall be seeded immediately and pro- tected by mulch. l If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded, sod must be installed. l If there are indications that concentrated flows are traveling across the vegetated strip, storm- water runoff controls must be installed to reduce the flows entering the vegetated strip, or addi- tional perimeter protection must be installed. BMP C235: Wattles Purpose Wattles are temporary erosion and sediment control barriers consisting of straw, compost, or other material that is wrapped in netting made of natural plant fiber or similar encasing material. They reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sed- iment. Conditions of Use l Wattles shall consist of cylinders of plant material such as weed-free straw, coir, wood chips, excelsior, or wood fiber or shavings encased within netting made of natural plant fibers unaltered by synthetic materials. l Use wattles: o In disturbed areas that require immediate erosion protection. o On exposed soils during the period of short construction delays, or over winter months. o On slopes requiring stabilization until permanent vegetation can be established. l The material used dictates the effectiveness period of the wattle. Generally, wattles are effect- ive for one to two seasons. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 377 l Prevent rilling beneath wattles by entrenching and overlapping wattles to prevent water from passing between them. Design Criteria l See Figure II-3.24: Wattles for typical construction details. l Wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length. l Install wattles perpendicular to the flow direction and parallel to the slope contour. l Place wattles in shallow trenches, staked along the contour of disturbed or newly constructed slopes. Dig narrow trenches across the slope (on contour) to a depth of 3- to 5-inches on clay soils and soils with gradual slopes. On loose soils, steep slopes, and areas with high rainfall, the trenches should be dug to a depth of 5- to 7- inches, or 1/2 to 2/3 of the thickness of the wattle. l Start building trenches and installing wattles from the base of the slope and work up. Spread excavated material evenly along the uphill slope and compact it using hand tamping or other methods. l Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches. l Install the wattles snugly into the trenches and overlap the ends of adjacent wattles 12 inches behind one another. l Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle. l If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. l Wooden stakes should be approximately 0.75 x 0.75 x 24 inches min. Willow cuttings or 3/8- inch rebar can also be used for stakes. l Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake pro- truding above the wattle. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 378 Figure II-3.24: Wattles 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 379 3' -4' (1,2 m) jjlSi\fc Viz Overlap adjacent rolls 12" behind one another / /■y \Straw rolls must be placed along slope contours /// \/ \ v-C »S \J/10' - 25' (3-8m)d ■■■ Spacing depends on soil type and slope steepness y. Sediment, organic matter, and native seeds are captured behind the rolls.*3 3"-5" (75-125mm) N\ 8"-10" Dia. (200-250mm)A///-<A.//A Live Stake // // // 1"x1" Stake £/ (25 x 25mm)/ \/ V NOTE:l 1. Straw roll installation requires the placement and secure staking of the roll in a trench, 3" - 5" (75-125mm) deep, dug on contour. Runoff must not be allowed to run under or around roll. A NOT TO SCALE Wattles Revised December 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Maintenance Standards l Wattles may require maintenance to ensure they are in contact with soil and thoroughly entrenched, especially after significant rainfall on steep sandy soils. l Inspect the slope after significant storms and repair any areas where wattles are not tightly abutted or water has scoured beneath the wattles. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C236: Vegetative Filtration Purpose Vegetative filtration as a BMP is used in conjunction with detention storage in the form of portable tanks or BMP C241: Sediment Pond (Temporary), BMP C206: Level Spreader, and a pumping sys- tem with surface intake. Vegetative filtration improves turbidity levels of stormwater discharges by fil- tering runoff through existing vegetation where undisturbed forest floor duff layer or established lawn with thatch layer are present. Vegetative filtration can also be used to infiltrate dewatering waste from foundations, vaults, and trenches as long as runoff does not occur. Conditions of Use l For every five acres of disturbed soil use one acre of grass field, farm pasture, or wooded area. Reduce or increase this area depending on project size, ground water table height, and other site conditions. l Wetlands shall not be used for vegetative filtration. l Do not use this BMP in areas with a high ground water table, or in areas that will have a high seasonal ground water table during the use of this BMP. l This BMP may be less effective on soils that prevent the infiltration of the water, such as hard till. l Using other effective source control measures throughout a construction site will prevent the generation of additional highly turbid water and may reduce the time period or area need for this BMP. l Stop distributing water into the vegetated filtration area if standing water or erosion results. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 380 Maintenance Standards l Remove sediment from the pond when it reaches 1 foot in depth. l Repair any damage to the pond embankments or slopes. BMP C250: Construction Stormwater Chemical Treatment Purpose This BMP applies when using chemicals to treat turbidity in stormwater by either batch or flow- through chemical treatment. Turbidity is difficult to control once fine particles are suspended in stormwater runoff from a con- struction site. BMP C241: Sediment Pond (Temporary) is effective at removing larger particulate matter by gravity settling, but is ineffective at removing smaller particulates such as clay and fine silt. Traditional Construction Stormwater BMPs may not be adequate to ensure compliance with the water quality standards for turbidity in the receiving water. Chemical treatment can reliably provide exceptional reductions of turbidity and associated pol- lutants. Chemical treatment may be required to meet turbidity stormwater discharge requirements, especially when construction proceeds through the wet season. Conditions of Use Formal written approval from Ecology is required for the use of chemical treatment, regardless of site size. See https://fortress.wa.gov/ecy/publications/SummaryPages/ecy070258.html for a copy of the Request for Chemical Treatment form. The Local Permitting Authority may also require review and approval. When authorized, the chemical treatment systems must be included in the Con- struction Stormwater Pollution Prevention Plan (SWPPP). Chemically treated stormwater discharged from construction sites must be nontoxic to aquatic organ- isms. The Chemical Technology Assessment Protocol - Ecology (CTAPE) must be used to evaluate chemicals proposed for stormwater treatment. Only chemicals approved by Ecology under the CTAPE may be used for stormwater treatment. The approved chemicals, their allowable application techniques (batch treatment or flow-through treatment), allowable application rates, and conditions of use can be found at the Department of Ecology Emerging Technologies website: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee- guidance-resources/Emerging-stormwater-treatment-technologies Background on Chemical Treatment Systems Coagulation and flocculation have been used for over a century to treat water. The use of coagu- lation and flocculation to treat stormwater is a very recent application. Experience with the treatment of water and wastewater has resulted in a basic understanding of the process, in particular factors 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 396 that affect performance. This experience can provide insights as to how to most effectively design and operate similar systems in the treatment of stormwater. Fine particles suspended in water give it a milky appearance, measured as turbidity. Their small size, often much less than 1 µm in diameter, give them a very large surface area relative to their volume. These fine particles typically carry a negative surface charge. Largely because of these two factors (small size and negative charge), these particles tend to stay in suspension for extended periods of time. Thus, removal is not practical by gravity settling. These are called stable suspensions. Chem- icals like polymers, as well as inorganic chemicals such as alum, speed the settling process. The added chemical destabilizes the suspension and causes the smaller particles to flocculate. The pro- cess consists of three primary steps: coagulation, flocculation, and settling or clarification. Ecology requires a fourth step, filtration, on all stormwater chemical treatment systems to reduce floc dis- charge and to provide monitoring prior to discharge. General Design and Installation Specifications l Chemicals approved for use in Washington State are listed on Ecology's TAPE website, http://www.ecy.wa.gov/programs/wq/stormwater/newtech/technologies.html, under the "Con- struction" tab. l Care must be taken in the design of the withdrawal system to minimize outflow velocities and to prevent floc discharge. Stormwater that has been chemically treated must be filtered through BMP C251: Construction Stormwater Filtration for filtration and monitoring prior to dis- charge. l System discharge rates must take into account downstream conveyance integrity. l The following equipment should be located on site in a lockable shed: o The chemical injector. o Secondary containment for acid, caustic, buffering compound, and treatment chemical. o Emergency shower and eyewash. o Monitoring equipment which consists of a pH meter and a turbidimeter. l There are two types of systems for applying the chemical treatment process to stormwater: the batch chemical treatment system and the flow-through chemical treatment system. See below for further details for both types of systems. Batch Chemical Treatment Systems A batch chemical treatment system consists of four steps: coagulation, flocculation, clarification, and polishing and monitoring via filtration. Step 1: Coagulation Coagulation is the process by which negative charges on the fine particles are disrupted. By dis- rupting the negative charges, the fine particles are able to flocculate. Chemical addition is one method of destabilizing the suspension, and polymers are one class of chemicals that are generally effective. Chemicals that are used for this purpose are called coagulants. Coagulation is complete 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 397 when the suspension is destabilized by the neutralization of the negative charges. Coagulants per- form best when they are thoroughly and evenly dispersed under relatively intense mixing. This rapid mixing involves adding the coagulant in a manner that promotes rapid dispersion, followed by a short time period for destabilization of the particle suspension. The particles are still very small and are not readily separated by clarification until flocculation occurs. Step 2: Flocculation Flocculation is the process by which fine particles that have been destabilized bind together to form larger particles that settle rapidly. Flocculation begins naturally following coagulation, but is enhanced by gentle mixing of the destabilized suspension. Gentle mixing helps to bring particles in contact with one another such that they bind and continually grow to form "flocs." As the size of the flocs increase, they become heavier and settle. Step 3: Clarification The final step is the settling of the particles, or clarification. Particle density, size and shape are important during settling. Dense, compact flocs settle more readily than less dense, fluffy flocs. Because of this, flocculation to form dense, compact flocs is particularly important during chemical treatment. Water temperature is important during settling. Both the density and viscosity of water are affected by temperature; these in turn affect settling. Cold temperatures increase viscosity and dens- ity, thus slowing down the rate at which the particles settle. The conditions under which clarification is achieved can affect performance. Currents can affect set- tling. Currents can be produced by wind, by differences between the temperature of the incoming water and the water in the clarifier, and by flow conditions near the inlets and outlets. Quiescent water, such as that which occurs during batch clarification, provides a good environment for settling. One source of currents in batch chemical treatment systems is movement of the water leaving the clarifier unit. Because flocs are relatively small and light, the velocity of the water must be as low as possible. Settled flocs can be resuspended and removed by fairly modest currents. Step 4: Filtration After clarification, Ecology requires stormwater that has been chemically treated to be filtered and monitored prior to discharge. The sand filtration system continually monitors the stormwater effluent for turbidity and pH. If the discharge water is ever out of an acceptable range for turbidity or pH, the water is returned to the untreated stormwater pond where it will begin the treatment process again. Design and Installation of Batch Chemical Treatment Systems A batch chemical treatment system consists of a stormwater collection system (either a temporary diversion or the permanent site drainage system), an untreated stormwater storage pond, pumps, a chemical feed system, treatment cells, a filtering and monitoring system, and interconnecting piping. The batch treatment system uses a storage pond for untreated stormwater, followed by a minimum of two lined treatment cells. Multiple treatment cells allow for clarification of chemically treated water in one cell, while other cells are being filled or emptied. Treatment cells may be ponds or tanks. Ponds with constructed earthen embankments greater than six feet high or which impound more than 10 acre-feet are subject to the Washington Dam Safety Regulations (Chapter 173-175 WAC). 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 398 See BMP D.1: Detention Ponds for more information regarding dam safety considerations for ponds. Stormwater is collected at interception point(s) on the site and is diverted by gravity or by pumping to an untreated stormwater storage pond or other untreated stormwater holding area. The stormwater is stored until treatment occurs. It is important that the storage pond is large enough to provide adequate storage. The first step in the treatment sequence is to check the pH of the stormwater in the untreated storm- water storage pond. The pH is adjusted by the application of carbon dioxide or a base until the storm- water in the untreated storage pond is within the desired pH range, 6.5 to 8.5. When used, carbon dioxide is added immediately downstream of the transfer pump. Typically sodium bicarbonate (bak- ing soda) is used as a base, although other bases may be used. When needed, base is added dir- ectly to the untreated stormwater storage pond. The stormwater is recirculated with the treatment pump to provide mixing in the storage pond. Initial pH adjustments should be based on daily bench tests. Further pH adjustments can be made at any point in the process. See BMP C252: Treating and Disposing of High pH Water for more information on pH adjustments as a part of chemical treat- ment. Once the stormwater is within the desired pH range (which is dependant on the coagulant being used), the stormwater is pumped from the untreated stormwater storage pond to a lined treatment cell as a coagulant is added. The coagulant is added upstream of the pump to facilitate rapid mixing. The water is kept in the lined treatment cell for clarification. In a batch mode process, clarification typ- ically takes from 30 minutes to several hours. Prior to discharge, samples are withdrawn for analysis of pH, coagulant concentration, and turbidity. If these levels are acceptable, the treated water is with- drawn, filtered, and discharged. Several configurations have been developed to withdraw treated water from the treatment cell. The original configuration is a device that withdraws the treated water from just beneath the water sur- face using a float with adjustable struts that prevent the float from settling on the cell bottom. This reduces the possibility of picking up floc from the bottom of the cell. The struts are usually set at a min- imum clearance of about 12 inches; that is, the float will come within 12 inches of the bottom of the cell. Other systems have used vertical guides or cables which constrain the float, allowing it to drift up and down with the water level. More recent designs have an H-shaped array of pipes, set on the hori- zontal.This scheme provides for withdrawal from four points rather than one. This configuration reduces the likelihood of sucking settled solids from the bottom. It also reduces the tendency for a vor- tex to form. Inlet diffusers, a long floating or fixed pipe with many small holes in it, are also an option. Safety is a primary concern. Design should consider the hazards associated with operations, such as sampling. Facilities should be designed to reduce slip hazards and drowning. Tanks and ponds should have life rings, ladders, or steps extending from the bottom to the top. Sizing Batch Chemical Treatment Systems Chemical treatment systems must be designed to control the velocity and peak volumetric flow rate that is discharged from the system and consequently the project site. See Element 3: Control Flow Rates for further details on this requirement. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 399 The total volume of the untreated stormwater storage pond and treatment cells must be large enough to treat stormwater that is produced during multiple day storm events. It is recommended that at a minimum the untreated stormwater storage pond be sized to hold 1.5 times the volume of runoff generated from the site during the 10-year, 24-hour storm event. Bypass should be provided around the chemical treatment system to accommodate extreme storm events. Runoff volume shall be calculated using the methods presented in III-2.3 Single Event Hydrograph Method. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases, this would be the land cover conditions just prior to final landscaping). Primary settling should be encouraged in the untreated stormwater storage pond. A forebay with access for maintenance may be beneficial. There are two opposing considerations in sizing the treatment cells. A larger cell is able to treat a lar- ger volume of water each time a batch is processed. However, the larger the cell, the longer the time required to empty the cell. A larger cell may also be less effective at flocculation and therefore require a longer settling time. The simplest approach to sizing the treatment cell is to multiply the allowable discharge flow rate (as determined by the guidance in Element 3: Control Flow Rates) times the desired drawdown time. A 4-hour drawdown time allows one batch per cell per 8-hour work period, given 1 hour of flocculation followed by two hours of settling. See BMP C251: Construction Stormwater Filtration for details on sizing the filtration system at the end of the batch chemical treatment system. If the chemical treatment system design does not allow you to discharge at the rates as required by Element 3: Control Flow Rates, and if the site has a permanent Flow Control BMP that will serve the planned development, the discharge from the chemical treatment system may be directed to the per- manent Flow Control BMP to comply with Element 3: Control Flow Rates. In this case, all discharge (including water passing through the treatment system and stormwater bypassing the treatment sys- tem) will be directed into the permanent Flow Control BMP. If site constraints make locating the untreated stormwater storage pond difficult, the permanent Flow Control BMP may be divided to serve as the untreated stormwater storage pond and the post-treatment temporary flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The designer must document in the Construction SWPPP how the per- manent Flow Control BMP is able to attenuate the discharge from the site to meet the requirements of Element 3: Control Flow Rates. If the design of the permanent Flow Control BMP was modified for temporary construction flow control purposes, the construction of the permanent Flow Control BMP must be finalized, as designed for its permanent function, at project completion. Flow-Through Chemical Treatment Systems Background on Flow-Through Chemical Treatment Systems A flow-through chemical treatment system adds a sand filtration component to the batch chemical treatment system's treatment train following flocculation. The coagulant is added to the stormwater upstream of the sand filter so that the coagulation and flocculation step occur immediately prior to the filter. The advantage of a flow-through chemical treatment system is the time saved by immediately filtering the water, as opposed to waiting for the clarification process necessary in a batch chemical 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 400 treatment system. See BMP C251: Construction Stormwater Filtration for more information on fil- tration. Design and Installation of Flow-Through Chemical Treatment Systems At a minimum, a flow-through chemical treatment system consists of a stormwater collection system (either a temporary diversion or the permanent site drainage system), an untreated stormwater stor- age pond, and a chemically enhanced sand filtration system. As with a batch treatment system, stormwater is collected at interception point(s) on the site and is diverted by gravity or by pumping to an untreated stormwater storage pond or other untreated storm- water holding area. The stormwater is stored until treatment occurs. It is important that the holding pond be large enough to provide adequate storage. Stormwater is then pumped from the untreated stormwater storage pond to the chemically enhanced sand filtration system where a coagulant is added. Adjustments to pH may be necessary before coagulant addition. The sand filtration system continually monitors the stormwater effluent for turbidity and pH. If the discharge water is ever out of an acceptable range for turbidity or pH, the water is returned to the untreated stormwater pond where it will begin the treatment process again. Sizing Flow-Through Chemical Treatment Systems Refer to BMP C251: Construction Stormwater Filtration for sizing requirements of flow-through chemical treatment systems. Factors Affecting the Chemical Treatment Process Coagulants Cationic polymers can be used as coagulants to destabilize negatively charged turbidity particles present in natural waters, wastewater and stormwater. Polymers are large organic molecules that are made up of subunits linked together in a chain-like structure. Attached to these chain-like struc- tures are other groups that carry positive or negative charges, or have no charge. Polymers that carry groups with positive charges are called cationic, those with negative charges are called anionic, and those with no charge (neutral) are called nonionic. In practice, the only way to determ- ine whether a polymer is effective for a specific application is to perform preliminary or on-site test- ing. Aluminum sulfate (alum) can also be used as a coagulant, as this chemical becomes positively charged when dispersed in water. Polymers are available as powders, concentrated liquids, and emulsions (which appear as milky liquids). The latter are petroleum based, which are not allowed for construction stormwater treat- ment. Polymer effectiveness can degrade with time and also from other influences. Thus, man- ufacturers' recommendations for storage should be followed. Manufacturer’s recommendations usually do not provide assurance of water quality protection or safety to aquatic organisms. Con- sideration of water quality protection is necessary in the selection and use of all polymers. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 401 Application Application of coagulants at the appropriate concentration or dosage rate for optimum turbidity removal is important for management of chemical cost, for effective performance, and to avoid aquatic toxicity. The optimum dose in a given application depends on several site-specific features. Turbidity of untreated water can be important with turbidities greater than 5,000 NTU. The surface charge of particles to be removed is also important. Environmental factors that can influence dosage rate are water temperature, pH, and the presence of constituents that consume or otherwise affect coagulant effectiveness. Laboratory experiments indicate that mixing previously settled sediment (floc sludge) with the untreated stormwater significantly improves clarification, therefore reducing the effective dosage rate. Preparation of working solutions and thorough dispersal of coagulants in water to be treated is also important to establish the appropriate dosage rate. For a given water sample, there is generally an optimum dosage rate that yields the lowest residual turbidity after settling. When dosage rates below this optimum value (underdosing) are applied, there is an insufficient quantity of coagulant to react with, and therefore destabilize, all of the turbidity present. The result is residual turbidity (after flocculation and settling) that is higher than with the optimum dose. Overdosing, application of dosage rates greater than the optimum value, can also negatively impact performance. Like underdosing, the result of overdosing is higher residual turbidity than that with the optimum dose. Mixing The G-value, or just "G", is often used as a measure of the mixing intensity applied during coagu- lation and flocculation. The symbol G stands for “velocity gradient”, which is related in part to the degree of turbulence generated during mixing. High G-values mean high turbulence, and vice versa. High G-values provide the best conditions for coagulant addition. With high G's, turbulence is high and coagulants are rapidly dispersed to their appropriate concentrations for effective destabilization of particle suspensions. Low G-values provide the best conditions for flocculation. Here, the goal is to promote formation of dense, compact flocs that will settle readily. Low G's provide low turbulence to promote particle col- lisions so that flocs can form. Low G's generate sufficient turbulence such that collisions are effective in floc formation, but do not break up flocs that have already formed. pH Adjustment The pH must be in the proper range for the coagulants to be effective, which is typically 6.5 to 8.5. As polymers tend to lower the pH, it is important that the stormwater have sufficient buffering capacity. Buffering capacity is a function of alkalinity. Without sufficient alkalinity, the application of the polymer may lower the pH to below 6.5. A pH below 6.5 not only reduces the effectiveness of the polymer as a coagulant, but it may also create a toxic condition for aquatic organisms. Stormwater may not be discharged without readjustment of the pH to above 6.5. The target pH should be within 0.2 stand- ard units of the receiving water's pH. Experience gained at several projects in the City of Redmond has shown that the alkalinity needs to be at least 50 mg/L to prevent a drop in pH to below 6.5 when the polymer is added. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 402 Maintenance Standards Monitoring At a minimum, the following monitoring shall be conducted. Test results shall be recorded on a daily log kept on site. Additional testing may be required by the NPDES permit based on site conditions. l Operational Monitoring o Total volume treated and discharged. o Flow must be continuously monitored and recorded at not greater than 15-minute inter- vals. o Type and amount of chemical used for pH adjustment. o Type and amount of coagulant used for treatment. o Settling time. l Compliance Monitoring o Influent and effluent pH, flocculent chemical concentration, and turbidity must be con- tinuously monitored and recorded at not greater than 15-minute intervals. o pH and turbidity of the receiving water. l Biomonitoring o Treated stormwater must be non-toxic to aquatic organisms. Treated stormwater must be tested for aquatic toxicity or residual chemicals. Frequency of biomonitoring will be determined by Ecology. o Residual chemical tests must be approved by Ecology prior to their use. o If testing treated stormwater for aquatic toxicity, you must test for acute (lethal) toxicity. Bioassays shall be conducted by a laboratory accredited by Ecology, unless otherwise approved by Ecology. Acute toxicity tests shall be conducted per the CTAPE protocol and Appendix G of Whole Effluent Toxicity Testing Guidance and Test Review Criteria (Marshall, 2016). Discharge Compliance Prior to discharge, treated stormwater must be sampled and tested for compliance with pH, floc- culent chemical concentration, and turbidity limits. These limits may be established by the Con- struction Stormwater General Permit or a site-specific discharge permit. Sampling and testing for other pollutants may also be necessary at some sites. pH must be within the range of 6.5 to 8.5 stand- ard units and not cause a change in the pH of the receiving water by more than 0.2 standard units. Treated stormwater samples and measurements shall be taken from the discharge pipe or another location representative of the nature of the treated stormwater discharge. Samples used for determ- ining compliance with the water quality standards in the receiving water shall not be taken from the 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 403 treatment pond prior to decanting. Compliance with the water quality standards is determined in the receiving water. Operator Training Each project site using chemical treatment must have a trained operator who is certified for oper- ation of an Enhanced Chemical Treatment system. The operator must be trained and certified by an organization approved by Ecology. Organizations approved for operator training are found at the fol- lowing website: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee- guidance-resources/Contaminated-water-on-construction-sites Sediment Removal and Disposal l Sediment shall be removed from the untreated stormwater storage pond and treatment cells as necessary. Typically, sediment removal is required at least once during a wet season and at the decommissioning of the chemical treatment system. Sediment remaining in the cells between batches may enhance the settling process and reduce the required chemical dosage. l Sediment that is known to be non-toxic may be incorporated into the site away from drain- ages. BMP C251: Construction Stormwater Filtration Purpose Filtration removes sediment from runoff originating from disturbed areas of the site. Conditions of Use Traditional Construction Stormwater BMPs used to control soil erosion and sediment loss from con- struction sites may not be adequate to ensure compliance with the water quality standard for tur- bidity in the receiving water. Filtration may be used in conjunction with gravity settling to remove sediment as small as fine silt (0.5 µm). The reduction in turbidity will be dependent on the particle size distribution of the sediment in the stormwater. In some circumstances, sedimentation and fil- tration may achieve compliance with the water quality standard for turbidity. The use of construction stormwater filtration does not require approval from Ecology as long as treat- ment chemicals are not used. Filtration in conjunction with BMP C250: Construction Stormwater Chemical Treatment requires testing under the Chemical Technology Assessment Protocol – Eco- logy (CTAPE) before it can be initiated. Approval from Ecology must be obtained at each site where chemical use is proposed prior to use. See https://- fortress.wa.gov/ecy/publications/SummaryPages/ecy070258.html for a copy of the Request for Chemical Treatment form. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 404 Design and Installation Specifications Two types of filtration systems may be applied to construction stormwater treatment: rapid and slow. Rapid filtration systems are the typical system used for water and wastewater treatment. They can achieve relatively high hydraulic flow rates, on the order of 2 to 20 gpm/sf, because they have auto- matic backwash systems to remove accumulated solids. Slow filtration systems have very low hydraulic rates, on the order of 0.02 gpm/sf, because they do not have backwash systems. Slow filtration systems have generally been used as post construction BMPs to treat stormwater (see V-6 Filtration BMPs). Slow filtration is mechanically simple in com- parison to rapid filtration, but requires a much larger filter area. Filter Types and Efficiencies Sand media filters are available with automatic backwashing features that can filter to 50 µm particle size. Screen or bag filters can filter down to 5 µm. Fiber wound filters can remove particles down to 0.5 µm. Filters should be sequenced from the largest to the smallest pore opening. Sediment removal efficiency will be related to particle size distribution in the stormwater. Treatment Process and Description Stormwater is collected at interception point(s) on the site and diverted to an untreated stormwater sediment pond or tank for removal of large sediment, and storage of the stormwater before it is treated by the filtration system. In a rapid filtration system, the untreated stormwater is pumped from the pond or tank through the filtration media. Slow filtration systems are designed using gravity to convey water from the pond or tank to and through the filtration media. Sizing Filtration treatment systems must be designed to control the velocity and peak volumetric flow rate that is discharged from the system and consequently the project site. See Element 3: Control Flow Rates for further details on this requirement. The untreated stormwater storage pond or tank should be sized to hold 1.5 times the volume of run- off generated from the site during the 10-year, 24-hour storm event, minus the filtration treatment system flowrate for an 8-hour period. For a chitosan-enhanced sand filtration system, the filtration treatment system flowrate should be sized using a hydraulic loading rate between 6-8 gpm/ft2. Other hydraulic loading rates may be more appropriate for other systems. Bypass should be provided around the filtration treatment system to accommodate extreme storm events. Runoff volume shall be calculated using the methods presented in III-2.3 Single Event Hydrograph Method. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases, this would be the land cover conditions just prior to final landscaping). If the filtration treatment system design does not allow you to discharge at the rates as required by Element 3: Control Flow Rates, and if the site has a permanent Flow Control BMP that will serve the planned development, the discharge from the filtration treatment system may be directed to the per- manent Flow Control BMP to comply with Element 3: Control Flow Rates. In this case, all discharge (including water passing through the treatment system and stormwater bypassing the treatment 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 405 system) will be directed into the permanent Flow Control BMP. If site constraints make locating the untreated stormwater storage pond difficult, the permanent Flow Control BMP may be divided to serve as the untreated stormwater storage pond and the post-treatment temporary flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The designer must document in the Construction SWPPP how the per- manent Flow Control BMP is able to attenuate the discharge from the site to meet the requirements of Element 3: Control Flow Rates. If the design of the permanent Flow Control BMP was modified for temporary construction flow control purposes, the construction of the permanent Flow Control BMP must be finalized, as designed for its permanent function, at project completion. Maintenance Standards l Rapid sand filters typically have automatic backwash systems that are triggered by a pre-set pressure drop across the filter. If the backwash water volume is not large or substantially more turbid than the untreated stormwater stored in the holding pond or tank, backwash return to the untreated stormwater pond or tank may be appropriate. However, other means of treat- ment and disposal may be necessary. l Screen, bag, and fiber filters must be cleaned and/or replaced when they become clogged. l Sediment shall be removed from the storage and/or treatment ponds as necessary. Typically, sediment removal is required once or twice during a wet season and at the decommissioning of the ponds. l Disposal of filtration equipment must comply with applicable local, state, and federal reg- ulations. BMP C252: Treating and Disposing of High pH Water Purpose When pH levels in stormwater rise above 8.5, it is necessary to lower the pH levels to the acceptable range of 6.5 to 8.5 prior to discharge to surface or ground water. A pH level range of 6.5 to 8.5 is typ- ical for most natural watercourses, and this neutral pH range is required for the survival of aquatic organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may become stressed and may die. Conditions of Use l The water quality standard for pH in Washington State is in the range of 6.5 to 8.5. Storm- water with pH levels exceeding water quality standards may be either neutralized on site or disposed of to a sanitary sewer or concrete batch plant with pH neutralization capabilities. l Neutralized stormwater may be discharged to surface waters under the Construction Storm- water General permit. l Neutralized process water such as concrete truck wash-out, hydro-demolition, or saw-cutting slurry must be managed to prevent discharge to surface waters. Any stormwater 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 406 contaminated during concrete work is considered process wastewater and must not be dis- charged to waters of the State or stormwater collection systems. l The process used for neutralizing and/or disposing of high pH stormwater from the site must be documented in the Construction Stormwater Pollution Prevention Plan. Causes of High pH High pH at construction sites is most commonly caused by the contact of stormwater with poured or recycled concrete, cement, mortars, and other Portland cement or lime containing construction materials. (See BMP C151: Concrete Handling for more information on concrete handling pro- cedures). The principal caustic agent in cement is calcium hydroxide (free lime). Calcium hardness can contribute to high pH values and cause toxicity that is associated with high pH conditions. A high level of calcium hardness in waters of the state is not allowed. Ground water stand- ard for calcium and other dissolved solids in Washington State is less than 500 mg/l. Treating High pH Stormwater by Carbon Dioxide Sparging Advantages of Carbon Dioxide Sparging l Rapidly neutralizes high pH water. l Cost effective and safer to handle than acid compounds. l CO2 is self-buffering. It is difficult to overdose and create harmfully low pH levels. l Material is readily available. The Chemical Process of Carbon Dioxide Sparging When carbon dioxide (CO2) is added to water (H2O), carbonic acid (H2CO3) is formed which can further dissociate into a proton (H+) and a bicarbonate anion (HCO3-) as shown below: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- The free proton is a weak acid that can lower the pH. Water temperature has an effect on the reac- tion as well. The colder the water temperature is, the slower the reaction occurs. The warmer the water temperature is, the quicker the reaction occurs. Most construction applications in Washington State have water temperatures in the 50°F or higher range so the reaction is almost simultaneous. The Treatment Process of Carbon Dioxide Sparging High pH water may be treated using continuous treatment, continuous discharge systems. These manufactured systems continuously monitor influent and effluent pH to ensure that pH values are within an acceptable range before being discharged. All systems must have fail safe automatic shut off switches in the event that pH is not within the acceptable discharge range. Only trained operators may operate manufactured systems. System manufacturers often provide trained operators or train- ing on their devices. The following procedure may be used when not using a continuous discharge system: 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 407 1. Prior to treatment, the appropriate jurisdiction should be notified in accordance with the reg- ulations set by the jurisdiction. 2. Every effort should be made to isolate the potential high pH water in order to treat it separately from other stormwater on-site. 3. Water should be stored in an acceptable storage facility, detention pond, or containment cell prior to pH treatment. 4. Transfer water to be treated for pH to the pH treatment structure. Ensure that the pH treat- ment structure size is sufficient to hold the amount of water that is to be treated. Do not fill the pH treatment structure completely, allow at least 2 feet of freeboard. 5. The operator samples the water within the pH treatment structure for pH and notes the clarity of the water. As a rule of thumb, less CO2 is necessary for clearer water. The results of the samples and water clarity observations should be recorded. 6. In the pH treatment structure, add CO2 until the pH falls into the range of 6.9-7.1. Adjusting pH to within 0.2 pH units of receiving water (background pH) is recommended. It is unlikely that pH can be adjusted to within 0.2 pH units using dry ice. Compressed carbon dioxide gas should be introduced to the water using a carbon dioxide diffuser located near the bottom of the pH treatment structure, this will allow carbon dioxide to bubble up through the water and diffuse more evenly. 7. Slowly discharge the water, making sure water does not get stirred up in the process. Release about 80% of the water from the pH treatment structure leaving any sludge behind. If turbidity remains above the maximum allowable, consider adding filtration to the treatment train. See BMP C251: Construction Stormwater Filtration. 8. Discharge treated water through a pond or drainage system. 9. Excess sludge needs to be disposed of properly as concrete waste. If several batches of water are undergoing pH treatment, sludge can be left in the treatment structure for the next batch treatment. Dispose of sludge when it fills 50% of the treatment structure volume. 10. Disposal must comply with applicable local, state, and federal regulations. Treating High pH Stormwater by Food Grade Vinegar Food grade vinegar that meets FDA standards may be used to neutralize high pH water. Food grade vinegar is only 4% to 18% acetic acid with the remainder being water. Food grade vinegar may be used if dosed just enough to lower pH sufficiently. Use a treatment process as described above for CO2 sparging, but add food grade vinegar instead of CO2. This treatment option for high pH stormwater does not apply to anything but food grade vinegar. Acetic acid does not equal vinegar. Any other product or waste containing acetic acid must go through the evaluation process in Appendix G of Whole Effluent Toxicity Testing Guidance and Test Review Criteria (Marshall, 2016). 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 408 Disposal of High pH Stormwater Sanitary Sewer Disposal Local sewer authority approval is required prior to disposal via the sanitary sewer. Concrete Batch Plant Disposal l Only permitted facilities may accept high pH water. l Contact the facility to ensure they can accept the high pH water. Maintenance Standards Safety and materials handling: l All equipment should be handled in accordance with OSHA rules and regulations. l Follow manufacturer guidelines for materials handling. Each operator should provide: l A diagram of the monitoring and treatment equipment. l A description of the pumping rates and capacity the treatment equipment is capable of treat- ing. Each operator should keep a written record of the following: l Client name and phone number. l Date of treatment. l Weather conditions. l Project name and location. l Volume of water treated. l pH of untreated water. l Amount of CO2 or food grade vinegar needed to adjust water to a pH range of 6.9-7.1. l pH of treated water. l Discharge point location and description. A copy of this record should be given to the client/contractor who should retain the record for three years. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 409 Page | 36 Appendix D – Site Inspection Form Construction Stormwater Site Inspection Form Page 1 Project Name Permit # Inspection Date Time Name of Certified Erosion Sediment Control Lead (CESCL) or qualified inspector if less than one acre Print Name: Approximate rainfall amount since the last inspection (in inches): Approximate rainfall amount in the last 24 hours (in inches): Current Weather Clear Cloudy Mist Rain Wind Fog A. Type of inspection: Weekly Post Storm Event Other B. Phase of Active Construction (check all that apply): Pre Construction/installation of erosion/sediment controls Clearing/Demo/Grading Infrastructure/storm/roads Concrete pours Vertical Construction/buildings Utilities Offsite improvements Site temporary stabilized Final stabilization C. Questions: 1. Were all areas of construction and discharge points inspected? Yes No 2. Did you observe the presence of suspended sediment, turbidity, discoloration, or oil sheen Yes No 3. Was a water quality sample taken during inspection? (refer to permit conditions S4 & S5) Yes No 4. Was there a turbid discharge 250 NTU or greater, or Transparency 6 cm or less?* Yes No 5. If yes to #4 was it reported to Ecology? Yes No 6. Is pH sampling required? pH range required is 6.5 to 8.5. Yes No If answering yes to a discharge, describe the event. Include when, where, and why it happened; what action was taken, and when. *If answering yes to # 4 record NTU/Transparency with continual sampling daily until turbidity is 25 NTU or less/ transparency is 33 cm or greater. Sampling Results: Date: Parameter Method (circle one) Result Other/Note NTU cm pH Turbidity tube, meter, laboratory pH Paper, kit, meter Construction Stormwater Site Inspection Form Page 2 D. Check the observed status of all items. Provide “Action Required “details and dates. Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 1 Clearing Limits Before beginning land disturbing activities are all clearing limits, natural resource areas (streams, wetlands, buffers, trees) protected with barriers or similar BMPs? (high visibility recommended) 2 Construction Access Construction access is stabilized with quarry spalls or equivalent BMP to prevent sediment from being tracked onto roads? Sediment tracked onto the road way was cleaned thoroughly at the end of the day or more frequent as necessary. 3 Control Flow Rates Are flow control measures installed to control stormwater volumes and velocity during construction and do they protect downstream properties and waterways from erosion? If permanent infiltration ponds are used for flow control during construction, are they protected from siltation? 4 Sediment Controls All perimeter sediment controls (e.g. silt fence, wattles, compost socks, berms, etc.) installed, and maintained in accordance with the Stormwater Pollution Prevention Plan (SWPPP). Sediment control BMPs (sediment ponds, traps, filters etc.) have been constructed and functional as the first step of grading. Stormwater runoff from disturbed areas is directed to sediment removal BMP. 5 Stabilize Soils Have exposed un-worked soils been stabilized with effective BMP to prevent erosion and sediment deposition? Construction Stormwater Site Inspection Form Page 3 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 5 Stabilize Soils Cont. Are stockpiles stabilized from erosion, protected with sediment trapping measures and located away from drain inlet, waterways, and drainage channels? Have soils been stabilized at the end of the shift, before a holiday or weekend if needed based on the weather forecast? 6 Protect Slopes Has stormwater and ground water been diverted away from slopes and disturbed areas with interceptor dikes, pipes and or swales? Is off-site storm water managed separately from stormwater generated on the site? Is excavated material placed on uphill side of trenches consistent with safety and space considerations? Have check dams been placed at regular intervals within constructed channels that are cut down a slope? 7 Drain Inlets Storm drain inlets made operable during construction are protected. Are existing storm drains within the influence of the project protected? 8 Stabilize Channel and Outlets Have all on-site conveyance channels been designed, constructed and stabilized to prevent erosion from expected peak flows? Is stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes and downstream conveyance systems? 9 Control Pollutants Are waste materials and demolition debris handled and disposed of to prevent contamination of stormwater? Has cover been provided for all chemicals, liquid products, petroleum products, and other material? Has secondary containment been provided capable of containing 110% of the volume? Were contaminated surfaces cleaned immediately after a spill incident? Were BMPs used to prevent contamination of stormwater by a pH modifying sources? Construction Stormwater Site Inspection Form Page 4 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 9 Cont. Wheel wash wastewater is handled and disposed of properly. 10 Control Dewatering Concrete washout in designated areas. No washout or excess concrete on the ground. Dewatering has been done to an approved source and in compliance with the SWPPP. Were there any clean non turbid dewatering discharges? 11 Maintain BMP Are all temporary and permanent erosion and sediment control BMPs maintained to perform as intended? 12 Manage the Project Has the project been phased to the maximum degree practicable? Has regular inspection, monitoring and maintenance been performed as required by the permit? Has the SWPPP been updated, implemented and records maintained? 13 Protect LID Is all Bioretention and Rain Garden Facilities protected from sedimentation with appropriate BMPs? Is the Bioretention and Rain Garden protected against over compaction of construction equipment and foot traffic to retain its infiltration capabilities? Permeable pavements are clean and free of sediment and sediment laden- water runoff. Muddy construction equipment has not been on the base material or pavement. Have soiled permeable pavements been cleaned of sediments and pass infiltration test as required by stormwater manual methodology? Heavy equipment has been kept off existing soils under LID facilities to retain infiltration rate. E. Check all areas that have been inspected. All in place BMPs All disturbed soils All concrete wash out area All material storage areas All discharge locations All equipment storage areas All construction entrances/exits Construction Stormwater Site Inspection Form Page 5 F. Elements checked “Action Required” (section D) describe corrective action to be taken. List the element number; be specific on location and work needed. Document, initial, and date when the corrective action has been completed and inspected. Element # Description and Location Action Required Completion Date Initials Attach additional page if needed Sign the following certification: “I certify that this report is true, accurate, and complete, to the best of my knowledge and belief” Inspected by: (print) (Signature) Date: Title/Qualification of Inspector: Page | 37 Appendix E – Construction Stormwater General Permit (CSWGP) A NPDES permit and coverage under the NPDES Construction Stormwater General Permit (CSWGP) will be required for this project as it will perform more than 1.0 acre of land disturbing activity. An NPDES Permit will be applied for by the Owner for the project prior to starting construction. The NPDES Permit will then be transferred to the contractor, Forma Construction, who will maintain both the NPDES and SWPPP for the project until the end of construction. CSWGP application was submitted 01/30/25 and approval was received for coverage by the DOE on 5/8/2025 (WAR314454). STATE OF WASHINGTON DEPARTMENT OF ECOLOGY PO Box 47600, Olympia, WA 98504-7600 • 360-407-6000 May 8, 2025 Mike Cato Renton School District 7812 S 124th ST Seattle, WA 98178 Sent by email only: michael.cato@rentonschools.us RE: Coverage under the Construction Stormwater General Permit Permit number: Site Name: Location: County: King Disturbed Acres: WAR314454 Hazen High School 1101 Hoquiam Ave NE Renton 4.3 Dear Mike Cato: The Washington State Department of Ecology (Ecology) received your Notice of Intent for coverage under Ecology’s Construction Stormwater General Permit (CSWGP). This is your permit coverage letter. Your permit coverage is effective May 8, 2025. Retain this letter as an official record of permit coverage for your site. You may keep your records in electronic format if you can easily access them from your construction site. You can get the CSWGP, permit forms, and other information at Ecology’s CSWGP eCoverage Packet webpage1. Contact your Permit Administrator, listed below, if you want a copy of the CSWGP mailed to you. Please read the permit and contact Ecology if you have any questions. Electronic Discharge Monitoring Reports (WQWebDMR) This permit requires you to submit monthly discharge monitoring reports (DMRs) for the full duration of permit coverage (from the first full month of coverage to termination). Your first sampling and reporting period will be for the month of June, 2025 and your first DMR must be submitted by July 15, 2025. You must submit your DMRs electronically using Ecology’s secure online system, WQWebDMR. To sign up for WQWebDMR go to Ecology’s WQWebPortal guidance webpage2. If you have 1 http://www.ecology.wa.gov/eCoverage-packet 2 https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Water-quality-permits- guidance/WQWebPortal-guidance Mike Cato May 8, 2025 Page 2 questions, contact the portal staff at (360) 407-7097 (Olympia area), or (800) 633-6193/Option 3, or email WQWebPortal@ecy.wa.gov. Appeal Process You have a right to appeal coverage under the general permit to the Pollution Control Hearing Board (PCHB). Appeals must be filed within 30 days of the date of receipt of this letter. Any appeal is limited to the general permit’s applicability or non-applicability to a specific discharger. The appeal process is governed by chapter 43.21B RCW and chapter 371-08 WAC. “Date of receipt” is defined in RCW 43.21B.001(2). For more information regarding your right to appeal, please reference Ecology’s Focus Sheet: Appeal of General Permit Coverage3. Annual Permit Fees RCW 90.48.465 requires Ecology to recover the costs of managing the permit program. Permit fees are invoiced annually until the permit is terminated. Termination conditions are described in the permit. For permit fee related questions, please contact the Water Quality Fee Unit at wqfeeunit@ecy.wa.gov or (800) 633-6193/Option 2. You can also visit Water Quality Permit Fees Webpage4 for more information. Ecology Field Inspector Assistance If you have questions regarding stormwater management at your construction site, please contact your Regional Inspector, Luis Buen Abad of Ecology’s Northwest Regional Office in Shoreline at luis.buenabad@ecy.wa.gov, or (425) 256-0891. Questions or Additional Information Ecology is here to help. Please review our Construction Stormwater General Permit webpage5 for more information. If you have questions about the Construction Stormwater General Permit, please contact your Permit Administrator, Alyssa Brewer at alyssa.brewer@ecy.wa.gov or (564) 669-4922. Sincerely, Jeff Killelea, Manager Permit and Technical Services Section Water Quality Program 3 https://apps.ecology.wa.gov/publications/summarypages/1710007.html 4 https://ecology.wa.gov/Water-Shorelines/Water-quality/Water-quality-permits/Fees 5 www.ecology.wa.gov/constructionstormwaterpermit Page | 38 Appendix G – Contaminated Site Information Hazen High School – Impacted Soil and Groundwater Technical Memorandum prepared by PBS Environmental. Contaminated Media Management Plan (CMMP) prepared by PBS Environmental. 214 E GALER STREET, SUITE 300, SEATTLE, WA 98102 206.233.9639 MAIN 866.727.0140 FAX PBSUSA.COM Technical Memorandum DATE: April 1, 2025 TO: Michael Cato, PE, Renton School District No. 403 FROM: Nasrin Bastami, PBS Engineering and Environmental LLC PROJECT: 24012360 REGARDING: Hazen High School – Impacted Soil and Groundwater Technical Memorandum INTRODUCTION At the request of Renton School District (RSD), we have reviewed available documentation regarding an inactive underground storage tank (UST) at Hazen High School, located at 1101 Hoquiam Avenue NE, Renton, Washington 98059. This review assesses potential contamination impacts in light of future stormwater runoff and discharge activities associated with planned development. This review considers potential residual petroleum hydrocarbon contamination from a former UST decommissioned in 2011 and a separate currently inactive UST, evaluates associated risks to human health and the environment, assesses potential stormwater runoff and discharge impacts related to potential contamination, and provides recommendations for future on-site construction activities based on soil and groundwater conditions. BACKGROUND In August 2011, a 12,000-gallon heating oil UST was removed and replaced with a 10,000-gallon diesel UST. During the removal of the heating oil UST, petroleum hydrocarbons were confirmed to impact both soil and groundwater. Subsequent investigations and remedial actions were carried out to assess and address the soil and groundwater conditions. Despite these efforts, the site remains listed by Ecology with an “awaiting cleanup” status due to incomplete characterization of the site, particularly, related to groundwater. FINDINGS A review of the Renton School District #403, Hazen Senior High School, Underground Storage Tank Site Assessment Final Report, conducted by EHS-International, Inc., dated October 7, 2011, identified the following: • A 12,000-gallon heating oil UST was removed in August 2011. A 1-inch hole was discovered at the bottom of the UST during decommissioning and removal activities. • Five soil samples were collected from the sidewalls of the excavation (north, south, east, west), and a composite sample from the presumed contaminated stockpile was analyzed. The composite sample showed concentrations of 1,000 milligrams per kilogram (mg/kg) diesel-range hydrocarbons, which did not exceed the Model Toxics Control Act (MTCA) Method A Cleanup Level of 2,000 mg/kg for soil. The sidewall samples also did not exceed MTCA Method A Cleanup Levels. • A grab groundwater sample from the excavation showed concentrations of 6,900 micrograms per liter (µg/L) diesel-range hydrocarbons and 1,300 µg/L heavy oil-range hydrocarbons, both exceeding the MTCA Method A Cleanup Levels for groundwater (500 µg/L each). • Approximately 442 tons of petroleum-impacted soil and 1,268 gallons of impacted groundwater were subsequently removed during the excavation. Hazen High School Impacted Soil and Groundwater Technical Memorandum April 1, 2025 Page 2 24012360 A review of the Renton School District #403, Hazen Senior High School, Phase II Environmental Site Assessment Final Report, conducted by EHS-International, Inc., dated December 9, 2011, identified the following: • Three soil borings (B-1, B-2, and B-3) were advanced in the vicinity of the UST excavation area to a maximum depth of 36 feet below ground surface (bgs). • Groundwater was not encountered in any of the boreholes, suggesting that the groundwater observed in the UST pit during the UST removal may have been perched water. • A composite soil sample from two boreholes (B-1 and B-3) at 12 feet bgs indicated a concentration of 65 mg/kg diesel-range hydrocarbons, which is well below the MTCA Method A Cleanup Levels. The intent of the composite soil sample was to demonstrate that soil conditions in the vicinity of the UST are in compliance with MTCA Cleanup regulations both vertically and horizontally. Washington State Department of Ecology - Regulatory Status In September 2015, Ecology added the site to its list of known or suspected contaminated sites due to incomplete characterization of the contamination. Ecology specifically recommended further investigation of groundwater to assess the potential for contaminant migration. Proposed UST Decommissioning Activities – 2025 Given the depth to groundwater (over 36 feet bgs), the absence of reported contaminated soil within the former UST excavation pit, a planned major modernization and development of the school, and the limited potential for human and environmental impacts, Renton School District has opted to decommission the newer inactive UST through closure-in-place as an interim measure. The UST will be removed in the future to comply with Ecology’s requirements and secure a No Further Action (NFA) determination. All UST decommissioning activities will be conducted in accordance with WAC 173-360A guidelines. CONCLUSIONS AND RECOMMENDATIONS Proposed Limited Construction Activities - Summer of 2025 Based on information provided by RSD and their teaming partners, redevelopment and construction and excavation activities are planned for specific, limited locations at the job site These excavation areas are located outside and away from previously identified petroleum hydrocarbon-impacted soil and groundwater within the UST pit and do not intersect potential areas of contamination. The planned activities are indicated in the attached site plan figure (Civil Site Plans – Sheet C010 and C207) and described below: • Installation of new heavy-duty asphalt pavement and a concrete curb north of the UST, with minimal ground disturbance (approximately 6 to 12 inches bgs); • Installation of new aboveground structures with minimal subsurface disturbance, including a concrete curb, fencing, and utility upgrades (approximately 6 to 24 inches bgs), such as relocating the existing generator and adjusting the irrigation control box to accommodate the new generator to the west-northwest; • Concrete sidewalk restoration and bollard installation east of the UST, with excavation depths of approximately 6 to 30 inches bgs; and • Excavation for the installation of a new fire hydrant, including piping and connection to the existing water main, located approximately 190 feet west of the UST, with an excavation depth of approximately 48 inches bgs. Hazen High School Impacted Soil and Groundwater Technical Memorandum April 1, 2025 Page 3 24012360 • Early utility work is expected to commence on the west side of the campus for the installation of ground source well piping as part of geothermal heating system upgrades, replacing the existing boiler system within the building. The geothermal wells will be approximately 350 feet deep, with the closest well located roughly 610 feet northwest of the UST. PBS notes that this area is situated cross-gradient to the UST with respect to the estimated groundwater flow direction. Contaminated Media Management Plan Although encountering petroleum-impacted soil and groundwater associated with the former or existing inactive UST is considered unlikely, PBS recommends the preparation and implementation of a Contaminated Media Management Plan (CMMP) to ensure the proper application of best management practices (BMPs), and the appropriate handling of any potentially impacted soil or groundwater encountered during future excavation activities. PBS understands that, at the request of the Renton School District, it will prepare the CMMP and provide it to the client and their contractors for use during future construction activities. Additionally, a copy of this document should be submitted to Ecology for review and approval, if necessary. Attachments: 1. Figure - Civil Site Plans – Sheet C010 and C207 2. Renton School District #403, Hazen Senior High School, Underground Storage Tank Site Assessment Final Report, EHS- International, Inc., October 7, 2011. 3. Renton School District #403, Hazen Senior High School, Phase II Environmental Site Assessment Final Report, EHS-International, Inc., December 9, 2011. 4. Early Notice letter – Facility Site # 64413781, Renton School District #403, Hazen Senior High School, Ecology, September 2, 2015. Reviewers: Nasrin Bastami, Bret Waldron X X X E E E E E E E E E E E SS CO SUB SUB SUB SUB S U B S U B S U B S U B SUB SUB SUB S U B S U B SUB SUB SUB S U B S U B SUB SUB SUB S U B S U B SUB SUB SUB S U B S U B SUB SUB SUB S U B S U B SUB SUB SUB S U B S U B SUB SUB SUB S U B S U B SUB SUB S U B S U B SUB SUB S U B S U B SUB SUB S U B S U B SUB SUB S U B S U B SUB SUB S U B S U B SUB SUB S U B S U B SUB SUB S U B S U B SUB S U B S U B SUB S U B S U B SUB S U B SUB S U B SUB S U B SUB S U B SUB S U B S U B S U B S U B SUB SUB SUB SU BSU B SU B SUB SU B SU B SUB SU B SU B SU B SUB SU B SD E E E E E E E E E E E E E E EE E E E E E E E EE E EE E E E EE EE E E E E E E E E E E E E E E SD EE E EEEEEE E E E E E DU V A L L A V E . N . E . HO Q U I A M A V E . N . E . N.E. 12TH ST. N.E. 10TH ST. N.E. 11TH PL N.E. 11TH CT N.E. 11TH ST N.E. 10TH PL GR A H A M AV E N . E . FI E L D AV E N . E . EXISTING FIRE HYDRANT NE 10TH ST ECO PAN FOR CONCRETE PUMPER TRUCK CLEANOUT; FINAL LOCATION TO BE COORDINATED IN FIELD DURING CONSTRUCTION. ECO PAN USED FOR CONCRETE POUR IN COURTYARD TO THE SOUTH FOR GREENHOUSE PAD AND CONCRETE SIDEWALK REPLACEMENT FOR INSTALLATION OF ACID WASTE PIPING CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS 43667 NSTATE O F WASHI N G T ON R EGIST E R E D P R O F E SSIONAL E N G IN EER O S B O CAJA.DLAREJ TE D - 4 0 - 4 3 2 6 C2 4 0 0 2 7 7 1 HAZEN HIGH SCHOOL MODERNIZATION OVERALL SITE PLAN R-432603 CX04 CX01 CX03 CX05 CX06 PROJECT WORK AREAS (TYP) IMPROVED BASEBALL FIELD AND GROUND SOURCE WELL ZONE CX02 EXISTING POWER POLE NEW ELECTRICAL PRIMARY SERVICE GROUND SOURCE WELL ZONE GROUND SOURCE PIPING IN/OUT OF BUILDING (2) TEMPORARY PORTABLES TO BE REMOVED AT END OF PROJECT UNDER SEPARATE PERMIT MAINTAIN 20' WIDE FIRE LANE CX07 GROUND SOURCE VAULT. LOCATION TBD. EX CHURCH PROPERTY NOTE: BREAKOUT SHEETS VARY IN DRAWING SCALE CONTRACTOR TO TAKE NOTE OF SCALES ON EVERY SHEET NE 10TH ST FROM EXISTING CUL-DE-SAC WEST ALONG SCHOOL'S FRONTAGE TO BE UPGRADED WITH PLANTER STRIP, STREET LIGHTING, AND CONCRETE SIDEWALK MEETING THE REQUIREMENTS FOR A RESIDENTIAL ACCESS STREET SECTION. SEE SHEETS C109 AND C209 EXISTING ADA RAMP AT THE NW CORNER OF INTERSECTION OF HOQUIAM AVE NE & NE 10TH ST TO BE UPGRADED TO MEET ACCESSIBILITY REQUIREMENTS. SEE SHEETS C109 AND C209 EXISTING ADA RAMP AT THE SE CORNER OF INTERSECTION OF HOQUIAM AVE NE & NE 11TH CT TO BE UPGRADED TO MEET ACCESSIBILITY REQUIREMENTS, INCLUDING INSTALLATION OF A NEW COMPANION RAMP ON EAST SIDE OF STREET. EXISTING CROSSWALK TO BE REPLACED WITH NEW THERMOPLASTIC CROSSWALK STRIPING SEE SHEETS C108 AND C208 EXISTING DRIVEWAY CURB CUT TO BE UPGRADED TO MEET ACCESSIBILITY REQUIREMENTS SEE SHEETS C108 AND C208 NOTE: FOR R.O.W. IMPROVEMENTS SEE DETAILS ON SHEETS C330 & C331 C109 C209 C109, C209 IMPROVED SOFTBALL FIELD EXISTING DRIVEWAY CURB CUT TO BE UPGRADED TO MEET ACCESSIBILITY REQUIREMENTS SEE SHEETS C108 AND C208 EXISTING DRIVEWAY CURB CUT TO BE UPGRADED TO MEET ACCESSIBILITY REQUIREMENTS SEE SHEETS C108 AND C208 C1 0 8 , C2 0 8 C1 0 8 , C2 0 8 SCALE 1"=80' 40 80 1600 EXISTING DRIVEWAY CURB CUT TO BE UPGRADED TO MEET ACCESSIBILITY REQUIREMENTS SEE SHEETS C109 AND C209 EXISTING LIGHT POLE AND HH EXISTING CABINET KEYNOTE: 1.DEMOLISH AND REMOVE EX SECURITY FENCING AND GATES, INCLUDING ANY HARDWARE, OUTSIDE THE GYM/CAFETERIA AREA COURTYARD. CONTRACTOR SHALL SAWCUT 2' AROUND POSTS AND REMOVE POSTS. PATCH WITH CONCRETE SIDEWALK PAVEMENT. 2.DEMOLISH AND REMOVE EX SECURITY FENCING AND GATES, INCLUDING ANY HARDWARE, OUTSIDE THE CTE/D-WING SCIENCE AREA COURTYARD. CONTRACTOR SHALL SAWCUT 2' AROUND POSTS AND REMOVE POSTS. PATCH WITH CONCRETE SIDEWALK PAVEMENT. 1 2 FOR WORK IN EX COURTYARD SEE DETAIL C303 10 CITY OF RENTON EROSION CONTROL WET SEASON REQUIREMENTS ANY SITE WITH EXPOSED SOILS DURING THE WET SEASON (OCTOBER 1 TO APRIL 30) SHALL BE SUBJECT TO THE SPECIAL PROVISIONS BELOW. IN ADDITION TO THE ESC COVER MEASURES (SEE SECTION D.2.1.2), THESE PROVISIONS INCLUDE COVERING ANY NEWLY SEEDED AREAS WITH MULCH AND IDENTIFYING AND SEEDING AS MUCH DISTURBED AREA AS POSSIBLE PRIOR TO SEPTEMBER 23 IN ORDER TO PROVIDE GRASS COVER FOR THE WET SEASON. A “WET SEASON ESC PLAN” MUST BE SUBMITTED AND APPROVED BY THE CITY BEFORE WORK PROCEEDS OR CONTINUES. THE FOLLOWING PROVISIONS FOR WET SEASON CONSTRUCTION ARE DETAILED IN APPENDIX D OF THE 2017 CITY OF RENTON SURFACE WATER DESIGN MANUAL. PLEASE ENSURE YOUR SITE IS PROTECTED AND COMPLIES WITH THE SPECIAL PROVISIONS OUTLINED BELOW. WET SEASON SPECIAL PROVISIONS ALL OF THE FOLLOWING PROVISIONS FOR WET SEASON CONSTRUCTION ARE DETAILED IN THE REFERENCED SECTIONS. THESE REQUIREMENTS ARE LISTED HERE FOR THE CONVENIENCE OF THE DESIGNER AND THE REVIEWER. 1.THE ALLOWED TIME THAT A DISTURBED AREA MAY REMAIN UNWORKED WITHOUT COVER MEASURES IS REDUCED TO TWO CONSECUTIVE WORKING DAYS, RATHER THAN SEVEN (SECTION D.2.1.2). 2.STOCKPILES AND STEEP CUT AND FILL SLOPES ARE TO BE PROTECTED IF UNWORKED FOR MORE THAN 12 HOURS (SECTION D.2.1.2). 3.COVER MATERIALS SUFFICIENT TO COVER ALL DISTURBED AREAS SHALL BE STOCKPILED ON SITE (SECTION D.2.1.2). 4.ALL AREAS THAT ARE TO BE UNWORKED DURING THE WET SEASON SHALL BE SEEDED WITHIN ONE WEEK OF THE BEGINNING OF THE WET SEASON (SECTION D.2.1.2.6). 5.MULCH IS REQUIRED TO PROTECT ALL SEEDED AREAS (SECTION D.2.1.2.2). 6.FIFTY LINEAR FEET OF SILT FENCE (AND THE NECESSARY STAKES) PER ACRE OF DISTURBANCE MUST BE STOCKPILED ON SITE (SECTION D.2.1.3.1). 7.CONSTRUCTION ROAD AND PARKING LOT STABILIZATION ARE REQUIRED FOR ALL SITES UNLESS THE SITE IS UNDERLAIN BY COARSE-GRAINED SOIL (SECTION D.2.1.4.2). 8.SEDIMENT RETENTION IS REQUIRED UNLESS NO OFFSITE DISCHARGE IS ANTICIPATED FOR THE SPECIFIED DESIGN FLOW (SECTION D.2.1.5). 9.SURFACE WATER CONTROLS ARE REQUIRED UNLESS NO OFFSITE DISCHARGE IS ANTICIPATED FOR THE SPECIFIED DESIGN FLOW (SECTION D.2.1.6). 10.PHASING AND MORE CONSERVATIVE BMPS MUST BE EVALUATED FOR CONSTRUCTION ACTIVITY NEAR SURFACE WATERS (SECTION D.2.4.3). 11.ANY RUNOFF GENERATED BY DEWATERING MAY BE REQUIRED TO DISCHARGE TO THE SANITARY SEWER (WITH APPROPRIATE DISCHARGE AUTHORIZATION), PORTABLE SAND FILTER SYSTEMS, OR HOLDING TANKS (SECTION D.2.2). SAWCUT AND REMOVE EX ASPHALT PAVEMENT FOR UTILITY INSTALLATION. PATCH WITH HEAVY ASPHALT PAVEMENT SECTION. SEE DETAIL C300 7 UST □ □ □ SUB S U B SUB SU B SU B SU B SU B SU B SUB SUB SU B SU B SU B SU B SUB SUB SU B SU B SU B SU B SUB SU B SU B SU B SUB SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SU B SUB SUB SUB SUB SUB SUB SUB SUB SUB SUB SUB SUB W E E E E E E E E E E E E E E E E EEE E EEEEEEEEEE EEEEEE E E IMPROVED SOFTBALL FIELD WITH SYNTHETIC SURFACE AND UNDERDRAINS PER LANDSCAPE PLANS ADS MC-3500 STORMTECH CHAMBER DETENTION SYSTEM REQUIRED LIVE STORAGE = 22,265 CF TOTAL STORAGE VOLUME = 27,943 CF 152 CHAMBERS AND 8 END CAPS IN 4 ROWS 9" GRAVEL BASE, 12" GRAVEL PERIMETER, AND 12" GRAVEL COVER SEE SHEET C314 AND SEE DETAIL RESTORE CONCRETE SIDEWALK SEE DETAIL (TYP) C300 3 NEW NON-REMOVEABLE HEAVY DUTY VEHICULAR RATED SECURITY BOLLARD (TYP UNLESS OTHERWISE NOTED) SEE DETAIL C301 6 PROPOSED TEMPORARY PORTABLE FFE 471.74 PROPOSED TEMPORARY PORTABLE FFE 471.90 470.62 (EX) 470.29 (EX) 470.38 (EX)470.93 (EX) 470.34 (EX) 470.67 (EX) 470.67 (EX) PROPOSED TEMPORARY MODULAR BUILDINGS PER ARCH'L PLANS TO BE REMOVED AT COMPLETION OF CONSTRUCTION UNDER SEPARATE PERMIT 25' 6' EX ACCESSIBLE ROUTE EX TABLE TOP CROSSING PROTECT EX CATCH BASIN TO REMAIN; LEAVE GAP IN TEMPORARY PORTABLE FOUNDATION SKIRTING FOR DRAINAGE TO THIS CB TO BE MAINTAINED 7.4'7.7' 4'6.6' 8' INSTALL NEW REMOVABLE HEAVY DUTY VEHICULAR RATED SECURITY BOLLARD (2 TOTAL) (FINAL BOLLARD LAYOUT TBD) SEE DETAIL C301 10 REPLACE EX CONCRETE CURB/GUTTER, SIDEWALK, AND ASPHALT PAVING HO Q U I U M A V E . N . E . (A D E D I C A T E D P U B L I C R I G H T O F W A Y ) 5' PAINTED "WHITE" PEDESTRIAN PATHWAY STRIPING SEE DETAIL 8' PAINTED "WHITE" CROSSWALK STRIPING SEE DETAIL C300 9 INSTALL TEMPORARY CATCH BASIN FILTER SOCKS ON ALL NEW CATCH BASINS UNTIL SITE IS STABILIZED. SEE DETAIL 7/C110. EX ACCESSIBLE RAMP INSTALL ROUND ACCESS COVERS IN LINE WITH LADDERS WITHIN TYPE II CATCH BASINS 470.54 (EX) C312 6 150-FT FIRE HYDRANT HOSE PULL DISTANCE EXISTING 10" WATER MAIN TO BE PROTECTED AT ALL TIMES. PROTECTION SHALL INCLUDE, BUT NOT LIMITED TO, PROHIBITION OF HEAVY MACHINERY AND DRILLING EQUIPMENT ON TOP OF MAIN OR WITHIN EASEMENT. VIBRATIONAL TESTING MAY BE REQUIRED FOR ANY DRILLING OR PILING OCCURRING NEAR THE MAIN. ADDITIONALLY, ANY MACHINERY CROSSING THE WATER MAIN IN UNPAVED AREAS WILL BE REQUIRED TO UTILIZE SHEETING OR SIMILAR MECHANISM TO ENSURE THAT THE MAIN IS NOT SUBJECT TO DAMAGE LOADS. EX GENERATOR TO BE RELOCATED PER ELEC'L PLANS EX TRANSFORMER TO BE RELOCATED PER ELEC'L PLANS RELOCATED EX GENERATOR PER ELEC'L PLANS NEW EXTRUDED CONCRETE CURB SEE DETAIL (TYP) C300 11 8' 3' 2' NEW EXTRUDED CONCRETE CURB NEW DOUBLE DOORS TO EX STORAGE ROOM PER ARCH'L PLANS PROTECT EX SECURITY CAMERA NEW 6' HIGH CHAINLINK FENCE WITH PRIVACY SLATS PER L'SCAPE PLANS NEW 6' HIGH BY 12' WIDE CHAINLINK GATE (2 - 6' LEAFS) WITH PRIVACY SLATS PER L'SCAPE PLANS NEW HEAVY DUTY ASPHALT SEE DETAIL 7' BOLLARD DEPTH IS 30" DEEP BY 16" WIDE. CONTRACTOR SHALL USE CAUTION WHEN PERFORMING CONSTRUCTION NEAR OR OVER EXISTING CHARGED WATERMAIN. SEE DETAIL C301 6 36 LF 6" DI CL52 WET-TAP FOR NEW FIRE HYDRANT ASSEMBLY W/ THRUST BLOCKING WET-TAPPING OF EXISTING 10-INCH WATERMAIN SHALL BE PERFORMED BY THE FOLLOWING LICENSED WET TAP CONTRACTORS 1. LEGACY TAPPING, INC. 2. SPEER TAPS, INC. SEE DETAILS C319 1 C319 4 REPLACE EX ASPHALT PAVEMENT WITH HEAVY DUTY ASPHALT PAVEMENT SEE DETAIL C300 7 REPLACE EX CONCRETE VERTICAL CURB AS REQUIRED TO INSTALL NEW FIRE HYDRANT ASSEMBLY NEW 15-FT WATER EASEMENT KC REC NO.___________ 15' 7. 5 ' REPLACE EX SHRUBS AND LANDSCAPING IN PLANTER AS NEEDED PROTECT EX LIGHT POLE TO REMAIN FIRE HYDRANT ASSEMBLY PROVIDE A 4'x4' CONCRETE PAD FOR NEW FIRE HYDRANT SEE DETAIL C319 2 C319 5 2' FIELD ADJUST EX IRRIGATION CONTROL BOX AND OTHER COMPONENTS IN THIS AREA TO AVOID CONFLICT WITH RELOCATED GENERATOR AND NEW FENCING 470.89 (EX) 470.69 (EX) 470.78 (EX) 470.69 (EX) 470.71 (EX) 470.57 (EX) 470.67 (EX) 470.44 (EX) 470.71 (EX) 470.60 (EX) 1. 7 % 2. 7 % 4. 7 % 2. 1 % 3. 9 % 0.2%0.2%0.1%0.3%0.3% 470.85 (EX) 470.86 (EX) 470.80 (EX)470.87 (EX) 1. 0 % 0. 1 % 471.67 (EX) 471.65 (EX) 471.18 (EX)471.17 (EX) 0.2% 0.4% C300 7 C300 9 SALVAGE AND REMOVE EX LIGHT POLE AND BASE TO BE REINSTALLED AT COMPLETION OF PROJECT REMOVE EX CONCRETE WALK, CURB, AND ASPHALT AS REQUIRED TO INSTALL ELECTRICAL CONDUITS AND VAULTS FOR TEMPORARY PORTABLE POWER BELOW TEMPORARY PORTABLE FOUNDATIONS REMOVE EX PLANTING MATERIAL AND SOIL DOWN TO SUBGRADE AND COMPACT TO 95% AS REQUIRED. SUBGRADE THAT DOES NOT MEET COMPACTION, SHALL BE REMOVED A MIN. OF 12" AND REPLACED WITH IMPORT FILL MATERIAL, THEN RECOMPACTED TO MEET 95%. INSPECTION PORT (TYP OF 8) ECO PAN FOR CONCRETE TRUCK CLEANOUT; FINAL LOCATION TO BE COORDINATED IN FIELD DURING CONSTRUCTION. INSPECTION PORT LIDS TO BE SET 6" BELOW TURF SURFACING WITH REMOVABLE ACCESS PANEL PER LANDSCAPE PLANS BID ALTERNATE #19.1 PROPOSED BOILER ROOM ACCESS IMPROVEMENTS SCOPE WITHIN THIS LIMITS OF WORK LINE, INCLUDING ASPHALT, DOORS, AND CURB REVISIONS. BASE BID KEEP EXISTING CONDITIONS 47 7 476.94 477.01(EX)476.99(EX) 476.93(EX) 4' CONTRACTOR SHALL MAKE A RECORD OF EXISTING SCORE/JOINT LINES FOR COURTYARD TO BE MATCHED FOR FINISHED CONCRETE CONDITION. (TYP) RESTORE EX CONCRETE PAVEMENT WITH STANDARD CONCRETE SIDEWALK SECTION SEE DETAIL C300 3 CITY OF RENTON IN COMPLIANCE WITH CITY OF RENTON STANDARDS 43667 NSTATE O F WASHI N G T ON R EGIST E R E D P R O F E SSIONAL E N G IN EER O S B O CAJA.DLAREJ TE D - 4 0 - 4 3 2 6 C2 4 0 0 2 7 7 1 LEGEND PROPERTY LINE CONTOUR (INDEX) CONTOUR GRADE BREAK SPOT ELEVATION 110 109.36 109 TC 109.86 BC 109.36 ASPHALT PAVEMENT CONCRETE CURB CONCRETE PAVEMENT SCALE 1"=20' 0 10 20 40 HAZEN HIGH SCHOOL MODERNIZATION CIVIL SITE PLAN R-432621 NOTE:SEE ELECTRICAL PLANS FOR POWER AND COMM FEEDS TO PORTABLE NOTE:CONTRACTOR SHALL UTILIZE PUBLIC AND PRIVATE UTILITY LOCATES TO VERIFY EX UTILITIES NOTE:PROPOSED PORTABLES ARE "DRY" AND WILL NOT HAVE NEW WATER OR SEWER SERVICES PROVIDED COORDINATE WITH SCHOOL DISTRICT FOR ACCESS TO AND FROM PROJECT SITE MATCHLINE - SEE SHEET C205 STORM DRAINAGE PIPE SD PROPOSED DETENTION SYSTEM FOR TYPICAL TRENCH AND BACKFILL, FOR STORM PIPING, SEE DETAIL 6/C310. FOR WORK IN THE RIGHT-OF-WAY SEE SHEET C208 MH / EX CB 2 / CB 2 / CB/ YD / CO NOTE: FOR ALL EXTERIOR CONCRETE PAVEMENT, PROVIDE SPRAY-LOCK P3 OR EQUAL CONCRETE PAVING SURFACE TREATMENT TO HELP PROTECT CONCRETE AGAINST WINTER DE-ICING SALT PER PROJET SPECIFICATION SECTION 321313.23 HEAVY DUTY ASPHALT PAVEMENT UST 214 EAST GALER STREET SUITE 300 SEATTLE, WA 98102 206.233.9639 MAIN 866.727.0140 FAX PBSUSA.COM Contaminated Media Management Plan Hazen High School 1101 Hoquiam Avenue NE Renton, Washington 98059 Prepared for: Renton School District No. 403 300 SW 7th Street Renton, Washington 98057 April 3, 2025 PBS Project No. 24012360 Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 i TABLE OF CONTENTS 1. INTRODUCTION ......................................................................................................................................................................... 1 1.1 Property Information ...................................................................................................................................................... 1 1.2 Objective ............................................................................................................................................................................. 1 1.3 Background ........................................................................................................................................................................ 2 1.4 Contaminants of Concern ............................................................................................................................................ 2 2. ADVANCE COORDINATION PRIOR TO SUBSURFACE DISTURBANCE ................................................................. 3 2.1 Responsible Charge ........................................................................................................................................................ 3 2.2 Activities with the Potential to Generate Contaminated Soil and/or Groundwater.............................. 3 2.3 Project Team ...................................................................................................................................................................... 3 2.4 Health and Safety Plan .................................................................................................................................................. 3 2.5 Waste Profiling ................................................................................................................................................................. 4 3. MATERIAL DEFINITIONS ......................................................................................................................................................... 4 3.1 Clean Soil ............................................................................................................................................................................ 4 3.2 Non-Dangerous Waste:................................................................................................................................................. 5 3.3 Dangerous Waste ............................................................................................................................................................ 5 4. CONTAMINATED MEDIA HANDLING ................................................................................................................................ 6 4.1 Contaminated Soil and Groundwater Management Procedures ................................................................. 6 4.2 Field Screening and Identification ............................................................................................................................ 6 4.3 Stockpiling .......................................................................................................................................................................... 7 4.4 Soil Sampling and Testing ........................................................................................................................................... 7 4.4.1 Sample Collection ............................................................................................................................................... 7 4.4.2 Decontamination ................................................................................................................................................. 8 4.4.3 Sampling Analysis Procedures ....................................................................................................................... 8 4.4.4 Evaluation of Analytical Results ..................................................................................................................... 8 4.5 Contaminated Water Management Procedures ................................................................................................. 8 4.6 Contaminated Demolition Debris Management Procedures ......................................................................... 9 4.7 Procedures for Specific Construction Activities ................................................................................................... 9 4.7.1 Utility Work ............................................................................................................................................................ 9 4.7.2 Grading..................................................................................................................................................................10 4.8 Dust and Odor Control ................................................................................................................................................10 4.9 Decontamination Procedures ...................................................................................................................................10 4.10 Contingency Plan for Unknown Contamination................................................................................................10 5. CONTAMINATED MEDIA TRANSPORT AND OFF-SITE DISPOSAL .......................................................................11 5.1 Waste Profile and Manifest........................................................................................................................................11 5.2 Contaminated Soil Transport ....................................................................................................................................11 5.3 Off-Site Disposal ............................................................................................................................................................11 6. POST CONSTRUCTION MANAGEMENT .........................................................................................................................12 7. REPORTING AND DOCUMENTATION .............................................................................................................................12 Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 ii 8. SIGNATURE ................................................................................................................................................................................13 9. REFERENCES ..............................................................................................................................................................................14 Supporting Documentation FIGURES Figure 1 – Site Plan EHSI - Hazen HS UST Assessment (Figure 3), October 2011 EHSI - Hazen HS Phase II Subsurface Investigation (Figure 3), December 2011 APPENDIX Appendix A: Ecology Guidance for Reuse of PCS, Tables 12.1 – 12.2 Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 1 1. INTRODUCTION This Contaminated Media Management Plan (CMMP) provides information and describes procedures regarding the management of petroleum contaminated soil (PCS) and water that may potentially be encountered during construction and redevelopment activities at the property. The CMMP was prepared by PBS Engineering and Environmental LLC (PBS) on behalf of the Renton School District No. 403. It is noted that there are currently no actionable items related to contaminated media management at the property. The plan shall be in place prior to subsurface work that disturbs soil and/or groundwater and implemented should potential contamination be encountered. 1.1 Property Information The site, known as Hazen High School, comprises ten King County parcels: 1023059277, 1023059094, 1023059278, 1023059072, 1023059201, 1023059292, 1023059084, 1023059057, 1023059146, and 7985000604, with a total area of approximately 30.6 acres (see Figure 1). In August 2011, a 12,000-gallon heating oil underground storage tank (UST) was removed and replaced with a 10,000-gallon diesel UST. During the removal of the heating oil UST, petroleum hydrocarbons were confirmed to impact both soil and groundwater. Subsequent investigations and remedial actions were carried out to assess and address the soil and groundwater conditions. Despite these efforts, the site remains listed by Washington State Department of Ecology (Ecology) with an “awaiting cleanup” status due to incomplete characterization of the site, particularly, related to groundwater. 1.2 Objective The objective of the CMMP is to provide information regarding the location, type, and source of contaminated media (soils and groundwater) present at the site, and to assist future subsurface or earthwork workers in proper media handling, management, and disposal, as needed. The CMMP addresses how the known contamination, and any new discoveries of previously unidentified contamination, will be handled safely and to avoid effects to schedule. The CMMP also provides information to contractors to develop a Health and Safety Plan (HASP) that is appropriate to protect site workers from exposure to contaminants. This CMMP contains: • Information on current environmental conditions and contaminants of concern. • Roles and responsibilities of project team members for the CMMP. • Procedures for the storage of contaminated soil or debris in stockpile or staging piles awaiting sampling, classification, load-out, and disposal (should temporary storage occur). • Procedures for the management and sampling of new discoveries of contaminated materials. • Procedures for the storage of contaminated water in temporary holding tanks or lined ponds awaiting sampling, classification, and disposal. • Required documentation for contaminated material handling, storage, loading, and disposal. Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 2 1.3 Background PBS developed this CMMP based on the information presented in the following report: A review of the Renton School District #403, Hazen Senior High School, Underground Storage Tank Site Assessment Final Report, conducted by EHS-International, Inc., dated October 7, 2011, identified the following: • A 12,000-gallon heating oil UST was removed in August 2011. A 1-inch hole was discovered at the bottom of the UST during decommissioning and removal activities. • Five soil samples were collected from the sidewalls of the excavation (north, south, east, west), and a composite sample from the presumed contaminated stockpile was analyzed. The composite sample had reported concentrations of 1,000 milligrams per kilogram (mg/kg) diesel-range hydrocarbons, which did not exceed the Model Toxics Control Act (MTCA) Method A Cleanup Level of 2,000 mg/kg for soil. The sidewall samples also did not exceed MTCA Method A Cleanup Levels. • A grab groundwater sample from the excavation had reported concentrations of 6,900 micrograms per liter (µg/L) diesel-range hydrocarbons and 1,300 µg/L heavy oil-range hydrocarbons, both exceeding the MTCA Method A Cleanup Levels for groundwater (500 µg/L each). • Approximately 442 tons of petroleum-impacted soil and 1,268 gallons of impacted groundwater were subsequently removed during the excavation. A review of the Renton School District #403, Hazen Senior High School, Phase II Environmental Site Assessment Final Report, conducted by EHS-International, Inc., dated December 9, 2011, identified the following: • Three soil borings (B-1, B-2, and B-3) were advanced in the vicinity of the UST excavation area to a maximum depth of 36 feet below ground surface (bgs). • Groundwater was not encountered in any of the boreholes, suggesting that the groundwater observed in the UST pit during the UST removal may have been perched water. • A composite soil sample from two boreholes (B-1 and B-3) at 12 feet bgs indicated a concentration of 65 mg/kg diesel-range hydrocarbons, which is well below the MTCA Method A Cleanup Levels. The intent of the composite soil sample was to assess soil conditions in the vicinity of the UST, and the results confirmed that the soil in the vicinity of the UST former is in compliance with MTCA Cleanup regulations both vertically and horizontally. Subsequently, in September 2015, Ecology added the site to its list of known or suspected contaminated sites due to incomplete characterization of the contamination. Ecology specifically recommended further investigation of groundwater to assess the potential for contaminant migration. 1.4 Contaminants of Concern Based on the investigations conducted on site and described above, the following are the contaminants of concern (COCs): • Total petroleum hydrocarbons (TPH) as diesel and heavy oil. Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 3 Soil impacted by the identified COCs will be profiled for disposal as summarized in Section 2.5. 2. ADVANCE COORDINATION PRIOR TO SUBSURFACE DISTURBANCE This section describes the activities that shall be conducted under the guidance of this CMMP, and considerations to be in place prior to earthwork. Any contractor should be aware of this document prior to planning for work that disturbs soil and/or groundwater on site. Controls and processes described in the CMMP may have an impact on the Work. 2.1 Responsible Charge The property owner shall make the information in this plan available to any site workers who may contact potentially contaminated media. 2.2 Activities with the Potential to Generate Contaminated Soil and/or Groundwater Construction activities that may generate soil or groundwater requiring appropriate management include the following: • Excavation for utilities • Building demolition • General grading • Excavation for footings and other foundation structures • Dewatering 2.3 Project Team Prior to earthworks activities, management roles shall be identified and are detailed per the following table: Title Name Affiliation E-mail Phone Numbers Owner Michael (Mike) Cato Renton School District No. 403 michael.cato@rentonschools.us 206.643.2887 Site Manager Charlie Blankenship Forma Construction CharlieB@formacc.com 206.261.9124 Project Environmental Consultant Nasrin Bastami PBS nasrin.bastami@ApexCos.com 206.817.1371 Project Consultant Alan Jacobson Jacobson Consulting Engineers alan@jacobsonengineers.com 206.399.6233 Earthworks Contractor TBD TBD TBD TBD 2.4 Health and Safety Plan Any contractor doing significant subsurface work (disturbing and handling soil and/or groundwater) should maintain a site-specific Health and Safety Plan (HASP) in accordance with applicable Occupational Safety and Health Administration (OSHA) and Washington Industrial Safety and Health Act (WISHA) regulations. The HASP will provide information for site workers that address the health risks and hazards for each site task, employee training assignments to assure compliance with WISHA, personal protective Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 4 equipment, site control measures, and decontamination procedures. The HASP will include procedures and controls that are site specific to the identified project. The Contractor is responsible for conducting on-site activities in accordance with the HASP. The Contractor will review the contents of the HASP with on-site workers and will ensure adequate training for on-site workers in accordance with the HASP. Outside contractors or consultants participating in soil management activities have responsibility for their employee’s health and safety while on site. 2.5 Waste Profiling Petroleum contaminated soil and water encountered during project work, which is to be removed from site, will be characterized for disposal. Soil containing petroleum hydrocarbons (gasoline, diesel, heavy oil) must be managed as petroleum contaminated soil consistent with the Solid Waste Handling Standards (WAC 173-350). The Contractor may elect to begin the waste profiling process at any time by selecting a receiving facility/landfill. Having contaminated media profiled and accepted by a facility in advance is recommended as it may prevent delays. Each facility may have differing cost structures and permitting processes. Proximity is also a factor the Contractor should consider. Receiving landfills are likely to require that the Contractor submit waste material sample analytical results so that they can profile the waste. This should be arranged prior to transport of the material. Discharge of water to the sanitary sewer or storm sewer will require an appropriate permit from the City of Renton or King County for sanitary sewer or Ecology for stormwater. Absent the appropriate permit, wastewater will require containerization during profiling for offsite disposal at an appropriately permitted treatment facility. It is noted that waste profiling can also be completed following ground disturbance, but that waste will need to be stored on site during profiling prior to disposal. 3. MATERIAL DEFINITIONS Contaminated soil and water encountered during project work will be characterized for reuse or disposal. This section describes the classification and management of the contaminated material as follows: 3.1 Clean Soil Clean soil is defined as soil exhibiting no odors, containing no detectable contaminants at concentrations exceeding either Model Toxics Control Act (MTCA) Method A cleanup levels (CULs) and meeting all definitions of Category 1 soil as defined by the Guidance for Remediation of Petroleum Contaminated Sites: 1. Reusable Soil 1: Soil that contains no detectable levels of contamination. Reusable Soil 1 can be reused on site or transported offsite for reuse at a location chosen by the contractor. Alternatively, Reusable Soil 1 may be disposed of at any facility willing to accept. It is noted that threshold concentrations for Reusable Soil 1 for certain constituents are lower than CULs. Concentrations of constituents in waste soil for which threshold concentrations have been established in Table 12.1 of the Guidance for Remediation of Petroleum Contaminated Sites must be below the threshold concentrations for the waste soil to meet the definition of Reusable Soil 1. CULs are only used for constituents for which threshold concentrations have not been established in Table 12.1 when Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 5 considering reuse. If concentrations of other constituents are detected in waste material above CULs, the material may not be reused on site and should be profiled for offsite disposal. 3.2 Non-Dangerous Waste Soil not meeting the definition of clean soil as established in Section 3.1 will require special handling and reuse and/or disposal to comply with local, state and federal regulations. All project soil must be handled in accordance with Chapter 173-350 WAC. Generally, soil with contamination relating to petroleum contamination is handled in in Washington State in accordance with Ecology’s Guidance for Remediation of Petroleum Contaminated Sites. The Guidance establishes 4 categories of petroleum contaminated soil for reuse and/or disposal. Category 1 soil is already defined in Section 3.1 and may be reused on site if deemed suitable for reuse by the geotechnical engineer on the project or disposed of/reused at any receiving facility. Category 2 through 4 soils can be reused or disposed of as specified below. 2. Reusable Soil 2: Soil that contains detectable levels of contaminants within the range of concentrations established for Soil Category 2 in Table 12.1, Guidelines for Reuse of Petroleum-Contaminated Soil (Appendix A). Reusable Soil 2 can be reused onsite if it is not laterally or vertically within 10-feet of water or disposed of at any facility licensed/permitted to accept it. Reuse of Reusable Soil 2 is subject to the limitations included in Table 12.1 (Appendix A). 3. Reusable Soil 3: Soil that contains detectable levels of contaminants within the range of concentrations established for Soil Category 3 in Table 12.1, Guidelines for Reuse of Petroleum-Contaminated Soil (Appendix A). Reusable Soil 3 can be reused as a pavement base material under public and private paved streets and roads or under commercial and industrial parking lots or disposed of at any facility licensed/permitted to accept it. Reuse of Reusable Soil 3 is subject to the limitations included in Table 12.1 (Appendix A). 4. Reusable Soil 4: Soil that contains detectable levels of contaminants within the range of concentrations established for Soil Category 4 in Table 12.1, Guidelines for Reuse of Petroleum-Contaminated Soil (Appendix A). Reusable Soil 4 can be reused as a landfill daily cover, for asphalt manufacturing or disposed of at any facility licensed/permitted to accept it. Reuse of Reusable Soil 4 is subject to the limitations included in Table 12.1 (Appendix A). 5. Contaminated Soil: Soil that contains one or more contaminant(s) at concentrations that exceed either the CUL(s) or concentrations established for Reusable Soil 4 in Table 12.1 (Appendix A). Ecology requires that Contaminated Soil be disposed of at a Resource Recovery and Conservation Act (RCRA) Subtitle D facility unless it meets the definition of a Dangerous Waste. Dangerous Waste must be disposed of at a RCRA Subtitle C facility. In addition to the requirements established above, soil containing petroleum hydrocarbons (gasoline, diesel, heavy oil) must be managed as petroleum contaminated soil consistent with the Solid Waste Handling Standards (WAC 173-350). Soil/material/debris/liquid of any kind that is defined as Dangerous Waste per WAC 173-303 may not be reused in any capacity on or offsite and must be handled in accordance with Section 3.3 below. 3.3 Dangerous Waste Soil/material/debris/liquid that has contaminant levels that potentially exceed the Washington State Dangerous Waste criteria in accordance with WAC 173-303 would be considered Dangerous Waste. Ecology requires that Dangerous Waste be disposed of at an RCRA Subtitle C facility. Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 6 Based on preliminary review of potential contaminant sources in the project area, dangerous waste is not expected to be encountered. If sampling and analysis determines material to be dangerous waste, it will be handled in accordance with Washington State and RCRA Regulations. 4. CONTAMINATED MEDIA HANDLING This section summarizes work that potentially generates contaminated media requiring proper management and disposal. 4.1 Contaminated Soil and Groundwater Management Procedures If applicable (Contractor to determine), Contractor will manage contaminated soil in accordance with an established Stormwater Pollution Prevention Plan (SWPPP)/Temporary Erosion and Sediment Control (TESC) Plan and Solid Waste Handling Standards in WAC 173-350 (Ecology, 2018). Soil disturbance will be limited to the minimum area required to execute project work and any potentially contaminated soils will be protected from contact with stormwater via the use of berms, plastic sheeting, and other best management practices (BMPs). An environmental consultant will collect soil samples (see section 4.4) when soils suspected to be contaminated are encountered or prior to removal. Soil containing observed or detectable levels of petroleum contaminants but not meeting the definition of Contaminated Soil per Section 3.1 will be managed and disposed of in accordance with Table 12.1 of the Guidance for Remediation of Petroleum Contaminated Sites (Appendix A) as summarized in Section 3.2. Soil that contains other contaminants (i.e., other volatile organic compounds [VOCs] or carcinogenic polyaromatic hydrocarbons [cPAHs]) at concentrations that exceed the CULs, but does not meet Dangerous Waste criteria, shall be disposed of at a RCRA Subtitle D facility. If applicable (Contractor to determine), Contractor will manage contaminated groundwater in accordance with the established Spill Prevention Control and Countermeasure (SPCC) Plan, Construction Stormwater General Permit (Ecology, 2020), SWPPP, TESC Plan and WAC Chapter 173-201A Water Quality Standards for Surface Waters of the State of Washington (Ecology, 2016b). Groundwater that contains contaminant(s) at concentrations that exceed CULs (but does not meet Dangerous Waste criteria) will be disposed of at an appropriately licensed facility. 4.2 Field Screening and Identification A Contractor foreman, subcontractor foreman, or other designated HAZWOPER certified monitor will be present during excavation activities to provide visual screening of soils. Soils will be monitored for visual and olfactory evidence of contamination based on location of work, observed discoloration, texture, and odor, or the presence of metal or plastic remnants of tanks or drums. Physical characteristics that may be observed in excavated soils that indicate the need for separate stockpiling and laboratory testing include: • Soils containing petroleum discoloration or odor; • Soils or debris containing other unusual or unnatural discoloration or odor; • Wood or wood fragments containing other unusual or unnatural discoloration or odor; Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 7 • Drums, tanks, or metallic debris encountered in the excavation; and • Garbage or other debris. A field instrument that can help to qualitatively assess the presence of contamination is a photoionization detector (PID). A PID can detect the presence of a volatile compound (such as benzene or gasoline) in the air but does not identify the chemical. It is not expected that a PID will be utilized during routine construction activities. If suspected contamination is encountered or could be expected to be encountered (i.e. for work in or near areas with petroleum contamination documented in the subsurface investigation reports), a PID would be useful to help identify and segregate contaminated media and can be used for worker protection. Should suspected contaminated media be identified, the Contractor will notify the owner immediately. 4.3 Stockpiling The Contractor shall provide proper storage of contaminated soil or debris in stockpiles/staging piles pending sampling, analysis, waste profiling, and disposal. Sufficient storage will be required so that the Contractor’s operations are not disrupted due to insufficient storage. General requirements for the temporary stockpile include: (a) prevent intermixing of stockpiled materials with underlying soils or materials from other sources/or with other contaminants; (b) prevent contact with storm water; (c) prevent erosion of stockpiled materials; (d) apply stormwater BMPs as appropriate for stockpile construction and maintenance; (e) maintain daily inventory of stockpile areas and provide information to the Project Engineer, as requested, and (f) appropriate site security such as fence areas to alleviate hazards to the public. Incidental stockpiling of contaminated soil within the boundaries of a known contaminated soil area can be conducted without any liners or controls if soil is located in an area where run-off from the stockpile cannot run-on to a clean area or an area with a different type of contamination. In circumstances where stockpiling will be required, such as during the temporary storage of contaminated soil in a clean area or area with a different type of contamination, or the discovery of undocumented contamination, stockpiles will adhere to the following: • Stockpiles will be underlain by plastic sheeting with a minimum thickness of 6 mil, with adjacent sheeting sections overlapping a minimum of 3-feet. • The perimeter of the stockpiles shall be surrounded by a berm to prevent run-on and/or run-off of precipitation. • Stockpiles shall be covered with plastic sheeting when not in use and the cover should be anchored (such as with sandbags or otherwise) to prevent it from being disturbed by wind. 4.4 Soil Sampling and Testing Trained environmental personnel will perform sampling of excavated materials for characterization of suspected contaminated soils. The following sections describe the procedures for soil sampling. 4.4.1 Sample Collection Soil samples will be collected by filling laboratory provided containers. Soil will be collected in a single 4-oz jar for the analysis of TPH as diesel, of metals, and dry weight for that sample. Soil samples for analysis Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 8 of VOCs or TPH as gasoline will be collected into Volatile Organic Analysis (VOA) vials in accordance with EPA Method 5035A. 4.4.2 Decontamination All non-disposable components of the sampling equipment (e.g., hand augers, shovels, spoons, or other equipment) used to collect samples that contact the soil will be decontaminated prior to, and in between, collection of individual samples as follows: • Scrub with potable water containing Alconox/Liquinox detergent. • Potable water rinse. The sampler will don new disposable gloves for the collection of each sample. Samples will be placed in coolers on ice under chain-of-custody documentation for transport to the analytical laboratory. In the case of stockpile sampling, the number of samples collected to characterize a given volume of soil will be based on Table 6.9 of the Guidance for Remediation of Petroleum Contaminated Sites. Soils will be collected from at least 1 ft below the surface of stockpiles. 4.4.3 Sampling Analysis Procedures Samples may be analyzed for the following: • TPH as Diesel Range by Method NWTPH-Dx • TPH as Gasoline Range by Method NWTPH-Gx • BTEX by EPA Method 8021B • PAHs by EPA Method 8270/625 • Total Metals (RCRA-8: arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver) by EPA Method 200.8/6020A/7471 • VOCs by EPA Method 8260C • PCBs by Method 8082 4.4.4 Evaluation of Analytical Results The analytical results from samples collected will be reviewed by the Environmental Consultant and used to support regulatory reporting and waste profiling for disposal. The analytical results will be compared to the criteria defined for the types of wastes this plan addresses: “Clean Soil’, “Non-Dangerous Waste” and “Dangerous Waste.” Petroleum and Volatile Organics For the case of petroleum contamination, results will be compared with Tables 12.1 and 12.2 from the Guidance for Remediation of Petroleum Contaminated Sites (See Appendix A), which indicate threshold concentrations for disposal and reuse categories for petroleum contaminated soil. Petroleum contaminated soil that is not otherwise classified as a dangerous waste is regulated under the Solid Waste Handling Standards, Chapter 173-350 WAC (Ecology, 2018) as well as Table 12.1. 4.5 Contaminated Water Management Procedures Water accumulation related to stormwater management, limited perched groundwater, or incidental rainwater that accumulates in excavations will be handled and disposed of in accordance with the Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 9 construction Stormwater Pollution Prevention Plan (SWPPP) for the project. If possible, water should not be discharged from the site in areas with known contamination. Groundwater pumped from excavations or footings will be managed as follows: • Contain and Analyze: Water suspected to be contaminated with petroleum hydrocarbons due to contact with contaminated soil or from pumped groundwater will be pumped into an appropriate container (temporary tanks or DOT approved drums) and sampled. The samples will be analyzed to assess the correct method of treatment and/or disposal. Laboratory analytical results will be compared to both the Water Quality Standards established in WAC 173-201A and the MTCA Method A Cleanup Levels established in WAC 173-340, along with standards promulgated by the EPA for Human Health Criteria for Consumption. • Halt Work: If significant indications of contamination are observed in groundwater, then construction work will be halted while analytical testing is conducted to determine options for treatment, disposal, and health and safety requirements. In the event that work is halted, the owner will be notified. Such indicators could include presence of free phase liquids, odor, sheen, or extreme discoloration of the groundwater. If unanticipated contamination is revealed because of the analyses, the owner shall notify Ecology. • Disposal: Based on the volume of water generated and the concentrations of the constituents of concern, the groundwater will be disposed of by one of the two following methods: 1. Infiltration back into the area from where it was pumped or discharge to storm/sanitary sewer. Any discharge to storm sewer or surface waters or infiltration into the work area must be authorized by Ecology under the National Pollutant Discharge Elimination System (NPDES) permit. 2. Off-site disposal by contacting a vendor to collect the water and transport it to a proper disposal or recycling facility. Groundwater that contains contaminants at concentrations that preclude discharge to storm sewer or infiltration in the work area (per the criteria noted above) shall be hauled offsite to an approved facility coordinated by the Contractor. Disposal shall be at a facility permitted to treat and indirectly discharge wastewater to the public sewer under 40 CFR 437 (centralized waste treatment facility). 4.6 Contaminated Demolition Debris Management Procedures Demolition debris will be characterized for disposal pursuant to WAC 173-303 and WAC 173-350. Demolition debris contaminated with PCBs or heavy metals at concentrations exceeding the applicable cleanup standard should be segregated with appropriate secondary containment (i.e., plastic sheeting with berms, metal container, etc.) for off-site disposal. 4.7 Procedures for Specific Construction Activities This section describes activities that may result in the generation of waste for off-site disposal. 4.7.1 Utility Work Subsurface utility work may be undertaken to support routine maintenance or upgrades. Contaminated soil identified during utility work will be managed in accordance with this CMMP. Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 10 4.7.2 Grading Mass grading may take place during significant redevelopment work. In general, grading will reuse soil cut and transported within the site. Contaminated soil identified during trenching or grading operations should be contained, characterized, and disposed of off-site at a permitted facility. 4.8 Dust and Odor Control There is the potential for nuisance dust or odors to be emitted during soil excavation activities. The goal is to eliminate visible airborne Fugitive Dust. Therefore, state and local regulatory agencies expect that as many of these control techniques be employed as necessary to achieve this goal. Should excessive dust or nuisance odors develop during excavation as determined by visual and olfactory observation by the Contractor, or complaints, the Contractor shall be prepared to implement one or more of the following odor control measures: • Minimize the open area where high concentrations of contaminants may be present. • Apply a mist of water over the area as needed to minimize odor and dust. The use of water for dust control will be sufficient to suppress dust but should not be excessive such that surface runoff of water used for dust control is permitted. • Cover exposed areas with elevated concentrations of contaminants with plastic sheeting at the end of each day and when excavation activities are not being performed. • Keep stockpiles covered when not in use. 4.9 Decontamination Procedures If contaminated soils are identified within work areas, procedures should be implemented to avoid spreading such material. In such areas, oil residue on equipment and excavator tracks/tires and truck tires will be removed using a combination of wet and dry methods. During dry conditions, soil residues will be removed by dry brushing. Soil that cannot be removed by this procedure will be removed from equipment by washing with high-pressure water. During wet season conditions, high-pressure water washing will be used to remove material residues and mud from equipment and tires. If a contaminated area can be delineated that will experience extensive vehicle traffic, a decontamination station will be constructed at an appropriate location on the site. The station will consist of a bermed bed of crushed aggregate rock equipped with a water collection sump. Water generated during decontamination activities will be handled as process water and disposed of to the sanitary sewer or disposed of off-site at an approved facility. The work areas will be kept clean and free of excessive soil or debris. 4.10 Contingency Plan for Unknown Contamination Contaminated soils may be encountered during the Work that have not previously been identified or characterized. The Contractor shall stop work and notify the Project Team if any of the following are encountered: • Obvious staining, sheen, or colored hues in soil or standing water in locations not previously designated. • Presence of gasoline- or oil-like vapor, odor, or unexpected petroleum products or other chemicals. • Utility pipelines with sludge or trapped liquid indicating potential petroleum, chemicals, or sludge. Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 11 • Unexpected buried pipes, conduits, tanks, or unexplained metallic objects or debris. • Vapors causing eye irritation or nose tingling or burning. In the event that suspected contaminated soil or groundwater are observed, the Contractor will notify the Project Team. Soil samples will be field screened, and samples will be collected and analyzed to ensure that the contaminated soil and/or groundwater is removed and properly characterized prior to disposal. 5. CONTAMINATED MEDIA TRANSPORT AND OFF-SITE DISPOSAL Transport of contaminated media to the appropriate disposal facilities will be performed by haulers licensed to transport that media. The Contractor shall submit a copy of its transporter’s permit/qualifications for shipping contaminated soil prior to any waste transfer. 5.1 Waste Profile and Manifest Prior to transport of contaminated material, the waste material must be properly manifested and approved for acceptance by the selected disposal facility. The Contractor shall provide the owner with copies of the waste profile, manifest, and approval notification from the selected disposal facility 3 days prior to removal of contaminated material from the project site. 5.2 Contaminated Soil Transport Transport of contaminated soil to the appropriate disposal facilities will be performed by haulers licensed to transport the type of contaminated soil. Contaminated soil will be loaded from stockpile or containers directly to the designated vehicle for transport to the approved disposal site. The Contractor shall provide the owner with copies of shipping records (manifest or bill of lading) and quantity tickets for all shipped wastes, indicating each waste shipment has been received at a disposal facility. 5.3 Off-Site Disposal Soil with detectable concentrations of petroleum hydrocarbons must be managed as petroleum contaminated soil and disposed of at a permitted solid waste facility in accordance with WAC 173-340. Soil with detectable concentrations of other contamination such as VOCs (including trichloroethene) must be managed according to its waste category and disposed of at a permitted solid waste facility in accordance with WAC 173-350. The Contractor is responsible for determining waste facility requirements and facilitating additional preliminary waste profiling if required. Sampling for waste profile analysis may be required by the receiving facility prior to approval. Once a permitted facility is selected, the Contractor will submit copies of the facility permits and environmental approvals to the owner for review and approval prior to transport and disposal of material. Example facilities that may be used for disposal of contaminated waste include: • Republic Services • Waste Management • Ecology permitted solid waste facilities • Other public health department approved facility Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 12 6. POST CONSTRUCTION MANAGEMENT This CMMP was created as guidance related to contamination encountered during the utility maintenance and/or a construction period. It is understood that additional management related to contamination may be appropriate once construction is complete. Ongoing management may include inspection, notification, maintenance, and monitoring. 7. REPORTING AND DOCUMENTATION Contractors and any subcontractors managing contaminated media will maintain all necessary permits and approvals related to the removal, excavation, management, storage, transportation, and/or treatment/disposal of the contaminated soil or water that might be generated during the project. Permits may include, but are not limited to, excavation permits, transportation permits and manifests, discharge permits and approvals, and permits for treatment or disposal of contaminated waste. Copies of permits and disposal receipts should be retained for future reporting by the property owner. In summary, documentation may include: • Quantity by weight as determined by number of truckloads and disposal facility weight tickets. • Quantity of water by gallons retained by dewatering activity for discharge or disposal. The destination (discharge or disposal) of the water will be documented. If off-site disposal, facility delivery receipts (gallons) shall be retained. • Physical characteristics including analytical results when applicable. • Disposal facility for each material disposed • Disposal facility receipts • Weight / truck tickets • Manifests / Bills of Lading • Fee receipts • Certification from each receiving facility owner that the facility’s operating permit conditions were met for materials disposed. • Copies of all analytical data will be provided to the landfill operator upon request. The documentation shall be presented to the property owner in a report that includes the attachment of all laboratory data. An accompanying narrative will describe the soil removal and any deviations to the procedures that occurred. Corrective actions will be identified as needed, and the resolution of any discrepancies will be reported. Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 13 8. SIGNATURE PBS Engineering and Environmental LLC Nasrin Bastami Environmental Practice Lead Reviewed by: Melanie Young, PE, PBS Senior Environmental Engineer Contaminated Media Management Plan 1101 Hoquiam Avenue NE Hazen High School Site Renton, Washington April 2025 PBS Project 24012360 14 9. REFERENCES Ecology, 2024. Model Toxics Control Act Regulation, Washington State Department of Ecology, Publication No. 94-06, revised January 2024. Ecology, 2014. Dangerous Waste Regulations WAC 173-303, Washington State Department of Ecology, December 2014. Ecology, 2016a. Guidance for Remediation of Petroleum Contaminated Sites, Washington State Department of Ecology, June 2016. Ecology, 2016b. Water Quality Standards for Surface Waters of the State of Washington, Washington State Department of Ecology, August 2016. Ecology, 2018. Solid Waste Handling Standards WAC 173-350, Washington State Department of Ecology, September 2018. Figures Figure 1 – Site Plan EHSI - Hazen HS UST Assessment (Figure 3)_October 2011 EHSI - Hazen HS Phase II Subsurface Investigation (Figure 3)_December 2011 April 202524012360SITE PLANHAZEN HIGH SCHOOL 1101 HOQUIAM AVENUE NE, RENTON, WASHINGTON FIGURE1 PREPERED FOR: RENTON SCHOOL DISTRICT LEGEND Not To Scale Beauty Parlor Approximate Subject Property Boundary Gate MY E R S R O A D E FOREST VIEW APARTMENTS UNDEVELOPED UNDEVELOPED UNDEVELOPED MULTI-TENANT COMMERCIAL SOURCE: GOOGLE EARTH Underground Storage Tank (UST) Appendix A Ecology Guidance for Reuse of PCS Tables 12.1 – 12.2 Guidance for Remediation of Petroleum Contaminated Sites Section 12-Re-use of Soils Washington State Department of Ecology Pub. No. 10-09-057 Page 188 Table 12.1 Guidelines for Reuse of Petroleum-Contaminated Soil Parameter Analytical Method Soil Category (8)(9)(10) 1 No detectable Petroleum Components (mg/kg) 2 Commercial Fill Above Water Table (mg/kg) 3 Paving Base Material & Road Construction (mg/kg) 4 Landfill Daily Cover or Asphalt Manufacturing (mg/kg) Total Petroleum Hydrocarbons (1)(2) See Table 7.1 for petroleum products that fall within these categories. Gasoline Range Organics NWTPH-Gx <5 5 - 30 >30 - 100 >100 Diesel Range Organics NWTPH-Dx <25 25 - 200 >200 - 500 >500 Heavy Fuels and Oils* NWTPH-Dx <100 100 - 200 >200 – 500 >500 Mineral Oil NWTPH-Dx <100 100 - 200 >200 – 500 >500 Volatile Petroleum Components Benzene SW8260B <0.005 0.005 - 0.03 0.03 or less See Table 12.2 Ethylbenzene SW8260B <0.005 0.005 - 6 6 or less >6 Toluene SW8260B <0.005 0.005 - 7 7 or less >7 Xylenes (3) SW8260B <0.015 0.015 - 9 9 or less >9 Fuel Additives & Blending Components (MTBE) Methyl Tert- Butyl Ether SW8260B <0.005 0.005 - 0.1 0.1 or less >0.1 Lead SW6010A <17 17 - 50 >50 - 220 See Table 12.2 Other Petroleum Components Polychlorinated (4) Biphenyls (PCBs) SW8082 <0.04 <0.04 <0.04 See Table 12.2 Naphthalenes (5) SW8260B <0.05 0.05 - 5 5 or less >5 cPAHs (6) SW8270C <0.05 0.05 - 0.1 >0.1 - 2 >2 Other Petroleum Characteristics (Applies to soils contaminated with any petroleum product.) Odors Smell No detectable odor Staining Visual No unusual color or staining Sheen Test See Footnote # 7 No visible sheen IMPORTANT: See Table 12.2 and the footnotes to this Table on the following pages! Test soil for the parameters specified in Table 7.2. *Does NOT include waste oil contaminated soils, which should be disposed of in a landfill. “<” means less than; “>” means greater than Table 12.1 Guidelines for reuse of petroleum-contaminated soil. Guidance for Remediation of Petroleum Contaminated Sites Section 12-Re-use of Soils Washington State Department of Ecology Pub. No. 10-09-057 Page 189 Table 12.2 Description and Recommended Best Management Practices for Soil Categories in Table 12.1 (continued next page) Category Acceptable Uses Limitations Category 1 Soils: Soils with no detectable/ quantifiable levels of petroleum hydrocarbons or constituents using the analytical methods listed in Table 7.3 and are not suspected of being contaminated with any other hazardous substances. Can be used anywhere the use is allowed under other regulations. Any use allowed for Category 2, 3 & 4 soils. These soils should be odor-free. Category 2 Soils: Soils with residual levels of petroleum hydrocarbons that could have adverse impacts on the environment in some circumstances. Any use allowed for Category 3 & 4 soils. Backfill at cleanup sites above the water table. Fill in commercial or industrial areas above the water table. Road and bridge embankment construction in areas above the water table. These soils may have a slight petroleum odor, depending on the sensitivity of the individual. This should be considered when reusing these soils. Should be placed above the highest anticipated high water table. If seasonal groundwater elevation information is not available, place at least 10 feet above the current water table. Should not be placed within 100 feet of any private drinking water well or within the 10 year wellhead protection area of a public water supply well. Should not be placed in or directly adjacent to wetlands or surface water where contact with water is possible. Should not be placed under a surface water infiltration facility or septic drain field. Any other limitations in state or local regulations. Category 3 Soils: Soils with moderate levels of residual petroleum contamination that could have adverse impacts on the environment unless re-used in carefully controlled situations. Any use allowed for Category 4 soils. Use as pavement base material under public and private paved streets and roads. Use as pavement base material under commercial and industrial parking lots. Should be placed above the highest anticipated high water table. If seasonal ground water elevation information is not available, place at least 10 feet above the water table. Should be a maximum of 2 feet thick to minimize potential for leaching or vapor impacts. Should not be placed within 100 feet of any private drinking water well or within the 10 year wellhead protection area of a public water supply well. Should not be placed in or directly adjacent to wetlands or surface water. Should not be placed under a surface water infiltration facility or septic drain field. When exposed, runoff from area in use should be contained or treated to prevent entrance to storm drains, surface water or wetlands. Any other limitations in state or local regulations. Table 12.2 Description and recommended best management practices for soil categories in Table 12.1 (continued next page). Guidance for Remediation of Petroleum Contaminated Sites Section 12-Re-use of Soils Washington State Department of Ecology Pub. No. 10-09-057 Page 190 Table 12.2 (continued) Description and Recommended Best Management Practices for Soil Categories in Table 12.1 Category Acceptable Uses Limitations Category 4 Soils: Soils with high levels of petroleum contamination that should not be re-used except in very limited circumstances. Use in the manufacture of asphalt. Use as daily cover in a lined municipal solid waste or limited purpose landfill provided this is allowed under the landfill operating permit. Landfill Limitations: The soil should be tested for and pass the following tests: Free liquids test. Soils that contain free liquids cannot be landfilled without treatment. TCLP for lead and benzene. Unless exempt under WAC 173-303-071(3)(t), soils that fail a TCLP for lead or benzene must be disposed of as hazardous waste. Flammability test. Soils that fail this test must be disposed of as hazardous waste. Bioassay test under WAC 173-303-100(5). Soils that fail this test must be disposed of as hazardous waste. PCBs. Soils with a total PCB content of 2 ppm or more must be disposed of as hazardous waste. Soil used for daily cover should be stockpiled within the landfill lined fill area. Soil containing more than 10,000 mg/kg TPH should be buried immediately with other wastes or daily covered to limit potential worker exposure. Any additional limitations specified in the landfill permit or in other state or local regulations. Asphalt Manufacturing Limitations: Soil storage areas should be contained in a bermed area to minimize contact with surface water runoff from adjacent areas. Runoff from storage areas should be considered contaminated until tested to prove otherwise. Soil storage areas should also be lined and covered with a roof or secured tarp to minimize contact with precipitation and potential groundwater contamination. Leachate from storage areas should be considered contaminated until tested to prove otherwise. The soil should be tested for and pass the following tests: TCLP for lead and benzene. Unless exempt under WAC 173-303-071(3)(t), soils that fail a TCLP for lead or benzene must be disposed of as hazardous waste. Flammability test. Soils that fail this test must be disposed of as hazardous waste. Bioassay test under WAC 173-303-100(5). Soils that fail this test must be disposed of as hazardous waste. No detectable levels of PCBs in soil (<0.04 mg/kg). Precautions should be taken to minimize worker exposure to soil storage piles and any dust or vapors from these piles prior to feeding into the asphalt batch plant. IMPORTANT: See the following page for additional information! Page | 39 Appendix H – Engineering Calculations ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 02/13/2025 1:45 PM Report Generation Date: 02/13/2025 1:45 PM ————————————————————————————————— Input File Name: 2024-08-19 Hazen HS Baseball TESC Sizing.fld Project Name: Hazen HS Analysis Title: TESC Sizing Comments: Baseball Basin ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 16 Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 3.750 3.750 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 3.750 3.750 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Forest, Flat 3.750 ---------------------------------------------- Subbasin Total 3.750 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Lawn, Flat 0.650 SIDEWALKS/FLAT 3.100 ---------------------------------------------- Subbasin Total 3.750 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 713.650 _____________________________________ Total: 713.650 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 83.780 _____________________________________ Total: 83.780 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 4.517 ac-ft/year, Post Developed: 0.530 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 9.442E-02 2-Year 1.340 5-Year 0.149 5-Year 1.753 10-Year 0.185 10-Year 2.098 25-Year 0.255 25-Year 2.550 50-Year 0.280 50-Year 3.161 100-Year 0.303 100-Year 3.932 200-Year 0.449 200-Year 4.153 500-Year 0.645 500-Year 4.433 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals TESC Sediment Trap Sizing (BMP C240) - Baseball Field Total Site: Pervious Area Impervious Area Total Area 0.38 ac 3.00 ac 3.38 ac SA = FS (Q2 / VS ) SA = Surface Area (ft2) FS = Factor of Safety = 2 Q2 = 2-year, 24-hour storm flow rate (ft3/s) VS = Settling Velocity = 0.00096 ft/s Per MGS TESC Sizing Report: 2-year, 24-hour storm event Q2 = 1.269 ft3/s Surface Area Calculation: SA = 2 (1.269 / 0.00096) SA = 2,643 ft2 VR = SA * 3.5 ft minimum storage depth VR = 2,643 * 3.5 VR = 9,253 ft3 Storage Volume Required VR = 9,253 ft3 * (7.48 gal/ 1 ft3) VR = 69,213 Gallons Required Volume Provided: (4) 18,900 Gallon sediment storage tanks V = 4 * 18,900 V = 75,600 Gallons Provided ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.62 Program License Number: 201910001 Project Simulation Performed on: 08/19/2024 11:17 AM Report Generation Date: 08/19/2024 11:17 AM ————————————————————————————————— Input File Name: 2024-08-19 Hazen HS Softball TESC Sizing.fld Project Name: Hazen HS Analysis Title: TESC Sizing Comments: Softball Basin ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 16 Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.000 1.000 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.000 1.000 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Forest, Flat 1.000 ---------------------------------------------- Subbasin Total 1.000 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 1.000 ---------------------------------------------- Subbasin Total 1.000 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 190.307 _____________________________________ Total: 190.307 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 0.000 _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 1.204 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 2.518E-02 2-Year 0.410 5-Year 3.967E-02 5-Year 0.529 10-Year 4.935E-02 10-Year 0.623 25-Year 6.799E-02 25-Year 0.781 50-Year 7.465E-02 50-Year 0.935 100-Year 8.092E-02 100-Year 1.165 200-Year 0.120 200-Year 1.241 500-Year 0.172 500-Year 1.339 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals TESC Sediment Trap Sizing (BMP C240) - Softball Field Total Site: Pervious Area Impervious Area Total Area 0 ac 1.0 ac 1.0 ac SA = FS (Q2 / VS ) SA = Surface Area (ft2) FS = Factor of Safety = 2 Q2 = 2-year, 24-hour storm flow rate (ft3/s) VS = Settling Velocity = 0.00096 ft/s Per MGS TESC Sizing Report: 2-year, 24-hour storm event Q2 = 0.41 ft3/s Surface Area Calculation: SA = 2 (0.41 / 0.00096) SA = 854 ft2 VR = SA * 3.5 ft minimum storage depth VR = 854 * 3.5 VR = 2,989 ft3 Storage Volume Required VR = 2,989 ft3 * (7.48 gal/ 1 ft3) VR = 22,362 Gallons Required Volume Provided: (2) 18,900 Gallon sediment storage tanks V = 2 * 18,900 V = 37,800 Gallons Provided HAZEN HIGH SCHOOL IMPROVEMENTS 27 APPENDIX D FACILITY SUMMARY SHEET DECLARATION OF COVENANT STORMWATER FACILITY SUMMARY SHEET ( provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Major Basin Name __ Immediate Basin Name GENERAL FACILITY INFORMATION: Detention Infiltration Water Quality Flow Control Type # of Type # of Type #of Performance Std Pond s Ponds Ponds □ Basic Vaults Tanks Vaults □ Conservation Tanks renches Tanks □ Flood Problem DPER Permit No. Date NPDES Permit No. Parcel No. Retired Parcel No. Project includes Landscape Management Plan? yes □ (include copy with TIR as Appendix) no □ Declarations of Covenant Recording No. Leachable Metals Impervious Surface Limit Flow Control BMPs Clearing Limit Drainage Facility Landscape Management Plan If no flow control facility, check one: □ Project qualifies for KCSWDM Exemption (KCSWDM 1.2.3): □ Basic Exemption □ Impervious Surface Exemption for Transportation Redevelopment projects □ Cost Exemption for Parcel Redevelopment projects □ Direct Discharge Exemption □ Other___________________ □ Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 □ No flow control required per approved KCSWDM Adjustment No.________________ □ Flow control provided in regional/shared facility per approved approved KCSWDM Adjustment No.________________ Shared Facility Name/Locati nn____________________ □ No flow control required (other, provide justification): TREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES (Applies to Commercial parcels only)Area % of Total Total Acreage (ac) Total Impervious Acreage (ac) Total impervious surface served by flow control facility(ies) (sq ft) Impervious surface served by flow control facility(ies) designed 1990 or later (sq ft) Impervious surface served by pervious surface absorption (sq ft) Impervious surface served by approved water quality facility(ies) (sq ft) PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEETS AS NEEDED FOR ADDITIONAL FACILITIES 2021 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 7/23/2021 Page 1 Hazen High School Improvements 1101 Hoquiam Ave NE, Renton WA, 98059 1023059201 & 1023059277 May Creek Cedar River 1 N/A 2.79 2.34 83.87% 102,104 100% 102,104 100% 0 0 ----- STORMWATER FACILITY PRELIMINARY SUMMARY SHEET - DISCHARGE LOCATION TDA #1 (BASEBALL FIELD) N/A ----- TBD1 STORMWATER FACILITY SUMMARY SHEET DPER Permit No. ( provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Project Name Project Location Downstream Drainage Basins: Major Basin Nam__________ Immediate Basin Nam______ FLOW CONTROL FACILITY: Basin: Facility Name/Number___________________________________□ New Facility □ Existing FacilityFacility Location UIC? □ yes □ no UIC Site ID: Live Storage □ cu.ft. Volume □ ac.ft. Live Storage Depth (ft) Volume Factor of Safety ______ Project Impervious Acres Served % of Total Project Impervious Acres Served No. of Lots Served Control Structure location:_ Type of Control Structure: □ Riser in vault □ Riser in Type II CB □ Weir in Type II CB No. of Orifices/Restrictions Size of Orifice/Restriction (in.) (numbered starting with lowest orifice): (inches in decimal format) N o . 1 No.2 No.3 No.4 Dam Safety Regulations (WA State Dept of Ecology): Re servoir Volume above natural grade □ cu.ft. □ ac.ft. Depth of Reservoir above natural grade (ft) WATER QUALITY FACILITIES Indicate no. of water quality facilities/BMPs for each type: _____Flow dispersion _____Filter strip _____Biofiltration swale □ regular, □ wet or □ continuous inflow _____Wetvault □ combined w/detention _____Wetpond □ basic □ large □ combined w/detention _____Pre-settling pond Design Information Water Quality design flow (cfs) Water Quality treated volume (sandfilter) (cu.ft.) Water Quality storage volume (wetpool) (cu.ft.) □ Landscape management plan □ Farm management plan High flow bypass structure (e.g., flow-splitter catch basin) Oil/water separator □ baffle □ coalescing plate _torm filter Stormwater wetland Sand filter □ basic □ large Sand bed depth Catch basin inserts (Manufacturer: ) □ regular □ linear □ vault (inches)__urce controls • Is facility lined? □ yes □ no If so, what marker is used above liner?What type of liner is used? Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred). 2021 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 7/23/2021 Page 2 Hazen High School Improvements 1101 Hoquiam Ave NE, Renton WA, 98059 May Creek Cedar River StormTrap Double Trap Precast Modular System West of Baseball Field 47,398 9.0'10% 2.34 100% 2 STORMWATER FACILITY PRELIMINARY SUMMARY SHEET - DISCHARGE LOCATION TDA #1 (BASEBALL FIELD) West of StormTrap Vault 3 1.0" 0.875" 1/2"0.75" N/A 0.056 cfs 1 Contech 4' X 6' Modular Wetland STORMWATER FACILITY SUMMARY SHEET ( provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Major Basin Name __ Immediate Basin Name GENERAL FACILITY INFORMATION: Detention Infiltration Water Quality Flow Control Type # of Type # of Type #of Performance Std Pond s Ponds Ponds □ Basic Vaults Tanks Vaults □ Conservation Tanks renches Tanks □ Flood Problem DPER Permit No. Date NPDES Permit No. Parcel No. Retired Parcel No. Project includes Landscape Management Plan? yes □ (include copy with TIR as Appendix) no □ Declarations of Covenant Recording No. Leachable Metals Impervious Surface Limit Flow Control BMPs Clearing Limit Drainage Facility Landscape Management Plan If no flow control facility, check one: □ Project qualifies for KCSWDM Exemption (KCSWDM 1.2.3): □ Basic Exemption □ Impervious Surface Exemption for Transportation Redevelopment projects □ Cost Exemption for Parcel Redevelopment projects □ Direct Discharge Exemption □ Other___________________ □ Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 □ No flow control required per approved KCSWDM Adjustment No.________________ □ Flow control provided in regional/shared facility per approved approved KCSWDM Adjustment No.________________ Shared Facility Name/Locati nn____________________ □ No flow control required (other, provide justification): TREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES (Applies to Commercial parcels only)Area % of Total Total Acreage (ac) Total Impervious Acreage (ac) Total impervious surface served by flow control facility(ies) (sq ft) Impervious surface served by flow control facility(ies) designed 1990 or later (sq ft) Impervious surface served by pervious surface absorption (sq ft) Impervious surface served by approved water quality facility(ies) (sq ft) PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEETS AS NEEDED FOR ADDITIONAL FACILITIES 2021 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 7/23/2021 Page 1 Hazen High School Improvements 1101 Hoquiam Ave NE, Renton WA, 98059 1023059201 May Creek Cedar River 1 N/A 1.06 0.98 92.45% 42,684 100% 42,684 100% 0 0 --- --- STORMWATER FACILITY PRELIMINARY SUMMARY SHEET - DISCHARGE LOCATION TDA #2 (SOFTBALL FIELD) N/A TBD1 STORMWATER FACILITY SUMMARY SHEET DPER Permit No. ( provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Project Name Project Location Downstream Drainage Basins: Major Basin Nam__________ Immediate Basin Nam______ FLOW CONTROL FACILITY: Basin: Facility Name/Number___________________________________□ New Facility □ Existing FacilityFacility Location UIC? □ yes □ no UIC Site ID: Live Storage □ cu.ft. Volume □ ac.ft. Live Storage Depth (ft) Volume Factor of Safety ______ Project Impervious Acres Served % of Total Project Impervious Acres Served No. of Lots Served Control Structure location:_ Type of Control Structure: □ Riser in vault □ Riser in Type II CB □ Weir in Type II CB No. of Orifices/Restrictions Size of Orifice/Restriction (in.) (numbered starting with lowest orifice): (inches in decimal format) N o . 1 No.2 No.3 No.4 Dam Safety Regulations (WA State Dept of Ecology): Re servoir Volume above natural grade □ cu.ft. □ ac.ft. Depth of Reservoir above natural grade (ft) WATER QUALITY FACILITIES Indicate no. of water quality facilities/BMPs for each type: _____Flow dispersion _____Filter strip _____Biofiltration swale □ regular, □ wet or □ continuous inflow _____Wetvault □ combined w/detention _____Wetpond □ basic □ large □ combined w/detention _____Pre-settling pond Design Information Water Quality design flow (cfs) Water Quality treated volume (sandfilter) (cu.ft.) Water Quality storage volume (wetpool) (cu.ft.) □ Landscape management plan □ Farm management plan High flow bypass structure (e.g., flow-splitter catch basin) Oil/water separator □ baffle □ coalescing plate _torm filter Stormwater wetland Sand filter □ basic □ large Sand bed depth Catch basin inserts (Manufacturer: ) □ regular □ linear □ vault (inches)__urce controls • Is facility lined? □ yes □ no If so, what marker is used above liner?What type of liner is used? Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred). 2021 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 7/23/2021 Page 2 Hazen High School Improvements 1101 Hoquiam Ave NE, Renton WA, 98059 May Creek Cedar River StormTech Chamber MC-3500 Softball Field 22,265 3.64' South of StormTech Chamber System 10% 0.98 100% 1 2 0.87" 1/4" STORMWATER FACILITY PRELIMINARY SUMMARY SHEET - DISCHARGE LOCATION TDA #2 (SOFTBALL FIELD) 0.5" N/A 0.025 cfs 1 Contech 4' X 6' Modular Wetland X XX CO SUB SUB SUB SUB SU B S U B SU B S U B SUB SUB SUB SU B SU B SUB SUB SUB SU B SU B SUB SUB SUB SU B SU B SUB SUB SUB SU B SU B SUB SUB SUB SU B S U B SUB SUB SUB SU B S U B SUB SUB SUB SU B S U B SUB SUB SU B S U B SUB SUB SU B SU B SUB SUB SU B SU B SUB SUB SU B SU B SUB SUB SU B SU B SUB SUB S U B SU B SUB SUB SU B SU B SUB SU B S U B SUB S U B SU B SUB SU B SUB SU B SUB SU B SUB SU B SUB S U B S U B S U B SU B SUB SUBSUB SU BSU B SU B SUB SU B SU B SUB SU BSU B SU B SUB SU B SD SD DU V A L L A V E . N . E . HO Q U I A M A V E . N . E . N.E. 10TH ST. HA M N.E . EL D VE N . E . NE 10TH ST 1 2 STORMTRAPDOUBLE TRAPDETENTION SYSTEM STORMTECH CHAMBERS MC-3500 DETENTION SYSTEM MODULAR WETLAND WATER QUALITY VAULT MODULAR WETLANDWATER QUALITY VAULT TDA #1 TDA #2 TDA #3 CONTECH CDS SEPARATORPRESETTLING STRUCTURE Page 1 of ___ Return Address: City Clerk’s Office City of Renton 1055 S Grady Way Renton, WA 98057 DECLARATION OF COVENANT FOR INSPECTION AND MAINTENANCE OF DRAINAGE FACILITIES AND ON-SITE BMPS Grantor: Grantee: City of Renton, a Washington municipal corporation Legal Description: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved City of Renton (check one of the following) Residential Building Permit Commercial Building Permit Clearing and Grading Permit Civil Construction or Utility Permit for Permit(s)_____________________ (Construction/Building/Utility Permit #) relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covenants (covenant) with the City of Renton (“City of Renton” or “City”), a municipal corporation of the state of Washington, that he/she (they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs 1 through 9 below with regard to the Property, and hereby grants (grant) an easement as described in Paragraphs 2 and 3. Grantor(s) hereby grants (grant), covenants (covenant), and agrees (agree) as follows: 1.The Grantor(s) or his/her (their) successors in interest and assigns ("Owners ") shall at their own cost, operate, maintain, and keep in good repair, the Property's drainage facilities constructed as required in the approved construction plans and specifications __________________ (Project Plan #) on file with the City of Renton and submitted to the City of Renton for the review and approval of permit(s) _____________________________ (Construction/Building/Utility Permit #). The Property's drainage facilities are shown and/or listed on Exhibit A – Site Plan. The Property’s drainage facilities shall be maintained in compliance with the operation and maintenance schedule included and attached herein as Exhibit B – Operations and Maintenance. Drainage facilities include pipes, channels, flow control facilities, water quality facilities, on-site best management practices (BMPs) and other engineered structures designed to manage and/or Renton School District No. 403 For Full Legal Description, Reference Exhibit C PTN NW 1/4 OF SEC 10 & THE NE 1/4 OF SEC 10, ALL IN TWP 23N, R05 E, W.M. 1023059201 & 1023059277 C24005771 N/A C24005771 47 4 Page 2 of ___ treat stormwater on the Property. On-site BMPs include dispersion and infiltration devices, bioretention, permeable pavements, rainwater harvesting systems, tree retention credit, reduced impervious surface footprint, vegetated roofs and other measures designed to mimic pre-developed hydrology and minimize stormwater runoff on the Property. 2.City of Renton shall have the right to ingress and egress over those portions of the Property necessary to perform inspections of the stormwater facilities and BMPs and conduct maintenance activities specified in this Declaration of Covenant and in accordance with the Renton Municipal Code. City of Renton shall provide at least thirty (30) days’ written notice to the Owners that entry on the Property is planned for the inspection of drainage facilities. After the thirty (30) days, the Owners shall allow the City of Renton to enter for the sole purpose of inspecting drainage facilities. In lieu of inspection by the City, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the drainage facilities and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the City of Renton within fifteen (15) days of receiving the City’s notice of inspection. Within thirty (30) days of giving this notice, the Owners, or engineer on behalf of the Owners, shall provide the engineer’s report to the City of Renton. If the report is not provided in a timely manner as specified above, the City of Renton may inspect the drainage facilities without further notice. 3.If City of Renton determines from its inspection, or from an engineer’s report provided in accordance with Paragraph 2, that maintenance, repair, restoration, and/or mitigation work is required to be done to any of the drainage facilities, City of Renton shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (“Work”) required pursuant to the Renton Municipal Code. The City shall also set a reasonable deadline for the Owners to complete the Work, or to provide an engineer’s report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the City access to re-inspect the drainage facilities unless an engineer’s report has been provided verifying completion of the Work. If the Work is not completed within the time frame set by the City, the City may initiate an enforcement action and/or perform the Work and hereby is given access to the Property for such purposes. Written notice will be sent to the Owners stating the City’s intention to perform such Work. This Work will not commence until at least seven (7) days after such notice is mailed. If, within the sole discretion of the City, there exists an imminent or present danger, the seven (7) day notice period will be waived and Work will begin immediately. 4.The Owners shall assume all responsibility for the cost of any Work, or any measures taken by the City to address conditions as described in Paragraph 3. Such responsibility shall include reimbursement to the City within thirty (30) days of the receipt of the invoice for any such Work performed. Overdue payments will require payment of interest at the maximum legal rate allowed by RCW 19.52.020 (currently twelve percent (12%)). If the City initiates legal action to enforce this agreement, the prevailing party in such action is entitled to recover reasonable litigation costs and attorney’s fees. 5.The Owners are required to obtain written approval from City of Renton prior to filling, piping, cutting, or removing vegetation (except in routine landscape maintenance) in open vegetated stormwater facilities (such as swales, channels, ditches, ponds, etc.), or performing any alterations or modifications to the drainage facilities referenced in this Declaration of Covenant. 47 Page 3 of ___ 6.Any notice or consent required to be given or otherwise provided for by the provisions of this Agreement shall be effective upon personal delivery, or three (3) days after mailing by Certified Mail, return receipt requested. 7.With regard to the matters addressed herein, this agreement constitutes the entire agreement between the parties, and supersedes all prior discussions, negotiations, and all agreements whatsoever whether oral or written. 8.This Declaration of Covenant is intended to protect the value and desirability and promote efficient and effective management of surface water drainage of the real property described above, and shall inure to the benefit of all the citizens of the City of Renton and its successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest, and assigns. 9.This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and the City that is recorded by King County in its real property records. IN WITNESS WHEREOF, this Declaration of Covenant for the Inspection and Maintenance of Drainage Facilities is executed this _____ day of ____________________, 20_____. GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this _____ day of ___________________, 20_____. Printed name Notary Public in and for the State of Washington, residing at My appointment expires DAMIEN PATTENAUDE, SUPERINTENDENT RENTON SCHOOL DISTRICT NO. 403 47 EXHIBIT A - SITE PLAN Page 4 of 47 X X X CO SD SD EE SDSD DU V A L L A V E . N . E . HO Q U I A M A V E . N . E . N.E. 10TH ST. AMN.E .LD E N . E . NE 10TH ST 1 STORMTRAPDOUBLE TRAPDETENTION SYSTEM STORMTECH CHAMBERSMC-3500 DETENTION SYSTEM MODULAR WETLANDWATER QUALITY VAULT MODULAR WETLANDWATER QUALITY VAULT TDA #1 TDA #2 CONTECH CDS SEPARATORPRESETTLING STRUCTURE MAINTENANCE INSTRUCTIONS FOR SOIL AMENDMENT Your property contains an on-site BMP (best management practice) called “soil amendment,” which was installed to mitigate the stormwater quantity and quality impacts of some or all of the pervious surfaces on your property. Soil amendment is a method of regaining greater stormwater functions in the post development landscape by increasing treatment of pollutants and sediments, and minimizing the need for some landscaping chemicals. To be successful, the soil condition must be able to soak water into the ground for a reasonable number of years. This on-site BMP shall be maintained per Appendix A of the City of Renton’s Surface Water Design Manual. MAINTENANCE RESTRICTIONS The size, placement, and composition of these devices as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES To be successful, the soil must be able to soak water into the ground for a reasonable number of years. • Return leaf fall and shredded woody materials from the landscape to the site when possible in order to replenish soil nutrients and structure. • On turf areas, “grasscycle” (mulch-mow or leave the clippings) to build turf health. • Maintain 2 to 3 inches of mulch over bare areas in landscape beds. • Re-seed bare turf areas until the vegetation fully covers the ground surface. • Avoid using pesticides (bug and weed killers) which damage the soil. • Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers, or slow-release synthetic balanced fertilizers. RECORDING REQUIREMENT These on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. EXHIBIT B - OPERATIONS AND MAINTENANCE Page 5 of 47 STORMTRAP MAINTENANCE MANUAL 1. Introduction Regular inspections are recommended to ensure that the system is functioning as designed. Please call your Authorized StormTrap Representative if you have questions in regards to the inspection and maintenance of the StormTrap system. Prior to entry into any underground storm sewer or underground detention systems, appropriate OSHA and local safety regulations and guidelines should be followed. 2. Inspection Schedules for Municipalities StormTrap Stormwater Management Systems are recommended for inspection whenever the upstream and downstream catch basins and stormwater pipes of the stormwater collection system are inspected or maintained. This will economize the cost of the inspection if it is done at the same time the Municipal crews are visiting the area. 3. Inspection Schedules for Private Development StormTrap Stormwater Mangement Systems, for a private development, are recommended for inspection after each major storm water event. At a minimum, until a cleaning schedule can be established, an annual inspection is recommended. If inspected on an annual basis, the inspection should be conducted before the stormwater season begins to be sure that everything is functioning properly for the upcoming storm season. 4. Inspection Process Inspections should be done such that at least 2-3 days has lapsed since the most recent rain event to allow for draining. Visually inspect the system at all manhole locations. Utilizing a sediment pole, measure and document the amount of silt at each manhole location (Figure 1). Inspect each pipe opening to ensure that the silt level or any foreign objects are not blocking the pipes. Be sure to inspect the outlet pipe(s) because this is typically the smallest STORMTRAP MAINTENANCE MANUAL 1. Introduction Regular inspections are recommended to ensure that the system is functioning as designed. Please call your Authorized StormTrap Representative if you have questions in regards to the inspection and maintenance of the StormTrap system. Prior to entry into any underground storm sewer or underground detention systems, appropriate OSHA and local safety regulations and guidelines should be followed. 2. Inspection Schedules for Municipalities StormTrap Stormwater Management Systems are recommended for inspection whenever the upstream and downstream catch basins and stormwater pipes of the stormwater collection system are inspected or maintained. This will economize the cost of the inspection if it is done at the same time the Municipal crews are visiting the area. 3. Inspection Schedules for Private Development StormTrap Stormwater Mangement Systems, for a private development, are recommended for inspection after each major storm water event. At a minimum, until a cleaning schedule can be established, an annual inspection is recommended. If inspected on an annual basis, the inspection should be conducted before the stormwater season begins to be sure that everything is functioning properly for the upcoming storm season. 4. Inspection Process Inspections should be done such that at least 2-3 days has lapsed since the most recent rain event to allow for draining. Visually inspect the system at all manhole locations. Utilizing a sediment pole, measure and document the amount of silt at each manhole location (Figure 1). Inspect each pipe opening to ensure that the silt level or any foreign objects are not blocking the pipes. Be sure to inspect the outlet pipe(s) because this is typically the smallest Page 6 of 47 PHONE 815 941 4559 WEB www.stormtrap.com 1287 Windham ParkwayFAX 331 318 5347 EMAIL info@stormtrap.com Romeoville, Illinois 60446 pipe in the system. It is common that most of the larger materials will be collected upstream of the system in catch basins, and it is therefore important at time of inspections to check these structures for large trash or blockages. Remove any blockages if you can during the inspection process only if you can do so safely from the top of the system without entering into the system. Do not go into the system under any circumstances without proper ventilation equipment and training. Pass any information requiring action onto the appropriate maintenance personnel if you cannot remove the blockages from above during the inspection process. Be sure to describe the location of each manhole and the type of material that needs to be removed. The sediment level of the system should also be measured and recorded during the inspection process. Recording the sediment level at each manhole is very important in order get a history of sediment that can be graphed over time (i.e. years) in order to estimate when the system will need to be maintained next. It is also important to keep these records to verify that the inspection process was actually performed if anyone asks for your records in the future. The sediment level in the underground detention system can be determined from the outside of the system by opening up all the manholes and using a sediment pole to measure the amount of sediment at each location. Force the stick to the bottom of the system and then remove it and measure the amount of sediment at that location. Again, do not go into the system under any circumstances without proper ventilation equipment and training. 5. When to Clean the System Any blockages should be safely removed as soon as practical so that the Stormwater detention system will fill and drain properly before the next stormwater event. The Dry Detention System should be completely cleaned whenever the sediment occupies more than 10% to 15% of the originally designed system’s volume. The Wet Detention System should be cleaned when the sediment occupies more than 30% or 1/3rd of the originally designed system’s volume. NOTE: Check with your municipality in regards to Page 7 of 47 PHONE 815 941 4559 WEB www.stormtrap.com 1287 Windham ParkwayFAX 331 318 5347 EMAIL info@stormtrap.com Romeoville, Illinois 60446 pipe in the system. It is common that most of the larger materials will be collected upstream of the system in catch basins, and it is therefore important at time of inspections to check these structures for large trash or blockages. Remove any blockages if you can during the inspection process only if you can do so safely from the top of the system without entering into the system. Do not go into the system under any circumstances without proper ventilation equipment and training. Pass any information requiring action onto the appropriate maintenance personnel if you cannot remove the blockages from above during the inspection process. Be sure to describe the location of each manhole and the type of material that needs to be removed. The sediment level of the system should also be measured and recorded during the inspection process. Recording the sediment level at each manhole is very important in order get a history of sediment that can be graphed over time (i.e. years) in order to estimate when the system will need to be maintained next. It is also important to keep these records to verify that the inspection process was actually performed if anyone asks for your records in the future. The sediment level in the underground detention system can be determined from the outside of the system by opening up all the manholes and using a sediment pole to measure the amount of sediment at each location. Force the stick to the bottom of the system and then remove it and measure the amount of sediment at that location. Again, do not go into the system under any circumstances without proper ventilation equipment and training. 5. When to Clean the System Any blockages should be safely removed as soon as practical so that the Stormwater detention system will fill and drain properly before the next stormwater event. The Dry Detention System should be completely cleaned whenever the sediment occupies more than 10% to 15% of the originally designed system’s volume. The Wet Detention System should be cleaned when the sediment occupies more than 30% or 1/3rd of the originally designed system’s volume. NOTE: Check with your municipality in regards to cleaning criteria, as the allowable sediment before cleaning may be more or less then described above. 6. How to Clean the StormTrap The system should be completely cleaned back to 100% of the originally designed storage volume whenever the above sediment levels have been reached. Be sure to wait at least 3 days after a stormwater event to be sure that the system is completely drained (if it is a Dry Detention System), and all of the sediments have settled to the bottom of the system (if it is a Wet Detention System). Do not enter the System unless you are properly trained, equipped, and qualified to enter a confined space as identified by local occupational safety and health regulations. There are many maintenance companies that are in business to help you clean your underground stormwater detention systems and water quality units. Please call your StormTrap representative for referrals in your area. A. Dry Detention System Cleaning Maintenance is typically performed using a vacuum truck. Sediment should be flushed towards a vacuum hose for thorough removal. For a Dry Detention System, remove the manhole cover at the top of the system and lower a vacuum hose into one of the rows of the StormTrap system. Open up the manhole at the opposite end of the StormTrap and use sewer jetting equipment to force water in the same row from one end of the StormTrap row to the opposite side. The rows of the StormTrap are completely open in one contiguous channel from one end to the other for easy cleaning. Place the vacuum hose and the sewer jetting equipment in the next row and repeat the process until all of the rows have been cleaned. When finished, replace all covers that were removed and dispose of the collected material properly. Page 8 of 47 PHONE 815 941 4559 WEB www.stormtrap.com 1287 Windham ParkwayFAX 331 318 5347 EMAIL info@stormtrap.com Romeoville, Illinois 60446 cleaning criteria, as the allowable sediment before cleaning may be more or less then described above. 6. How to Clean the StormTrap The system should be completely cleaned back to 100% of the originally designed storage volume whenever the above sediment levels have been reached. Be sure to wait at least 3 days after a stormwater event to be sure that the system is completely drained (if it is a Dry Detention System), and all of the sediments have settled to the bottom of the system (if it is a Wet Detention System). Do not enter the System unless you are properly trained, equipped, and qualified to enter a confined space as identified by local occupational safety and health regulations. There are many maintenance companies that are in business to help you clean your underground stormwater detention systems and water quality units. Please call your StormTrap representative for referrals in your area. A. Dry Detention System Cleaning Maintenance is typically performed using a vacuum truck. Sediment should be flushed towards a vacuum hose for thorough removal. For a Dry Detention System, remove the manhole cover at the top of the system and lower a vacuum hose into one of the rows of the StormTrap system. Open up the manhole at the opposite end of the StormTrap and use sewer jetting equipment to force water in the same row from one end of the StormTrap row to the opposite side. The rows of the StormTrap are completely open in one contiguous channel from one end to the other for easy cleaning. Place the vacuum hose and the sewer jetting equipment in the next row and repeat the process until all of the rows have been cleaned. When finished, replace all covers that were removed and dispose of the collected material properly. B. Wet Detention System Cleaning If the system was designed to maintain a permanent pool of water, floatables and any oil should be removed in a separate procedure prior to the removal of all sediment. The floatable trash is removed first by using a bucket strainer to capture and remove any floating debris. The floatable oils are then removed off the top of the water by using the vacuum truck to suck off any floatable fluids and liquids. The next step is to use the vacuum truck to gently remove the clarified water above the sediment layer. The final step is to clean the sediment for each row as described above in the paragraph “A. Dry Detention System Cleaning”. For smaller systems, the vacuum truck can remove all of the sediment in the basin without using the sewer jetting equipment because of the smaller space. 7. Inspection Reports Proof of these inspections is the responsibility of the property owner. All inspection reports and data should be kept on site or at a location where they will be accessible for years in the future. Some municipalities require these inspection and cleaning reports to be forwarded to the proper governmental permitting agency on an annual basis. Refer to your local and national regulations for any additional maintenance requirements and schedules not contained herein. Inspections should be a part of your standard operating procedure. Page 9 of 47 PHONE 815 941 4559 WEB www.stormtrap.com 1287 Windham ParkwayFAX 331 318 5347 EMAIL info@stormtrap.com Romeoville, Illinois 60446 B. Wet Detention System Cleaning If the system was designed to maintain a permanent pool of water, floatables and any oil should be removed in a separate procedure prior to the removal of all sediment. The floatable trash is removed first by using a bucket strainer to capture and remove any floating debris. The floatable oils are then removed off the top of the water by using the vacuum truck to suck off any floatable fluids and liquids. The next step is to use the vacuum truck to gently remove the clarified water above the sediment layer. The final step is to clean the sediment for each row as described above in the paragraph “A. Dry Detention System Cleaning”. For smaller systems, the vacuum truck can remove all of the sediment in the basin without using the sewer jetting equipment because of the smaller space. 7. Inspection Reports Proof of these inspections is the responsibility of the property owner. All inspection reports and data should be kept on site or at a location where they will be accessible for years in the future. Some municipalities require these inspection and cleaning reports to be forwarded to the proper governmental permitting agency on an annual basis. Refer to your local and national regulations for any additional maintenance requirements and schedules not contained herein. Inspections should be a part of your standard operating procedure. Figure 1. During inspection, measure the distance from finished grade to the top of the sediment inside the system. Sample inspection and maintenance log Page 10 of 47 PHONE 815 941 4559 WEB www.stormtrap.com 1287 Windham ParkwayFAX 331 318 5347 EMAIL info@stormtrap.com Romeoville, Illinois 60446 Figure 1. During inspection, measure the distance from finished grade to the top of the sediment inside the system. Sample inspection and maintenance log MEASURINGDEVICEFINISHED GRADE PERMANENTPOOL SURFACE SEDIMENT FLOATABLES 11 | P a g e Page 11 of 47 PHONE 815 941 4559 WEB www.stormtrap.com 1287 Windham ParkwayFAX 331 318 5347 EMAIL info@stormtrap.com Romeoville, Illinois 60446 Facility: Location/Address: Date:Time:Weather Conditions:Date of Last Inspection: Inspector: Rain the last 48 hours:Yes No Title: If yes, list amount and timing: Pretreatment:vegetated filter strip swale turf grass forebay other, specify: Site plan or As-built plan available Yes No none Sediment has accumulated. Trash and debris have accumulated. Inlets are in poor structural condition. Sediment, trash, or debris haveaccumulated and/or is blocking theinlets. Sediment accumulation threshold hasbeen reached. Trash and debris have accumulatedin chambers. Structural deterioration is evident. Outlets in poor structural condition. Sediment, trash or debris are blockingoutlets. Erosion is occurring around theoutlets. Evidence of ponding water on areadraining to system. Evidence that water is not beingconveyed through the system. Wet weather inspection needed Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 1 OF 5 StormTrap Guide Specification StormTrap 2 DoubleTrap on Stone Groundwater BELOW Invert Revised 11/21/18 This product guide specification is written according to the Construction Specifications Institute (CSI) 3-Part Format, including MasterFormat, SectionFormat, and PageFormat, contained in the CSI Manual of Practice. The section must be carefully reviewed and edited by the Engineer to meet the requirements of the project and local building code. Coordinate this section with other specification sections and the Drawings. Delete all “Specifier Notes” when editing this section. Section numbers are from MasterFormat 2016 Edition. Update section numbers to versions if required. Specifier Notes: This section covers “StormTrap®” precast concrete, modular, storm water detention. StormTrap is custom designed to meet the specific requirements of the project. Consult StormTrap for assistance in editing this section for the specific application. Page 12 of 47 Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 1 OF 5 StormTrap Guide Specification StormTrap 2 DoubleTrap on Stone Groundwater BELOW Invert Revised 11/21/18 This product guide specification is written according to the Construction Specifications Institute (CSI) 3-Part Format, including MasterFormat, SectionFormat, and PageFormat, contained in the CSI Manual of Practice. The section must be carefully reviewed and edited by the Engineer to meet the requirements of the project and local building code. Coordinate this section with other specification sections and the Drawings. Delete all “Specifier Notes” when editing this section. Section numbers are from MasterFormat 2016 Edition. Update section numbers to versions if required. Specifier Notes: This section covers “StormTrap®” precast concrete, modular, storm water detention. StormTrap is custom designed to meet the specific requirements of the project. Consult StormTrap for assistance in editing this section for the specific application. Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 2 OF 5 SECTION 33 46 23 – MODULAR BURIED STORMWATER STORAGE UNITS PART 1 - GENERAL 1.01 SECTION INCLUDES A. StormTrap Precast concrete, modular stormwater detention. 1.02 RELATED SECTIONS A. Section 31 00 00 – Earthwork B. Section 03 40 00 – Precast Concrete 1.03 REFERENCE STANDARDS A. AASHTO – Standard Specifications for Highway Bridges – Seventh (7th) Edition B. ACI 318 - Building Code Requirements for Structural Concrete. C. ASTM A 615/A 615M - Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement. D. ASTM C 857 - Standard Practice for Minimum Structural Design Loading for Underground Precast Concrete Utility Structures. E. ASTM C 858 - Standard Specification for Underground Precast Concrete Utility Structures. F. ASTM C 891 - Standard Practice for Installation of Underground Precast Concrete Utility Structures. G. ASTM C 990 - Standard Specification for Joints for Concrete Pipe, Manholes, and Precast Box Sections Using Preformed Flexible Joint Sealants. H. ASTM A 1064 – Standard Specification for Carbon-Steel Wire and Welded Wire Reinforcement, Plain and Deformed, for Concrete. 1.04 DESIGN REQUIREMENTS A. Precast Concrete Modular Stormwater Detention shall comply with ASTM C858. B. Underground precast concrete stormwater management system shall be sized in accordance with the design requirements provided by the Engineer of Record (EOR) and approved by the reviewing agency. C. The system shall be designed so modules are aligned and have channels that extend to the bottom of the modules allowing for relatively unrestricted fluid flow in both directions. D. Minimum Structural Design Loading: ASTM C 857. 1. Total Cover: a. Minimum: As indicated on the drawings. b. Maximum: As indicated on the drawings. 2. Concrete chamber shall be designed for AASHTO HS-20 wheel load. Page 13 of 47 Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 2 OF 5 SECTION 33 46 23 – MODULAR BURIED STORMWATER STORAGE UNITS PART 1 - GENERAL 1.01 SECTION INCLUDES A. StormTrap Precast concrete, modular stormwater detention. 1.02 RELATED SECTIONS A. Section 31 00 00 – Earthwork B. Section 03 40 00 – Precast Concrete 1.03 REFERENCE STANDARDS A. AASHTO – Standard Specifications for Highway Bridges – Seventh (7th) Edition B. ACI 318 - Building Code Requirements for Structural Concrete. C. ASTM A 615/A 615M - Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement. D. ASTM C 857 - Standard Practice for Minimum Structural Design Loading for Underground Precast Concrete Utility Structures. E. ASTM C 858 - Standard Specification for Underground Precast Concrete Utility Structures. F. ASTM C 891 - Standard Practice for Installation of Underground Precast Concrete Utility Structures. G. ASTM C 990 - Standard Specification for Joints for Concrete Pipe, Manholes, and Precast Box Sections Using Preformed Flexible Joint Sealants. H. ASTM A 1064 – Standard Specification for Carbon-Steel Wire and Welded Wire Reinforcement, Plain and Deformed, for Concrete. 1.04 DESIGN REQUIREMENTS A. Precast Concrete Modular Stormwater Detention shall comply with ASTM C858. B. Underground precast concrete stormwater management system shall be sized in accordance with the design requirements provided by the Engineer of Record (EOR) and approved by the reviewing agency. C. The system shall be designed so modules are aligned and have channels that extend to the bottom of the modules allowing for relatively unrestricted fluid flow in both directions. D. Minimum Structural Design Loading: ASTM C 857. 1. Total Cover: a. Minimum: As indicated on the drawings. b. Maximum: As indicated on the drawings. 2. Concrete chamber shall be designed for AASHTO HS-20 wheel load. Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 3 OF 5 3. Minimum Soil Pressure: a. DoubleTrap Modules: As indicated on the drawings. 4. Vertical and lateral soil pressures shall be determined using: a. Groundwater: At or below invert of system. b. Lateral soil pressures to be based on Active earth pressure 1) Lateral soil pressure = 35 pcf for 120 pcf backfill unit weight c. Vertical soil pressures 1) Live load = HS-20-44 and Dead load = 120 pcf cover fill unit weight d. Engineer to verify geotechnical requirements 1.05 QUALITY ASSURANCE A. The manufacture of the concrete modules shall be performed at a precast production facility certified by the NPCA or PCI. 1.06 SUBMITTALS A. Comply with Section 01 33 00 - Submittal Procedures, except shop drawings shall be eleven inches (11”) by seventeen inches (17”). B. Product Data: Submit manufacturer’s product data and installation instructions. C. Record Documents: 1. Shop Drawings: a. Submit manufacturer’s shop drawings, including plans, elevations, sections, and details indicating layout, dimensions, foundation, cover, and joints. b. Indicate size and location of roof openings and inlet and outlet pipe openings. c. Indicate sealing of joints. D. Operation and Maintenance Data: Submit manufacturer’s operation and maintenance instructions 1.07 DELIVERY, STORAGE AND HANDLING A. Delivery of Accessories: Deliver to site in manufacturer’s original, unopened containers and packaging, with labels clearly identifying product name and manufacturer. B. Storage of Accessories: 1. Store in accordance with manufacturer’s instructions. 2. Store in clean, dry area, out of direct sunlight. C. Handling: Protect materials during handling and installation to prevent damage. 1.08 WARRANTY A. The Manufacturer shall provide a minimum five (5) year limited warranty. Page 14 of 47 Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 3 OF 5 3. Minimum Soil Pressure: a. DoubleTrap Modules: As indicated on the drawings. 4. Vertical and lateral soil pressures shall be determined using: a. Groundwater: At or below invert of system. b. Lateral soil pressures to be based on Active earth pressure 1) Lateral soil pressure = 35 pcf for 120 pcf backfill unit weight c. Vertical soil pressures 1) Live load = HS-20-44 and Dead load = 120 pcf cover fill unit weight d. Engineer to verify geotechnical requirements 1.05 QUALITY ASSURANCE A. The manufacture of the concrete modules shall be performed at a precast production facility certified by the NPCA or PCI. 1.06 SUBMITTALS A. Comply with Section 01 33 00 - Submittal Procedures, except shop drawings shall be eleven inches (11”) by seventeen inches (17”). B. Product Data: Submit manufacturer’s product data and installation instructions. C. Record Documents: 1. Shop Drawings: a. Submit manufacturer’s shop drawings, including plans, elevations, sections, and details indicating layout, dimensions, foundation, cover, and joints. b. Indicate size and location of roof openings and inlet and outlet pipe openings. c. Indicate sealing of joints. D. Operation and Maintenance Data: Submit manufacturer’s operation and maintenance instructions 1.07 DELIVERY, STORAGE AND HANDLING A. Delivery of Accessories: Deliver to site in manufacturer’s original, unopened containers and packaging, with labels clearly identifying product name and manufacturer. B. Storage of Accessories: 1. Store in accordance with manufacturer’s instructions. 2. Store in clean, dry area, out of direct sunlight. C. Handling: Protect materials during handling and installation to prevent damage. 1.08 WARRANTY A. The Manufacturer shall provide a minimum five (5) year limited warranty. Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 4 OF 5 PART 2 - PRODUCTS 2.01 MANUFACTURER A. StormTrap, LLC, 1287 Windham Parkway, Romeoville, Illinois 60446. Phone (877) 867-6872. Fax (331) 318-5347. Website www.stormtrap.com. 2.02 STORMWATER DETENTION A. All material shall meet or exceed all applicable referenced standards, federal, state and local requirements, and conform to codes and ordinances of authorities having jurisdiction. B. Stormwater Detention Modules: 1. Description: Engineered, precast concrete, modular stormwater detention. 2. Module Type: StormTrap DoubleTrap 3. Size: As indicated on the drawings. 4. Concrete: Manufacturer’s Approved Mix design providing a minimum compressive strength of 6,000 psi at 28 days. 5. Reinforcing Bars: ASTM A 615, Grade 60. 6. Reinforcing Mesh: ASTM A 1064, Grade 80. 7. Cover for Reinforcing Bars: ACI 318 2.03 ACCESSORIES A. Joint Tape: 1. ASTM C 990. 2. Seven eights inch (7/8”) diameter, preformed butyl mastic joint sealer. 3. Approved by manufacturer. B. Joint Wrap: 1. Eight inch (8”) wide self-adhesive elastomeric resin bonded woven puncture resistant polymer wrap. 2. Approved by manufacturer. PART 3 - EXECUTION 3.01 EXAMINATION A. Examine area to receive stormwater detention modules. Notify Engineer if area is not acceptable. Do not begin installation until unacceptable conditions have been corrected. B. Verify in field before installation, dimensions and soils conditions, including groundwater and soil bearing capacity. Page 15 of 47 Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 4 OF 5 PART 2 - PRODUCTS 2.01 MANUFACTURER A. StormTrap, LLC, 1287 Windham Parkway, Romeoville, Illinois 60446. Phone (877) 867-6872. Fax (331) 318-5347. Website www.stormtrap.com. 2.02 STORMWATER DETENTION A. All material shall meet or exceed all applicable referenced standards, federal, state and local requirements, and conform to codes and ordinances of authorities having jurisdiction. B. Stormwater Detention Modules: 1. Description: Engineered, precast concrete, modular stormwater detention. 2. Module Type: StormTrap DoubleTrap 3. Size: As indicated on the drawings. 4. Concrete: Manufacturer’s Approved Mix design providing a minimum compressive strength of 6,000 psi at 28 days. 5. Reinforcing Bars: ASTM A 615, Grade 60. 6. Reinforcing Mesh: ASTM A 1064, Grade 80. 7. Cover for Reinforcing Bars: ACI 318 2.03 ACCESSORIES A. Joint Tape: 1. ASTM C 990. 2. Seven eights inch (7/8”) diameter, preformed butyl mastic joint sealer. 3. Approved by manufacturer. B. Joint Wrap: 1. Eight inch (8”) wide self-adhesive elastomeric resin bonded woven puncture resistant polymer wrap. 2. Approved by manufacturer. PART 3 - EXECUTION 3.01 EXAMINATION A. Examine area to receive stormwater detention modules. Notify Engineer if area is not acceptable. Do not begin installation until unacceptable conditions have been corrected. B. Verify in field before installation, dimensions and soils conditions, including groundwater and soil bearing capacity. Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 5 OF 5 3.02 INSTALLATION A. Install stormwater detention modules in accordance with manufacturer’s instructions and ASTM C 891. B. Install modules plumb, on line, and to proper elevation. C. Install modules with a maximum space of three quarters inch (3/4”) between adjacent modules. If the space exceeds three quarters inch (3/4”), the modules shall be reset with appropriate adjustment made to line and grade to bring the space into compliance. D. DoubleTrap: 1. Place modules on level, six-inch (6”) pad of three quarters inch (3/4”) stone that extends two feet (2’-0”) past the outside of the system as indication on the drawings. E. Joint Tape: 1. Seal perimeter horizontal joint between modules with joint tape in accordance with ASTM C 891, 8.8 and 8.12. 2. Prepare surfaces and install joint tape in accordance with manufacturer’s instructions. F. Joint Wrap: 1. Seal exterior joints between adjacent modules with joint wrap in accordance with ASTM C 891. 2. Prepare surfaces and install joint wrap in accordance with manufacturer’s instructions. G. Field Modifications to the modules is strictly prohibited without prior written consent of StormTrap. H. Excavation and fill shall be as specified in Sections 31 00 00. I. Fill: 1. Backfill material shall consist of a GW, GP, SW, or SP material as defined by the Unified Soil Classification System and that meets the gradation requirements as indicated on the drawings. 2. Native materials shall be separated from backfill materials with a geotextile filter fabric unless the drawings indicate separation is not required. 3. Deposit fill on both sides of modules at same time and to approximate same elevation. 4. Prevent wedging action against structure by stepping or serrating slopes bounding or within area to be backfilled. 5. Do not disrupt or damage joint wrap during backfilling. J. Do not use stormwater detention modules that are damaged, as determined by manufacturer. K. Contractor is responsible for installation in accordance with project plans, specifications, and all federal, state, and local regulations. END OF SECTION 33 46 23 Page 16 of 47 Project Owner MODULAR BURIED STORMWATER STORAGE UNITS Project Name 33 46 23 Project # 5 OF 5 3.02 INSTALLATION A. Install stormwater detention modules in accordance with manufacturer’s instructions and ASTM C 891. B. Install modules plumb, on line, and to proper elevation. C. Install modules with a maximum space of three quarters inch (3/4”) between adjacent modules. If the space exceeds three quarters inch (3/4”), the modules shall be reset with appropriate adjustment made to line and grade to bring the space into compliance. D. DoubleTrap: 1. Place modules on level, six-inch (6”) pad of three quarters inch (3/4”) stone that extends two feet (2’-0”) past the outside of the system as indication on the drawings. E. Joint Tape: 1. Seal perimeter horizontal joint between modules with joint tape in accordance with ASTM C 891, 8.8 and 8.12. 2. Prepare surfaces and install joint tape in accordance with manufacturer’s instructions. F. Joint Wrap: 1. Seal exterior joints between adjacent modules with joint wrap in accordance with ASTM C 891. 2. Prepare surfaces and install joint wrap in accordance with manufacturer’s instructions. G. Field Modifications to the modules is strictly prohibited without prior written consent of StormTrap. H. Excavation and fill shall be as specified in Sections 31 00 00. I. Fill: 1. Backfill material shall consist of a GW, GP, SW, or SP material as defined by the Unified Soil Classification System and that meets the gradation requirements as indicated on the drawings. 2. Native materials shall be separated from backfill materials with a geotextile filter fabric unless the drawings indicate separation is not required. 3. Deposit fill on both sides of modules at same time and to approximate same elevation. 4. Prevent wedging action against structure by stepping or serrating slopes bounding or within area to be backfilled. 5. Do not disrupt or damage joint wrap during backfilling. J. Do not use stormwater detention modules that are damaged, as determined by manufacturer. K. Contractor is responsible for installation in accordance with project plans, specifications, and all federal, state, and local regulations. END OF SECTION 33 46 23 12.0 Inspection and Maintenance Looking down the Isolator Row PLUS A typical JetVac truck (This is not a StormTech product.) Examples of culvert cleaning nozzles appropriate for Isolator Row PLUS maintenance. (These are not StormTech products). 12.1 Isolator Row Plus Inspection Regular inspection and maintenance are essential to assure a properly functioning stormwater system. Inspection is easily accomplished through the manhole or optional inspection ports of an Isolator Row PLUS. Please follow local and OSHA rules for a confined space entry. Inspection ports can allow inspection to be accomplished completely from the surface without the need for a confined space entry. Inspection ports provide visual access to the system with the use of a flashlight. A stadia rod may be inserted to determine the depth of sediment. If upon visual inspection it is found that sediment has accumulated to an average depth exceeding 3” (75 mm), cleanout is required. A StormTech Isolator Row PLUS should initially be inspected immediately after completion of the site’s construction. While every effort should be made to prevent sediment from entering the system during construction, it is during this time that excess amounts of sediments are most likely to enter any stormwater system. Inspection and maintenance, if necessary, should be performed prior to passing responsibility over to the site’s owner. Once in normal service, a StormTech Isolator Row PLUS should be inspected bi-annually until an understanding of the sites characteristics is developed. The site’s maintenance manager can then revise the inspection schedule based on experience or local requirements. 12.2 Isolator Row Plus Maintenance JetVac maintenance is recommended if sediment has been collected to an average depth of 3” (75 mm) inside the Isolator Row PLUS. More frequent maintenance may be required to maintain minimum flow rates through the Isolator Row PLUS. The JetVac process utilizes a high pressure water nozzle to propel itself down the Isolator Row PLUS while scouring and suspending sediments. As the nozzle is retrieved, a wave of suspended sediments is flushed back into the manhole for vacuuming. Most sewer and pipe maintenance companies have vacuum/ JetVac combination vehicles. Fixed nozzles designed for culverts or large diameter pipe cleaning are preferable. Rear facing jets with an effective spread of at least 45” (1125 mm) are best. StormTech recommends a maximum nozzle pressure of 2000 psi be utilized during cleaning. The JetVac process shall only be performed on StormTech Rows that have ADS PLUS fabric over the foundation stone. Page 17 of 47 Page 18 of 47 12.0 Inspection & Maintenance 12.3 Eccentric Pipe Header Inspection Theses guidelines do not supercede a pipe manufacturer’s recommended I&M procedures. Consult with the manufacturer of the pipe header system for specific I&M procedures. Inspection of the header system should be carried out quarterly. On sites which generate higher levels of sediment more frequent inspections may be necessary. Headers may be accessed through risers, access ports or manholes. Measurement of sediment may be taken with a stadia rod or similar device. Cleanout of sediment should occur when the sediment volume has reduced the storage area by 25% or the depth of sediment has reached approximately 25% of the diameter of the structure. 12.4 Eccentric Pipe Manifold Maintenance Cleanout of accumulated material should be accomplished by vacuum pumping the material from the header. Cleanout should be accomplished during dry weather. Care should be taken to avoid flushing sediments out through the outlet pipes and into the chamber rows. Eccentric Header Step-by-Step Maintenance Procedures 1. Locate manholes connected to the manifold system 2. Remove grates or covers 3. Using a stadia rod, measure the depth of sediment 4. If sediment is at a depth of about 25% pipe volume or 25% pipe diameter proceed to step 5. If not proceed to step 6. 5. Vacuum pump the sediment. Do not flush sediment out inlet pipes. 6. Replace grates and covers 7. Record depth and date and schedule next inspection StormTech Isolator Row Plus - Step-by-StepMaintenance Procedures Step 1: Inspect Isolator Row PLUS for sediment A) Inspection ports (if present) i. Remove lid from floor box frame ii. Remove cap from inspection riser iii. Using a flashlight and stadia rod, measure depth of sediment iv. If sediment is at, or above, 3” (76 mm) depth proceed to Step 2. If not proceed to Step 3. B) All Isolator Plus Rows i. Remove cover from manhole at upstream end of Isolator Row PLUS ii. Using a flashlight, inspect down Isolator Row PLUS through outlet pipe 1. Follow OSHA regulations for confined space entry if entering manhole 2. Mirrors on poles or cameras may be used to avoid a confined space entry iii. If sediment is at or above the lower row of sidewall holes [approximately 3” (76 mm)]proceed to Step 2. If not proceed to Step 3. Step 2: Clean out Isolator Row PLUS using the JetVac process A) A fixed floor cleaning nozzle with rear facing nozzle spread of 45” (1125 mm) or more is preferable B) Apply multiple passes of JetVac until backflush water is clean C) Vacuum manhole sump as required during jetting Step 3: Replace all caps, lids and covers Step 4: Inspect and clean catch basins and manholes upstream of the StormTech system following local guidelines. Figure 18 – StormTech Isolator Row Plus (not to scale) Figure 19 – Eccentric Manifold Maintenance 1, 2, 6 3, 4, 5 Please contact StormTech’s Technical Services Department at 888-892-2894 for a spreadsheet to estimate cleaning intervals. 1) B)1) A) 4 2 1, 2, 6 3, 4, 5 ENGINEERED SOLUTIONS Modular Wetlands® Linear Operations & Maintenance Manual Page 19 of 47 ENGINEERED SOLUTIONS Modular Wetlands® Linear Operations & Maintenance Manual 2 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR OOPPEERRAATTIIOONN && MMAAIINNTTEENNAANNCCEE MMAANNUUAALL TTAABBLLEE OOFF CCOONNTTEENNTTSS OOvveerrvviieeww ........................................................................................................................................................................ 3 SSaaffeettyy NNoottiiccee && PPeerrssoonnaall SSaaffeettyy EEqquuiippmmeenntt ................................................................................................................. 4 MMoodduullaarr WWeettllaannddss LLiinneeaarr CCoommppoonneennttss LLiisstt ................................................................................................................. 5 IInnssppeeccttiioonn SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt ......................................................................................................................... 6 IInnssppeeccttiioonn && MMaaiinntteennaannccee NNootteess .................................................................................................................................. 7 IInnssppeeccttiioonn PPrroocceessss ......................................................................................................................................................... 7 MMaaiinntteennaannccee IInnddiiccaattoorrss ................................................................................................................................................. 9 MMaaiinntteennaannccee SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt..................................................................................................................... 9 MMaaiinntteennaannccee IInnssttrruuccttiioonnss .............................................................................................................................................11 RReeppllaacciinngg BBiiooffiillttrraattiioonn MMeeddiiaa iiff RReeqquuiirreedd ....................................................................................................................14 RReeppllaacciinngg DDrraaiinn DDoowwnn FFiilltteerr MMeeddiiaa ((OOnnllyy oonn OOllddeerr CCaalliiffoorrnniiaa MMooddeellss)) .....................................................................16 NNootteess .............................................................................................................................................................................17 IInnssppeeccttiioonn RReeppoorrtt .........................................................................................................................................................18 CClleeaanniinngg && MMaaiinntteennaannccee RReeppoorrtt ..................................................................................................................................19 Page 20 of 47 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR OOPPEERRAATTIIOONN && MMAAIINNTTEENNAANNCCEE MMAANNUUAALL TTAABBLLEE OOFF CCOONNTTEENNTTSS OOvveerrvviieeww ........................................................................................................................................................................ 3 SSaaffeettyy NNoottiiccee && PPeerrssoonnaall SSaaffeettyy EEqquuiippmmeenntt ................................................................................................................. 4 MMoodduullaarr WWeettllaannddss LLiinneeaarr CCoommppoonneennttss LLiisstt ................................................................................................................. 5 IInnssppeeccttiioonn SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt ......................................................................................................................... 6 IInnssppeeccttiioonn && MMaaiinntteennaannccee NNootteess .................................................................................................................................. 7 IInnssppeeccttiioonn PPrroocceessss ......................................................................................................................................................... 7 MMaaiinntteennaannccee IInnddiiccaattoorrss ................................................................................................................................................. 9 MMaaiinntteennaannccee SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt..................................................................................................................... 9 MMaaiinntteennaannccee IInnssttrruuccttiioonnss .............................................................................................................................................11 RReeppllaacciinngg BBiiooffiillttrraattiioonn MMeeddiiaa iiff RReeqquuiirreedd ....................................................................................................................14 RReeppllaacciinngg DDrraaiinn DDoowwnn FFiilltteerr MMeeddiiaa ((OOnnllyy oonn OOllddeerr CCaalliiffoorrnniiaa MMooddeellss)) .....................................................................16 NNootteess .............................................................................................................................................................................17 IInnssppeeccttiioonn RReeppoorrtt .........................................................................................................................................................18 CClleeaanniinngg && MMaaiinntteennaannccee RReeppoorrtt ..................................................................................................................................19 3 OOVVEERRVVIIEEWW This operation and maintenance (O&M) manual is for the Modular Wetlands Linear Biofilter (MWL). Please read the instructions and equipment lists closely prior to starting. It is important to follow all necessary safety procedures associated with state and local regulations. Please contact Contech for more information on pre-authorized third-party service providers who can provide inspection and maintenance services in your area. For a list of service providers in your area, please visit www.conteches.com/maintenance. PPLLAACCEEHHOOLLDDEERR FFOORR MMAARRKKEETTIINNGG PPHHOOTTOO WWAARRNNIINNGG Confined space entry may be required. Contractor to obtain all equipment and training to meet applicable local and OSHA regulations regarding confined space entry. It is the Contractor’s or entry personnel’s responsibility to always proceed safely. Page 21 of 47 OOVVEERRVVIIEEWW This operation and maintenance (O&M) manual is for the Modular Wetlands Linear Biofilter (MWL). Please read the instructions and equipment lists closely prior to starting. It is important to follow all necessary safety procedures associated with state and local regulations. Please contact Contech for more information on pre-authorized third-party service providers who can provide inspection and maintenance services in your area. For a list of service providers in your area, please visit www.conteches.com/maintenance. PPLLAACCEEHHOOLLDDEERR FFOORR MMAARRKKEETTIINNGG PPHHOOTTOO WWAARRNNIINNGG Confined space entry may be required. Contractor to obtain all equipment and training to meet applicable local and OSHA regulations regarding confined space entry. It is the Contractor’s or entry personnel’s responsibility to always proceed safely. 4 SSAAFFEETTYY NNOOTTIICCEE && PPEERRSSOONNAALL SSAAFFEETTYY EEQQUUIIPPMMEENNTT Job site safety is a topic and a practice addressed comprehensively by others. The inclusions here are merely reminders to whole areas of Safety Practice that are the responsibility of the Owner(s), Manager(s), and Service Provider(s). OSHA and Canadian OSH, Federal, State/Provincial, and Local Jurisdiction Safety Standards apply on any given site or project. The knowledge and applicability of those responsibilities is the Service Provider’s responsibility and outside the scope of Contech Engineered Solutions. Safety Boots Gloves Hard Hat Eye Protection Maintenance and Protection of Traffic Plan Page 22 of 47 SSAAFFEETTYY NNOOTTIICCEE && PPEERRSSOONNAALL SSAAFFEETTYY EEQQUUIIPPMMEENNTT Job site safety is a topic and a practice addressed comprehensively by others. The inclusions here are merely reminders to whole areas of Safety Practice that are the responsibility of the Owner(s), Manager(s), and Service Provider(s). OSHA and Canadian OSH, Federal, State/Provincial, and Local Jurisdiction Safety Standards apply on any given site or project. The knowledge and applicability of those responsibilities is the Service Provider’s responsibility and outside the scope of Contech Engineered Solutions. Safety Boots Gloves Hard Hat Eye Protection Maintenance and Protection of Traffic Plan 5 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR CCOOMMPPOONNEENNTTSS LLIISSTT The MWL system comes in multiple sizes and configurations, including side by side or end to end layouts, both as open planters or underground systems. See shop drawings (plans) for project specific details. The standard MWL system is comprised of the following components: Page 23 of 47 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR CCOOMMPPOONNEENNTTSS LLIISSTT The MWL system comes in multiple sizes and configurations, including side by side or end to end layouts, both as open planters or underground systems. See shop drawings (plans) for project specific details. The standard MWL system is comprised of the following components: Vertical Perforated Underdrain Biofiltration Media Media ContainmentCage Native Vegetation Biofiltration Chamber Pre-treatment Chamber Inlet Pipe ConcreteStructure Pre-filter Cartridge Discharge Chamber Control Riser Outlet Pipe 6 IINNSSPPEECCTTIIOONN SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT Stormwater regulations require BMPs be inspected and maintained to ensure they are operating as designed to allow for effective pollutant removal and provide protection to receiving water bodies. It is recommended that inspections be performed multiple times during the first year to assess the site-specific loading conditions. The first year of inspections can be used to set inspection and maintenance intervals for subsequent years to ensure appropriate maintenance is provided. Inspect pre-treatment, biofiltration, and discharge chambers an average of once every six to twelve months. Varies based on site specific and local conditions. Average inspection time is approximately 15 minutes. Always ensure appropriate safety protocol and procedures are followed. The following is a list of equipment required to allow for simple and effective inspection of the MWL: Modular Wetlands Linear Inspection Form Flashlight Tape Measure Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) Page 24 of 47 IINNSSPPEECCTTIIOONN SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT Stormwater regulations require BMPs be inspected and maintained to ensure they are operating as designed to allow for effective pollutant removal and provide protection to receiving water bodies. It is recommended that inspections be performed multiple times during the first year to assess the site-specific loading conditions. The first year of inspections can be used to set inspection and maintenance intervals for subsequent years to ensure appropriate maintenance is provided. Inspect pre-treatment, biofiltration, and discharge chambers an average of once every six to twelve months. Varies based on site specific and local conditions. Average inspection time is approximately 15 minutes. Always ensure appropriate safety protocol and procedures are followed. The following is a list of equipment required to allow for simple and effective inspection of the MWL: Modular Wetlands Linear Inspection Form Flashlight Tape Measure Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) 7 IINNSSPPEECCTTIIOONN && MMAAIINNTTEENNAANNCCEE NNOOTTEESS 1.Following maintenance and/or inspection, it is recommended that the maintenance operator prepare a maintenance/inspection record. The record should include any maintenance activities performed, amount and description of debris collected, and condition of the system and its various filter mechanisms. 2.The owner should keep maintenance/inspection record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspection upon request at any time. 3.Transport all debris, trash, organics, and sediments to approved facility for disposal in accordance with local and state requirements. 4.Entry into chambers may require confined space training based on state and local regulations. 5.No fertilizer shall be used in the biofiltration chamber. 6.Irrigation should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigation required is dependent on plant species. Some plants may not require irrigation after initial establishment. IINNSSPPEECCTTIIOONN PPRROOCCEESSSS 1.Prepare the inspection form by writing in the necessary information including project name, location, date & time, unit number and other information (see inspection form). 2.Observe the inside of the system through the access covers. If minimal light is available and vision into the unit is impaired, utilize a flashlight to see inside the system and all chambers. 3.Look for any out of the ordinary obstructions in the inflow pipe, pre-treatment chamber, biofiltration chamber, discharge chamber or outflow pipe. Write down any observations on the inspection form. 4.Through observation and/or digital photographs, estimate the amount of trash, debris accumulated in the pre- treatment chamber. Utilizing a tape measure or measuring stick, estimate the amount of sediment in this chamber. Record this depth on the inspection form. 5.Through visual observation, inspect the condition of the pre-filter cartridges. Look for excessive build-up of sediment on the cartridges, any build-up on the tops of the cartridges, or clogging of the holes. Record this information on the inspection form. The pre-filter cartridges can be further inspected by removing the cartridge tops and assessing the color of the BioMediaGREEN filter cubes (requires entry into pre-treatment chamber - see notes previous notes regarding confined space entry). Record the color of the material. New material is a light green color. As the media becomes clogged, it will turn darker in color, eventually becoming dark brown or black. The closer to black the media is the higher percentage that the media is exhausted and in need of replacement. IINNSSPPEECCTTIIOONN && MMAAIINNTTEENNAANNCCEE NNOOTTEESS 1.Following maintenance and/or inspection, it is recommended that the maintenance operator prepare a maintenance/inspection record. The record should include any maintenance activities performed, amount and description of debris collected, and condition of the system and its various filter mechanisms. 2.The owner should keep maintenance/inspection record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspection upon request at any time. 3.Transport all debris, trash, organics, and sediments to approved facility for disposal in accordance with local and state requirements. 4.Entry into chambers may require confined space training based on state and local regulations. 5.No fertilizer shall be used in the biofiltration chamber. 6.Irrigation should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigation required is dependent on plant species. Some plants may not require irrigation after initial establishment. IINNSSPPEECCTTIIOONN PPRROOCCEESSSS 1.Prepare the inspection form by writing in the necessary information including project name, location, date & time, unit number and other information (see inspection form). 2.Observe the inside of the system through the access covers. If minimal light is available and vision into the unit is impaired, utilize a flashlight to see inside the system and all chambers. 3.Look for any out of the ordinary obstructions in the inflow pipe, pre-treatment chamber, biofiltration chamber, discharge chamber or outflow pipe. Write down any observations on the inspection form. 4.Through observation and/or digital photographs, estimate the amount of trash, debris accumulated in the pre- treatment chamber. Utilizing a tape measure or measuring stick, estimate the amount of sediment in this chamber. Record this depth on the inspection form. 5.Through visual observation, inspect the condition of the pre-filter cartridges. Look for excessive build-up of sediment on the cartridges, any build-up on the tops of the cartridges, or clogging of the holes. Record this information on the inspection form. The pre-filter cartridges can be further inspected by removing the cartridge tops and assessing the color of the BioMediaGREEN filter cubes (requires entry into pre-treatment chamber - see notes previous notes regarding confined space entry). Record the color of the material. New material is a light green color. As the media becomes clogged, it will turn darker in color, eventually becoming dark brown or black. The closer to black the media is the higher percentage that the media is exhausted and in need of replacement. Page 25 of 47 8 6.The biofiltration chamber is generally maintenance-free due to the system’s advanced pre-treatment chamber. For units which have open planters with vegetation, it is recommended that the vegetation be inspected. Look for any plants that are dead or showing signs of disease or other negative stressors. Record the general health of the plants on the inspection form and indicate through visual observation or digital photographs if trimming of the vegetation is required. 7.The discharge chamber houses the control riser (if applicable), drain down filter (only in California - older models), and is connected to the outflow pipe. It is important to check to ensure the orifice is in proper operating condition and free of any obstructions. It is also important to assess the condition of the drain down filter media which utilizes a block form of the BioMediaGREEN. Assess in the same manner as the cubes in the pre-filter cartridge as mentioned above. 8.Finalize the inspection report for analysis by the maintenance manager to determine if maintenance is required. Page 26 of 47 6.The biofiltration chamber is generally maintenance-free due to the system’s advanced pre-treatment chamber. For units which have open planters with vegetation, it is recommended that the vegetation be inspected. Look for any plants that are dead or showing signs of disease or other negative stressors. Record the general health of the plants on the inspection form and indicate through visual observation or digital photographs if trimming of the vegetation is required. 7.The discharge chamber houses the control riser (if applicable), drain down filter (only in California - older models), and is connected to the outflow pipe. It is important to check to ensure the orifice is in proper operating condition and free of any obstructions. It is also important to assess the condition of the drain down filter media which utilizes a block form of the BioMediaGREEN. Assess in the same manner as the cubes in the pre-filter cartridge as mentioned above. 8.Finalize the inspection report for analysis by the maintenance manager to determine if maintenance is required. NewBioMediaGREEN0% ExhaustedBioMediaGREEN100%85% 9 MMAAIINNTTEENNAANNCCEE IINNDDIICCAATTOORRSS Based upon the observations made during inspection, maintenance of the system may be required based on the following indicators: Missing or damaged internal components or cartridges. Obstructions in the system or its inlet and/or outlet pipes. Excessive accumulation of floatables in the pre-treatment chamber in which the length and width of the chamber is fully impacted more than 18”. Excessive accumulation of sediment in the pre-treatment chamber of more than 6” in depth. Excessive accumulation of sediment on the BioMediaGREEN media housed within the pretreatment cartridges. When media is more than 85% clogged, replacement is required. The darker the BioMediaGREEN, the more clogged it is and in need of replacement. Excessive accumulation of sediment on the BioMediaGREEN media housed within the drain down filter (California only - older models). Overgrown vegetation. MMAAIINNTTEENNAANNCCEE SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT The time has come to maintain your MWL. All necessary pre-maintenance steps must be carried out before maintenance occurs. Once traffic control has been set up per local and state regulations and access covers have been safely opened, the maintenance process can begin. It should be noted that some maintenance activities require confined space entry. All confined space requirements must be strictly followed before entry into the system. In addition, the following is recommended: Prepare the maintenance form by writing in the necessary information including project name, location, date & time, unit number and other info (see maintenance form). Set up all appropriate safety and maintenance equipment. Ensure traffic control is set up and properly positioned. Prepared pre-checks (OSHA, safety, confined space entry) are performed. o A gas meter should be used to detect the presence of any hazardous gases prior to entering the system. If hazardous gases are present, do not enter the vault. Following appropriate confined space procedures, take steps such as utilizing a venting system to address the hazard. Once it is determined to be safe, enter the system utilizing appropriate entry equipment such as a ladder and tripod with harness. Page 27 of 47 MMAAIINNTTEENNAANNCCEE IINNDDIICCAATTOORRSS Based upon the observations made during inspection, maintenance of the system may be required based on the following indicators: Missing or damaged internal components or cartridges. Obstructions in the system or its inlet and/or outlet pipes. Excessive accumulation of floatables in the pre-treatment chamber in which the length and width of the chamber is fully impacted more than 18”. Excessive accumulation of sediment in the pre-treatment chamber of more than 6” in depth. Excessive accumulation of sediment on the BioMediaGREEN media housed within the pretreatment cartridges. When media is more than 85% clogged, replacement is required. The darker the BioMediaGREEN, the more clogged it is and in need of replacement. Excessive accumulation of sediment on the BioMediaGREEN media housed within the drain down filter (California only - older models). Overgrown vegetation. MMAAIINNTTEENNAANNCCEE SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT The time has come to maintain your MWL. All necessary pre-maintenance steps must be carried out before maintenance occurs. Once traffic control has been set up per local and state regulations and access covers have been safely opened, the maintenance process can begin. It should be noted that some maintenance activities require confined space entry. All confined space requirements must be strictly followed before entry into the system. In addition, the following is recommended: Prepare the maintenance form by writing in the necessary information including project name, location, date & time, unit number and other info (see maintenance form). Set up all appropriate safety and maintenance equipment. Ensure traffic control is set up and properly positioned. Prepared pre-checks (OSHA, safety, confined space entry) are performed. o A gas meter should be used to detect the presence of any hazardous gases prior to entering the system. If hazardous gases are present, do not enter the vault. Following appropriate confined space procedures, take steps such as utilizing a venting system to address the hazard. Once it is determined to be safe, enter the system utilizing appropriate entry equipment such as a ladder and tripod with harness. 10 The following is a list of equipment required for maintenance of the MWL: Modular Wetlands Linear Maintenance Form Flashlight Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) Vacuum Assisted Truck with Pressure Washer Replacement BioMediaGREEN (If Required) (order BioMediaGREEN from Contech’s Maintenance Team members at https://www.conteches.com/maintenance) Page 28 of 47 The following is a list of equipment required for maintenance of the MWL: Modular Wetlands Linear Maintenance Form Flashlight Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) Vacuum Assisted Truck with Pressure Washer Replacement BioMediaGREEN (If Required) (order BioMediaGREEN from Contech’s Maintenance Team members at https://www.conteches.com/maintenance) 11 MMAAIINNTTEENNAANNCCEE IINNSSTTRRUUCCTTIIOONNSS 11..AACCCCEESSSS CCOOVVEERR RREEMMOOVVAALL Upon determining that the vault is safe for entry, remove all access cover(s) and position the vacuum truck accordingly. 22..PPRREESSSSUURREE WWAASSHH SSYYSSTTEEMM CCHHAAMMBBEERRSS With the pressure washer, spray down pollutants accumulated on the walls and floors of the pre- treatment and discharge chambers. Then wash any accumulated sediment from the pre-filter cartridge(s). 33..VVAACCUUUUMM SSYYSSTTEEMM CCHHAAMMBBEERRSS Vacuum out pre-treatment and discharge chambers and remove all accumulated pollutants including trash, debris, and sediments. Be sure to vacuum the pre- treatment floor until the pervious pavers are visible and clean.((MMWWLL ssyysstteemmss oouuttssiiddee ooff CCaalliiffoorrnniiaa mmaayy oorr mmaayy nnoott hhaavvee ppeerrvviioouuss ppaavveerrss oonn tthhee fflloooorr iinn tthhee pprree-- ttrreeaattmmeenntt cchhaammbbeerr)) If pre-filter cartridges require media replacement, proceed to SStteepp 44. If not, replace the access cover(s) and proceed to SStteepp 77. Page 29 of 47 MMAAIINNTTEENNAANNCCEE IINNSSTTRRUUCCTTIIOONNSS 11..AACCCCEESSSS CCOOVVEERR RREEMMOOVVAALL Upon determining that the vault is safe for entry, remove all access cover(s) and position the vacuum truck accordingly. 22..PPRREESSSSUURREE WWAASSHH SSYYSSTTEEMM CCHHAAMMBBEERRSS With the pressure washer, spray down pollutants accumulated on the walls and floors of the pre- treatment and discharge chambers. Then wash any accumulated sediment from the pre-filter cartridge(s). 33..VVAACCUUUUMM SSYYSSTTEEMM CCHHAAMMBBEERRSS Vacuum out pre-treatment and discharge chambers and remove all accumulated pollutants including trash, debris, and sediments. Be sure to vacuum the pre- treatment floor until the pervious pavers are visible and clean.((MMWWLL ssyysstteemmss oouuttssiiddee ooff CCaalliiffoorrnniiaa mmaayy oorr mmaayy nnoott hhaavvee ppeerrvviioouuss ppaavveerrss oonn tthhee fflloooorr iinn tthhee pprree-- ttrreeaattmmeenntt cchhaammbbeerr)) If pre-filter cartridges require media replacement, proceed toSStteepp 44. If not, replace the access cover(s) and proceed toSStteepp 77. 12 44..PPRREE--FFIILLTTEERR CCAARRTTRRIIDDGGEE LLIIDD RREEMMOOVVAALL After successfully cleaning out the pre-treatment chamber, enter the chamber and remove the lid(s) from the pre-filter cartridge(s) by removing the two thumb screws. (Older pre-filter cartridges have two bolts holding the lids on that require a 7/16” socket to remove) 55..VVAACCUUUUMM EEXXIISSTTIINNGG PPRREE--FFIILLTTEERR MMEEDDIIAA Utilize the vacuum truck hose or hose extension to remove the filter media from each of the individual media cages. Once filter media has been sucked out, use a pressure washer to spray down the inside of the cartridge and its media cages. Remove cleaned media cages and place to the side. Once removed, the vacuum hose can be inserted into the cartridge to vacuum out any remaining material near the bottom of the cartridge. 66..PPRREE--FFIILLTTEERR MMEEDDIIAA RREEPPLLAACCEEMMEENNTT Reinstall media cages and fill with new media from the manufacturer or outside supplier. Manufacturer will provide specification of media and sources to purchase. The easiest way to fill the media cages is to utilize a refilling tray that can also be sourced from the manufacturer. Place the refilling tray on top of the cartridge and fill with new bulk media shaking it down into the cages. Using your hands, lightly compact the media into each filter cage. Once the cages are full (each cartridge will hold five heaping 5gal buckets of bulk media),remove the refilling tray and replace the cartridge top, ensuring fasteners are properly tightened. Page 30 of 47 44..PPRREE--FFIILLTTEERR CCAARRTTRRIIDDGGEE LLIIDD RREEMMOOVVAALL After successfully cleaning out the pre-treatment chamber, enter the chamber and remove the lid(s) from the pre-filter cartridge(s) by removing the two thumb screws. (Older pre-filter cartridges have two bolts holding the lids on that require a 7/16” socket to remove) 55..VVAACCUUUUMM EEXXIISSTTIINNGG PPRREE--FFIILLTTEERR MMEEDDIIAA Utilize the vacuum truck hose or hose extension to remove the filter media from each of the individual media cages. Once filter media has been sucked out, use a pressure washer to spray down the inside of the cartridge and its media cages. Remove cleaned media cages and place to the side. Once removed, the vacuum hose can be inserted into the cartridge to vacuum out any remaining material near the bottom of the cartridge. 66..PPRREE--FFIILLTTEERR MMEEDDIIAA RREEPPLLAACCEEMMEENNTT Reinstall media cages and fill with new media from the manufacturer or outside supplier. Manufacturer will provide specification of media and sources to purchase. The easiest way to fill the media cages is to utilize a refilling tray that can also be sourced from the manufacturer. Place the refilling tray on top of the cartridge and fill with new bulk media shaking it down into the cages. Using your hands, lightly compact the media into each filter cage. Once the cages are full(each cartridge will hold five heaping 5gal buckets of bulk media),remove the refilling tray and replace the cartridge top, ensuring fasteners are properly tightened. 13 77..MMAAIINNTTAAIINNIINNGG VVEEGGEETTAATTIIOONN In general, the biofiltration chamber is maintenance-free with the exception of maintaining the vegetation. The MWL utilizes vegetation similar to surrounding landscape areas, therefore, trim vegetation to match surrounding vegetation. If any plants have died, replace them with new ones. 88..IINNSSPPEECCTT UUNNDDEERRDDRRAAIINN SSYYSSTTEEMM Each vertical under drain on the biofiltration chamber has a removable threaded cap that can be taken off to check for any blockages or root growth. Once removed, a jetting attachment to the pressure washer can be used to clean out the under drain and orifice riser if needed. 99..RREEPPLLAACCEE AACCCCEESSSS CCOOVVEERRSS Once maintenance is complete, replace all access cover(s) Page 31 of 47 77..MMAAIINNTTAAIINNIINNGG VVEEGGEETTAATTIIOONN In general, the biofiltration chamber is maintenance-free with the exception of maintaining the vegetation. The MWL utilizes vegetation similar to surrounding landscape areas, therefore, trim vegetation to match surrounding vegetation. If any plants have died, replace them with new ones. 88..IINNSSPPEECCTT UUNNDDEERRDDRRAAIINN SSYYSSTTEEMM Each vertical under drain on the biofiltration chamber has a removable threaded cap that can be taken off to check for any blockages or root growth. Once removed, a jetting attachment to the pressure washer can be used to clean out the under drain and orifice riser if needed. 99..RREEPPLLAACCEE AACCCCEESSSS CCOOVVEERRSS Once maintenance is complete, replace all access cover(s) 14 RREEPPLLAACCIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA IIFF RREEQQUUIIRREEDD As with all biofilter systems, at some point the biofiltration media will need to be replaced, either due to physical clogging or sorptive exhaustion (for dissolved pollutants) of the media ion exchange capacity (to remove dissolved metals and phosphorous). The general life of this media is 10 to 20 years based on site specific conditions and pollutant loading, so replacing the biofiltration media should not be a common occurrence. In the event that the biofiltration media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new biofiltration media. The quantity of media needed can be determined by providing the model number and unit depth. Media will be provided in super sacks for easy installation. Each sack will weigh between 1,000 and 2,000 lbs. Biofiltration media replacement can be done following the steps below: 11..VVAACCUUUUMM EEXXIISSTTIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Remove the mulch and vegetation to access the biofiltration media, and then position the vacuum truck accordingly. Utilize the vacuum truck to vacuum out all the media. Once all media is removed, use the pressure washer to spray down all the netting and underdrain systems on the inside of the media containment cage. Vacuum out any remaining debris after spraying down netting. Inspect the netting for any damage or holes. If the netting is damaged, it can be repaired or replaced with guidance by the manufacturer. 22..IINNSSTTAALLLLIINNGG NNEEWW BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Ensure that the chamber is fully cleaned prior to installation of new media into the media containment cage(s). Media will be provided in super sacks for easy installation. A lifting apparatus (forklift, backhoe, boom truck, or other) is recommended to position the super sack over the biofiltration chamber. Add media in lifts to ensure that the riser pipes remain vertical. Be sure to only fill the media cage(s) up to the same level as the old media. Page 32 of 47 RREEPPLLAACCIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA IIFF RREEQQUUIIRREEDD As with all biofilter systems, at some point the biofiltration media will need to be replaced, either due to physical clogging or sorptive exhaustion (for dissolved pollutants) of the media ion exchange capacity (to remove dissolved metals and phosphorous). The general life of this media is 10 to 20 years based on site specific conditions and pollutant loading, so replacing the biofiltration media should not be a common occurrence. In the event that the biofiltration media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new biofiltration media. The quantity of media needed can be determined by providing the model number and unit depth. Media will be provided in super sacks for easy installation. Each sack will weigh between 1,000 and 2,000 lbs. Biofiltration media replacement can be done following the steps below: 11..VVAACCUUUUMM EEXXIISSTTIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Remove the mulch and vegetation to access the biofiltration media, and then position the vacuum truck accordingly. Utilize the vacuum truck to vacuum out all the media. Once all media is removed, use the pressure washer to spray down all the netting and underdrain systems on the inside of the media containment cage. Vacuum out any remaining debris after spraying down netting. Inspect the netting for any damage or holes. If the netting is damaged, it can be repaired or replaced with guidance by the manufacturer. 22..IINNSSTTAALLLLIINNGG NNEEWW BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Ensure that the chamber is fully cleaned prior to installation of new media into the media containment cage(s). Media will be provided in super sacks for easy installation. A lifting apparatus (forklift, backhoe, boom truck, or other) is recommended to position the super sack over the biofiltration chamber. Add media in lifts to ensure that the riser pipes remain vertical. Be sure to only fill the media cage(s) up to the same level as the old media. 15 33..RREEPPLLAANNTT VVEEGGEETTAATTIIOONN Once the media has been replaced, replant the vegetation and cover biofiltration chamber with approved mulch (if applicable). If the existing vegetation is not being reused, and new vegetation is being planted, you will need to acquire new plant establishment media that will be installed just below the mulch layer at each plant location. (see plan drawings for details). Contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new plant establishment media. Page 33 of 47 33..RREEPPLLAANNTT VVEEGGEETTAATTIIOONN Once the media has been replaced, replant the vegetation and cover biofiltration chamber with approved mulch (if applicable). If the existing vegetation is not being reused, and new vegetation is being planted, you will need to acquire new plant establishment media that will be installed just below the mulch layer at each plant location. (see plan drawings for details). Contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new plant establishment media. 16 RREEPPLLAACCIINNGG DDRRAAIINN DDOOWWNN FFIILLTTEERR MMEEDDIIAA ((OONNLLYY OONN OOLLDDEERR CCAALLIIFFOORRNNIIAA MMOODDEELLSS)) NOTE: The drain down filter is only found on units installed in California prior to 2023 If during inspection it was determined that the drain down filter media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new media. 11..RREEMMOOVVEE EEXXIISSTTIINNGG DDRRAAIINN DDOOWWNN MMEEDDIIAA Pull knob back to unlock the locking mechanism and lift the drain down filter housing to remove the used BioMediaGREEN filter block. 22..IINNSSTTAALLLL NNEEWW DDRRAAIINN DDOOWWNN MMEEDDIIAA Ensure that the chamber and housing are fully cleaned prior to installation of new media, and then insert the new BioMediaGREEN filter block. The media filter block should fit snugly between the chamber walls and be centered under the filter housing. Lower the housing over the filter block and secure the locking mechanism. Page 34 of 47 RREEPPLLAACCIINNGG DDRRAAIINN DDOOWWNN FFIILLTTEERR MMEEDDIIAA ((OONNLLYY OONN OOLLDDEERR CCAALLIIFFOORRNNIIAA MMOODDEELLSS)) NOTE: The drain down filter is only found on units installed in California prior to 2023 If during inspection it was determined that the drain down filter media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new media. 11..RREEMMOOVVEE EEXXIISSTTIINNGG DDRRAAIINN DDOOWWNN MMEEDDIIAA Pull knob back to unlock the locking mechanism and lift the drain down filter housing to remove the used BioMediaGREEN filter block. 22..IINNSSTTAALLLL NNEEWW DDRRAAIINN DDOOWWNN MMEEDDIIAA Ensure that the chamber and housing are fully cleaned prior to installation of new media, and then insert the new BioMediaGREEN filter block. The media filter block should fit snugly between the chamber walls and be centered under the filter housing. Lower the housing over the filter block and secure the locking mechanism. 17 NOTES _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ 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_______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ 18 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No YesType of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. Inspection Report Modular Wetlands Linear Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging the unit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance ENGINEERED SOLUTIONS Page 36 of 47 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No YesType of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. Inspection Report Modular Wetlands Linear Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging theunit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance ENGINEERED SOLUTIONS Project Name Project Address (city)(Zip Code)Owner/Management Company Contact Inspector Name Phone Date Time Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours?No Yes Weather Condition Additional Notes Modular Wetland System Type (Curb, Grate or UG Vault): Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened usingnormal lifting pressure?Damage to discharge chamber access cover (manhole cover/grate) or cannot be openedusing normal lifting pressure?Does the MWS unit show signs of structural deterioration (cracks in the wall, damage toframe?Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioningproperly? Is there evidence of illicit discharge or excessive oil, grease or other automobile fluidsentering and clogging the unit? Is there standing water in inappropriate areas after a dry period? Is the filter insert (if applicable) at capacity and/or is there an accumulation ofdebris/trash on the shelf system?Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass orcartridge filter? If yes specify which one in the comments section. Note depth of accumulation.Does the cartridge filter media need replacement in pre-treatment chamber and/ordischarge chamber?Any signs of improper functioning in the discharge chamber? Note issues in the commentsection. Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plantinformation below. Is there a septic or foul odor coming from the inside of the system? Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves /Foliage No Cleaning Needed Schedule Maintenance Needs Immediate Maintenance Damage to Plants Plant Replacement Plant Trimming Additional Notes: 19 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Site Map # Comments: Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed@ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands LinearENGINEERED SOLUTIONS Page 37 of 47 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Site Map # Comments: Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed@ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands LinearENGINEERED SOLUTIONS Project Name Project Address (city)(Zip Code)Owner/Management Company Contact Inspector Name Phone Date Time Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours?No Yes Weather Condition Additional Notes SiteMap #GPS Coordinatesof Insert Manufacturer /Description / Sizing TrashAccum-ulation FoliageAccum-ulation SedimentAccum-ulation Total DebrisAccum-ulation Condition ofMedia25/50/75/100 Operational PerManufacturers'Specifications MWS Catch Basins MWS SedimentationBasin Media FilterCondition Plant Condition Drain Down MediaCondition Discharge ChamberCondition Drain Down PipeCondition Inlet and OutletPipe Condition SUPPORT DRAWINGS AND SPECIFICATIONS ARE AVAILABLE AT WWW.CONTECHES.COM © 2024 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 WWW.CONTECHES.COM ALL RIGHTS RESERVED. PRINTED IN THE USA. CONTECH ENGINEERED SOLUTIONS LLC PROVIDES SITE SOLUTIONS FOR THE CIVIL ENGINEERING INDUSTRY. CONTECH’S PORTFOLIO INCLUDES BRIDGES, DRAINAGE, SANITARY SEWER, STORMWATER AND EARTH STABILIZATION PRODUCTS. FOR INFORMATION ON OTHER CONTECH DIVISION OFFERINGS, VISIT CONTECHES.COM OR CALL 800-338-1122. ModWetLinear OM Manual 03/24 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. ENGINEERED SOLUTIONS Page 38 of 47 SUPPORT DRAWINGS AND SPECIFICATIONS ARE AVAILABLE AT WWW.CONTECHES.COM © 2024 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 WWW.CONTECHES.COM ALL RIGHTS RESERVED. PRINTED IN THE USA. CONTECH ENGINEERED SOLUTIONS LLC PROVIDES SITE SOLUTIONS FOR THE CIVIL ENGINEERING INDUSTRY. CONTECH’S PORTFOLIO INCLUDES BRIDGES, DRAINAGE, SANITARY SEWER, STORMWATER AND EARTH STABILIZATION PRODUCTS. FOR INFORMATION ON OTHER CONTECH DIVISION OFFERINGS, VISIT CONTECHES.COM OR CALL 800-338-1122. ModWetLinear OM Manual 03/24 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. ENGINEERED SOLUTIONS ENGINEERED SOLUTIONS © 2024 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 WWW.CONTECHES.COM ALL RIGHTS RESERVED. PRINTED IN THE USA. CONTECH ENGINEERED SOLUTIONS LLC PROVIDES SITE SOLUTIONS FOR THE CIVIL ENGINEERING INDUSTRY. CONTECH’S PORTFOLIO INCLUDES BRIDGES, DRAINAGE, SANITARY SEWER, STORMWATER AND EARTH STABILIZATIONPRODUCTS. FOR INFORMATION ON OTHER CONTECH DIVISION OFFERINGS, VISIT CONTECHES.COM OR CALL800-338-1122. NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHERGUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTYWHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. SUPPORT DRAWINGS AND SPECIFICATIONS ARE AVAILABLE AT WWW.CONTECHS.COM ModWetLinear OM Manual 03/24 CDS Guide Operation, Design, Performance and Maintenance ENGINEERED SOLUTIONS Page 39 of 47 CDS Guide Operation, Design, Performance and Maintenance ENGINEERED SOLUTIONS 2 CDS® Using patented continuous deflective separation technology, the CDS system screens, separates and traps debris, sediment, and oil and grease from stormwater runoff. The indirect screening capability of the system allows for 100% removal of floatables and neutrally buoyant material without blinding. Flow and screening controls physically separate captured solids, and minimize the re-suspension and release of previously trapped pollutants. Inline units can treat up to 6 cfs, and internally bypass flows in excess of 50 cfs (1416 L/s). Available precast or cast-in- place, offline units can treat flows from 1 to 300 cfs (28.3 to 8495 L/s). The pollutant removal capacity of the CDS system has been proven in lab and field testing. Operation Overview Stormwater enters the diversion chamber where the diversion weir guides the flow into the unit’s separation chamber and pollutants are removed from the flow. All flows up to the system’s treatment design capacity enter the separation chamber and are treated. Swirl concentration and screen deflection force floatables and solids to the center of the separation chamber where 100% of floatables and neutrally buoyant debris larger than the screen apertures are trapped. Stormwater then moves through the separation screen, under the oil baffle and exits the system. The separation screen remains clog free due to continuous deflection. During the flow events exceeding the treatment design capacity, the diversion weir bypasses excessive flows around the separation chamber, so captured pollutants are retained in the separation cylinder. Design Basics There are three primary methods of sizing a CDS system. The Water Quality Flow Rate Method determines which model size provides the desired removal efficiency at a given flow rate for a defined particle size. The Rational Rainfall Method™ or the and Probabilistic Method is used when a specific removal efficiency of the net annual sediment load is required. Typically in the Unites States, CDS systems are designed to achieve an 80% annual solids load reduction based on lab generated performance curves for a gradation with an average particle size (d50) of 125 microns (μm). For some regulatory environments, CDS systems can also be designed to achieve an 80% annual solids load reduction based on an average particle size (d50) of 75 microns (μm) or 50 microns (μm). Water Quality Flow Rate Method In some cases, regulations require that a specific treatment rate, often referred to as the water quality design flow (WQQ), be treated. This WQQ represents the peak flow rate from either an event with a specific recurrence interval, e.g. the six-month storm, or a water quality depth, e.g. 1/2-inch (13 mm) of rainfall. The CDS is designed to treat all flows up to the WQQ. At influent rates higher than the WQQ, the diversion weir will direct most flow exceeding the WQQ around the separation chamber. This allows removal efficiency to remain relatively constant in the separation chamber and eliminates the risk of washout during bypass flows regardless of influent flow rates. Treatment flow rates are defined as the rate at which the CDS will remove a specific gradation of sediment at a specific removal efficiency. Therefore the treatment flow rate is variable, based on the gradation and removal efficiency specified by the design engineer. Rational Rainfall Method™ Differences in local climate, topography and scale make every site hydraulically unique. It is important to take these factors into consideration when estimating the long-term performance of any stormwater treatment system. The Rational Rainfall Method combines site-specific information with laboratory generated performance data, and local historical precipitation records to estimate removal efficiencies as accurately as possible. Short duration rain gauge records from across the United States and Canada were analyzed to determine the percent of the total annual rainfall that fell at a range of intensities. US stations’ depths were totaled every 15 minutes, or hourly, and recorded in 0.01-inch increments. Depths were recorded hourly with 1-mm resolution at Canadian stations. One trend was consistent at all sites; the vast majority of precipitation fell at low intensities and high intensity storms contributed relatively little to the total annual depth. These intensities, along with the total drainage area and runoff coefficient for each specific site, are translated into flow rates using the Rational Rainfall Method. Since most sites are relatively small and highly impervious, the Rational Rainfall Method is appropriate. Based on the runoff flow rates calculated for each intensity, operating rates within a proposed CDS system are GRATE INLET(CAST IRON HOOD FORCURB INLET OPENING) CREST OF BYPASS WEIR(ONE EACH SIDE) INLET(MULTIPLE PIPES POSSIBLE) OIL BAFFLE SUMP STORAGESEPARATION SLAB TREATMENT SCREEN OUTLET INLET FLUME SEPARATION CYLINDER CLEAN OUT(REQUIRED) DEFLECTION PAN, 3 SIDED(GRATE INLET DESIGN) Page 40 of 472 CDS® Using patented continuous deflective separation technology, the CDS system screens, separates and traps debris, sediment, and oil and grease from stormwater runoff. The indirect screening capability of the system allows for 100% removal of floatables and neutrally buoyant material without blinding. Flow and screening controls physically separate captured solids, and minimize the re-suspension and release of previously trapped pollutants. Inline units can treat up to 6 cfs, and internally bypass flows in excess of 50 cfs (1416 L/s). Available precast or cast-in- place, offline units can treat flows from 1 to 300 cfs (28.3 to 8495 L/s). The pollutant removal capacity of the CDS system has been proven in lab and field testing. Operation Overview Stormwater enters the diversion chamber where the diversion weir guides the flow into the unit’s separation chamber and pollutants are removed from the flow. All flows up to the system’s treatment design capacity enter the separation chamber and are treated. Swirl concentration and screen deflection force floatables and solids to the center of the separation chamber where 100% of floatables and neutrally buoyant debris larger than the screen apertures are trapped. Stormwater then moves through the separation screen, under the oil baffle and exits the system. The separation screen remains clog free due to continuous deflection. During the flow events exceeding the treatment design capacity, the diversion weir bypasses excessive flows around the separation chamber, so captured pollutants are retained in the separation cylinder. Design Basics There are three primary methods of sizing a CDS system. The Water Quality Flow Rate Method determines which model size provides the desired removal efficiency at a given flow rate for a defined particle size. The Rational Rainfall Method™ or the and Probabilistic Method is used when a specific removal efficiency of the net annual sediment load is required. Typically in the Unites States, CDS systems are designed to achieve an 80% annual solids load reduction based on lab generated performance curves for a gradation with an average particle size (d50) of 125 microns (μm). For some regulatory environments, CDS systems can also be designed to achieve an 80% annual solids load reduction based on an average particle size (d50) of 75 microns (μm) or 50 microns (μm). Water Quality Flow Rate Method In some cases, regulations require that a specific treatment rate, often referred to as the water quality design flow (WQQ), be treated. This WQQ represents the peak flow rate from either an event with a specific recurrence interval, e.g. the six-month storm, or a water quality depth, e.g. 1/2-inch (13 mm) of rainfall. The CDS is designed to treat all flows up to the WQQ. At influent rates higher than the WQQ, the diversion weir will direct most flow exceeding the WQQ around the separation chamber. This allows removal efficiency to remain relatively constant in the separation chamber and eliminates the risk of washout during bypass flows regardless of influent flow rates. Treatment flow rates are defined as the rate at which the CDS will remove a specific gradation of sediment at a specific removal efficiency. Therefore the treatment flow rate is variable, based on the gradation and removal efficiency specified by the design engineer. Rational Rainfall Method™ Differences in local climate, topography and scale make every site hydraulically unique. It is important to take these factors into consideration when estimating the long-term performance of any stormwater treatment system. The Rational Rainfall Method combines site-specific information with laboratory generated performance data, and local historical precipitation records to estimate removal efficiencies as accurately as possible. Short duration rain gauge records from across the United States and Canada were analyzed to determine the percent of the total annual rainfall that fell at a range of intensities. US stations’ depths were totaled every 15 minutes, or hourly, and recorded in 0.01-inch increments. Depths were recorded hourly with 1-mm resolution at Canadian stations. One trend was consistent at all sites; the vast majority of precipitation fell at low intensities and high intensity storms contributed relatively little to the total annual depth. These intensities, along with the total drainage area and runoff coefficient for each specific site, are translated into flow rates using the Rational Rainfall Method. Since most sites are relatively small and highly impervious, the Rational Rainfall Method is appropriate. Based on the runoff flow rates calculated for each intensity, operating rates within a proposed CDS system are GRATE INLET(CAST IRON HOOD FORCURB INLET OPENING) CREST OF BYPASS WEIR(ONE EACH SIDE) INLET(MULTIPLE PIPES POSSIBLE) OIL BAFFLE SUMP STORAGESEPARATION SLAB TREATMENT SCREEN OUTLET INLET FLUME SEPARATION CYLINDER CLEAN OUT(REQUIRED) DEFLECTION PAN, 3 SIDED(GRATE INLET DESIGN) CLEAN OUT(REQUIRED) GRATE INLET DEFLECTIONPAN, 3 SIDED SEPARATIONCYLINDER CREST OFBYPASS WEIR INLET FLUME INLET OUTLET TREATMENTSCREEN SEPARATION SLAB OIL BAFFLE SUMPSTORAGE 3 determined. Performance efficiency curve determined from full scale laboratory tests on defined sediment PSDs is applied to calculate solids removal efficiency. The relative removal efficiency at each operating rate is added to produce a net annual pollutant removal efficiency estimate. Probabilistic Rational Method The Probabilistic Rational Method is a sizing program Contech developed to estimate a net annual sediment load reduction for a particular CDS model based on site size, site runoff coefficient, regional rainfall intensity distribution, and anticipated pollutant characteristics. The Probabilistic Method is an extension of the Rational Method used to estimate peak discharge rates generated by storm events of varying statistical return frequencies (e.g. 2-year storm event). Under the Rational Method, an adjustment factor is used to adjust the runoff coefficient estimated for the 10-year event, correlating a known hydrologic parameter with the target storm event. The rainfall intensities vary depending on the return frequency of the storm event under consideration. In general, these two frequency dependent parameters (rainfall intensity and runoff coefficient) increase as the return frequency increases while the drainage area remains constant. These intensities, along with the total drainage area and runoff coefficient for each specific site, are translated into flow rates using the Rational Method. Since most sites are relatively small and highly impervious, the Rational Method is appropriate. Based on the runoff flow rates calculated for each intensity, operating rates within a proposed CDS are determined. Performance efficiency curve on defined sediment PSDs is applied to calculate solids removal efficiency. The relative removal efficiency at each operating rate is added to produce a net annual pollutant removal efficiency estimate. Treatment Flow Rate The inlet throat area is sized to ensure that the WQQ passes through the separation chamber at a water surface elevation equal to the crest of the diversion weir. The diversion weir bypasses excessive flows around the separation chamber, thus preventing re-suspension or re-entrainment of previously captured particles. Hydraulic Capacity The hydraulic capacity of a CDS system is determined by the length and height of the diversion weir and by the maximum allowable head in the system. Typical configurations allow hydraulic capacities of up to ten times the treatment flow rate. The crest of the diversion weir may be lowered and the inlet throat may be widened to increase the capacity of the system at a given water surface elevation. The unit is designed to meet project specific hydraulic requirements. Performance Full-Scale Laboratory Test Results A full-scale CDS system (Model CDS2020-5B) was tested at the facility of University of Florida, Gainesville, FL. This CDS unit was evaluated under controlled laboratory conditions of influent flow rate and addition of sediment. Two different gradations of silica sand material (UF Sediment & OK-110) were used in the CDS performance evaluation. The particle size distributions (PSDs) of the test materials were analyzed using standard method “Gradation ASTM D-422 “Standard Test Method for Particle-Size Analysis of Soils” by a certified laboratory. UF Sediment is a mixture of three different products produced by the U.S. Silica Company: “Sil-Co-Sil 106”, “#1 DRY” and “20/40 Oil Frac”. Particle size distribution analysis shows that the UF Sediment has a very fine gradation (d50 = 20 to 30 μm) covering a wide size range (Coefficient of Uniformity, C averaged at 10.6). In comparison with the hypothetical TSS gradation specified in the NJDEP (New Jersey Department of Environmental Protection) and NJCAT (New Jersey Corporation for Advanced Technology) protocol for lab testing, the UF Sediment covers a similar range of particle size but with a finer d50 (d50 for NJDEP is approximately 50 μm) (NJDEP, 2003). The OK-110 silica sand is a commercial product of U.S. Silica Sand. The particle size distribution analysis of this material, also included in Figure 1, shows that 99.9% of the OK-110 sand is finer than 250 microns, with a mean particle size (d50) of 106 microns. The PSDs for the test material are shown in Figure 1. Figure 1. Particle size distributions Tests were conducted to quantify the performance of a specific CDS unit (1.1 cfs (31.3-L/s) design capacity) at various flow rates, ranging from 1% up to 125% of the treatment design capacity of the unit, using the 2400 micron screen. All tests were conducted with controlled influent concentrations of approximately 200 mg/L. Effluent samples were taken at equal time intervals across the entire duration of each test run. These samples were then processed with a Dekaport Cone sample splitter to obtain representative sub-samples for Suspended Sediment Concentration (SSC) testing using ASTM D3977-97 “Standard Test Methods for Determining Sediment Concentration in Water Samples”, and particle size distribution analysis. Results and Modeling Based on the data from the University of Florida, a performance model was developed for the CDS system. A regression analysis was used to develop a fitting curve representative of the scattered data points at various design flow rates. This model, which demonstrated good agreement with the laboratory data, can then be used to predict CDS system performance with respect Page 41 of 47 3 determined. Performance efficiency curve determined from full scale laboratory tests on defined sediment PSDs is applied to calculate solids removal efficiency. The relative removal efficiency at each operating rate is added to produce a net annual pollutant removal efficiency estimate. Probabilistic Rational Method The Probabilistic Rational Method is a sizing program Contech developed to estimate a net annual sediment load reduction for a particular CDS model based on site size, site runoff coefficient, regional rainfall intensity distribution, and anticipated pollutant characteristics. The Probabilistic Method is an extension of the Rational Method used to estimate peak discharge rates generated by storm events of varying statistical return frequencies (e.g. 2-year storm event). Under the Rational Method, an adjustment factor is used to adjust the runoff coefficient estimated for the 10-year event, correlating a known hydrologic parameter with the target storm event. The rainfall intensities vary depending on the return frequency of the storm event under consideration. In general, these two frequency dependent parameters (rainfall intensity and runoff coefficient) increase as the return frequency increases while the drainage area remains constant. These intensities, along with the total drainage area and runoff coefficient for each specific site, are translated into flow rates using the Rational Method. Since most sites are relatively small and highly impervious, the Rational Method is appropriate. Based on the runoff flow rates calculated for each intensity, operating rates within a proposed CDS are determined. Performance efficiency curve on defined sediment PSDs is applied to calculate solids removal efficiency. The relative removal efficiency at each operating rate is added to produce a net annual pollutant removal efficiency estimate. Treatment Flow Rate The inlet throat area is sized to ensure that the WQQ passes through the separation chamber at a water surface elevation equal to the crest of the diversion weir. The diversion weir bypasses excessive flows around the separation chamber, thus preventing re-suspension or re-entrainment of previously captured particles. Hydraulic Capacity The hydraulic capacity of a CDS system is determined by the length and height of the diversion weir and by the maximum allowable head in the system. Typical configurations allow hydraulic capacities of up to ten times the treatment flow rate. The crest of the diversion weir may be lowered and the inlet throat may be widened to increase the capacity of the system at a given water surface elevation. The unit is designed to meet project specific hydraulic requirements. Performance Full-Scale Laboratory Test Results A full-scale CDS system (Model CDS2020-5B) was tested at the facility of University of Florida, Gainesville, FL. This CDS unit was evaluated under controlled laboratory conditions of influent flow rate and addition of sediment. Two different gradations of silica sand material (UF Sediment & OK-110) were used in the CDS performance evaluation. The particle size distributions (PSDs) of the test materials were analyzed using standard method “Gradation ASTM D-422 “Standard Test Method for Particle-Size Analysis of Soils” by a certified laboratory. UF Sediment is a mixture of three different products produced by the U.S. Silica Company: “Sil-Co-Sil 106”, “#1 DRY” and “20/40 Oil Frac”. Particle size distribution analysis shows that the UF Sediment has a very fine gradation (d50 = 20 to 30 μm) covering a wide size range (Coefficient of Uniformity, C averaged at 10.6). In comparison with the hypothetical TSS gradation specified in the NJDEP (New Jersey Department of Environmental Protection) and NJCAT (New Jersey Corporation for Advanced Technology) protocol for lab testing, the UF Sediment covers a similar range of particle size but with a finer d50 (d50 for NJDEP is approximately 50 μm) (NJDEP, 2003). The OK-110 silica sand is a commercial product of U.S. Silica Sand. The particle size distribution analysis of this material, also included in Figure 1, shows that 99.9% of the OK-110 sand is finer than 250 microns, with a mean particle size (d50) of 106 microns. The PSDs for the test material are shown in Figure 1. Figure 1. Particle size distributions Tests were conducted to quantify the performance of a specific CDS unit (1.1 cfs (31.3-L/s) design capacity) at various flow rates, ranging from 1% up to 125% of the treatment design capacity of the unit, using the 2400 micron screen. All tests were conducted with controlled influent concentrations of approximately 200 mg/L. Effluent samples were taken at equal time intervals across the entire duration of each test run. These samples were then processed with a Dekaport Cone sample splitter to obtain representative sub-samples for Suspended Sediment Concentration (SSC) testing using ASTM D3977-97 “Standard Test Methods for Determining Sediment Concentration in Water Samples”, and particle size distribution analysis. Results and Modeling Based on the data from the University of Florida, a performance model was developed for the CDS system. A regression analysis was used to develop a fitting curve representative of the scattered data points at various design flow rates. This model, which demonstrated good agreement with the laboratory data, can then be used to predict CDS system performance with respect 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 1 10 100 1000 UF Sediment (Avg) OK 110 (Avg) NJCAT 4 to SSC removal for any particle size gradation, assuming the particles are inorganic sandy-silt. Figure 2 shows CDS predictive performance for two typical particle size gradations (NJCAT gradation and OK-110 sand) as a function of operating rate. Figure 2. CDS stormwater treatment predictive performance for various particle gradations as a function of operating rate. Many regulatory jurisdictions set a performance standard for hydrodynamic devices by stating that the devices shall be capable of achieving an 80% removal efficiency for particles having a mean particle size (d50) of 125 microns (e.g. Washington State Department of Ecology — WASDOE - 2008). The model can be used to calculate the expected performance of such a PSD (shown in Figure 3). The model indicates (Figure 4) that the CDS system with 2400 micron screen achieves approximately 80% removal at the design (100%) flow rate, for this particle size distribution (d50 = 125 μm). Figure 3. WASDOE PSD Figure 4. Modeled performance for WASDOE PSD. Maintenance The CDS system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. For example, unstable soils or heavy winter sanding will cause the grit chamber to fill more quickly but regular sweeping of paved surfaces will slow accumulation. Inspection Inspection is the key to effective maintenance and is easily performed. Pollutant transport and deposition may vary from year to year and regular inspections will help ensure that the system is cleaned out at the appropriate time. At a minimum, inspections should be performed twice per year (e.g. spring and fall) however more frequent inspections may be necessary in climates where winter sanding operations may lead to rapid accumulations, or in equipment washdown areas. Installations should also be inspected more frequently where excessive amounts of trash are expected. The visual inspection should ascertain that the system components are in working order and that there are no blockages or obstructions in the inlet and separation screen. The inspection should also quantify the accumulation of hydrocarbons, trash, and sediment in the system. Measuring pollutant accumulation can be done with a calibrated dipstick, tape measure or other measuring instrument. If absorbent material is used for enhanced removal of hydrocarbons, the level of discoloration of the sorbent material should also be identified Page 42 of 47 4 to SSC removal for any particle size gradation, assuming the particles are inorganic sandy-silt. Figure 2 shows CDS predictive performance for two typical particle size gradations (NJCAT gradation and OK-110 sand) as a function of operating rate. Figure 2. CDS stormwater treatment predictive performance for various particle gradations as a function of operating rate. Many regulatory jurisdictions set a performance standard for hydrodynamic devices by stating that the devices shall be capable of achieving an 80% removal efficiency for particles having a mean particle size (d50) of 125 microns (e.g. Washington State Department of Ecology — WASDOE - 2008). The model can be used to calculate the expected performance of such a PSD (shown in Figure 3). The model indicates (Figure 4) that the CDS system with 2400 micron screen achieves approximately 80% removal at the design (100%) flow rate, for this particle size distribution (d50 = 125 μm). Figure 3. WASDOE PSD Figure 4. Modeled performance for WASDOE PSD. Maintenance The CDS system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. For example, unstable soils or heavy winter sanding will cause the grit chamber to fill more quickly but regular sweeping of paved surfaces will slow accumulation. Inspection Inspection is the key to effective maintenance and is easily performed. Pollutant transport and deposition may vary from year to year and regular inspections will help ensure that the system is cleaned out at the appropriate time. At a minimum, inspections should be performed twice per year (e.g. spring and fall) however more frequent inspections may be necessary in climates where winter sanding operations may lead to rapid accumulations, or in equipment washdown areas. Installations should also be inspected more frequently where excessive amounts of trash are expected. The visual inspection should ascertain that the system components are in working order and that there are no blockages or obstructions in the inlet and separation screen. The inspection should also quantify the accumulation of hydrocarbons, trash, and sediment in the system. Measuring pollutant accumulation can be done with a calibrated dipstick, tape measure or other measuring instrument. If absorbent material is used for enhanced removal of hydrocarbons, the level of discoloration of the sorbent material should also be identified 100.00 80.00 60.00 40.00 20.00 0.00 140%120%100%80%60%40%20%0% % Design Flow Rate 10090807060504030201001 10 100 1000 10000 Particle Size Distribution Particle Size (micron) 100 80 60 40 20 00%20%40%60%80%100%120%140% % Design Flow Rate 5 during inspection. It is useful and often required as part of an operating permit to keep a record of each inspection. A simple form for doing so is provided. Access to the CDS unit is typically achieved through two manhole access covers. One opening allows for inspection and cleanout of the separation chamber (cylinder and screen) and isolated sump. The other allows for inspection and cleanout of sediment captured and retained outside the screen. For deep units, a single manhole access point would allows both sump cleanout and access outside the screen. The CDS system should be cleaned when the level of sediment has reached 75% of capacity in the isolated sump or when an appreciable level of hydrocarbons and trash has accumulated. If absorbent material is used, it should be replaced when significant discoloration has occurred. Performance will not be impacted until 100% of the sump capacity is exceeded however it is recommended that the system be cleaned prior to that for easier removal of sediment. The level of sediment is easily determined by measuring from finished grade down to the top of the sediment pile. To avoid underestimating the level of sediment in the chamber, the measuring device must be lowered to the top of the sediment pile carefully. Particles at the top of the pile typically offer less resistance to the end of the rod than consolidated particles toward the bottom of the pile. Once this measurement is recorded, it should be compared to the as-built drawing for the unit to determine weather the height of the sediment pile off the bottom of the sump floor exceeds 75% of the total height of isolated sump. Cleaning Cleaning of a CDS systems should be done during dry weather conditions when no flow is entering the system. The use of a vacuum truck is generally the most effective and convenient method of removing pollutants from the system. Simply remove the manhole covers and insert the vacuum hose into the sump. The system should be completely drained down and the sump fully evacuated of sediment. The area outside the screen should also be cleaned out if pollutant build-up exists in this area. In installations where the risk of petroleum spills is small, liquid contaminants may not accumulate as quickly as sediment. However, the system should be cleaned out immediately in the event of an oil or gasoline spill. Motor oil and other hydrocarbons that accumulate on a more routine basis should be removed when an appreciable layer has been captured. To remove these pollutants, it may be preferable to use absorbent pads since they are usually less expensive to dispose than the oil/water emulsion that may be created by vacuuming the oily layer. Trash and debris can be netted out to separate it from the other pollutants. The screen should be cleaned to ensure it is free of trash and debris. Manhole covers should be securely seated following cleaning activities to prevent leakage of runoff into the system from above and also to ensure that proper safety precautions have been followed. Confined space entry procedures need to be followed if physical access is required. Disposal of all material removed from the CDS system should be done in accordance with local regulations. In many jurisdictions, disposal of the sediments may be handled in the same manner as the disposal of sediments removed from catch basins or deep sump manholes. Check your local regulations for specific requirements on disposal. Page 43 of 47 during inspection. It is useful and often required as part of an operating permit to keep a record of each inspection. A simple form for doing so is provided. Access to the CDS unit is typically achieved through two manhole access covers. One opening allows for inspection and cleanout of the separation chamber (cylinder and screen) and isolated sump. The other allows for inspection and cleanout of sediment captured and retained outside the screen. For deep units, a single manhole access point would allows both sump cleanout and access outside the screen. The CDS system should be cleaned when the level of sediment has reached 75% of capacity in the isolated sump or when an appreciable level of hydrocarbons and trash has accumulated. If absorbent material is used, it should be replaced when significant discoloration has occurred. Performance will not be impacted until 100% of the sump capacity is exceeded however it is recommended that the system be cleaned prior to that for easier removal of sediment. The level of sediment is easily determined by measuring from finished grade down to the top of the sediment pile. To avoid underestimating the level of sediment in the chamber, the measuring device must be lowered to the top of the sediment pile carefully. Particles at the top of the pile typically offer less resistance to the end of the rod than consolidated particles toward the bottom of the pile. Once this measurement is recorded, it should be compared to the as-built drawing for the unit to determine weather the height of the sediment pile off the bottom of the sump floor exceeds 75% of the total height of isolated sump. Cleaning Cleaning of a CDS systems should be done during dry weather conditions when no flow is entering the system. The use of a vacuum truck is generally the most effective and convenient method of removing pollutants from the system. Simply remove the manhole covers and insert the vacuum hose into the sump. The system should be completely drained down and the sump fully evacuated of sediment. The area outside the screen should also be cleaned out if pollutant build-up exists in this area. In installations where the risk of petroleum spills is small, liquid contaminants may not accumulate as quickly as sediment. However, the system should be cleaned out immediately in the event of an oil or gasoline spill. Motor oil and other hydrocarbons that accumulate on a more routine basis should be removed when an appreciable layer has been captured. To remove these pollutants, it may be preferable to use absorbent pads since they are usually less expensive to dispose than the oil/water emulsion that may be created by vacuuming the oily layer. Trash and debris can be netted out to separate it from the other pollutants. The screen should be cleaned to ensure it is free of trash and debris. Manhole covers should be securely seated following cleaning activities to prevent leakage of runoff into the system from above and also to ensure that proper safety precautions have been followed. Confined space entry procedures need to be followed if physical access is required. Disposal of all material removed from the CDS system should be done in accordance with local regulations. In many jurisdictions, disposal of the sediments may be handled in the same manner as the disposal of sediments removed from catch basins or deep sump manholes. Check your local regulations for specific requirements on disposal. 6 Note: To avoid underestimating the volume of sediment in the chamber, carefully lower the measuring device to the top of the sediment pile. Finer silty particles at the top of the pile may be more difficult to feel with a measuring stick. These finer particles typically offer less resistance to the end of the rod than larger particles toward the bottom of the pile. CDS Model Diameter Distance from Water Surface to Top of Sediment Pile Sediment Storage Capacity ft m ft m y3 m3 CDS1515 3 0.9 3.0 0.9 0.5 0.4 CDS2015 4 1.2 3.0 0.9 0.9 0.7 CDS2015 5 1.5 3.0 0.9 1.3 1.0 CDS2020 5 1.5 3.5 1.1 1.3 1.0 CDS2025 5 1.5 4.0 1.2 1.3 1.0 CDS3020 6 1.8 4.0 1.2 2.1 1.6 CDS3025 6 1.8 4.0 1.2 2.1 1.6 CDS3030 6 1.8 4.6 1.4 2.1 1.6 CDS3035 6 1.8 5.0 1.5 2.1 1.6 CDS4030 8 2.4 4.6 1.4 5.6 4.3 CDS4040 8 2.4 5.7 1.7 5.6 4.3 CDS4045 8 2.4 6.2 1.9 5.6 4.3 CDS5640 10 3.0 6.3 1.9 8.7 6.7 CDS5653 10 3.0 7.7 2.3 8.7 6.7 CDS5668 10 3.0 9.3 2.8 8.7 6.7 CDS5678 10 3.0 10.3 3.1 8.7 6.7 Table 1: CDS Maintenance Indicators and Sediment Storage Capacities Page 44 of 47 Note: To avoid underestimating the volume of sediment in the chamber, carefully lower the measuring device to the top of the sediment pile. Finer silty particles at the top of the pile may be more difficult to feel with a measuring stick. These finer particles typically offer less resistance to the end of the rod than larger particles toward the bottom of the pile. CDS Model Diameter Distance from Water Surface to Top of Sediment Pile Sediment Storage Capacity ft m ft m y3 m3 CDS1515 3 0.9 3.0 0.9 0.5 0.4 CDS2015 4 1.2 3.0 0.9 0.9 0.7 CDS2015 5 1.5 3.0 0.9 1.3 1.0 CDS2020 5 1.5 3.5 1.1 1.3 1.0 CDS2025 5 1.5 4.0 1.2 1.3 1.0 CDS3020 6 1.8 4.0 1.2 2.1 1.6 CDS3025 6 1.8 4.0 1.2 2.1 1.6 CDS3030 6 1.8 4.6 1.4 2.1 1.6 CDS3035 6 1.8 5.0 1.5 2.1 1.6 CDS4030 8 2.4 4.6 1.4 5.6 4.3 CDS4040 8 2.4 5.7 1.7 5.6 4.3 CDS4045 8 2.4 6.2 1.9 5.6 4.3 CDS5640 10 3.0 6.3 1.9 8.7 6.7 CDS5653 10 3.0 7.7 2.3 8.7 6.7 CDS5668 10 3.0 9.3 2.8 8.7 6.7 CDS5678 10 3.0 10.3 3.1 8.7 6.7 Table 1: CDS Maintenance Indicators and Sediment Storage Capacities 7 CDS Inspection & Maintenance Log CDS Model: Location: Water Floatable Describe Maintenance Date depth to Layer Maintenance Personnel Comments sediment1 Thickness2 Performed —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— 1. The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the values listed in table 1 the system should be cleaned out. Note: to avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. 2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness. In the event of an oil spill, the system should be cleaned immediately. Page 45 of 47 7 CDS Inspection & Maintenance Log CDS Model: Location: Water Floatable Describe Maintenance Date depth to Layer Maintenance Personnel Comments sediment1 Thickness2 Performed —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— 1. The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the values listed in table 1 the system should be cleaned out. Note: to avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. 2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness. In the event of an oil spill, the system should be cleaned immediately. 1. The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the values listed in table 1 the system should be cleaned out. Note: to avoid underestimating the volume ofsediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile.2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciablethickness. In the event of an oil spill, the system should be cleaned immediately. SUPPORT • Drawings and specifications are available at www.ContechES.com. • Site-specific design support is available from our engineers. ©2017 Contech Engineered Solutions LLC, a QUIKRETE Company Contech Engineered Solutions provides site solutions for the civil engineering industry. Contech’s portfolio includes bridges, drainage, sanitary sewer, earth stabilization and stormwater treatment products. For information on other Contech division offerings, visit www.ContechES.com or call 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. The product(s) described may be protected by one or more of the following US patents: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6,406,218; 6,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038; 7,186,058; 7,296,692; 7,297,266; related foreign patents or other patents pending. 800-338-1122 www.ContechES.com cds_manual 3/17 PDF ENGINEERED SOLUTIONS Page 46 of 47 SUPPORT • Drawings and specifications are available at www.ContechES.com. • Site-specific design support is available from our engineers. ©2017 Contech Engineered Solutions LLC, a QUIKRETE Company Contech Engineered Solutions provides site solutions for the civil engineering industry. Contech’s portfolio includes bridges, drainage, sanitary sewer, earth stabilization and stormwater treatment products. For information on other Contech division offerings, visit www.ContechES.com or call 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. The product(s) described may be protected by one or more of the following US patents: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6,406,218; 6,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038; 7,186,058; 7,296,692; 7,297,266; related foreign patents or other patents pending. 800-338-1122 www.ContechES.com cds_manual 3/17 PDF ENGINEERED SOLUTIONS ©2017 Contech Engineered Solutions LLC, a QUIKRETE Company Contech Engineered Solutions provides site solutions for the civil engineering industry. Contech’s portfolio includes bridges, drainage, sanitary sewer, earth stabilization and stormwater treatment products. For information on other Contech division offerings, visitwww.ContechES.com or call 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITYFOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS,MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. The product(s) described may be protected by one or more of the following US patents: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6,406,218; 6,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038; 7,186,058; 7,296,692; 7,297,266; related foreign patents or other patents pending. cds_manual 3/17 PDF nd specifications are available at www.ContechES.com. SUPPORT • Drawings and specifications are available at www.ContechES.com. • Site-specific design support is available from our engineers.800-338-1122 www.ContechES.com ENGINEERED SOLUTIONS sit www.Con EIR OWN EVALUA Page 47 of 47 EXHIBIT C – FULL LEGAL DESCRIPTION PARCEL C: LOT 2 OF CITY OF RENTON LOT LINE ADJUSTMENT NO. LUA-00-148-LLA, RECORDED UNDER RECORDING NO. 20010529900002, IN KING COUNTY, WASHINGTON. (1023059201) PARCEL H: THE WEST HALF OF THE NORTHEAST QUARTER OF THE NORTHEAST QUARTER OF THE NORTHWEST QUARTER OF SECTION 10, TOWNSHIP 23 NORTH, RANGE 5 EAST, WILLAMETTE MERIDIAN, IN KING COUNTY, WASHINGTON; EXCEPT THE NORTH 275 FEET, THEREOF; ALSO EXCEPT THAT PORTION LYING WITHIN THE COUNTY ROAD. (1023059277)