HomeMy WebLinkAboutRS_DrainageReport_240925_v1.pdf 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 September 24, 2024 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
i Technical Information Report for HAZEN HIGH SCHOOL IMPROVEMENTS JCE Project No. C240033-0208 September 24, 2024 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 ..................................................................................... 5 CORE REQUIREMENT #1: DISCHARGE AT THE NATURAL LOCATION .................................................. 5 CORE REQUIREMENT #2: OFFSITE ANALYSIS ......................................................................................... 5 CORE REQUIREMENT #3: FLOW CONTROL FACILITIES.......................................................................... 6 CORE REQUIREMENT #4: CONVEYANCE SYSTEM .................................................................................. 6 CORE REQUIREMENT #5: CONSTRUCTION STORMWATER POLLUTION PREVENTION ................... 6 CORE REQUIREMENT #6: MAINTENANCE AND OPERATIONS ............................................................... 6 CORE REQUIREMENT #7: FINANCIAL GUARANTEES AND LIABILITY.................................................... 7 CORE REQUIREMENT #8: WATER QUALITY FACILITIES ......................................................................... 7 CORE REQUIREMENT #9: ON-SITE BMPS .................................................................................................. 7 SPECIAL REQUIREMENT #1: OTHER ADOPTED AREA-SPECIFIC REQUIREMENTS ........................... 8 SPECIAL REQUIREMENT #2: FLOOD HAZARD AREA DELINEATION ..................................................... 8 SPECIAL REQUIREMENT #3: FLOOD PROTECTION FACILITIES ............................................................ 8 SPECIAL REQUIREMENT #4: SOURCE CONTROLS .................................................................................. 8 SPECIAL REQUIREMENT #5: OIL CONTROL .............................................................................................. 9 SPECIAL REQUIREMENT #6: AQUIFER PROTECTION AREA .................................................................. 9 3. OFFSITE ANALYSIS .......................................................................................................................... 10 FIELD INSPECTION ......................................................................................................................................10 DRAINAGE SYSTEM PROBLEM DESCRIPTIONS .....................................................................................10 UPSTREAM ANALYSIS .................................................................................................................................10 DOWNSTREAM ANALYSIS ..........................................................................................................................10 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS .........................................................................10 4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER QUALITY FACILITY ANALYSIS AND DESIGN .................................................................................................................................................. 11 FLOW CONTROL SYSTEM (PART D) .........................................................................................................12 WATER QUALITY SYSTEM (PART E) .........................................................................................................12 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................................................. 13 6. SPECIAL REPORTS AND SUMMARY ................................................................................................... 15 7. OTHER PERMITS ............................................................................................................................. 16 8. CSWPP ANALYSIS AND DESIGN ......................................................................................................... 17
HAZEN HIGH SCHOOL IMPROVEMENTS ii STANDARD REQUIREMENTS .....................................................................................................................17 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ..................................... 18 BOND QUANTITIES WORKSHEET..............................................................................................................18 FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH .......................18 DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND WQ FACILITIES .....................................................................................................................................................18 10. OPERATIONS AND MAINTENANCE MANUAL ....................................................................................... 19 11. FIGURES ......................................................................................................................................... 20 12. APPENDICES ................................................................................................................................... 21
HAZEN HIGH SCHOOL IMPROVEMENTS 3 1. PROJECT OVERVIEW GENERAL DESCRIPTION The following Drainage Report provides the design narrative and discussion for the Hazen High School Improvements project scheduled to begin construction in the Summer of 2025. The stormwater design for the project was based on the requirements outlined in the 2022 City of Renton Water Design Manual (RSWDM). Hazen High School is within the City of Renton jurisdictional limits at 1101 Hoquiam Ave NE, Renton, WA, 98059 (Parcel Numbers 1023059057, 1023059072, 1023059201, 1023059278, 1023059292, 1023059084, 1023059277, & 1023059094). The site borders Duvall Ave NE on the west, the north borders NE 12th St, the south borders an access road and a paved pedestrian pathway along NE 10th St, the east borders Hoquiam Ave NE, and the west borders single-family homes. Additionally, in the center of the campus, Hazen High School property surrounds an existing church at 1063 Hoquiam Ave NE 98059 (Parcel Number 1023059146) and shares the eastern parking lot north of the tennis courts with the school. See Figure 2 - Vicinity Map. The proposed project consists of replacing the existing baseball and softball and adjacent multipurpose fields with new synthetic turf fields. Along with field improvements, geothermal and electrical utilities, a security vestibule, temporary portables, and new/replaced associated paving will be added. Proposed paving includes utility trenching, a new mechanical yard, replaced sidewalk for security bollard installation, and replaced sidewalk around the new main entry security vestibule. EXISTING CONDITIONS The school property is currently occupied by (1) one large building on the northeast side of the property with associated sidewalks, parking, and driving areas surrounding all sides of the building. The school additionally has a baseball field to the west, a rubberized track and grass field at the southwest corner, a softball field to the south, and tennis courts at the southeast corner. There is landscaping, trees, and vegetation in between the building and around driving surfaces, with a pocket of existing dense vegetation to the west of the baseball field. See Figure 4 – Existing Conditions. 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 Lodgement 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 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 below 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. TABLE 1 – DISTURBED AREA EXISTING SITE CONDITIONS Land Cover TDA #1 TDA #2 TDA #3 TOTAL Impervious Surface 0 3,937 4,886 8,823 Pervious Surface 115,417 106,548 40,793 160,641 Total Area 115,417 110,485 45,679 271,581 % Impervious 0% 3.6% 10.7% 3.2%
HAZEN HIGH SCHOOL IMPROVEMENTS 4 PROPOSED DRAINAGE SYSTEM As described above, 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 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. Duvall Ave NE was recently improved to include new curb, gutter and sidewalk with stormwater improvements to include water quality treatment and a new 12” storm main. The proposed improvements will continue to discharge toward Duvall Ave NE. The stormwater runoff from the redeveloped areas within TDA #1 will be collected through the new underdrained synthetic turf baseball field, which is considered 100% impervious, and flow to a new RainVault detention system located to the west, connect to a 54” Type II SDMH flow control structure, and finally drain through a 12” storm pipe to connect to the existing storm main in Duvall Avenue NE. See Figure 5A – Offsite Drainage for a continuation of the downstream storm system. 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 in a 12” storm pipe toward the existing storm system in NE 10th St. Stormwater runoff from the proposed synthetic softball field will be collected within the new underdrain system and routed to a new RainVault detention system, then flow west to a 54” Type II SDMH flow control structure, and finally drain through a 12” storm pipe to connect at the existing 12” storm pipe that is flowing to the south, connecting to the existing storm system within NE 10th Street. See Figure 5B – Offsite Drainage for a continuation of the downstream storm system. TDA #3 consists of parking areas north, east and south of the school building, the existing grass multipurpose field, and tennis courts. TDA #3 connects to the existing storm system in Hoquiam Ave NE at multiple locations along the eastern school property line. Flow from the redeveloped areas in TDA #3 will utilize one existing connection to the Hoquiam Ave NE storm system for the new security vestibule and bollard installation, and the synthetic multipurpose field underdrains will propose a new connection to Hoquiam Ave NE. The stormwater runoff from the proposed areas within the third Threshold Discharge Area on the north side of the site will be collected within the existing system on-site. Stormwater runoff will also be collected within the new underdrained synthetic turf multipurpose field and routed through a new RainVault detention system, then flow to a 54” Type II SDMH flow control structure, and finally drain through a 12” storm pipe connecting to the existing storm system within Hoquiam Ave NE. 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 102,118 42,345 39,201 183,664 Replaced Impervious Surface 0 410 2,879 3,289 Total Area 102,118 42,755 42,080 186,953 WATER QUALITY TREATMENT No water quality facilities are proposed to be installed for this project, as the surface area for new plus replaced pollution generating impervious surfaces (PGIS) will be below the threshold of 5,000 square feet. The project will also create less than 3/4 acres of new pollution generating pervious surface area (PGPS). All proposed synthetic fields will have a non-pollution generating infill material. See Figure 3 – New + Replaced Impervious Areas.
HAZEN HIGH SCHOOL IMPROVEMENTS 5 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 currently discharges 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.
HAZEN HIGH SCHOOL IMPROVEMENTS 6 CORE REQUIREMENT #3: FLOW CONTROL FACILITIES All proposed projects, including redevelopment projects, must provide onsite flow control facilities to 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 considering 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 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 considering 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. 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 consistent with the requirements in Section 1.2.5.3 that apply to the proposed project. A 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 7 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. 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. No water quality facilities are proposed to be installed for this project, as the surface area for new plus replaced pollution generating impervious surfaces (PGIS) will be below the threshold of 5,000 square feet. The project will also create less than 3/4 acres of new pollution generating pervious surface area (PGPS). All proposed synthetic fields will have a non-pollution generating infill material. See Figure 3 – New + Replaced Impervious Areas. 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 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 – The project site does not contain enough native vegetated surface to fully disperse all impervious surfaces proposed with this project. 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 or 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. 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.
HAZEN HIGH SCHOOL IMPROVEMENTS 8 No driveways are proposed with this project therefore the Wheel Strip Driveway credit is not feasible for this 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 consists of small pockets of existing trees, with the vast majority being landscaped, therefore the Native Growth Retention Credit is not feasible for this site. 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 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 should 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.
HAZEN HIGH SCHOOL IMPROVEMENTS 9 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 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 10 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 anticipated 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. See Figure 5 – Offsite Drainage. 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 and discharging 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 11 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 Lodgement 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) Storm water mitigation will be provided for all new plus replaced impervious and new pervious surfaces for each TDA, to include the new synthetic turf play fields, security vestibule roof, and sidewalks will be required of the new project redevelopment. Note that impervious surfaces replaced for the sole purpose of utility installation or maintenance are excluded from the definition of replaced impervious surfaces and are therefore not required to provide flow control for those surfaces. Stormwater in each TDA will be discharged from the proposed detention facilities and routed to the existing point of discharge for each TDA. Table 2 in Section 1 of this report summarizes the land cover characteristics of the proposed project site redevelopment disturbed area (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 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 three detention systems, one for each TDA, to provide the required flow control volume. 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, some 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 12 TABLE 3 – FLOW CONTROL BASINS Land Cover TDA #1 TDA #2 TDA #3 TARGET SURFACES BASIN Flat Sidewalk 2.344 0.977 0.931 Flat Sidewalk (Bypass) 0.047 Flat Roof (Bypass) 0.013 FLOW THROUGH BASIN Flat Sidewalk 0.113 0.085 Flat Lawn 0.097 0.014 Moderate Sidewalk 0.016 Moderate Lawn 0.146 0.007 Steep Lawn 0.076 0.060 Total Area 2.792 AC 1.062 AC 1.072 AC FLOW CONTROL SYSTEM (PART D) This project proposes to install three RainVault detention systems, one in each TDA for this site. At this time, the proposed detention systems are still tentative and the product to be installed is subject to change. TDA #1 currently proposes to install a RainVault Pent (5) stack to provide the required live storage volume. The total live storage volume required is 42,624 CF, and 47,150 CF of live storage is proposed with the current system. TDA #2 currently proposes to install a RainVault Double (2) stack to provide the required live storage volume. The total live storage volume required is 17,332 CF, and 19,250 CF of live storage is proposed with the current system. TDA #3 currently proposes to install a RainVault Double (2) stack to provide the required live storage volume. The total live storage volume required is 22,342 CF, and 25,150 CF of live storage is proposed with the current system. See Stormwater Calculations in Appendix B of this drainage report for all MGS Flood calculations. WATER QUALITY SYSTEM (PART E) No water quality facilities are proposed to be installed for this project, as the surface area for new plus replaced pollution generating impervious surfaces (PGIS) will be below the threshold of 5,000 square feet. The project will also create less than 3/4 acres of new pollution generating pervious surface area (PGPS). All proposed synthetic fields will have a non-pollution generating infill material. See Figure 3 – New + Replaced Impervious Areas.
HAZEN HIGH SCHOOL IMPROVEMENTS 13 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. 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.
HAZEN HIGH SCHOOL IMPROVEMENTS 14 - No tightline conveyance systems that traverse a steep slope are proposed with this project. 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.
HAZEN HIGH SCHOOL IMPROVEMENTS 15 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:\GIS_Projects\aaY2021\210251 Hazen HS\APRX\E003\20210251E003 F1 VM_HazenHS.aprx | 20210251E003 F1 VM_Hazen HS | 2024-01-24 | mtropCOUNTY 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 STATE
ROUTES 24K (12/20). KING CO: PARCELS
(4/23), ROADS (5/23).
NOTE: LOCATION AND DISTANCES SHOWNARE APPROXIMATE. BLACK AND WHITEREPRODUCTION OF THIS COLOR ORIGINAL
MAY REDUCE ITS EFFECTIVENESS AND LEAD
TO INCORRECT INTERPRETATION.
King County
DUVALL AVE NEHOQUIAM AVE NENE 12TH ST
NE 10TH STCHELAN AVE NE900
KING COUNTYRENTON
NEWCAS
T
L
E
RENTONRENTON
RENTON NEWCASTLENEWCASTLE
0 2,000
FEET
±
SITE
BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY
REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION.
LOCATION AND DISTANCES SHOWN ARE APPROXIMATE.G:\GIS_Projects\aaY2021\210251 Hazen HS\APRX\E003\20210251E003 F2 ES_HazenHS.aprx | 20210251E003 F2 ES_HazenHS | 2024-01-24 | mtropPROJECT 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
FEETDuvall Ave NEHoquiam Ave NENE 10th St
NE 12th St
NE 12th St
NE 11th Pl
NE 11th Ct
NE 10th St
NE 10th Pl
NE 11th St
Duvall Pl NEEB-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
HAZEN HIGH
SCHOOL
470460450440430420460
450
480
470
46
0
450
450440470
470470
440440LEGEND
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)HighlyOrganicSoilsFine-Grained Soils - 50% or More Passes No. 200 Sieve(1)Coarse-Grained Soils - More than 50% Retained on No. 200 SieveGravels - More than 50% of Coarse FractionRetained on No. 4 Sieve12% Fines5% FinesSands - 50% or More of Coarse FractionPasses No. 4 SieveSilts and ClaysLiquid Limit Less than 50Silts and ClaysLiquid Limit 50 or More(1)(1)12% Fines5% Fines(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:
A1Blocks\ dwg \ log_key 2022.dwg LAYOUT: Layout 5 - 2022 Logdraft
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"
31
50/4"
22
28
48
50/5"
50/4"
Associated Earth Sciences, Inc.
Exploration Boring EB-1
Hazen High School Modernization
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 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"
37
50/4"
50/6"
50/4"
Associated Earth Sciences, Inc.
Exploration Boring EB-1
Hazen High School Modernization
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 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"
27
33
50/5"
13
16
23
50/5"
50/5"
Associated Earth Sciences, Inc.
Exploration Boring EB-2
Hazen High School Modernization
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 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"
18
50/6"
10
18
33
50/5"
50/6"
Associated Earth Sciences, Inc.
Exploration Boring EB-3
Hazen High School Modernization
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 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
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 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
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 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
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 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
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): ()Depth (ft)Sample TypeSample% RecoveryGraphic SymbolDescription
Water LevelBlows/6"Blows/Foot
10 20 30 40 50+Other Tests20210251E0031/24/2024Sheet: 1 of 1
APPENDIX B
Historical Exploration Logs
(AESI 2009, 2021, 2022)
Asphalt - 2 inches
Fill
Upper 3 inches: Moist, grayish dark brown, silty, fine SAND, trace medium to
coarse 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 Outwash
Moist, grayish brown, silty, fine SAND, trace gravel; unsorted (SM).
S-1
S-2
15
10
10
11
18
21
Bottom of exploration boring at 3.5 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~466
5
10
EB-1
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20222020
3939
Asphalt - 2 inches
Fill
Moist, dark brown, silty, fine SAND, some gravel; organics observed; faint
organic odor (SM).
Moist, brownish gray, silty, fine SAND, some gravel; some organics; faint
organic odor; gravel in tip; poor recovery (SM).
S-1
S-2
8
5
5
6
11
14
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~466
5
10
EB-2
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20221010
2525
Asphalt - 1.75 inches
Fill
Moist, 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 (wood
stuck in tip) (SM).
S-1
S-2
7
5
5
6
9
10
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~465
5
10
EB-3
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20221010
1919
Asphalt - 1.5 inches
Fill
Moist, 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
6
4
5
5
8
8
9
13
17
Bottom of exploration boring at 5 feet
Groundwater encountered at 3 feet.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~465
5
10
EB-4
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 202299
1616
3030
Asphalt - 1.75 inches
Gravel Base Course - 1 inch
Vashon Recessional Outwash
Moist, reddish brown, fine SAND, some silt, trace gravel; massive (SP-SM).
As above.
S-1
S-2
14
13
14
12
16
22
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~465
5
10
EB-5
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20222727
3838
Asphalt - 3 inches (2 lifts)
Fill
Upper 6 inches: Moist, dark brown, silty, fine SAND, some gravel; unsorted
(SM).
Vashon Recessional Outwash
Lower 12 inches: Moist, reddish brown, fine SAND,some silt, trace gravel;
massive (SP-SM).
As above.
S-1
S-2
7
13
12
11
12
19
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~466
5
10
EB-6
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20222525
3131
Asphalt - 2 inches
Gravel Base Course - 3 inches
Fill
Moist, 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
5
2
5
3
11
16
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~466
5
10
EB-7
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 202277
2727
Asphalt - 1 inch
Fill
Moist, brownish gray, silty, fine SAND, some gravel; unsorted (SM).
As above; contains organics.
S-1
S-2
14
10
10
10
14
14
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~466
5
10
EB-8
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20222020
2828
Asphalt - 3 inches (2 lifts)
Gravel Base Course - 2 inches
Fill
Moist, 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; abundant
organics; organic odor (SM).
S-1
S-2
19
18
16
5
22
28
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~465
5
10
EB-9
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20223434
5050
Asphalt - 3 inches (2 lifts)
Fill
Moist, dark brown to grayish brown, silty, fine SAND, to fine sandy, SILT, trace
gravel; organics observed; organic odor (SM-ML).
As above.
S-1
S-2
6
6
5
7
13
19
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~464
5
10
EB-10
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 20221111
3232
Asphalt - 3 inches (2 lifts)
Gravel Base Course - 3 inches
Fill
Moist, dark brown, silty, fine SAND, some gravel; abundant organics; organic
odor; unsorted (SM).
Moist, bluish gray, silty, fine SAND; massive (SM).
S-1
S-2
13
5
4
8
14
12
Bottom of exploration boring at 3 feet
No groundwater encountered.
Ground Surface Elevation (ft)
Grab SampleSymbol 2
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~466
5
10
EB-11
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
ART2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210251E002
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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210251E002.GPJ March 21, 202299
2626
Topsoil - 6 inches
Fill
Cuttings are brown GRAVEL.
Very gravelly drilling 0 to 4 feet.
Moist, brown, silty, fine SAND; trace gravel; blowcount likely overstated
due to oversized gravel; not representative (SM).
Upper 6 inches: As above.
Vashon Recessional Outwash
Lower 12 inches: Moist, brown with occasional planes of oxidation, fine
SAND, some silt, trace gravel; bedded with occasional thin interbeds of
silty, 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, fine
SAND, some gravel; unsorted (SM).
S-1
S-2
S-3
S-4
S-5
17
18
10
7
8
13
8
12
12
12
16
17
27
31
30
Bottom of exploration boring at 21.5 feet
Groundwater encountered 8 to 12 feet.
Ground Surface Elevation (ft)
Grab SampleSymbol 6
40
Datum
Hammer Weight/Drop
Sampler Type (ST):
~460
5
10
15
20
EB-1
Ring Sample
No RecoveryGraphic 10 Other TestsHole Diameter (in)
DESCRIPTION
Driller/Equipment
Blows/6"JHS
JG2" OD Split Spoon Sampler (SPT)
3" OD Split Spoon Sampler (D & M)Water LevelProject Name
Water Level ()Approved by:
30
Blows/Foot
SamplesDepth (ft)S
T
Exploration Number
20210397E001
10/20/21,10/20/21
Logged by:
Shelby Tube Sample
140# / 30
Geologic 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
CompletionLocation
Sheet
1 of 1
NAVD 88
WellAESIBOR 20210397E001.GPJ November 5, 20212828
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 16 7. OTHER PERMITS DOE Construction Stormwater General Permit - NPDES (PENDING)
HAZEN HIGH SCHOOL IMPROVEMENTS 17 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, parking lot, and asphalt play adjacent to the west side of the field 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 protect 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 – 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 18 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT BOND QUANTITIES WORKSHEET A bond quantities worksheet will be included in Appendix A in a forthcoming submittal. 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 19 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
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
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.
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.
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.
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.
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.
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.
Operation and Maintenance Manual for Introduction This manual is designed to provide you with comprehensive guidance on how to inspect and
o If your system was designed with a First Flush Filter (F3), pay extra attention to these areas, as they were designed to collect the bulk of sediment and debris. • OUTLET o Inspect the outlet structure (where applicable) for sediment and debris. o Ensure the outlet orifice (where applicable) is free of blockages. o If the outlet daylights into a natural waterway, check for signs of erosion or other degradation. • DOCUMENTATION o Record your inspection findings, including photos and descriptions of any issues or observations. o Be sure to include a date in your report Maintenance If excessive sediment or debris is found in your RainVault System, maintenance will be required. • Using the inspection report as your guide, access all areas where sediment or debris was documented and should be removed • Standard jet-vac equipment is recommended • INLET o Block the inlet pipe to the RainVault o Begin by cleaning any proprietary pre-treatment systems as required by the manufacturer’s recommendations o Flush all other inlet structures and pipes toward the final structure prior to the
Contact Information For inquiries, support, or assistance regarding your RainVault system, please contact: • Ripple Stormwater Technologies ACF West • 904-763-7632 800-878-5115 • info@ripplestormwater.com stormwater@acfwest.com Conclusion Regular inspection and maintenance of your RainVault underground stormwater detention system
DIVISION 33 – UTILITIES SECTION 33 45 13 - STORMWATER DETENTION SYSTEM - RAINVAULT PART 1 - GENERAL 1.01 DESCRIPTION A.
2. Modules shall be designed to interlock securely with adjacent modules forming
3.
2. Subgrade must provide a minimum bearing capacity of 2,000 lbs/sf prior to installing base materials and/or RainVault. If subgrade is pumping or appears
B. When sediment within the RainVault reaches 6” in depth, backflush the system using standard equipment. Beginning furthest from the system, vacuum the following components: a.
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.
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.
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.
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
6/22/2022 2022 City of Renton Surface Water Design Manual
A-22
NO. 16 – WETPOND
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris accumulated on the
wetpond site.
Wetpond site free of any trash or debris.
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.
Side Slopes of Dam,
Berm, internal berm
or Embankment
Rodent holes Any evidence of rodent holes if facility is
acting as a dam or berm, or any evidence
of water piping through dam or berm via
rodent holes.
Rodents removed or destroyed and dam or
berm repaired.
Tree growth Tree growth threatens integrity of dams,
berms or slopes, does not allow
maintenance access, or interferes with
maintenance activity. If trees are not a
threat to dam, berm or embankment
integrity, are not interfering with access or
maintenance or leaves do not cause a
plugging problem they do not need to be
removed.
Trees do not hinder facility performance or
maintenance activities.
Erosion Eroded damage over 2 inches deep where
cause of damage is still present or where
there is potential for continued erosion.
Any erosion observed on a compacted
slope.
Slopes stabilized using appropriate erosion
control measures. If erosion is occurring on
compacted slope, a licensed civil engineer
should be consulted to resolve source of
erosion.
Top or Side Slopes
of Dam, Berm,
internal berm or
Embankment
Settlement Any part of a dam, berm or embankment
that has settled 4 inches lower than the
design elevation.
Top or side slope restored to design
dimensions. If settlement is significant, a
licensed civil engineer should be consulted
to determine the cause of the settlement.
Irregular surface on
internal berm
Top of berm not uniform and level. Top of berm graded to design elevation.
Pond Areas Sediment
accumulation (except
first wetpool cell)
Accumulated sediment that exceeds 10%
of the designed pond depth.
Sediment cleaned out to designed pond
shape and depth.
Sediment
accumulation (first
wetpool cell)
Sediment accumulations in pond bottom
that exceeds the depth of sediment
storage (1 foot) plus 6 inches.
Sediment storage contains no sediment.
Liner damaged (If
applicable)
Liner is visible or pond does not hold water
as designed.
Liner repaired or replaced.
Low water level (all
wetpool cells)
Cell level(s) drops more than 12 inches in
any 7-day period.
Cell level(s) drops less than 12 inches in
any 7-day period.
Algae mats (first
wetpool cell)
Algae mats develop over more than 10%
of the water surface should be removed.
Algae mats removed (usually in the late
summer before Fall rains, especially in
Sensitive Lake Protection Areas.)
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2022 City of Renton Surface Water Design Manual 6/22/2022
A-23
NO. 16 – WETPOND
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Pond Areas (cont.) Sparse or dying
design planting and
poor vegetation
survival
Sparse or dying design planting, or when
design plantings are not thriving across
80% or more of the design vegetated
areas within the pond; invasive vegetation
(e.g., cattails)
Design plantings and vegetation are
thriving and appropriately spaced across
80% or more of the design vegetated
areas within the pond; invasives removed
including root clumps
Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally.
Valve won’t seal Valve does not seal completely. Valve completely seals closed.
Emergency
Overflow Spillway
Tree growth Tree growth impedes flow or threatens
stability of spillway.
Trees removed.
Rock missing Only one layer of rock exists above native
soil in area five square feet or larger, or
any exposure of native soil at the top of out
flow path of spillway. Rip-rap on inside
slopes need not be replaced.
Spillway restored to design standards.
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.
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.
HAZEN HIGH SCHOOL IMPROVEMENTS 20 11. FIGURES FIGURE 1 – TIR WORKSHEET FIGURE 2 – VICINITY MAP FIGURE 3 – NEW + REPLACED IMPERVIOUS AREAS FIGURE 4 – EXISTING CONDITIONSFIGURE 5 – 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
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
TBD
09/24/2024
TBD
FIGURE 1: TIR WORKSHEET
N/A
N/A
N/A
May Creek
N/A
N/A
FIGURE 1: TIR WORKSHEET
N/A
AgC 8% - 15%Moderate
Softball, Multipurpose, and Baseball Fields
3
N/A
TBD
TBD
TBD
Flow Control Duration - Matching Forested Site Conditions
FIGURE 1: TIR WORKSHEET
< 5,000 SF
Compost Amended Soil BMP T5.13
N/A
N/A
N/A
FIGURE 1: TIR WORKSHEET
RainVault
N/A
FIGURE 1: TIR WORKSHEET
BMP T5.13
N/A N/A
FIGURE 1: TIR WORKSHEET
9/24/2024
255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM
FIGURE 2: VICINITY MAP
SCALE: NTS
206.426.2600
Project Sites
Project Site
FIGURE 2: VICINITY MAP
SCALE: NTS
PROJECT
SITE
FIGURE 3: NEW + REPLACED IMPERVIOUS AREASNOTE:SHEET HAS BEENPRINTED TO BE 11X17AND NOT TO SCALESCALE: NTSNew + Replaced Impervious Areas - Drainage Basin #1DescriptionQuantityUnitNew Impervious Surface - Drainage Basin #1102,118sfNew + Replaced Impervious Areas - Drainage Basin #2DescriptionQuantityUnitNew Impervious Surface - Drainage Basin #242,345sfReplaced Impervious Surface - Drainage Basin #2410sfNew + Replaced Impervious Areas - Drainage Basin #3DescriptionQuantityUnitNew Impervious Surface - Drainage Basin #339,201sfReplaced Impervious Surface - Drainage Basin #32,879sfSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUB
SUB
SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUBN.E. 12TH ST.(A DEDICATED PUBLIC RIGHT OF WAY)N.E. 10TH ST.( A DEDICATED PUBLIC RIGHT OF WAY)DUVALL AVE. N.E.( A DEDICATED PUBLIC RIGHT OF WAY)HOQUIUM AVE. N.E.(A DEDICATED PUBLIC RIGHT OF WAY)X
X
XXEEEEEEEEEEE
GTGTGTSSGT
GT
SDSDSDGT
GT GTGTGTGTGTGTGTGTGTSDSDSDCITY OFRENTON43667N
STATE OF WASHIN G T ON
REGISTEREDP R O F E SSIONALENGINEEROSBOCAJ
A.DLAREJDRAINAGE BASIN #1 -WEST TO DUVALL AVENESEE FIGURE 5A -OFFSITE DRAINAGEDRAINAGE BASIN #2 -SOUTH TO NE 10TH STDRAINAGE BASIN #3 -EAST TO HOQUIAMAVE NEDRAINAGE BASIN #3 -EAST TO HOQUIAMAVE NESEE FIGURE 5B -OFFSITE DRAINAGESEE FIGURE 5C -OFFSITE DRAINAGESEE FIGURE 5C -OFFSITE DRAINAGEFIGURE 3: NEW AND REPLACED IMPERVIOUS AREASSCALE: 1" = 150'
FIGURE 4: EXISTING CONDITIONS
SCALE: 1" = 150'
Existing Conditions - Drainage Basin #2
Description Quantity Unit
Impervious Surface - Drainage Basin #2 3,937 sf
Pervious Surface - Drainage Basin #2 106,548 sf
Existing Conditions - Drainage Basin #3
Description Quantity Unit
Impervious Surface - Drainage Basin #3 4,886 sf
Pervious Surface - Drainage Basin #3 40,793 sf
Existing Conditions - Drainage Basin #1
Description Quantity Unit
Pervious Surface - Drainage Basin #1 115,418 sf
SUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBN.E. 12TH ST.
(A DEDICATED PUBLIC RIGHT OF WAY)
N.E. 10TH ST.
( A DEDICATED PUBLIC RIGHT OF WAY)DUVALL AVE. N.E.( A DEDICATED PUBLIC RIGHT OF WAY)HOQUIUM AVE. N.E.(A DEDICATED PUBLIC RIGHT OF WAY)XXXXCITY OF
RENTON
43667 NSTATE O F WASHI
NGTONR
EGI S T E R E DPROF
E
SSIONAL E N G INEEROSBOCAJA.DLAREJDRAINAGE 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
DRAINAGE BASIN #3 -
EAST TO HOQUIAM
AVE NE
DRAINAGE BASIN #3 -
EAST TO HOQUIAM
AVE NE
SEE FIGURE 5C -
OFFSITE DRAINAGE
SEE FIGURE 5C -
OFFSITE DRAINAGE
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
PROJECT SITE
OFFSITE OUTLET
#3.1
SURFACE WATER
FACILITY: HONEY
CREEK
0.35 MI DOWNSTREAM
0.25 MILE
DOWNSTREAM
PROJECT SITE
OFFSITE OUTLET
#3.2
PROJECT SITE
FEMA FLOOD MAP
# 53033C0669G
FIGURE 7: 100 YR FLOODPLAIN
FIGURE 8: SOILS MAP
255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM
FIGURE 9: DRAINAGE COMPLAINTS
206.426.2600
PROJECT
SITE
255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM
FIGURE 10: EROSION HAZARDS
206.426.2600
PROJECT
SITE
PROJECT SITE
255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM
FIGURE 11: SENSITIVE AREAS
206.426.2600
PROJECT
SITE
PROJECT SITE
□
□
□
□SUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBHOQUIUM AVE. N.E.(A DEDICATED PUBLIC RIGHT OF WAY)N.E. 10TH ST.
( A DEDICATED PUBLIC RIGHT OF WAY)
N.E. 10TH ST.
( A DEDICATED PUBLIC RIGHT OF WAY)DUVALL AVE. N.E.( A DEDICATED PUBLIC RIGHT OF WAY)HOQUIUM AVE. N.E.(A DEDICATED PUBLIC RIGHT OF WAY)DUVALL AVE. N.E.XXXXXX X
XXXXXXXX
XXT
EEE E E EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
E
E E E E
E
E
E
G
T
GTGTGTGTGTGTGTGTGT GT GT GT SSSSSSSSSSG
TGT
G
T
G
TGTGT
G
T
G
T
GTGT
G
T
G
TGT
G
T
G
TGT
GT
GTGTGTGTGTGTGTGTGT GT GT GTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGTGT 468457460460458459458459HOQUIUM AVE. N.E.(A DEDICATED PUBLIC RIGHT OF WAY)2.344 ac
0.977 ac
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'
Flow Control Areas - Drainage Basin #3
Description Quantity Unit
Multipurpose Bypass Flat Paving 0.047 ac
Multipurpose Bypass Roof 0.013 ac
Multipurpose Existing Flat Lawn 0.014 ac
Multipurpose Existing Moderate Lawn 0.007 ac
Multipurpose Existing Steep Lawn 0.060 ac
Multipurpose Flat Impervious 0.931 ac
Flow Control Areas - Drainage Basin #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 2.344 ac
Flow Control Areas - Drainage Basin #2
Description Quantity Unit
Softball Existing Flat Impervious 0.085 ac
Softball Field 0.977 ac
HAZEN HIGH SCHOOL IMPROVEMENTS 21 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 22 APPENDIX A BOND QUANTITY WORKSHEET (TO BE PROVIDED IN A FORTHCOMING SUBMITTAL)
HAZEN HIGH SCHOOL IMPROVEMENTS 23 APPENDIX B STORMWATER CALCULATIONS
————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.62 Program License Number: 201910001 Project Simulation Performed on: 09/24/2024 12:24 PM Report Generation Date: 09/24/2024 12:24 PM ————————————————————————————————— Input File Name: 2024-09-20 Hazen Detention Sizing Baseball Rainvault Pent.fld Project Name: Hazen HS Analysis Title: Detention Sizing - Baseball Comments: RainVault Pent ———————————————— 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) 2.792 2.792 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.792 2.792 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- C, Forest, Flat 2.344 ----------------------------------------------
Subbasin Total 2.344 ---------- 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 2.344 ---------------------------------------------- Subbasin Total 2.344 ---------- 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: RainVault
Link Type: Structure Downstream Link: None Prismatic Pond Option Used Pond Floor Elevation (ft) : 448.09 Riser Crest Elevation (ft) : 454.75 Max Pond Elevation (ft) : 455.25 Storage Depth (ft) : 6.66 Pond Bottom Length (ft) : 80.0 Pond Bottom Width (ft) : 80.0 Pond Side Slopes (ft/ft) : Z1= 0.00 Z2= 0.00 Z3= 0.00 Z4= 0.00 Bottom Area (sq-ft) : 6400. Area at Riser Crest El (sq-ft) : 6,400. (acres) : 0.147 Volume at Riser Crest (cu-ft) : 42,624. (ac-ft) : 0.979 Area at Max Elevation (sq-ft) : 6400. (acres) : 0.147 Vol at Max Elevation (cu-ft) : 45,824. (ac-ft) : 1.052 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) : 0.060 Riser Crest Elevation : 454.75 ft Hydraulic Structure Geometry Number of Devices: 4 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 448.09 Diameter (in) : 1.13 Orientation : Horizontal Elbow : No ---Device Number 2 --- Device Type : Circular Orifice Control Elevation (ft) : 451.55 Diameter (in) : 0.75 Orientation : Horizontal Elbow : Yes ---Device Number 3 --- Device Type : Circular Orifice Control Elevation (ft) : 452.50 Diameter (in) : 0.75 Orientation : Horizontal
Elbow : Yes --- Device Number 4 --- Device Type : Rectangular Weir that Intersects the Riser Top Invert Elevation (ft) : 453.50 Length (ft) : 0.060 **********************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: RainVault ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 449.939 1.11-Year 450.204 1.25-Year 450.478 2.00-Year 451.275 3.33-Year 451.786 5-Year 452.412 10-Year 453.394 25-Year 453.922 50-Year 454.230 100-Year 454.413 ***********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 446.079 Subbasin: Flow Through 40.752 Link: New Copy Lnk1 0.000 _____________________________________ Total: 486.831 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Target Surfaces 0.000 Subbasin: Flow Through 40.752
Link: RainVault 0.000 _____________________________________ Total: 40.752 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 3.081 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 : 0.123 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): 429.43 Inflow Volume Including PPT-Evap (ac-ft): 429.43 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): 429.43 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: RainVault ********** Basic Wet Pond Volume (91% Exceedance): 12278. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 18416. cu-ft 2-Year Discharge Rate : 0.060 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): 1318.31 Inflow Volume Including PPT-Evap (ac-ft): 1318.31 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): 1318.17 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: RainVault *** 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 0.123 2-Year 6.027E-02 5-Year 0.189 5-Year 8.345E-02 10-Year 0.240 10-Year 0.111 25-Year 0.352 25-Year 0.164 50-Year 0.397 50-Year 0.226 100-Year 0.430 100-Year 0.268 200-Year 0.553 200-Year 0.290 500-Year 0.717 500-Year 0.318 ** 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%): -0.7% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -0.7% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -4.1% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS -------------------------------------------------------------------------------------------------
————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.62 Program License Number: 201910001 Project Simulation Performed on: 09/20/2024 2:18 PM Report Generation Date: 09/20/2024 2:19 PM ————————————————————————————————— Input File Name: 2024-09-20 Hazen Softball Detention Sizing Rainvault.fld Project Name: Hazen HS Analysis Title: Detention Sizing - Softball Comments: RainVault Double ———————————————— 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) 1.062 1.062 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.062 1.062 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- C, Forest, Flat 0.977 ----------------------------------------------
Subbasin Total 0.977 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.085 ---------------------------------------------- Subbasin Total 0.085 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.977 ---------------------------------------------- Subbasin Total 0.977 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.085 ---------------------------------------------- Subbasin Total 0.085 ************************* 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: RainVault Double Link Type: Structure Downstream Link: None Prismatic Pond Option Used Pond Floor Elevation (ft) : 473.11 Riser Crest Elevation (ft) : 475.75 Max Pond Elevation (ft) : 476.25 Storage Depth (ft) : 2.64
Pond Bottom Length (ft) : 79.1 Pond Bottom Width (ft) : 83.0 Pond Side Slopes (ft/ft) : Z1= 0.00 Z2= 0.00 Z3= 0.00 Z4= 0.00 Bottom Area (sq-ft) : 6565. Area at Riser Crest El (sq-ft) : 6,565. (acres) : 0.151 Volume at Riser Crest (cu-ft) : 17,332. (ac-ft) : 0.398 Area at Max Elevation (sq-ft) : 6565. (acres) : 0.151 Vol at Max Elevation (cu-ft) : 20,615. (ac-ft) : 0.473 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 : 475.75 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 473.11 Diameter (in) : 0.87 Orientation : Horizontal Elbow : No --- Device Number 2 --- Device Type : Rectangular Weir that Intersects the Riser Top Invert Elevation (ft) : 474.67 Length (ft) : 0.020 **********************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: RainVault Double ********** Link WSEL Stats
WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 473.896 1.11-Year 473.985 1.25-Year 474.104 2.00-Year 474.411 3.33-Year 474.636 5-Year 474.895 10-Year 475.227 25-Year 475.418 50-Year 475.582 100-Year 475.640 ***********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 185.930 Subbasin: Flow Through 0.000 Link: New Copy Lnk1 0.000 _____________________________________ Total: 185.930 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Target Surfaces 0.000 Subbasin: Flow Through 0.000 Link: RainVault Double 0.000 _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 1.177 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** 2-Year Discharge Rate : 0.048 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.02 cfs Off-line Design Discharge Rate (91% Exceedance): 0.01 cfs
Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 161.53 Inflow Volume Including PPT-Evap (ac-ft): 161.53 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): 161.53 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: RainVault Double ********** Basic Wet Pond Volume (91% Exceedance): 5100. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 7650. cu-ft 2-Year Discharge Rate : 0.023 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.17 cfs Off-line Design Discharge Rate (91% Exceedance): 0.10 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 532.02 Inflow Volume Including PPT-Evap (ac-ft): 532.02 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): 531.96 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: RainVault Double *** 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 4.765E-02 2-Year 2.330E-02 5-Year 6.989E-02 5-Year 3.300E-02 10-Year 8.807E-02 10-Year 5.192E-02 25-Year 0.115 25-Year 6.553E-02 50-Year 0.128 50-Year 7.850E-02
100-Year 0.139 100-Year 8.337E-02 200-Year 0.187 200-Year 0.112 500-Year 0.251 500-Year 0.150 ** 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%): -0.3% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -0.3% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 9.7% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 15.6% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS -------------------------------------------------------------------------------------------------
————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.62 Program License Number: 201910001 Project Simulation Performed on: 09/20/2024 2:48 PM Report Generation Date: 09/20/2024 2:50 PM ————————————————————————————————— Input File Name: 2024-09-20 Hazen Multipurpose Detention Sizing Rainvault.fld Project Name: Hazen HS Analysis Title: Detention Sizing - Multipurpose Comments: RainVault Double ———————————————— 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) 1.072 1.072 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.072 1.072 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- C, Forest, Flat 0.991 ----------------------------------------------
Subbasin Total 0.991 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- C, Lawn, Flat 0.014 C, Lawn, Mod 0.007 C, Lawn, Steep 0.060 ---------------------------------------------- Subbasin Total 0.081 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 3 ---------- Subbasin : Target Surfaces ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.931 ---------------------------------------------- Subbasin Total 0.931 ---------- Subbasin : Flow Through ---------- -------Area (Acres) -------- C, Lawn, Flat 0.014 C, Lawn, Mod 0.007 C, Lawn, Steep 0.060 ---------------------------------------------- Subbasin Total 0.081 ---------- Subbasin : Bypass ---------- -------Area (Acres) -------- ROOF TOPS/FLAT 0.013 SIDEWALKS/FLAT 0.047 ---------------------------------------------- Subbasin Total 0.060 ************************* 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: 2
------------------------------------------ Link Name: RainVault Double Link Type: Structure Downstream Link Name: New Copy Lnk2 Prismatic Pond Option Used Pond Floor Elevation (ft) : 473.11 Riser Crest Elevation (ft) : 475.75 Max Pond Elevation (ft) : 476.25 Storage Depth (ft) : 2.64 Pond Bottom Length (ft) : 91.0 Pond Bottom Width (ft) : 93.0 Pond Side Slopes (ft/ft) : Z1= 0.00 Z2= 0.00 Z3= 0.00 Z4= 0.00 Bottom Area (sq-ft) : 8463. Area at Riser Crest El (sq-ft) : 8,463. (acres) : 0.194 Volume at Riser Crest (cu-ft) : 22,342. (ac-ft) : 0.513 Area at Max Elevation (sq-ft) : 8463. (acres) : 0.194 Vol at Max Elevation (cu-ft) : 26,574. (ac-ft) : 0.610 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 : 475.75 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 473.11 Diameter (in) : 0.62 Orientation : Horizontal Elbow : No --- Device Number 2 --- Device Type : Rectangular Weir that Intersects the Riser Top Invert Elevation (ft) : 474.76 Length (ft) : 0.020 ------------------------------------------ Link Name: New Copy Lnk2
Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 Number of Links: 1 ********** Subbasin: Target Surfaces ********** Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 2.495E-02 5-Year 3.931E-02 10-Year 4.891E-02 25-Year 6.737E-02 50-Year 7.398E-02 100-Year 8.019E-02 200-Year 0.119 500-Year 0.170 ********** Subbasin: Flow Through ********** Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.107E-02 5-Year 1.723E-02 10-Year 2.391E-02 25-Year 3.253E-02 50-Year 4.665E-02 100-Year 5.654E-02 200-Year 6.316E-02 500-Year 7.174E-02 ********** Link: New Copy Lnk1 ********** Link Inflow Frequency Stats Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 3.049E-02 5-Year 5.281E-02 10-Year 6.912E-02 25-Year 9.129E-02 50-Year 0.105 100-Year 0.119 200-Year 0.163 500-Year 0.223
----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 3 Number of Links: 2 ********** Subbasin: Target Surfaces ********** Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 0.382 5-Year 0.493 10-Year 0.580 25-Year 0.727 50-Year 0.871 100-Year 1.084 200-Year 1.155 500-Year 1.247 ********** Subbasin: Flow Through ********** Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.107E-02 5-Year 1.723E-02 10-Year 2.391E-02 25-Year 3.253E-02 50-Year 4.665E-02 100-Year 5.654E-02 200-Year 6.316E-02 500-Year 7.174E-02 ********** Subbasin: Bypass ********** Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 2.463E-02 5-Year 3.175E-02 10-Year 3.739E-02 25-Year 4.683E-02 50-Year 5.612E-02 100-Year 6.987E-02 200-Year 7.446E-02 500-Year 8.035E-02
********** Link: RainVault Double ********** Link Inflow Frequency Stats Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 0.393 5-Year 0.508 10-Year 0.605 25-Year 0.751 50-Year 0.918 100-Year 1.141 200-Year 1.219 500-Year 1.319 ********** Link: RainVault Double ********** Link Outflow 1 Frequency Stats Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.249E-02 5-Year 2.369E-02 10-Year 3.938E-02 25-Year 5.028E-02 50-Year 5.686E-02 100-Year 5.917E-02 200-Year 8.958E-02 500-Year 0.131 ********** Link: RainVault Double ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 474.032 1.11-Year 474.096 1.25-Year 474.236 2.00-Year 474.547 3.33-Year 474.847 5-Year 475.068 10-Year 475.344 25-Year 475.503 50-Year 475.592 100-Year 475.622 ********** Link: New Copy Lnk2 ********** Link Inflow Frequency Stats Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 3.356E-02 5-Year 4.521E-02 10-Year 5.587E-02 25-Year 6.661E-02 50-Year 7.141E-02 100-Year 8.133E-02 200-Year 0.102 500-Year 0.129 ***********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 188.594 Subbasin: Flow Through 10.163 Link: New Copy Lnk1 0.000 _____________________________________ Total: 198.757 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Target Surfaces 0.000 Subbasin: Flow Through 10.163 Subbasin: Bypass 0.000 Link: RainVault Double 0.000 Link: New Copy Lnk2 0.000 _____________________________________ Total: 10.163 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 1.258 ac-ft/year, Post Developed: 0.064 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** 2-Year Discharge Rate : 0.030 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.02 cfs Off-line Design Discharge Rate (91% Exceedance): 0.01 cfs
Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 141.37 Inflow Volume Including PPT-Evap (ac-ft): 141.37 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): 141.37 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: 2 ********** Link: RainVault Double ********** Basic Wet Pond Volume (91% Exceedance): 4619. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 6928. cu-ft 2-Year Discharge Rate : 0.012 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.15 cfs Off-line Design Discharge Rate (91% Exceedance): 0.08 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 487.11 Inflow Volume Including PPT-Evap (ac-ft): 487.11 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): 487.00 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% ********** Link: New Copy Lnk2 ********** 2-Year Discharge Rate : 0.034 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 999.00 cfs Off-line Design Discharge Rate (91% Exceedance): 999.00 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 517.05 Inflow Volume Including PPT-Evap (ac-ft): 517.05 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): 517.05 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: New Copy Lnk2 *** 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 3.049E-02 2-Year 3.356E-02 5-Year 5.281E-02 5-Year 4.521E-02 10-Year 6.912E-02 10-Year 5.587E-02 25-Year 9.129E-02 25-Year 6.661E-02 50-Year 0.105 50-Year 7.141E-02 100-Year 0.119 100-Year 8.133E-02 200-Year 0.163 200-Year 0.102 500-Year 0.223 500-Year 0.129 ** 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%): -4.4% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -4.4% 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%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS -------------------------------------------------------------------------------------------------
————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.62 Program License Number: 201910001 Project Simulation Performed on: 08/19/2024 11:39 AM Report Generation Date: 08/19/2024 11:41 AM ————————————————————————————————— 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): 5 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) 3.380 3.380 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 3.380 3.380 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Forest, Flat 3.380 ----------------------------------------------
Subbasin Total 3.380 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- C, Lawn, Flat 0.380 SIDEWALKS/FLAT 3.000 ---------------------------------------------- Subbasin Total 3.380 ************************* 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 1 642.314 _____________________________________ Total: 642.314 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 48.963 _____________________________________ Total: 48.963
Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 4.065 ac-ft/year, Post Developed: 0.310 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 8.923E-02 2-Year 1.587 5-Year 0.135 5-Year 2.070 10-Year 0.190 10-Year 2.618 25-Year 0.240 25-Year 3.168 50-Year 0.277 50-Year 3.988 100-Year 0.327 100-Year 4.937 200-Year 0.607 200-Year 5.886 500-Year 0.984 500-Year 7.140 ** 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 24 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 Project Contractor (TBD) Permittee / Owner Developer Operator / Contractor Renton School District Renton School District TBD 1101 Hoquiam Avenue NE, Renton, WA, 98059 Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD TBD TBD SWPPP Prepared By Name Organization Contact Phone Number Sascha Eastman Jacobson Consulting Engineers Office: (206) 293-9134 SWPPP Preparation Date 09 / 24 / 2024 Project Construction Dates Activity / Phase Start Date End Date Sitework and Building Construction TBD TBD
Page | 1 Table of Contents 1.0 Project Information .......................................................................................................................... 4 1.1 Existing Conditions ......................................................................................................................... 4 1.2 Proposed Construction Activities .................................................................................................... 5 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 – N/A 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 Certified Erosion and Sediment Control Lead 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: 5.09-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 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. Duvall Ave NE was recently improved to include new curb, gutter and sidewalk with stormwater improvements to include water quality treatment and a new 12” storm main. The proposed improvements will continue to discharge toward Duvall Ave NE. The stormwater runoff from the redeveloped areas within TDA #1 will be collected through the new underdrained synthetic turf baseball field, which is considered 100% impervious, and flow to a new RainVault detention system located to the west, connect to a
Page | 5 54” Type II SDMH flow control structure, and finally drain through a 12” storm pipe to connect to the existing storm main in Duvall Avenue NE. 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 in a 12” storm pipe toward the existing storm system in NE 10th St. Stormwater runoff from the proposed synthetic softball field will be collected within the new underdrain system and routed to a new RainVault detention system, then flow west to a 54” Type II SDMH flow control structure, and finally drain through a 12” storm pipe to connect at the existing 12” storm pipe that is flowing to the south, connecting to the existing storm system within NE 10th Street. TDA #3 consists of parking areas north, east and south of the school building, the existing grass multipurpose field, and tennis courts. TDA #3 connects to the existing storm system in Hoquiam Ave NE at multiple locations along the eastern school property line. Flow from the redeveloped areas in TDA #3 will utilize one existing connection to the Hoquiam Ave NE storm system for the new security vestibule and bollard installation, and the synthetic multipurpose field underdrains will propose a new connection to Hoquiam Ave NE. The stormwater runoff from the proposed areas within the third Threshold Discharge Area on the north side of the site will be collected within the existing system on-site. Stormwater runoff will also be collected within the new underdrained synthetic turf multipurpose field and routed through a new RainVault detention system, then flow to a 54” Type II SDMH flow control structure, and finally drain through a 12” storm pipe connecting to the existing storm system within Hoquiam Ave NE. 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.
Page | 6 Table 1 – Summary of Site Pollutant Constituents Constituent (Pollutant) Location Depth Concentration Oil and Grease Parking Lot Surface Typical concentration from parking lots Total Suspended Solids Buildings and Parking Lots Surface N/A pH Newly installed concrete areas Surface N/A 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, one along the west property line, the south property line, and the east property line. Water will flow into a detention system and flow through onsite flow control systems before being connected to an 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) - There are no contaminated soil or groundwater conditions known at the project site and therefore no proposed activities for the cleanup of existing contamination.
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: • N/A; contractor shall utilize existing paved asphalt, concrete, or gravel areas adjacent to the proposed project site for construction access, laydown, and staging. 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 Sediment Trap (BMP C240) 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) • Sediment Trap (BMP C240) • 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, relatively 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: TBD End date: TBD Will you construct during the wet season? Yes No TBD 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) • Sediment Trap (BMP C240) • 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 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, if 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). • 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).
Page | 16 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: • Other BMPs will be administered as necessary to address any additional pollutant sources on site. 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 Will wheel wash or tire bath system BMPs be used during construction? Yes No List and describe BMPs: N/A 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.
Page | 17 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. 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
Page | 18 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. 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) 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 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 assure 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. 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) TBD Resident Engineer TBD Emergency Ecology Contact TBD Emergency Permittee/ Owner Contact TBD Non-Emergency Owner Contact TBD Monitoring Personnel TBD Ecology Regional Office Northwest Regional Office 425-649-7098
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 is required for this project as it will disturb more than 1.0 acres of land.
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 – N/A H. Engineering Calculations
Page | 34 Appendix A – Site Map Vicinity Map Temporary Erosion and Sediment Control (TESC) Plan TESC Details
255 S. King Street, Suite 800, Seattle, WA 98104 | 206.399.6233 | JACOBSONENGINEERS.COM
FIGURE 2: VICINITY MAP
SCALE: NTS
206.426.2600
Project Sites
Project Site
FIGURE 2: VICINITY MAP
SCALE: NTS
PROJECT
SITE
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB
SUB
SUB
SUB
SUB
SUBSUB
SUBSUBSUBSUBSUBSUBSUBSUBSUBSUBN.E. 12TH ST.(A DEDICATED PUBLIC RIGHT OF WAY)N.E. 10TH ST.( A DEDICATED PUBLIC RIGHT OF WAY)DUVALL AVE. N.E.( A DEDICATED PUBLIC RIGHT OF WAY)
HOQUIUM AVE. N.E.
(A DEDICATED PUBLIC RIGHT OF WAY)XXXXEEEEEEEEEEE GTGTGT
SS GTGTSDSDSDGTGTGTGTGTGTGTGTGTGTGT
SDSDSDCITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450HAZEN HIGH SCHOOL MODERNIZATION OVERALL SITE PLAN CX04CX01SCALE 1"=70'35701400CX03CX05CX06PROJECT WORKAREAS (TYP)IMPROVED BASEBALL FIELDAND GEOTHERMAL WELL ZONEIMPROVEDSOFTBALL FIELDCX02EXISTINGPOWER POLENEW ELECTRICALPRIMARY SERVICEGEOTHERMALWELL ZONEGEOTHERMALPIPING IN/OUTOF BUILDINGGEOTHERMAL VAULT.LOCATION TBD.(2) TEMPORARYPORTABLES TO BEREMOVED AT ENDOF PROJECTMAINTAIN 20'WIDE FIRE LANECX07GEOTHERMAL VAULT.LOCATION TBD.EX CHURCH PROPERTYIMPROVED MULTIPURPOSEFIELD OPTION W/ FIELDLIGHTINGNOTE: BREAKOUT SHEETSVARY IN DRAWING SCALECONTRACTOR TO TAKE NOTEOF SCALES ON EVERY SHEETNOTE - PLANS HAVE BEENSCALED TO 11X17
SWSWSWSWSWSWSWSW4'4.5'9.9'16.4'PROTECT EXCONCRETE CURBTO REMAIN (TYP)SAWCUT AND REMOVEEX CONCRETESIDEWALKPROTECT EXCONCRETE CROSSINGAND CROSSWALKSTRIPING TO REMAININSTALL STRAWWATTLESSEE DETAIL (TYP)C110817.7'REMOVE ALL (14) EX. 24" CONCRETEBOLLARDS AND SURROUNDINGPAVING (TYP.) THE EXTENTS ISAPPROXIMATE AND WILL BE ADJUSTEDWHEN SURVEYED JOINT LINES ARERECEIVED. SEE SHEET C201IPIPINSTALL CB PROTECTIONSEE DETAIL (TYP)C1107PROTECT EX 10" STORMDRAIN PIPE TO REMAIN. TOPOF PIPE IS APPROXIMATELY2-FT BELOW EX GRADEPROTECT EX PEDESTRIALLIGHT POLE TO REMAINPROTECT EX STORMCLEANOUT CASTINGTO REMAINSALVAGE AND REMOVE, CLEAN,PAINT, AND REINSTALL EX BOLTDOWN BENCH. SEE SHEETC201 FOR BENCH LOCATIONS.REMOVE EX FDC TOBE RELOCATED.COORDINATE WITHMECH'L ENGINEERREMOVE EX METAL RAILINGEXTENTS OF PROPOSEDBUILDING VESTIBULEPROTECT EX STORMCLEANOUT CASTING TOREMAINREMOVE EX BENCHAND POSTS CASTINTO EX CONCRETEPROTECT EX BUILDINGCOLUMNS TO REMAINREMOVE EXCONCRETE STAIRPADSAWCUT AND REMOVE EX CONCRETEPAVEMENT AS REQUIRED TO CONSTRUCTNEW BLDG VESTIBULE AND REGRADEDPORTION OF CONCRETE PLAZA.SEE SHEET C201SWSWSWSWSWINSTALL STRAWWATTLESSEE DETAIL (TYP)C1108PROTECT EXCONCRETE CURBTO REMAIN (TYP)SWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWSWPROTECT EX CONCRETEACCESSIBLE RAMP TOREMAINPROTECT EXPEDESTRIAL LIGHTPOLE TO REMAININSTALL TREEPROTECTION FENCINGSEE DETAILC11011VEGPROTECT EX "STOP" SIGNAND POST TO REMAINPROTECT EX FLAGPOLE TO REMAINCONTRACTOR SHALL MAKE ARECORD OF EXISTING SCORE/JOINTLINES TO BE MATCHED FORFINISHED CONCRETE CONDITION.SEE SHEET C201SWEX BUILDINGOVERHANG/CANOPYABOVE (TYP)4'SAWCUT AND REMOVE EXCONCRETE SIDEWALK7.7
'4'PROTECT EXCONCRETE CURBTO REMAIN (TYP)REMOVE 6" AND10" CEDAR TREESREMOVE AND REINSTALL ADAPARKING SIGN AND POSTREMOVE AND REINSTALL ADAPARKING SIGN AND POST7.6'REMOVE AND REINSTALLBUS LOADING SIGN ANDPOSTCONTRACTOR SHALL MAKE ARECORD OF EXISTING SCORE/JOINTLINES TO BE MATCHED FORFINISHED CONCRETE CONDITION.SEE SHEET C201CONTRACTOR SHALL MAKE ARECORD OF EXISTING CORE/JOINTLINES TO BE MATCHED FORFINISHED CONCRETE CONDITION.SEE SHEET C201TEMPORARYCONSTRUCTIONFENCING (TYP)SEE DETAILC1109CITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450LEGENDSCALE 1"=10'510200HAZEN HIGH SCHOOL MODERNIZATION DEMOLITION AND TESC PLAN TREE PROTECTIONINLET PROTECTIONPROPERTY LINETEMP CONSTRUCTION FENCINGCFIPVEGSAWCUT LINEREMOVE CURBINGREMOVE ASPHALT PAVEMENTREMOVE CONCRETE PAVEMENT1.SCHEDULE MAJOR LAND DISTURBING ACTIVITIES DURING THE DRY MONTHSAND ALLOW TIME BEFORE THE WET SEASON BEGINS TO ADEQUATELYSTABILIZE THE DISTURBED GROUND.2.PHASE AND/OR SCHEDULE CONSTRUCTION TO LIMIT THE AMOUNT OFDISTURBED, UNSTABILIZED SOIL EXPOSED AT ANY ONE TIME.3.FENCE OR FLAG AREAS TO BE PROTECTED OR LEFT UNDISTURBED DURINGCONSTRUCTION, INCLUDING INSTALLATION OF TEMPORARY CONSTRUCTIONFENCING.4.STRIP AND CLEAR AND GRUB FIELD SUFFICIENTLY FOR INSTALLATION OFTEMPORARY EROSION SEDIMENTATION CONTROL (ESC) BMPS.5.INSTALL TEMPORARY ESC MEASURES INDICATED ON PLANS, INCLUDINGSILT FENCE, CATCH BASIN INSERTS, AND STRAW WATTLES. COORDINATEWITH CITY OF RENTON INSPECTOR.6.BEGIN GRADING AND EXCAVATION FOR FIELD UNDERDRAIN AND IRRIGATIONPIPING, AND FOR PAVEMENT SUBGRADES.7.TEMPORARILY STABILIZE SITE, THROUGH RE-VEGETATION, HYDROSEED,MULCHING OR OTHER APPROPRIATE BMPS AS A RESULT OF SITE GRADINGIN AREAS THAT WILL NOT RECEIVE HARDSCAPE.8.CONSTRUCT STORM AND IRRIGATION UTILITIES, CONCRETE, ASPHALT, ANDPERMEABLE PAVEMENTS, AS WELL AS STAIRS, CHEEK WALLS, AND MOWSTRIPS FOR FENCING.9.PLACE FILL SECTION AND LAWN/SEED FOR PLAYFIELD.10.REMOVE TEMPORARY ESC FACILITIES UPON COMPLETION OFCONSTRUCTION AND ONLY ONCE SITE IS STABILIZED, INSPECTED, ANDAPPROVED BY CITY OF RENTON INSPECTOR,TESC CONSTRUCTION SEQUENCENOTE:INSTALL CONSTRUCTION FENCING AROUND LIMITS OFWORK TO PROTECT STAFF AND STUDENTS AND SECUREJOBSITE. CONTRACTOR SHALL ERECT FENCE AROUNDJOBSITE AND ADJUST AS CONSTRUCTION CONDITIONSCHANGE OR AS PHASING ALLOWS. CONTRACTOR CAN UTILIZEEXISTING PERIMETER FENCING AS SECURITY FENCING ANDTHEN SUPPLEMENT ON THE WEST SIDE OF THE SITE ASNEEDED. ANY SECTIONS OF EXISTING FENCING THAT IS NOT6-FT HIGH SHALL HAVE TEMPORARY 6-FT HIGH CHAINLINKFENCING INSTALLED NEXT TO IT. SEE DETAIL 9/C110.SEE SHEET C001 FOR CITY OF RENTONESC STANDARD PLAN NOTESCONTINUATION - SEE TOP RIGHTCONTINUATION - SEE BOTTOM LEFTREMOVE TREE(S)NOTE - PLANS HAVE BEENSCALED TO 11X17
□IPIPINSTALL CB PROTECTIONSEE DETAIL (TYP)C1107FFISFFISFFINTERCEPTOR SWALEWITH ROCK CHECK DAMSAT 50' O.C. SPACINGSEE DETAILSC1106C1118INSTALL SILT FENCEAROUND PERIMETEROF FIELD (TYP)SEE DETAILC1117SEDIMENT TRAP WITH55 GALLON DRUM ANDSUMP INSTALLED ATLOW POINT ON-SITE.SEE DETAILSC1112C1105FFCONTRACTOR TO UTILIZEEXISTING SITE FENCINGFOR CONSTRUCTIONPERIMETER FENCING ANDSUPPLEMENT AS NEEDEDCITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450SCALE 1"=20'0102040HAZEN HIGH SCHOOL MODERNIZATION DEMOLITION AND TESC PLAN LEGENDSAWCUT LINEREMOVE CURBINGREMOVE ASPHALT PAVEMENTREMOVE CONCRETE PAVEMENTTREE PROTECTIONINLET PROTECTIONPROPERTY LINETEMP CONSTRUCTION FENCINGCFIPVEG1.SCHEDULE MAJOR LAND DISTURBING ACTIVITIES DURING THE DRY MONTHSAND ALLOW TIME BEFORE THE WET SEASON BEGINS TO ADEQUATELYSTABILIZE THE DISTURBED GROUND.2.PHASE AND/OR SCHEDULE CONSTRUCTION TO LIMIT THE AMOUNT OFDISTURBED, UNSTABILIZED SOIL EXPOSED AT ANY ONE TIME.3.FENCE OR FLAG AREAS TO BE PROTECTED OR LEFT UNDISTURBED DURINGCONSTRUCTION, INCLUDING INSTALLATION OF TEMPORARY CONSTRUCTIONFENCING.4.STRIP AND CLEAR AND GRUB FIELD SUFFICIENTLY FOR INSTALLATION OFTEMPORARY EROSION SEDIMENTATION CONTROL (ESC) BMPS.5.INSTALL TEMPORARY ESC MEASURES INDICATED ON PLANS, INCLUDINGSILT FENCE, CATCH BASIN INSERTS, AND STRAW WATTLES. COORDINATEWITH CITY OF RENTON INSPECTOR.6.BEGIN GRADING AND EXCAVATION FOR FIELD UNDERDRAIN AND IRRIGATIONPIPING, AND FOR PAVEMENT SUBGRADES.7.TEMPORARILY STABILIZE SITE, THROUGH RE-VEGETATION, HYDROSEED,MULCHING OR OTHER APPROPRIATE BMPS AS A RESULT OF SITE GRADINGIN AREAS THAT WILL NOT RECEIVE HARDSCAPE.8.CONSTRUCT STORM AND IRRIGATION UTILITIES, CONCRETE, ASPHALT, ANDPERMEABLE PAVEMENTS, AS WELL AS STAIRS, CHEEK WALLS, AND MOWSTRIPS FOR FENCING.9.PLACE FILL SECTION AND LAWN/SEED FOR PLAYFIELD.10.REMOVE TEMPORARY ESC FACILITIES UPON COMPLETION OFCONSTRUCTION AND ONLY ONCE SITE IS STABILIZED, INSPECTED, ANDAPPROVED BY CITY OF RENTON INSPECTOR,TESC CONSTRUCTION SEQUENCENOTE:INSTALL CONSTRUCTION FENCING AROUND LIMITS OFWORK TO PROTECT STAFF AND STUDENTS AND SECUREJOBSITE. CONTRACTOR SHALL ERECT FENCE AROUNDJOBSITE AND ADJUST AS CONSTRUCTION CONDITIONSCHANGE OR AS PHASING ALLOWS. CONTRACTOR CAN UTILIZEEXISTING PERIMETER FENCING AS SECURITY FENCING ANDTHEN SUPPLEMENT ON THE WEST SIDE OF THE SITE ASNEEDED. ANY SECTIONS OF EXISTING FENCING THAT IS NOT6-FT HIGH SHALL HAVE TEMPORARY 6-FT HIGH CHAINLINKFENCING INSTALLED NEXT TO IT. SEE DETAIL 9/C110.SEE SHEET C001 FOR CITY OF RENTONESC STANDARD PLAN NOTESMATCHLINE - SEE SHEET C103NOTE - PLANS HAVE BEENSCALED TO 11X17
DUVALL AVE. N.E.IMPROVED BASEBALL FIELD.SEE LANDSCAPE PLANS ANDCX03 CIVIL PLANSEXISTING CITY OFRENTON WATEREASEMENT15'IPINSTALL CB PROTECTIONSEE DETAIL (TYP)C1107IPIPPUMP "CLEAN" STORMWATER FROMTEMP SEDIMENT SETTLEMENT TANKS TOEXISTING CATCH BASIN. CONTRACTOR TOENSURE ALL DISCHARGE MEETSTURBIDITY REQUIREMENTS.FFISFFFFISPUMP CONSTRUCTIONSTORMWATER TO SEDIMENTSETTLEMENT TANKSFFINTERCEPTOR SWALEWITH ROCK CHECK DAMSAT 50' O.C. SPACINGSEE DETAILSC1106C1118SEDIMENT TRAP WITH55 GALLON DRUM ANDSUMP INSTALLED ATLOW POINT ON-SITE.SEE DETAILSC1112C1105PUMP CONSTRUCTIONSTORMWATER TO SEDIMENTSETTLEMENT TANKSINSTALL SILT FENCEAROUND PERIMETER OFFIELD (TYP)SEE DETAILC1117INTERCEPTOR SWALEWITH ROCK CHECK DAMSAT 50' O.C. SPACINGSEE DETAILSC1106C1118FFBOE = 447.09FFAPPROXIMATE LIMITS OFPROPOSED DETENTION SYSTEMEXCAVATION FOR BASEBALL FIELD.SEE SHEET C203SALVAGE AND REMOVE EX PULLUP BARS TO BE REINSTALLEDAFTER COMPLETION OFGEOTHERMAL WELL FIELD(4) 18,900 GALLON CAPACITY TEMPORARYSEDIMENT SETTLEMENT TANKS ("BAKER TANK" OREQUAL). CONTRACTOR SHALL PROVIDE ALL PUMPSREQUIRED TO MANAGE CONSTRUCTIONSTORMWATER AND DISCHARGE AT THE SITE.PROTECT EX FIELDPERIMETER FENCINGTO REMAINSAWCUT AND REMOVEEXISTING CONCRETE SIDEWALKPROTECT EXISTINGDUGOUTS TO REMAINPROTECT EXISTINGCONCRETE TO REMAINPROTECT EXISTINGDUGOUTS TO REMAININFILL EX STORMWATER PONDCONTRACTOR MAY UTILIZE ASTEMPORARY SEDIMENT PONDDURING CONSTRUCTION(VOLUME PROVIDE ISAPPROXIMATELY 3,512 CF(26,270 GALLONS)ABANDON-IN-PLACE EXSTORM PIPING. REMOVE ASNEEDED FOR GEOTHERMALWELL HEAD INSTALLATIONREMOVE EXCB TYPE 2ABANDON-IN-PLACE EXSTORM PIPING. REMOVE ASNEEDED FOR GEOTHERMALWELL HEAD INSTALLATION.SEE SHEET C203 (TYP)PROTECT EXCONCRETE RETAININGWALL AND FENCEREMOVE AND REPLACEPORTION OF EXISTINGFENCE AS NEEDED FORUTILITY INSTALLATIONREMOVE AND REPLACE PORTIONOF EXISTING SIDEWALK ANDASPHALT AS NEEDED FORUTILITY INSTALLATIONIPSUPPLEMENT SITE FENCINGDURING CONSTRUCTION ASNEEDED TO SECURECONSTRUCTION WORK AREASCITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450SCALE 1"=20'0102040HAZEN HIGH SCHOOL MODERNIZATION DEMOLITION AND TESC PLAN LEGENDSAWCUT LINEREMOVE CURBINGREMOVE ASPHALT PAVEMENTREMOVE CONCRETE PAVEMENTTREE PROTECTIONINLET PROTECTIONPROPERTY LINETEMP CONSTRUCTION FENCINGCFIPVEGNOTE:INSTALL CONSTRUCTION FENCING AROUND LIMITS OFWORK TO PROTECT STAFF AND STUDENTS AND SECUREJOBSITE. CONTRACTOR SHALL ERECT FENCE AROUNDJOBSITE AND ADJUST AS CONSTRUCTION CONDITIONSCHANGE OR AS PHASING ALLOWS. CONTRACTOR CAN UTILIZEEXISTING PERIMETER FENCING AS SECURITY FENCING ANDTHEN SUPPLEMENT ON THE WEST SIDE OF THE SITE ASNEEDED. ANY SECTIONS OF EXISTING FENCING THAT IS NOT6-FT HIGH SHALL HAVE TEMPORARY 6-FT HIGH CHAINLINKFENCING INSTALLED NEXT TO IT. SEE DETAIL 9/C110.SEE SHEET C001 FOR CITY OF RENTONESC STANDARD PLAN NOTESSEE SHEET C102 FOR TESCCONSTRUCTION SEQUENCE NOTESMATCHLINE - SEE SHEET C102MATCHLINE - SEE SHEET C104PROPOSED DETENTION SYSTEMNOTE - PLANS HAVE BEENSCALED TO 11X17
IMPROVED BASEBALL FIELD.SEE LANDSCAPE PLANS ANDCX03 CIVIL PLANS15'EXISTING CITY OFRENTON WATEREASEMENT15'EXISTING CITY OFRENTON WATEREASEMENTPRIVATESTORM MAINCITY OF RENTONWATER MAINREMOVE PORTION OF EXGRASS FIELD AS REQ'D TOINSTALL NEW GEOTHERMALSERVICE AND RETURN PIPINGAND VAULT AND ELECTRICALCONDUITS. SEE SHEET C204 (TYP)IPIPINSTALL CB PROTECTIONSEE DETAIL (TYP)C1107IPRELOCATE EX BASEBALL STORAGESHIPPING CONTAINERCOORDINATE LOCATION WITH OWNER.CONTRACTOR SHALL ASSUME A 600 SQ FT6" THICK CONCRETE PAD FOR STORAGECONTAINER AND 250 SF 6" CONCRETE PADFOR PORTABLE TOILETS FOR PRICINGSAWCUT AND REMOVE EXASPHALT PAVEMENT FORUTILITY INSTALLATIONSEE SHEET C204FFREMOVE GRAVELSAWCUT AND REMOVEPORTION OF EX CONCRETEPAVEMENT FOR NEW MECH'LPAD INSTALLATION. SEESHEET C204EX BASEBALL FIELD SUBDRAINAGETIE IN POC AT EX CATCH BASIN.STORMWATER THEN DRAINS WEST.SEE SHEET C103SAWCUT AND REMOVE EXASPHALT PAVEMENT FORUTILITY INSTALLATIONSEE SHEET C204PROTECT EXISTINGBASEBALL FIELD PERIMETERFENCING TO REMAINSILT FENCE (TYP)SEE DETAILC1117CITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450SCALE 1"=10'510200HAZEN HIGH SCHOOL MODERNIZATION DEMOLITION AND TESC PLAN NOTE:INSTALL CONSTRUCTION FENCING AROUND LIMITS OFWORK TO PROTECT STAFF AND STUDENTS AND SECUREJOBSITE. CONTRACTOR SHALL ERECT FENCE AROUNDJOBSITE AND ADJUST AS CONSTRUCTION CONDITIONSCHANGE OR AS PHASING ALLOWS. CONTRACTOR CAN UTILIZEEXISTING PERIMETER FENCING AS SECURITY FENCING ANDTHEN SUPPLEMENT ON THE WEST SIDE OF THE SITE ASNEEDED. ANY SECTIONS OF EXISTING FENCING THAT IS NOT6-FT HIGH SHALL HAVE TEMPORARY 6-FT HIGH CHAINLINKFENCING INSTALLED NEXT TO IT. SEE DETAIL 9/C110.SEE SHEET C001 FOR CITY OF RENTONESC STANDARD PLAN NOTESSEE SHEET C102 FOR TESCCONSTRUCTION SEQUENCE NOTESLEGENDSAWCUT LINEREMOVE CURBINGREMOVE ASPHALT PAVEMENTREMOVE CONCRETE PAVEMENTTREE PROTECTIONINLET PROTECTIONPROPERTY LINETEMP CONSTRUCTION FENCINGCFIPVEGMATCHLINE - SEE SHEET C103NOTE - PLANS HAVE BEENSCALED TO 11X17
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB SUB SUB SUB
SUB SUB SUB SUB
SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB
SUB SUB SUB SUB SUB
SUB SUB SUB SUB
SUB SUB SUB
SUB SUB
SUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUB
SUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBSUBN.E. 10TH ST.( A DEDICATED PUBLIC RIGHT OF WAY)IMPROVED SOFTBALL FIELD.SEE LANDSCAPE PLANS ANDCX05 CIVIL PLANSIPIPIPISFFISFFPUMP "CLEAN" STORMWATER FROMTEMP SEDIMENT SETTLEMENT TANKS TOEXISTING CATCH BASIN. CONTRACTOR TOENSURE ALL DISCHARGE MEETSTURBIDITY REQUIREMENTS.INSTALL CB PROTECTIONSEE DETAIL (TYP)C1107PUMP CONSTRUCTIONSTORMWATER TO SEDIMENTSETTLEMENT TANKSSEDIMENT TRAP WITH55 GALLON DRUM ANDSUMP INSTALLED ATLOW POINT ON-SITE.SEE DETAILSC1105C1112FFFFISINTERCEPTOR SWALEWITH ROCK CHECK DAMSAT 50' O.C. SPACINGSEE DETAILSC1106C1118INSTALL SILT FENCEAROUND PERIMETEROF FIELD (TYP)SEE DETAILC1117BOE = 472.53BOE = 472.53SAWCUT AND REMOVE EXASPHALT PAVEMENT FORUTILITY INSTALLATIONSEE SHEET C205REMOVE PORTION OF EXLAWN, GRAVEL PATH ANDASPHALT AS REQ'D TO INSTALLNEW ELECTRICAL CONDUITS. SEESHEET C205APPROXIMATE LIMITS OF PROPOSEDDETENTION SYSTEM EXCAVATION FORSOFTBALL FIELD. SEE SHEET C205APPROXIMATE LIMITS OF PROPOSEDDETENTION SYSTEM EXCAVATION FORMULTIPURPOSE FIELD OPTION WHICHWOULD ALSO INCLUDE SOFTBALL FIELDDETENTION EXCAVATION. SEE SHEET C205IPIPIPIPIPIPREMOVE AND REPLACEPORTION OF EXISTING FENCEFOR STORM INSTALLATIONIPIRRIGATION CON REMOVE AND REPLACEPORTION OF EXISTINGFENCE AS NEEDED FORUTILITY INSTALLATIONPROTECT EXISTINGFENCE AND TRACKSURFACING TO REMAINPROTECT EXCOVERED DUGOUTSAWCUT AND REMOVEEX CONCRETE FORUTILITY INSTALLATIONREMOVE AND RELOCATE EXBLEACHER FOR UTILITYINSTALLATIONPROTECT EXSYNTHETIC GRASSSURFACINGPROTECT EXSYNTHETIC GRASSSURFACINGPROTECT PORTIONOF EXISTING FENCETO REMAINREMOVE EXISTING FENCECONTRACTOR TO MAINTAINFENCE AS LONG AS PRACTICALDURING CONSTRUCTION FORPERIMETER FENCING MEASURESPROTECT EXISTINGFENCE TO REMAINREMOVE EXISTINGBENCHESPROTECT PORTION OFEXISTING FENCE TO REMAINPROTECT EX CATCHBASIN TO REMAINREMOVE EXISTINGBACKSTOP FENCINGREMOVE EXISTINGBENCHESCITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450SCALE 1"=20'0102040HAZEN HIGH SCHOOL MODERNIZATION DEMOLITION AND TESC PLAN NOTE:INSTALL CONSTRUCTION FENCING AROUNDLIMITS OF WORK TO PROTECT STAFF ANDSTUDENTS AND SECURE JOBSITE.CONTRACTOR SHALL ERECT FENCE AROUNDJOBSITE AND ADJUST AS CONSTRUCTIONCONDITIONS CHANGE OR AS PHASINGALLOWS. CONTRACTOR CAN UTILIZEEXISTING PERIMETER FENCING AS SECURITYFENCING AND THEN SUPPLEMENT ON THEWEST SIDE OF THE SITE AS NEEDED. ANYSECTIONS OF EXISTING FENCING THAT ISNOT 6-FT HIGH SHALL HAVE TEMPORARY6-FT HIGH CHAINLINK FENCING INSTALLEDNEXT TO IT. SEE DETAIL 9/C110.SEE SHEET C001 FOR CITY OF RENTONESC STANDARD PLAN NOTESSEE SHEET C102 FOR TESCCONSTRUCTION SEQUENCE NOTESLEGENDSAWCUT LINEREMOVE CURBINGREMOVE ASPHALT PAVEMENTREMOVE CONCRETE PAVEMENTTREE PROTECTIONINLET PROTECTIONPROPERTY LINETEMP CONSTRUCTION FENCINGCFIPVEGMATCHLINE - SEE SHEET C107PROPOSED DETENTION SYSTEMREMOVE AND REPLACEPORTION OF EXISTINGFENCE AS NEEDED FORUTILITY INSTALLATIONNOTE - PLANS HAVE BEENSCALED TO 11X17
SWSWSWSWSWSWSWSWPROTECT EX VAULT ACCESS HATCH;IF OPEN GRATING, CONTRACTORSHALL COVER WITH FABRIC AND ORPVC LINER AND TIE DOWN TOPROTECT VAULT OPENINGSAWCUT AND REMOVE EX CONCRETEPAVEMENT AS REQUIRED TOCONSTRUCT NEW 6" CONCRETEGREENHOUSE PAD.SEE SHEET C206INSTALL STRAW WATTLESSEE DETAIL (TYP)C1108EXISTING IRRIGATION LINE.CONTRACTOR TO CONFIRM ANDSHALL POTHOLE AND CONFIRMLOCATION, DEPTH, AND MATERIALPROTECT EXISTINGWATER SPIGOT ONBUILDINGEXISTING DILUTION TRAPTO BE DEMOLISHEDEXISTING 10"SEWER LINE TOREMAINEXISTING 10" STORMPIPE TO REMAINEXISTING 6" ACID WASTE LINETO BE ABANDONED CUT ANDCAP AND FILL WITH CDF PERPROJECT SPECIFICATIONSEXISTING ACID WASTELINE TO BE BUILDINGTO BE ABANDONED.CUT & CAP (TYP)EXISTING ACID WASTELINE TO BE BUILDING TOBE ABANDONED.REMOVE EX 8"DECIDUOUS TREEIPVEGREMOVE EX 5"DECIDUOUS TREEINSTALL TREEPROTECTION FENCINGSEE DETAILC11011IPIPINSTALL CBPROTECTIONSEE DETAIL (TYP)C1107PROTECT EXISTING 2"IRRIGATION LINE TO REMAINREMOVE EXSEWER CLEANOUTSAWCUT AND DEMO EXCONCRETE PAVEMENT TO CUT,CAP, AND ABANDON-IN-PLACEEX ACID WASTE PIPING (TYP)EXISTING ACID WASTELINE TO BE BUILDING TOBE ABANDONED.CUT, CAP, AND REMOVEPORTION OF EX SEWERPIPE TO BE REPLACED.SEE SHEET C206SAWCUT AND DEMO EXCONCRETE PAVEMENT TO CUT,CAP, AND ABANDON-IN-PLACEEX ACID WASTE PIPING (TYP) DEMOLITION AND TESC PLAN CITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450SCALE 1"=10'510200HAZEN HIGH SCHOOL MODERNIZATION DEMOLITION AND TESC PLAN NOTE:INSTALL CONSTRUCTION FENCING AROUND LIMITS OFWORK TO PROTECT STAFF AND STUDENTS AND SECUREJOBSITE. CONTRACTOR SHALL ERECT FENCE AROUNDJOBSITE AND ADJUST AS CONSTRUCTION CONDITIONSCHANGE OR AS PHASING ALLOWS. CONTRACTOR CAN UTILIZEEXISTING PERIMETER FENCING AS SECURITY FENCING ANDTHEN SUPPLEMENT ON THE WEST SIDE OF THE SITE ASNEEDED. ANY SECTIONS OF EXISTING FENCING THAT IS NOT6-FT HIGH SHALL HAVE TEMPORARY 6-FT HIGH CHAINLINKFENCING INSTALLED NEXT TO IT. SEE DETAIL 9/C110.SEE SHEET C001 FOR CITY OF RENTONESC STANDARD PLAN NOTESSEE SHEET C102 FOR TESCCONSTRUCTION SEQUENCE NOTESLEGENDSAWCUT LINEREMOVE CURBINGREMOVE ASPHALT PAVEMENTREMOVE CONCRETE PAVEMENTTREE PROTECTIONINLET PROTECTIONPROPERTY LINETEMP CONSTRUCTION FENCINGCFIPVEGNOTE - PLANS HAVE BEENSCALED TO 11X17
□□□IMPROVED SOFTBALL FIELD.SEE LANDSCAPE PLANS ANDCX05 CIVIL PLANSIPISFF(2) 18,900 GALLON CAPACITY TEMPORARYSEDIMENT SETTLEMENT TANKS ("BAKER TANK" OREQUAL). CONTRACTOR SHALL PROVIDE ALL PUMPSREQUIRED TO MANAGE CONSTRUCTIONSTORMWATER AND DISCHARGE AT THE SITE.PUMP "CLEAN" STORMWATER FROMTEMP SEDIMENT SETTLEMENT TANKS TOEXISTING CATCH BASIN. CONTRACTOR TOENSURE ALL DISCHARGE MEETSTURBIDITY REQUIREMENTS.INSTALL CB PROTECTIONSEE DETAIL (TYP)C1107PUMP CONSTRUCTIONSTORMWATER TO SEDIMENTSETTLEMENT TANKSSEDIMENT TRAP WITH55 GALLON DRUM ANDSUMP INSTALLED ATLOW POINT ON-SITE.SEE DETAILSC1105C1112FFIPIPINSTALL CB PROTECTIONSEE DETAIL (TYP)C1107SWSWSWSWREMOVE ALL (5) EX. 24" CONCRETEBOLLARDS AND SURROUNDINGPAVING (TYP.) THE EXTENTS ISAPPROXIMATE AND WILL BE ADJUSTEDWHEN SURVEYED JOINT LINES ARERECEIVED. SEE SHEET C207INSTALL STRAWWATTLESSEE DETAIL (TYP)C1108PROTECT EXCONCRETE CURBTO REMAIN (TYP)4'IPREMOVE/RELOCATE EX "POOLPARKING ONLY" SIGN AND POSTFOR INSTALLATION OF NEWPORTABLE BUIDINGS.SEE SHEET C207PROTECT EXLIGHT TO REMAINBOE = 472.53BOE = 472.53APPROXIMATE LIMITS OF PROPOSEDDETENTION SYSTEM EXCAVATION FORMULTIPURPOSE FIELD OPTION WHICHWOULD ALSO INCLUDE SOFTBALL FIELDDETENTION EXCAVATION. SEE SHEET C205DECOMMISSION EX BELOW GRADE 10,000GAL. FUEL OIL TANK. COORDINATE W/ PBSENVIRONMENTAL FORREMEDIATION/DECOMMISSIONINGAND SEQUENCING PROCEDURESTANK EXTENTS UNKNOWN AND ARE SHOWN ASAPPROXIMATE TO BE DETERMINED IN FIELD.CUT, CAP, AND ABANDON-IN-PLACE ANY FUELOIL PIPING CONNECTED TO EX FUEL OIL TANK.PROTECT EX CURBWALL TO REMAINIPPROTECT EX CURBWALL TO REMAINSAWCUT AND REMOVE EXASPHALT PAVEMENT AS REQ'DFOR FUEL OIL TANK REMOVALREMOVE (2) EXDECIDUOUS TREESIPREMOVE AND REPLACEPORTION OF EXISTING FENCEFOR STORM INSTALLATIONIPIPRELOCATE EXISTINGIRRIGATION CONTROLBOX FOR STORMINSTALLATIONVEGIPIPIPREMOVEEXISTING TREEREMOVE ANDREINSTALL SIGN FORSTORM INSTALLATIONRELOCATE EXISTINGIRRIGATION CONTROL BOXFOR STORM INSTALLATIONREMOVE AND REINSTALLSTOP SIGN FOR STORMINSTALLATIONTREE PROTECTIONSEE DETAILC11011SAWCUT AND REMOVE EX CURBAND ASPHALT AS REQUIRED TOINSTALL NEW STORM PIPING.SEE SHEET C207SAWCUT AND REMOVE EX CURBAND ASPHALT AS REQUIRED TOINSTALL NEW STORM PIPING.SEE SHEET C207HOQUIUM AVE. N.E.
(A DEDICATED PUBLIC RIGHT OF WAY)PROTECT EXSYNTHETIC GRASSSURFACINGCITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450SCALE 1"=20'0102040HAZEN HIGH SCHOOL MODERNIZATION DEMOLITION AND TESC PLAN NOTE:INSTALL CONSTRUCTION FENCING AROUNDLIMITS OF WORK TO PROTECT STAFF ANDSTUDENTS AND SECURE JOBSITE.CONTRACTOR SHALL ERECT FENCE AROUNDJOBSITE AND ADJUST AS CONSTRUCTIONCONDITIONS CHANGE OR AS PHASINGALLOWS. CONTRACTOR CAN UTILIZEEXISTING PERIMETER FENCING AS SECURITYFENCING AND THEN SUPPLEMENT ON THEWEST SIDE OF THE SITE AS NEEDED. ANYSECTIONS OF EXISTING FENCING THAT ISNOT 6-FT HIGH SHALL HAVE TEMPORARY6-FT HIGH CHAINLINK FENCING INSTALLEDNEXT TO IT. SEE DETAIL 9/C110.SEE SHEET C001 FOR CITY OF RENTONESC STANDARD PLAN NOTESSEE SHEET C102 FOR TESCCONSTRUCTION SEQUENCE NOTESLEGENDSAWCUT LINEREMOVE CURBINGREMOVE ASPHALT PAVEMENTREMOVE CONCRETE PAVEMENTTREE PROTECTIONINLET PROTECTIONPROPERTY LINETEMP CONSTRUCTION FENCINGCFIPVEGMATCHLINE - SEE SHEET C105NOTE - PLANS HAVE BEENSCALED TO 11X17
CITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450HAZEN HIGH SCHOOL MODERNIZATION TESC DETAILS 5' POST HEIGHT2' POST BURIAL DEPTH1.A MINIMUM 4 FOOT HIGH TEMPORARY FENCE MUST BE PLACED AT THE DRIP LINE OF TREES PRIOR TOTHE COMMENCEMENT OF CLEARING OR EARTHWORK. NOTIFY THE CLEARING AND GRADINGINSPECTOR TO GET BOTH THE INSPECTION AND WRITTEN APPROVAL OF FLAGGED TREES ANDTEMPORARY PROTECTION FENCING AROUND TREES TO BE SAVED PER THE APPROVED CLEARING ANDGRADING PLAN.2.NO STOCKPILING OF MATERIAL AND NO VEHICULAR TRAFFIC ARE ALLOWED WITHIN THE LIMITS OFTHE TEMPORARY FENCING. FILLING, EXCAVATION, AND CLEARING MUST BE ACCOMPLISHED BY HANDMETHODS ONLY.3.ROOTS OF TREES TO BE SAVED WHICH ARE DAMAGED DURING CONSTRUCTION MUST BE TREATED INTHE FOLLOWING WAY: FOR DAMAGED ROOTS OVER 1" IN DIAMETER, MAKE A CLEAN, STRAIGHT CUTTO REMOVE THE DAMAGED PORTION OF THE ROOT. ALL EXPOSED ROOTS WILL BE TEMPORARILYCOVERED WITH DAMP BURLAP OR WOOD SHAVINGS TO PREVENT DRYING AND COVERED WITH EARTHAS SOON AS POSSIBLE.4.SEE TESC PLANS FOR LOCATION OF EXISTING TREES TO RECEIVE TEMPORARY FENCING.NOTES:METAL SUPPORTPOST 6'-8' ONCENTER SPACINGMIN 5' HEIGHTBARRICADE FENCING (ORANGECONSTRUCTION FENCE) MIN 4'HEIGHT SURROUND TREE ORGROUP OF TREES AT DRIP LINEOR AS SHOWN ON PLANSSEE DETAILDRIPLINE
DRIPLINE
6' FENCE LINE POST (TYP)2.375 INCH 0.D.TOP RAIL1.666 INCH O.D.STRETCHERBARBRACE RAILAND CABLE1.666 INCH O.D.TRUSS ROD 3/8" DIAW/ TENSION DEVICETENSION WIRECONCRETE BLOCKSTD WGT GALVANIZEDCORNER POST5/8" WIRE ROPE PROVIDE SECUREEND ATTACHMENT AT CORNER ANDGATE POSTS AND PROVIDE RUNNINGATTACHMENT AT LINE POSTS ANDNEAR CENTER OF EACH FENCE PANELTree Protection Fence11NTSInlet Protection7NTSStraw Wattle8NTSConstruction Fence9NTSSediment Trap5NTSCheck Dams6NTSC1116NOTE - PLANS HAVE BEENSCALED TO 11X17
CITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450HAZEN HIGH SCHOOL MODERNIZATION TESC DETAILS Not Used5NTSNot Used1NTS6"=12" PERFORATEPIPE AS NECESSARY1'TOP OF PIPE SHALL BE6" MIN ABOVE GRADEPROVIDE SOLID COVERDISCHARGE TO SEDIMENTPOND VIA TEMP FORCE MAIN5%30" MIN RUNOFF WITHSEDIMENTFILTERED RUNOFFWATER LEVELCONCRETE BLOCKSSUMP PUMP AND MOTORWIRE TIES24"-36" PVC OR HDPE PIPEW/ 2" DIA WEEP HOLES ORAPPROVED EQUALWRAP WITH PERMEABLEFILTER FABRICPROVIDE 12" MINWASHED ROCK AROUNDPERIMETER OF PIPENot Used9NTSNot Used11NTSTemporary Sump and Pump2NTSSilt Fence7NTSInterceptor Swale8NTS10'TENSAR GS-1 SAFETYFENCE OR EQUALGALVANIZED WIRE OROTHER APPROVEDMATERIALSTEEL FENCE POSTCLIP FENCE TO WIREWIRE FENCETO STEEL POSTClearing Limits Fence6NTSNOTE - PLANS HAVE BEENSCALED TO 11X17
Page | 35 Appendix B – BMP Details Preserving Natural Vegetation (BMP C101) 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
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 lining
Plan 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
\ri
y
l-j
X
-
NOT TO SCALE
Prefabricated Concrete Washout Container
w/Ramp
Revised June 2016
DEPARTMENT 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 3K
o..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 x
oi Rx Xxx>-X>:X X
X X X’
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 (H 2O), carbonic acid (H2CO3) is formed which can
further dissociate into a proton (H+) and a bicarbonate anion (HCO3-) as shown below:
CO2 + H 2O ↔ 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 General Contractor (TBD) who will maintain both the NPDES and SWPPP for the project until the end of construction.
HAZEN HIGH SCHOOL IMPROVEMENTS 25 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 N/A
2.79
2.34 83.87%
102,118 100%
102,118 100%
0
0
-----
STORMWATER FACILITY PRELIMINARY
SUMMARY SHEET - DISCHARGE
LOCATION #1
N/A
-----
TBD
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
RainVault 5.0 Stack
West of Baseball Field
47,150 6.66
West of RainVault System
10%
2.34
100%
2
STORMWATER FACILITY PRELIMINARY
SUMMARY SHEET - DISCHARGE
LOCATION #1
West of RainVault System
3
1.13"
0.75"
0.06'0.75"
N/A
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 N/A
1.06
0.98 92.45%
42,689 100%
42,689 100%
0
0
---
---
STORMWATER FACILITY PRELIMINARY
SUMMARY SHEET - DISCHARGE
LOCATION #2
N/A
TBD
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
RainVault 2.0 Stack
Softball Field
19,250 2.72'
West of RainVault System
10%
0.98
100%
1
1
0.87"
0.20'
STORMWATER FACILITY PRELIMINARY
SUMMARY SHEET - DISCHARGE
LOCATION #2
N/A
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 N/A
1.07
0.93 86.92%
40,555 100%
40,555 100%
0
0
---
---
STORMWATER FACILITY PRELIMINARY
SUMMARY SHEET - DISCHARGE
LOCATION #3
N/A
TBD
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
RainVault 2.0 Stack
Multipurpose Field
25,150 2.72'
Northeast of RainVault System
10%
0.97
100%
1
1
0.62"
0.20'
STORMWATER FACILITY PRELIMINARY
SUMMARY SHEET - DISCHARGE
LOCATION #3
N/A
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB SUB
SUB
SUB
SUB
SUB
SUB
SUBSUB
SUBSUBSUBSUBSUBSUBSUBSUBSUBSUBN.E. 12TH ST.(A DEDICATED PUBLIC RIGHT OF WAY)N.E. 10TH ST.( A DEDICATED PUBLIC RIGHT OF WAY)DUVALL AVE. N.E.( A DEDICATED PUBLIC RIGHT OF WAY)
HOQUIUM AVE. N.E.
(A DEDICATED PUBLIC RIGHT OF WAY)XXXXEEEEEEEEEEE GTGTGT
SS GTGTSDSDSDGTGTGTGTGTGTGTGTGTGTGT
SDSDSDCITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDS43667NSTATE OF WASHINGTONREGISTEREDPROFESSIONALENGINEER OSBOCAJA.DLAREJ
C24000450HAZEN HIGH SCHOOL MODERNIZATION OVERALL SITE PLAN CX04CX01SCALE 1"=70'35701400CX03CX05CX06PROJECT WORKAREAS (TYP)IMPROVED BASEBALL FIELDAND GEOTHERMAL WELL ZONEIMPROVEDSOFTBALL FIELDCX02EXISTINGPOWER POLENEW ELECTRICALPRIMARY SERVICEGEOTHERMALWELL ZONEGEOTHERMALPIPING IN/OUTOF BUILDINGGEOTHERMAL VAULT.LOCATION TBD.(2) TEMPORARYPORTABLES TO BEREMOVED AT ENDOF PROJECTMAINTAIN 20'WIDE FIRE LANECX07GEOTHERMAL VAULT.LOCATION TBD.EX CHURCH PROPERTYIMPROVED MULTIPURPOSEFIELD OPTION W/ FIELDLIGHTINGNOTE: BREAKOUT SHEETSVARY IN DRAWING SCALECONTRACTOR TO TAKE NOTEOF SCALES ON EVERY SHEETFLOW CONTROLFACILITYFLOW CONTROLFACILITYFLOW CONTROLFACILITY