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255 S. King Street, Suite #800, Seattle, WA 98104 | 206.426.2600 | JACOBSONENGINEERS.COM TECHNICAL INFORMATION REPORT for Storm Water Management Lindbergh High School Field Improvements 16426 128th Ave SE, Renton, WA 98058 June 6, 2025 _______________________________________________ Prepared for Renton School District Contact: Andrew Hollenback (425) 204-4437 andrew.hollenback@rentonschools.us _______________________________________________ Prepared through McGranahan PBK Contact: Kris Stamon (253) 383-3084 kris.stamon@mcgranahan.com _______________________________________________ Prepared by Jacobson Consulting Engineers Contact: Alan Jacobson (206) 426-2600 alan@jacobsonengineers.com DEVELOPMENT ENGINEERING HBray 06/24/2025 Surface Water Enginering jfarah 06/24/2025 i Technical Information Report for Lindbergh High School Field Improvements JCE Project No. C240004-0215 June 6, 2025 TABLE OF CONTENTS 1. PROJECT OVERVIEW ................................................................................................................................ 3 GENERAL DESCRIPTION .............................................................................................................................. 3 EXISTING CONDITIONS ................................................................................................................................. 3 PROPOSED DRAINAGE SYSTEM ................................................................................................................. 4 2. CONDITIONS AND REQUIREMENTS SUMMARY ......................................................................................... 4 CORE REQUIREMENT #1: DISCHARGE AT THE NATURAL LOCATION .................................................. 4 CORE REQUIREMENT #2: OFFSITE ANALYSIS ......................................................................................... 5 CORE REQUIREMENT #3: FLOW CONTROL FACILITIES.......................................................................... 5 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.................................................... 6 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 .................................................................................. 9 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) .........................................................................................................13 WATER QUALITY SYSTEM (PART E) .........................................................................................................14 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ...................................................................................... 15 6. SPECIAL REPORTS AND SUMMARY ........................................................................................................ 17 7. OTHER PERMITS ................................................................................................................................... 17 8. CSWPP ANALYSIS AND DESIGN ............................................................................................................. 17 STANDARD REQUIREMENTS .....................................................................................................................18 LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS ii 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ....................................... 19 BOND QUANTITIES WORKSHEET..............................................................................................................19 FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH .......................19 DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND WQ FACILITIES .....................................................................................................................................................19 10. OPERATIONS AND MAINTENANCE MANUAL ........................................................................................... 19 11. FIGURES ............................................................................................................................................... 20 Appendices: APPENDIX A – GEOTECHNICAL REPORT APPENDIX B – STORMWATER CALCULATIONS APPENDIX C – STORMWATER POLLUTION PREVENTION PLAN (SWPPP) APPENDIX D – OPERATIONS AND MAINTENANCE MANUAL APPENDIX E – BOND QUANTITIES WORKSHEET, FACILITY SUMMARY SHEET, DECLARATION OF COVENANT LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 3 1. PROJECT OVERVIEW GENERAL DESCRIPTION The following Technical Information Report (TIR) is for the Lindbergh High School Field Improvements project. The stormwater design for the project was based on the requirements outlined in the 2022 City of Renton Water Design Manual (RSWDM), as currently adopted by the City of Renton. See Figure 1 – TIR Worksheet, for general project information. Lindbergh High School is within the City of Renton jurisdictional limits, addressed at 16426 128th Ave SE, Renton, WA, 98058 (Parcel Number 12823059004). The site is bounded by 128th Ave SE on the west, single- family residences on the north and east, and a church to the south. See Figure 2 - Vicinity Map. The proposed project consists of replacing the existing baseball and softball fields (natural grass outfields, compacted dirt infields) with new synthetic turf fields. The fields are currently underdrained, so this project will either involve the installation of a new underdrain system or utilizing the existing system. Detention facilities will need to be installed to meet flow control requirements. Other field amenities proposed include field lighting, speaker system, scoreboards, paved pedestrian walkways/access, dugouts, and batting cages. EXISTING CONDITIONS The school property is currently occupied by (1) one large building at the center of the property with associated sidewalks, parking, and driving areas surrounding all sides of the building. The school additionally has baseball and softball fields to the west, a rubberized track and grass field at the southeast corner, and a natatorium just south of the building with tennis courts at the south of that. There is landscaping, trees, and vegetation between the building and around driving surfaces, with a pocket of existing dense vegetation surrounding the tennis courts and track/field. The project disturbance area consists of the baseball and softball fields on the west side of the parcel that are currently surfaced with compacted dirt infields and natural grass outfields. See Figure 3 – Existing Conditions. For determination of minimum requirements, a project is considered a “redevelopment” if the impervious coverage of the site/lot is 35% or greater. This site will have about 56.8% impervious coverage and would thus be considered a “redevelopment”. Refer to Figure 4 – Existing Impervious Coverage. According to NRCS Web Soil Survey, the project site soils are predominantly composed of Alderwood gravelly sandy loam, 8 to 15 percent slopes, while small portion on the west side is underlain with Arents, Alderwood material, 6 to 15% slopes. See Figure 5 – Soils Map. A previous geotechnical report (for the same project disturbance area) had been prepared by Associated Earth Sciences, Inc. (AESI), dated January 8, 2000. Based on the subsurface exploration, fill soils were observed ranging from 2.5 to 9 feet below ground surface. Beneath the fill layer consisted mostly of dense to very dense sand with silt, which was interpreted as lodgement till. The existing project site topography is moderately sloped, with the softball field being essentially flat, sloping gently out toward the field perimeter. The baseball field slopes from south to north at around 1%. The transition from the softball field down to the baseball field is a steep grass slope at an approximate 25% grade. There is an existing staircase that connects the field areas. The softball field terrace (which includes batting cage facilities) has significant slopes down to adjacent areas, such as the school building (east) and 128th Avenue NE frontage (west). There is a natural drainage collection area south of the softball field that is between the field and adjacent walkway. With the baseball field terrace, slopes continue down towards an adjacent driveway (north) and a parking lot (east). The scope of the project includes the field areas on the west side of the school campus, which drain to one Threshold Discharge Area (TDA). The existing fields are underdrained, and currently discharged to an on-site piped conveyance system. Stormwater leaves the site at its northwest corner and enters a municipal system within 128th Ave SE and flows approximately 0.61 miles northwest to an existing wetland. Stormwater would flow to Ginger Creek and ultimately to the Cedar River. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 4 See Table 1 below and Figure 3 – Existing Conditions for a summary of the existing land cover characteristics for the areas associated with this project. TABLE 1 – PROJECT AREA EXISTING SITE CONDITIONS Land Cover Area Impervious Surface 150,866 SF Pervious Surface 69,159 SF Total Project Area 220,025 SF % Impervious 68.6% PROPOSED DRAINAGE SYSTEM Proposed drainage from the TDA will continue to discharge to the same point of connection in the final condition. The TDA consists of the existing baseball field and softball field, which are currently underdrained and routed into the existing municipal system within 128th Ave SE, with a connection located near the northwest corner of the property. The existing underdrain system will need to be cut and capped to construct the new detention system meeting the City’s flow control standards. The detention system will have a flow control structure that is designed to attenuate flow and utilize the storage available within that system. Table 2 below summarizes the land cover characteristics of the proposed conditions of the project site area. TABLE 2 – DISTURBED AREA PROPOSED SITE CONDITIONS Land Cover Area Impervious Surface 156,292 SF Pervious Surface 63,733 SF Total Project Area 220,025 SF % Impervious 71.0% 2. CONDITIONS AND REQUIREMENTS SUMMARY The proposed Lindbergh High School Field Improvements project will result in more than 7,000 square feet of land disturbing activity and 2,000 square feet of new plus replaced impervious surface. Therefore, based on Figure 1.1.2.A of the Renton Surface Water Design Manual (RSWDM), Full Drainage Review is required. 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, on-site BMP, water quality facility, erosion and sediment control facility, and any other structure and appurtenance that provides for drainage. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 5 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 from the field area is currently discharged from the site at the northwest corner of the property. Both fields are underdrained, either connecting to the piped system running through the fields or the system to the north in the adjacent fire lane. The proposed drainage system will not change the natural discharge location and maintain the same threshold discharge area (TDA). The proposed drainage systems will continue directing stormwater to the same natural location. There will be no alteration of the existing TDA, as the proposed field underdrain systems, after flow control facilities, will connect to the stormwater system in the paved area east of the baseball field and follow the same downstream drainage course. 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. A Level 1 Downstream Analysis has been performed for this project; see Section 3 of this report for more information. 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 site is located within Flow Control Duration Standard Area, as designated by Renton mapping. Specifically, it is located within the forested land cover area, which means that flow from the developed site must be controlled and released at a rate for a flow duration matching forested “historical” land cover. This project is not exempt from flow control facilities. The proposed design involves the installation of a StormTech chamber detention system with a flow control structure at the downstream end, which attenuates the release rate and utilizes the storage available in the chambers and the surrounding permeable aggregate. The flow control system will be described in greater detail in Section 4 of this report. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 6 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 will require a conveyance and backwater analysis of the new drainage systems. See Section 5 of this report for more information. 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 Construction SWPPP has been prepared for this project and is included in Appendix C of this report. A concept ESC plan with requirements for the Contractor to provide and implement a design for a system to treat construction runoff to no more than 25 NTU’s over baseline has also been prepared. 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 Appendix D of this drainage report and will be provided to the owner for all stormwater BMPs proposed for this project that are maintained by the School District. 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), will provide a Public Agency Services Agreement (PASA) in lieu of cash bonding. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 7 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. While the project site is located within a Basic Water Quality Treatment Area, the school is considered a commercial site, and thus enhanced water quality treatment would be required per section 1.2.8.1 of the Renton SWDM. The playfields will exceed the thresholds of 5,000 square feet of pollution-generating hard surface (PGHS) or ¾ acre of pollution-generating pervious surface (PGPS), so water quality treatment is required. The project proposes to utilize a Modular Wetland System to address water quality, located downstream of the detention system. See the Water Quality section of this report for more information. CORE REQUIREMENT #9: ON-SITE BMPS All proposed projects, including redevelopment projects, must provide on-site 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. On-site BMPs are methods and designs for dispersing, infiltrating, or otherwise reducing or preventing development-related increases in runoff at or near the sources of those increases. On-site BMPs include, but are not limited to, preservation and use of native vegetated surfaces to fully disperse runoff; use of other pervious surfaces to disperse runoff; roof downspout infiltration; permeable pavements; bioretention; limited infiltration systems; and reduction of development footprint. 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 – Full Dispersion is not feasible because the amount of impervious area would exceed 15% of the total native vegetated surface being preserved on the site. Additionally, the playfields are vertically-draining surfaces, and thus cannot be dispersed nor used as a vegetated flow path. 2. Full Roof Infiltration – This BMP is infeasible because the setbacks from steep slope hazard areas cannot be met. 3. Full Infiltration – Full infiltration would not be feasible because setbacks could not be maintained from steep slope hazard areas, as there are 15% (or greater) slopes per City of Renton GIS around each field. There is some area northwest of the baseball field that has slopes less than 15% slopes. However, any infiltration facility would be within the buffer, as the area immediately north has slopes greater than 15%. Furthermore, geotechnical borings have shown existing fill in this area to a depth of 9 feet, which is not a suitable infiltration receptor. 4. Limited Infiltration – Limited infiltration would not be feasible because setbacks could not be maintained from steep slope hazard areas, as there are 15% (or greater) slopes per City of Renton GIS around each field. There is some area northwest of the baseball field that has slopes less than 15% slopes. However, any infiltration facility would be within the buffer, as the area immediately north has slopes greater than 15%. Furthermore, geotechnical borings have shown existing fill in this area to a depth of 9 feet, which is not a suitable infiltration receptor. 5. Bioretention – Bioretention would not be feasible for this project due to the presence of steep slopes steeper than 20%. This BMP is not allowable per section 6.8.1 of the Renton SWDM. There are slopes less than 20% to the northwest of the baseball field; however, a bioretention BMP would not be feasible here due to elevations. Based on the depth of the detention system and the depth of the bioretention LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 8 section, a connection to the existing drainage system could not be made via gravity. Additionally, the construction staging area will be in this location. 6. Permeable Pavement – Permeable pavement would not be feasible for the plaza areas of this site due to the proximity to slopes steeper than 15%. It would not be feasible for stairs or ramps, where the longitudinal slope exceeds 5%. Note that while the underdrained turf fields are considered impervious areas, they function similarly to that of permeable pavement by promoting vertical drainage and slowing runoff from impervious surfaces. However, the underdrained fields themselves do not count as a Flow Control BMP. 7. Basic Dispersion – Basic dispersion is not feasible due to the presence of slopes that exceed 15%, and thus would not meet the design requirements outlined by section C.2.4.1 of the Renton SWDM. While the underdrained fields are pervious (modeled as impervious), vertically-draining surfaces, they are not eligible as a vegetated flow path. This applies to the area northwest of the baseball outfield; the turf would not be able to be dispersed because it is a vertically-draining surface (counted as impervious). 8. Reduced Impervious Surface Credit – The proposed site improvements propose more than 4,000 SF of impervious surface and therefore the Restricted Footprint credit is NOT feasible for this site. No driveways are proposed with this project therefore the Wheel Strip Driveway credit is NOT feasible for this site. There are no proposed building improvements, therefore the Minimum Disturbance Foundation credit is NOT feasible 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 – This BMP is infeasible because the available donor native vegetated surface is not 3.5 times the area of impervious surface to be mitigated (section C.2.10.1 of the Renton SWDM). 10. Perforated Pipe Connection – No new downspouts are proposed with the base bid of this project; therefore, Perforated Pipe Connections are NOT feasible. However, in the alternate design, there is a roofed batting cage with downspouts. Perforated pipe connections are not feasible for this application, as they cannot be placed on steep slopes per section C.2.11.1 of the Renton SWDM. SPECIAL REQUIREMENT #1: OTHER ADOPTED AREA-SPECIFIC REQUIREMENTS The RSWDM is one of several adopted regulations in the City of Renton that apply requirements for controlling drainage on an area-specific basis. Other adopted area-specific regulations with requirements that have a direct bearing on the drainage design of a proposed project are found in Section 1.3.1 of the RSWDM. To the best of our knowledge, there are no adopted area-specific requirements in the proposed project site development that would impact the current Renton Surface Water Design Manual (SWDM) requirements for this project. Therefore, the project will adhere to the requirements outlined in the 2022 Renton SWDM. 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. In reviewing both FEMA Flood Insurance Rate Maps, 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. The site does not have any existing flood protection facilities installed on LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 9 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. Based on an evaluation of the 2021 King County Stormwater Pollution Prevention Manual, the following source controls are applicable to this project: • A-26: Landscaping Activities, Vegetation Management, and Irrigation: This project will involve irrigation improvements, and limited landscaping activities. The proposed turf fields are not subject to the use of fertilizers or pesticides. Irrigation required BMPs and landscaping/vegetation management required BMPs shall be implemented on the project, along with any supplemental BMPs as needed. • A-32: Sidewalk Maintenance – This project will propose concrete walking surfaces that will be periodically cleaned and must adhere to the required BMPs of A-32. 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, and thus this requirement is not applicable. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 10 3. OFFSITE ANALYSIS FIELD INSPECTION A preliminary site visit has been done to observe the site, but future site visits will be conducted to check project- specific conditions and confirm the downstream drainage path for future permit submittals. This offsite analysis was based on extensive existing drainage information, such as a site survey, City of Renton GIS, and as-built drawings from the 2001 field renovation project. Please refer to the Downstream Analysis below for more information. DRAINAGE SYSTEM PROBLEM DESCRIPTIONS There are no known drainage concerns or any existing drainage problems per review of the site with the Renton School District and the King County iMap and City of Renton COR Maps ‘Drainage Complaints’ Layer. As such, no drainage problems are expected to be present in the redevelopment or exacerbate any existing problems. UPSTREAM ANALYSIS Based on topography of the project site, there would be very limited upstream area running onto the fields. Along 128th Avenue SE, there is a curb and sidewalk sloping toward the street. Steep slopes to the north, east, and west of each field ensure there will be no upstream contribution. Each field has a perimeter drainage system along the south edge, consisting of pipes and catch basins, that prevent any upstream runoff from getting to the field. Thus, upstream areas are not expected to have any impact or adverse effects on this project. DOWNSTREAM ANALYSIS The existing softball and baseball fields are equipped with sub-drainage systems consisting of 4-inch perforated lateral drain lines running to 6-inch collector lines. Both fields eventually connect to the existing piped stormwater system in the drive lane/parking lot to the southeast of the baseball field. This system conveys runoff north and then west along the paved access north of the project area, connecting to a 12-inch concrete pipe system in 128th Ave SE and leaves the site at its northwest corner. From here, the downstream drainage course is as follows: 1. From the catch basin on the east side of 128th Ave SE, it flows north for approximately 190 feet to a manhole at the intersection of 128th Ave and SE 164th Street. 2. The runoff then transitions to a 24-inch concrete pipe within SE 164th St, continuing west for approximately 740 feet. 3. The water then flows north through a 36-inch concrete pipe within SE 163rd St for 260 feet before converging with additional flow and turning west. 4. After converging, the stormwater continues west in a 36-inch pipe for approximately 640 feet, passing between single-family residences and entering a structure on the west side of 126th Ave SE. 5. Stormwater flows west and then north, via a 36-inch corrugated metal pipe (CMP) beneath Cascade Park for approximately 1,610 feet. 6. The system becomes 48” CMP and passes beneath SE 150th St, entering a wetland. Stormwater eventually flows to Ginger Creek and ultimately to the Cedar River. See Figure 7 – Downstream Drainage for a visual representation of the described downstream path. 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. The proposed project is providing flow control facilities where there currently is not, and so there will be no adverse impact on the downstream drainage system. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 11 4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY (PART A) The existing site topography features moderate to steep slopes dropping from southwest to northeast across the project site. Existing curbs, gutters, drive lanes, and stormwater conveyance systems are located north and south of the softball and baseball fields. No upstream flow runs onto the fields. Stormwater falling upon the softball field is captured by a sub-drainage system comprised of 4-inch perforated lateral drain lines running northwest-southeast that drains to a 6-inch perforated corrugated polyethylene collector pipe running down the middle of the field. The collector pipe discharges to a Type I catch basin on the field's northeast side, outside of the field footprint. From there, stormwater flows via a piped system down the slope and connecting with a catch basin in the drive aisle to the east of the baseball field. This system is tributary to the northwest drainage discharge point from the site that goes into 128th Avenue SE. Similarly, the baseball field has a sub-drainage system lateral drain lines that connect with a 6-inch collector line, which brings stormwater to a structure at the east end of the field. The stormwater joins the same piped system downstream of the softball field. The downstream drainage path is as described in the preceding Offsite Analysis section. See Table 1 of this report and Figure 3 – Existing Conditions for a summary of the existing land cover characteristics for the project site. DEVELOPED SITE HYDROLOGY (PART B) The previous field renovation from 2001 did not include flow control facilities. Due to current code, flow control facilities would be required for this project. However, the current underdrain system has been investigated and was found to be in good working condition. Thus, the softball field underdrain system will remain, while the baseball field underdrains will be cut and capped as necessary to install the new detention system. The flow control structure (and thus outlet point of baseball field) will be placed outside of the field footprint to accommodate installation and provide the proper connection to the existing storm system. Table 2 of this report outlines the land cover characteristics in the proposed condition. The flow control facilities proposed with this project will provide mitigation for the new plus replaced impervious surfaces. Thus, this total was tabulated in Table 3 below and in Figure 8 – New + Replaced Impervious Areas. This represents the ‘target surface’, which will further be described in the Performance Standards section. The various new plus replaced impervious surfaces include underdrained turf playfields, paved surfaces, and roofed surfaces. 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. TABLE 3 – NEW PLUS REPLACED IMPERVIOUS AREAS Land Cover Area (sf) Area (acres) Underdrained Turf Playfield 137,493 3.156 Pavement Roof 7,796 1,480 0.179 0.034 Total New + Replaced Impervious Area (Target Surface) 148,769 3.369 LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 12 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. Per Table 1.2.3.A of the Renton SWDM, there are no identified downstream problems, and thus the flow control facilities must match project flow durations to pre-developed forested conditions for the range of 50% of the 2-year flow up to the full 50-year flow. Additionally, peak flows from the project must not exceed pre-developed flows for the 2-year and 10-year return periods. In accordance with the RSWDM (section 3.1.3), MGS Flood, an approved continuous-modeling software, is used to model the flow control required. 9 According to section 1.2.3.1.B of the Renton SWDM, the Target Surfaces are the surfaces requiring mitigation to the pre-developed forested condition. The following outlines the potential target surfaces from the SWDM and how they apply to this project: 1. New impervious surface that is not fully dispersed per the criteria on Section 1.2.3.2.C as specified in Appendix C. For individual lots within residential subdivision projects, the extent of new impervious surface shall be assumed as specified in Chapter 3. Note, any new impervious surface such as a bridge or boardwalk that spans the ordinary high water of a stream, pond, or lake may be excluded as a target surface if the runoff from such span is conveyed to the ordinary high water area in accordance with Criteria (b), (c), (d), and (e) of the “Direct Discharge Exemption“. New impervious surface is considered a target surface for this project, as there will not be any fully dispersed areas. 2. New pervious surface that is not fully dispersed as specified in Appendix C. For individual lots within residential subdivision projects, the extent of new pervious surface shall be assumed to be the entire lot area, except the assumed impervious portion and any portion in which native conditions are preserved by covenant, tract, or easement. In addition, the new pervious surface on individual lots shall be assumed to be 100% grass. New pervious surface will not be considered a target surface, as this project does not consist of any new pervious surface. Per the definition in the Renton SWDM, new pervious surface is “the conversion of a native vegetated surface or other native surface to a nonnative pervious surface or any alteration of existing nonnative pervious surface that significantly increases surface and stormwater runoff”. The field site is already developed and there will be no significant changes in runoff characteristics for nonnative pervious surfaces; thus, this item is not applicable. 3. Replaced impervious surface that is not fully dispersed as specified in Appendix C on a non- redevelopment project in which the total of new plus replaced impervious surface is 5,000 square feet or more, OR new pervious surface is ¾ acre or more. This project is a redevelopment project (see Figure 4), and thus this item is not applicable. 4. Replaced impervious surface that is not fully dispersed on a transportation redevelopment project in which new impervious surface is 5,000 square feet or more and totals 50% or more of the existing impervious surface within the project limits. This project is not a transportation redevelopment project, and thus this item is not applicable. 5. Replaced impervious surface that is not fully dispersed as specified in Appendix C, on a parcel redevelopment project in which the total of new plus replaced impervious surface is 5,000 square feet or more and whose valuation of proposed improvements (including interior improvements and excluding required mitigation improvements) exceeds 50% of the assessed value of: (a) the existing project site improvements on commercial or industrial projects, or (b) the existing site improvements on other projects. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 13 Replaced impervious surface is considered a target surface. Schools are considered “commercial” projects. This project involves more than 5,000 square feet of new plus replaced impervious surface and the valuation of the proposed improvements exceeds 50% of the assessed value of the existing project site improvements. Therefore, for this project, the target surface will consist of new plus replaced impervious surface. This is the minimum amount of area that must be mitigated to the historical (forested) predeveloped condition in the flow control model. This total is listed in Table 3 of this report. This project proposes a single detention system to provide the adequate flow control volume for both field areas. In the modeled pre-developed conditions, all areas considered as target surface are modeled as having forested surface cover. All surfaces have been broken out appropriately into flat (0-6%), moderate (6-15%) and steep (15%+) slopes. In the proposed conditions, new and replaced impervious areas (excluding utility trenches) have been classified by 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. The underdrained synthetic turf surface will be modeled as 100% impervious. The project does have some bypass target surfaces areas, which cannot be feasibly collected and routed to the detention system. This includes various walkways and dugout roofs. These areas will be entered into the model as a bypass basin that will connect directly to the point of compliance, instead of to the detention element. However, they must still be mitigated to the forested condition regardless. There are compensatory areas that can be collected and routed to detention to mitigate for some of the bypass area. This involves existing walkways that drain to the existing system that is being intercepted for routing into the proposed StormTech facility. These areas are tributary to detention, so they must be accounted for in the model; however, they do not need to be mitigated to the forested condition and are thus counted as predeveloped “extra” impervious area. Similarly, tributary pervious surfaces are non-converted, and thus not part of the target surface. Those surfaces have been entered as lawn in the predeveloped basin. See Table 4-6 below and Figure 9 – Flow Control Basins. TABLE 4 – PREDEVELOPED BASIN Surfacing Square feet Acres Forested (flat) 146,769 3.369 Sidewalk (flat) 4,867 0.112 Lawn (flat) 9,165 0.210 Lawn (steep) 4,419 0.101 Total 165,221 3.792 TABLE 5 – POSTDEVELOPED DETENTION BASIN Surfacing Square feet Acres Roof 360 0.008 Sidewalk (flat) 146,834 3.371 Lawn (flat) 9,165 0.210 Lawn (steep) 4,420 0.101 Total 160,779 3.690 LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 14 TABLE 6 – POSTDEVELOPED BYPASS BASIN Surfacing Square feet Acres Roof 1,120 0.026 Sidewalk (flat) 2,062 0.047 Sidewalk (moderate) 1,260 0.029 Total 4,442 0.102 FLOW CONTROL SYSTEM (PART D) This project proposes installing a StormTech chamber detention system to provide flow control, which provides storage in the surrounding permeable gravel, as well as the chambers themselves. The flow control structure will attenuate outflow from the system and utilize the storage available. Due to the non-uniform storage section, a stage storage table will be used in the model, which is attached in Appendix B. The appropriate data was brought into MGS Flood to accurately represent the detention in the model. The project will propose the MC-7200 StormTech chamber. The detention system will be configured on the eastern portion of the baseball field. A flow control riser within a type-2 catch basin at the downstream end of the system, outside of the field footprint. There will be 279 total MC-7200 StormTech chambers. The top of the flow control riser will be 12” above the top of chamber to utilize the gravel storage. The bottom gravel section is 9”, which will be dead storage, as there is on underdrain on this system. This system provides approximately 73,339 cubic feet of total live storage. The 12-inch CMP flow control riser will have a bottom orifice diameter of 1.0625”. There will be a rectangular notch with a width of 0.25” and a height of 15” from the top of the riser. See Appendix B – Stormwater Calculations of this drainage report for all MGS Flood calculations. See the compliant Flow Duration Plot below: WATER QUALITY SYSTEM (PART E) Water quality treatment will be required, as the turf playfield surfaces will exceed the threshold of ¾ acre of new/replaced pollution-generating pervious surface (PGPS). All other hard surfaces are non-pollution-generating. Because the school is considered a commercial site, enhanced water quality treatment will be required. Due to site LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 15 conditions, the project proposes utilizing a Modular Wetland System, which has GULD approval for enhanced treatment from the Department of Ecology. The Modular Wetland System will be downstream of detention, and thus per section 6.2.1 of the Renton SWDM, the full 2-year release rate form the detention facility shall be used as the water quality design flow. Per Contech Engineered Solutions (manufacturer), this will require a 4’x8’ modular wetland system. This facility has been incorporated into the drainage design and will treat any polluted water prior to discharge to the existing storm system. 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN For this project, conveyance analysis of the new pipe system is required, in accordance with section 1.2.4.1 of the KCSWDM. The new pipe system must have sufficient capacity to convey and contain (at minimum) the 25-year peak flow for the tributary areas of the developed condition. Per Table 3.2 of the KCSWDM, the Rational Method or MGS Flood (Approved Model) is allowable for use in the conveyance analysis, as the tributary area is less than 10 acres, and the majority of tributary area is detained. The method used to analyze the stormwater conveyance capacity for the proposed site development uses the Rational Method to estimate peak flows to the inlets (catch basins, trench drains, etc.) and the Continuity Equation/Manning’s Formula to determine the required size of pipe. The continuity equation is shown below: Q = A × V Where: Q = flow rate (ft3/s) A = cross-sectional area of conveyance pipe (ft2) V = velocity of flow in pipe, derived from Manning’s Formula (ft/s) Manning’s Formula: Manning’s equation is used to estimate flows through channels and is based on the assumption of uniform flow, where flow, depth, area of cross-section, velocity of flow, and discharge are the same at every section of the pipe segment. The formula can be derived by equating the propulsive force due to the weight of water in the direction of flow with the retarding shear force at the pipe boundary. This empirical formula is shown below: 𝑉=1.486 𝑛𝑅2/3𝑅1/2 Where: V = velocity of flow (ft/s) n = roughness coefficient R = hydraulic radius (ft) S = slope of pipe (ft/ft) Once the velocity of flow is found in the pipe using Manning’s Formula, the continuity equation is used to calculate the flow rate for each pipe. Rational Method: The Rational Method refers to a method of computing peak storm water flows from small urban watersheds. The method is an empirical approach, derived from storm water observations and tests. The basic equation of the rational method has the form: QR = C × IR × A Where: QR = peak rate of flow (ft3/s) for storm frequency (R) C = runoff coefficient IR = peak rainfall intensity (in/hr) for storm frequency (R) A = drainage basin area (ac) LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 16 The runoff coefficient, C, is a highly critical element that serves the function of converting the average rainfall rate of a particular recurrence interval to the peak runoff intensity of the same frequency. Therefore, it accounts for many complex phenomena in the runoff process. Its magnitude will be affected by antecedent moisture conditions, ground slope, ground cover, depression storage, soil moisture, shape of drainage area, overland flow velocity, intensity of rain, and so on. Yet its value is considered fixed for any drainage area, depending only on the surface type. Values of the coefficient are given below in Table 7: TABLE 7 – TYPICAL RUNOFF COEFFICIENTS Land Cover C Value Dense Forest 0.10 Light Forest 0.15 Pasture 0.20 Lawns 0.25 Playgrounds 0.30 Gravel Areas 0.80 Pavement and Roofs 0.90 Open Water 1.00 For an area having different types of surfaces, a composite coefficient is determined by estimating the fraction of each type of surface within the total area, multiplying each fraction by the appropriate coefficient of that type of surface, and then summing the products for all types of surfaces. The coefficients are selected to reflect the conditions that are expected at the end of the design period. The drainage basin area, A, represents the drainage area for a site under consideration. For a natural system it represents the watershed. For a storm system network, it is the area tributary to a point of inlet, such as a catch basin or downspout. If a system consists of several inlets and pipes, the complete area is sub-dived into component parts separating a tributary area to each inlet point of every storm system segment, or pipe. For this project, each sub-basin for the existing system that is being intercepted, as well as new stormwater infrastructure, was outlined and delineated by surface type to find a composite C value for each subbasin. See Figure 10 – Catchment Areas and Appendix B for subbasin C Value calculations. Rainfall intensity, IR, is dependent on the duration of rainfall (short duration storms are more intense) and the storm frequency (or recurrence interval). The peak rainfall intensity IR for the specified design storm of return frequency R is determined using a unit peak rainfall intensity factor IR in the following equation: Where: IR = rainfall intensity (in/hr) for storm frequency (R) PR = total precipitation at project site for 24-hour duration storm event for the given return frequency iR = unit peak rainfall intensity factor The unit peak rainfall intensity factor is found by this equation: Where: aR, bR = coefficients used to adjust the equation for the design storm return frequency (R) LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 17 Tc = time of concentration (minutes) The values for constants aR and bR are shown in Table 8 below: TABLE 8 – COEFFICIENTS FOR THE RATIONAL METHOD “IR” EQUATION Design Storm Return Frequency aR bR 2-year 1.58 0.58 5-year 2.33 0.63 10-year 2.44 0.64 25-year 2.66 0.65 50-year 2.75 0.65 100-year 2.61 0.63 Time of concentration, Tc, is defined as the time required for rainfall from the hydraulically most remote part of the drainage basin to reach the point of reference (or inlet). Since rainfall intensity reduces with increase in storm duration, the duration should be as short as possible. However, if the rainfall duration is less than Tc, then only a part of the drainage area will be contributing to the runoff. For an entire area to contribute, the shortest storm duration should equal Tc. Thus, the time of concentration is used as a unit duration for which rainfall intensity is determined. In storm system design, in addition to the time required for the rain falling on the most remote point of the tributary area to flow across the ground surface, along streets, and gutters, to the point of entry into the storm system, the time of flow through the storm pipe is also important. The surface runoff and subsurface storm pipe flow times are added together when computing the capacity for the downstream system. Due to the mathematical limits of the peak rainfall intensity equation coefficients, values of Tc less than 6.3 minutes or greater than 100 minutes cannot be used. Therefore, real values of Tc less than 6.3 minutes must be assumed to be equal to 6.3 minutes, and values greater than 100 minutes must be assumed to be equal to 100 minutes. See Appendix B – Engineering Calculations for the 25-year, 24-hour storm and 100-year, 24-hour storm conveyance and backwater analysis results. 6. SPECIAL REPORTS AND SUMMARY Please refer to the past geotechnical report from the prior field improvements project. The Subsurface Exploration and Geotechnical Engineering Report by Associated Earth Sciences, dated January 8, 2000, attached in Appendix A. 7. OTHER PERMITS This project will involve more than one acre of land disturbance, and therefore a Department of Ecology Construction Stormwater General Permit (NPDES) will be required. This will be permitted directly through the Department of Ecology. Building permits will be required for fences over 6 feet in height and for the proposed stairs. There are no retaining walls over 4 feet in height requiring building permits. 8. CSWPP ANALYSIS AND DESIGN This section and the SWPPP narrative in Appendix D will accompany the erosion sedimentation control plan in the project drawings to address the requirements of the SWPPP. The project will be publicly bid and a sub-contractor, LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 18 an earthwork and utility contractor will be determined at a future date, who will implement the TESC measures for the project during construction. 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. Silt fence will be used to prevent sediment-laden water from discharging from the site. 4. Traffic Area Stabilization – The existing driveways at the north and south end of the field area can be utilized for construction access. The area east of the softball field can be utilized for staging and laydown. 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 – Inlet protection will also be installed in all existing and new drain structures and remain until the site is stabilized. Sediment settling tanks will be used to discharge clean stormwater from the construction site. 6. Surface Water Collection – Interceptor swales will be used in the appropriate areas of the site to collect stormwater runoff, as necessary. Construction stormwater will be collected within a sump and pumped to the sediment settling facility. 7. Dewatering Control – Dewatering is not anticipated to be necessary for this site. Should dewatering become necessary, a sump and pump shall be used to within the excavation and water shall be pumped to the sediment settling facility. 8. Dust Control – Dry soils will be appropriately sprinkled with water to limit airborne dust during dry weather. 9. Flow Control – The TESC design proposed utilizing sediment settling tank(s) to control flow rates of sediment-laden stormwater from the site. The volume of tanks was determined based on the site area and sediment trap sizing outlined by the Renton SWDM. 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 excavation for the detention facility will be protected with silt fence or high-visibility construction fencing to avoid damage or over-compaction from construction or pedestrian traffic. 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. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 19 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. 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT BOND QUANTITIES WORKSHEET A bond quantities worksheet is included in Appendix E. FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH A Facility Summary Sheet has been completed for the project and is included in Appendix E. DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND WQ FACILITIES A draft Declaration of Covenant has been included in Appendix E for City review and will be recorded prior to permit issuance. 10. OPERATIONS AND MAINTENANCE MANUAL As stated in the Renton Surface Water Design Manual (RSWDM), the owner (Renton School District) will maintain all privately owned facilities. Sections of the RSWDM outlining the operations and maintenance of these facilities, along with maintenance manuals from proposed proprietary products, are included in Appendix D of this report. LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS 20 11. FIGURES FIGURE 1 – TIR WORKSHEET FIGURE 2 – VICINITY MAP FIGURE 3 – EXISTING CONDITIONS FIGURE 4 – EXISTING IMPERVIOUS COVERAGE FIGURE 5 – SOILS MAP FIGURE 6 – PROJECT MINIMUM REQUIREMENTS FLOW CHART FIGURE 7 – DOWNSTREAM DRAINAGE FIGURE 8 – NEW + REPLACED IMPERVIOUS AREAS FIGURE 9 – FLOW CONTROL BASINS FIGURE 10 – CATCHMENT AREAS Renton School District (425) 204-2300 300 Southwest 7th Street, Renton, WA 98057 Alan Jacobson Jacobson Consulting Engineers (206) 426-2600 Lindbergh High School Field Improvements 23N 5E 28 16426 128th Ave SE, Renton, WA 98058 Civil Construction Permit N/A 02/19/2025 FIGURE 1: TIR WORKSHEET 02/19/2025 C25000977 04/18/2025 04/18/2025 06/06/202506/06/2025 N/A N/A N/A Cedar River N/A FIGURE 1: TIR WORKSHEET N/A 15-40% AgC 8% - 15%Moderate Fields (NW site) 1 N/A TBD TBD TBD Flow Control Duration Standard FIGURE 1: TIR WORKSHEET AmC 6% - 15%Moderate TBD Compost Amended Soil BMP T5.13 N/A N/A N/A FIGURE 1: TIR WORKSHEET StormTech Chambers BMP T5.13 FIGURE 1: TIR WORKSHEET Modular Wetland N/A Stormwater DOC FIGURE 1: TIR WORKSHEET 06/06/2025 PROJECT SITE FIGURE 2 - VICINITY MAP SCALE: NTS SE 164TH ST 12 8 T H A V E S E FIGURE 3: EXISTING CONDITIONS SCALE 1" = 80' 0 40 80 160 TOTAL SITE AREA 220,025 sf IMPERVIOUS % 68.6% 12 8 T H A V E N U E S E EXISTING CONDITIONS Description Quantity Unit Impervious Area 150,866 sf Pervious Area 69,159 sf 4,800 400 FIGURE 4: EXISTING IMPERVIOUS COVERAGE SCALE 1" = 200' 0 100 200 400 IMPERVIOUS COVERAGE Description Quantity Unit Existing Impervious 921,229 sf Existing Pervious 657,781 sf Total Site Area 1,657,115 sf % Impervious 56.78% 1,622,480 701,251 FIGURE 5 - SOILS MAP 9 Custom Soil Resource Report Soil Map (Lindbergh High School) 52 5 5 6 5 0 52 5 5 7 3 0 52 5 5 8 1 0 52 5 5 8 9 0 52 5 5 9 7 0 52 5 6 0 5 0 52 5 6 1 3 0 52 5 6 2 1 0 52 5 5 6 5 0 52 5 5 7 3 0 52 5 5 8 1 0 52 5 5 8 9 0 52 5 5 9 7 0 52 5 6 0 5 0 52 5 6 1 3 0 52 5 6 2 1 0 52 5 6 2 9 0 562540 562620 562700 562780 562860 562940 563020 562620 562700 562780 562860 562940 563020 47° 27' 25'' N 12 2 ° 1 0 ' 1 3 ' ' W 47° 27' 25'' N 12 2 ° 9 ' 4 9 ' ' W 47° 27' 4'' N 12 2 ° 1 0 ' 1 3 ' ' W 47° 27' 4'' N 12 2 ° 9 ' 4 9 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 150 300 600 900 Feet0 45 90 180 270 MetersMap Scale: 1:3,140 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI AgC Alderwood gravelly sandy loam, 8 to 15 percent slopes 33.1 86.6% AmC Arents, Alderwood material, 6 to 15 percent slopes 1.8 4.7% EvC Everett very gravelly sandy loam, 8 to 15 percent slopes 3.0 7.9% Ur Urban land 0.3 0.9% Totals for Area of Interest 38.3 100.0% MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: King County Area, Washington Survey Area Data: Version 20, Aug 27, 2024 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 31, 2022—Aug 8, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. FIGURE 6: PROJECT MINIMIMUM REQUIREMENTS FLOW CHART FIGURE 8: DOWNSTREAM DRAINAGE SCALE: NTS PROJECT SITE 1 2 3 4 5 SURFACE WATER FACILITY: WETLAND 0.61 MI DOWNSTREAM 0.25 MI DOWNSTREAM DISCHARGE POINT CONTINUES TO GINGER GREEK AND ULTIMATELY TO THE CEDAR RIVER PROJECT SITE 6 SCALE 1" = 80' 0 40 80 160 FIGURE 8: NEW AND REPLACED IMPERVIOUS AREAS New Plus Replaced Hard Surface Description Quantity Unit Concrete Paving 5,176 sf Roof 5,857 sf Underdrained Field 137,493 sf Total New Plus Replaced Hard Surface (Target Surface) 149,769 sf 12 8 T H A V E N U E S E SE 166TH STREET SE 167TH STREET 12 8 T H A V E N U E S E 405 404.5 404 403.5 43 0 42 9 . 5 429 New Plus Replaced Hard Surface Description Quantity Unit Concrete Paving 7,796 sf Roof 1,480 sf Underdrained Field 137,493 sf FIGURE 9: FLOW CONTROL BASINS SCALE 1" = 80' 0 40 80 160 Forested - Flat 3.369 ac Sidewalk - Flat 0.112 ac Lawn - Flat 0.210 ac Lawn - Steep 0.101 ac Predeveloped Basin Total 3.792 ac Total 3.690 ac Total 0.102 ac Bypass Basin Description Quantity Unit Roof (Bypass)0.026 ac Sidewalk - Flat (Bypass)0.047 ac Sidewalk - Moderate (Bypass)0.029 ac Detention Basin Description Quantity Unit Ex Impervious to Detention (Sidewalk - Flat) 0.113 ac Lawn - Flat 0.210 ac Lawn - Steep 0.101 ac Roof 0.008 ac Sidewalk - Flat 3.258 ac 12 8 T H A V E N U E S E SE 166TH STREET SE 167TH STREET 12 8 T H A V E N U E S E 405 404.5 404 403.5 43 0 42 9 . 5 429 FIGURE 10: CATCHMENT AREAS CATCHMENT AREAS Description Quantity Unit EX 1 - LAWN 873 sf EX 1 - PAVEMENT 271 sf EX 2 - LAWN 570 sf EX 2 - PAVEMENT 1,473 sf EX 2 - ROOF 372 sf EX 3 - LAWN 2,172 sf EX 3 - PAVEMENT 1,130 sf EX 4 - LAWN 2,910 sf EX 4 - PAVEMENT 1,245 sf EX 5 - LAWN 504 sf EX 5 - PAVEMENT 155 sf EX 5 - ROOF 2,130 sf EX 6 - LAWN 1,020 sf EX 6 - PAVEMENT 42,121 sf EX 6 - ROOF 2,256 sf EX 7 - LAWN 2,465 sf EX 7 - PAVEMENT 727 sf EX 8 - LAWN 2,046 sf EX 8 - PAVEMENT 407 sf SD 1 - LAWN 49 sf SD 1 - PAVEMENT 1,044 sf SD 2 & 3 - PAVEMENT 95,626 sf 405 404.5 404 403.5 43 0 42 9 . 5 429 EX #1 EX #2 EX #3 EX #4 EX #5 EX #6 EX #6 EX #7 EX #8 SD #1 SD #2 & #3 SCALE 1" = 80' 0 40 80 160 LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS APPENDIX A GEOTECHNICAL REPORT LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS APPENDIX B STORMWATER CALCULATIONS ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 06/05/2025 11:26 AM Report Generation Date: 06/05/2025 11:33 AM ————————————————————————————————— Input File Name: Lindbergh HS - Detention.fld Project Name: Lindbergh High School Analysis Title: Detention Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 15 Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 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) 3.792 3.792 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 3.792 3.792 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predeveloped ---------- -------Area (Acres) -------- C, Forest, Flat 3.360 C, Forest, Mod 0.009 FLOW CONTROL C, Lawn, Flat 0.210 C, Lawn, Steep 0.101 SIDEWALKS/FLAT 0.112 ---------------------------------------------- Subbasin Total 3.792 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 ---------- Subbasin : DETENTION BASIN ---------- -------Area (Acres) -------- C, Lawn, Flat 0.210 C, Lawn, Steep 0.101 ROOF TOPS/FLAT 0.008 SIDEWALKS/FLAT 3.371 ---------------------------------------------- Subbasin Total 3.690 ---------- Subbasin : BYPASS ---------- -------Area (Acres) -------- ROOF TOPS/FLAT 0.026 SIDEWALKS/FLAT 0.047 SIDEWALKS/MOD 0.029 ---------------------------------------------- Subbasin Total 0.102 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: StormTech MC-7200 Link Type: Structure Downstream Link Name: New Copy Lnk2 User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 395.25 0. 395.33 600. 395.42 1201. 395.50 1801. 395.58 2402. 395.67 3002. 395.75 3602. FLOW CONTROL 395.83 4203. 395.92 4803. 396.00 5404. 396.08 6721. 396.17 8034. 396.25 9346. 396.33 10654. 396.42 11960. 396.50 13263. 396.58 14562. 396.67 15860. 396.75 17152. 396.83 18443. 396.92 19728. 397.00 21010. 397.08 22289. 397.17 23564. 397.25 24832. 397.33 26096. 397.42 27357. 397.50 28611. 397.58 29860. 397.67 31103. 397.75 32340. 397.83 33571. 397.92 34797. 398.00 36014. 398.08 37226. 398.17 38430. 398.25 39628. 398.33 40816. 398.42 41998. 398.50 43170. 398.58 44335. 398.67 45490. 398.75 46637. 398.83 47772. 398.92 48899. 399.00 50015. 399.08 51121. 399.17 52215. 399.25 53296. 399.33 54366. 399.42 55423. 399.50 56467. 399.58 57496. 399.67 58512. 399.75 59511. 399.83 60494. 399.92 61458. 400.00 62403. 400.08 63331. 400.17 64235. 400.25 65117. 400.33 65972. 400.42 66794. FLOW CONTROL 400.50 67581. 400.58 68307. 400.67 68986. 400.75 69648. 400.83 70294. 400.92 70927. 401.00 71538. 401.08 72138. 401.17 72738. 401.25 73339. 401.33 73939. 401.42 74540. 401.50 75140. 401.58 75740. 401.67 76341. 401.75 76941. 401.83 77542. 401.92 78142. 402.00 78742. 402.08 79343. 402.17 79943. 402.25 80544. 402.33 81144. 402.42 81744. 402.50 82345. Constant Infiltration Option Used Infiltration Rate (in/hr): 0.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 402.00 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 396.00 Diameter (in) : 1.06 Orientation : Horizontal Elbow : No --- Device Number 2 --- Device Type : Vertical Rectangular Orifice Control Elevation (ft) : 400.75 Length (in) : 0.25 Height (in) : 15.00 Orientation : Vertical Elbow : No ------------------------------------------ FLOW CONTROL Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 2 Number of Links: 2 ********** Subbasin: DETENTION BASIN ********** Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.354 5-Year 1.733 10-Year 2.016 25-Year 2.633 50-Year 3.255 100-Year 3.959 200-Year 4.178 500-Year 4.461 ********** Subbasin: BYPASS ********** Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 4.173E-02 5-Year 5.510E-02 10-Year 6.519E-02 25-Year 8.377E-02 50-Year 0.100 100-Year 0.124 200-Year 0.134 500-Year 0.147 ********** Link: StormTech MC-7200 ********** Link Inflow Frequency Stats Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.354 FLOW CONTROL 5-Year 1.733 10-Year 2.016 25-Year 2.633 50-Year 3.255 100-Year 3.959 200-Year 4.178 500-Year 4.461 ********** Link: StormTech MC-7200 ********** Link Outflow 1 Frequency Stats Flood Frequency Data (cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 4.603E-02 5-Year 5.572E-02 10-Year 6.370E-02 25-Year 7.964E-02 50-Year 0.112 100-Year 0.197 200-Year 0.276 500-Year 0.381 ********** Link: StormTech MC-7200 ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 397.433 1.11-Year 397.571 1.25-Year 397.762 2.00-Year 398.331 3.33-Year 398.800 5-Year 399.415 10-Year 400.463 25-Year 401.098 50-Year 401.571 100-Year 402.015 ********** 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 7.159E-02 5-Year 9.153E-02 10-Year 0.101 25-Year 0.118 50-Year 0.149 FLOW CONTROL 100-Year 0.203 200-Year 0.283 500-Year 0.389 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predeveloped 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 0.114 2-Year 7.159E-02 5-Year 0.185 5-Year 9.153E-02 10-Year 0.249 10-Year 0.101 25-Year 0.319 25-Year 0.118 50-Year 0.375 50-Year 0.149 100-Year 0.444 100-Year 0.203 200-Year 0.556 200-Year 0.283 500-Year 0.705 500-Year 0.389 ** 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%): -43.1% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -43.1% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -83.3% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- FLOW CONTROL MWS Sizing Letter 12901 SE 97th Ave, Suite 400. Clackamas, OR 97015 Toll-free: 800.548.4667 Fax: 800.561.1271 ©2012 Contech Engineered Solutions LLC www.conteches.com Page 1 of 1 TS-P027 Prepared by Baylee Koski on April 4, 2025 Lindbergh High School Baseball/Softball Field Improvements Renton, WA This unit is sized as MWS-L-4-8-V-UG Structure ID SD A9 Water Quality Flow Rate (cfs) 0.067 Peak Flow Rate (cfs) 0.235 Pre-Filter cartridges 1 Loading Rate (Pre-Filter) (gpm/sq ft) 1.23 Loading Rate (Wetland Media) (gpm/sf) 1.0 Operating Head 2.06 Weir Height Above outlet (ft) 2.25 Additional Information provided: Rim to Outlet Elevation- 9.71’ Internal Bypass H-20 Loading The Modular Wetlands System (MWS) Linear units for this project are sized in accordance with the Washington State Technological Assessment Protocol – Ecology (TAPE) General Use Level Designation (GULD) approval. The MWS wetland media is approved at a loading rate of less or equal to 1 gpm/sq ft of surface area, and the prefilters are approved at a loading rate of 2.1 gpm/sq ft or less of surface area. The MWS Linear has GULD designation at these loading rates for total suspended solids (basic), phosphorous, and dissolved metals (enhanced). For this project, the design, sizing, and loading are all confirmed by a Contech representative to ensure the systems are sized appropriately. Sub- Total Pavement Roof Lawn/Landscape Composite Basin Area Area Area Area C Value C=0.90 C=0.90 C=0.25 (Acres)(Sq. Ft.)(Sq. Ft.)(Sq. Ft.) EX 1 0.026 271 0 873 0.40 EX 2 0.055 1475 372 570 0.75 EX 3 0.076 1130 0 2172 0.47 EX 4 0.095 1245 0 2910 0.44 EX 5 0.064 155 2130 504 0.78 EX 6 1.036 42100 2256 752 0.89 EX 7 0.073 752 0 2439 0.40 EX 8 0.056 407 0 2046 0.36 SD 1 0.025 1044 0 49 0.87 SD 2 3.722 142669 5857 13584 0.85 SD 3 3.722 142669 5857 13584 0.85 Drainage Inlet Sub-Basin Areas Lindbergh High School Lindbergh High School Conveyance / Backwater Analysis 2/18/2025 CONVEYANCE SYSTEM ANALYSIS AND SIZING TABLE USING THE RATIONAL METHOD Location Sub Area C C*A Sum Tc i Q(R) Pipe Typ. Slope Q(F) V V L Tt % d/D Basin (ac) C*A (min.) (cfs) (in.) n (ft.ft.) (pipe (pipe (at (ft.) (min.)From To Number full)full)Q(R)) EX 1 EX 2 EX 1 0.026 0.40 0.01 0.01 6.3 2.01 0.02 6 0.011 0.5%0.47 2.39 5.81 66 0.19 0.89% EX 2 EX 3 EX 2 0.055 0.75 0.04 0.05 6.5 1.97 0.10 6 0.011 0.5%0.47 2.39 27.96 112 0.07 21.83% EX 3 EX 4 EX 3 0.076 0.47 0.04 0.09 6.6 1.96 0.17 6 0.011 0.5%0.47 2.39 2.16 52 0.40 36.62% EX 4 EX 5 EX 4 0.095 0.44 0.04 0.13 7.0 1.88 0.25 6 0.011 0.5%0.47 2.39 2.41 50 0.35 52.25% EX 5 EX 6 EX 5 0.064 0.78 0.05 0.18 7.3 1.83 0.33 6 0.011 0.5%0.47 2.39 2.62 50 0.32 70.09% EX 6 EX 7 EX 6 1.036 0.89 0.92 1.10 7.6 1.78 1.96 6 0.011 20.2%2.98 15.18 16.06 115 0.12 65.64% EX 8 EX 7 EX 8 0.056 0.36 0.02 0.02 6.3 2.01 0.04 6 0.011 0.5%0.47 2.39 11.04 34 0.05 8.62% EX 7 SD 1 EX 7 0.073 0.40 0.030 1.15 7.7 1.76 2.02 12 0.011 1.3%4.81 6.12 5.74 10 0.03 42.08% SD 1 Detention SD 1 0.025 0.87 0.02 1.17 7.8 1.75 2.06 12 0.011 1.6%5.34 6.80 6.18 125 0.34 38.53% SD 2 SD 3 SD 2 3.722 0.85 3.15 3.15 6.3 2.01 6.33 12 0.011 6.6%10.85 13.81 14.29 4 0.00 58.30% SD 3 EX 9 SD 3 3.722 0.85 3.15 3.15 6.30 2.01 6.32 12 0.011 6.6%10.85 13.81 14.28 46 0.05 58.27% Project: Lindbergh High School R= 25 yr Calcs by: EMD Job No: C240004-0215 Location:Renton, WA Date:Page 12/19/2025 Lindbergh High School Conveyance Analysis - 25 Year 2/19/2025 Backwater Analysis Table Proposed Site Conditions 25-Yr Backwater Backwater Mannings Coefficient 0.011 Q L Diameter TYP Outlet Inlet Barrel Barrel Velocity Excel Critical TW Friction HGL Entry Entry Exit Outlet Headwater Inlet Approach Bend Bend Junction Headwater Rim Elev. O.K.?Downstream Upstream (cfs) (FT) (in). n Elev Elev Area Velocity Head Check Depth Elev Loss Elev Coef Loss Loss Control Depth Control Head Coefficient Loss Loss Elevation Difference Q L D n ELVO ELVI A V H dc TW Floss HGL Ke ENLoss Eloss Eloc HW/D Elic Hv Kb Bl Junc HW Rim HGL EX 9 SD 3 6.32 46 12 0.011 389.15 392.28 0.79 8.05 1.01 1.00 0.96 392.76 1.03 393.79 0.50 0.50 1.01 395.30 2.13 394.41 -1.01 0.00 0.00 0.30 394.59 401.55 6.96 yes SD 3 SD 2 6.33 4 12 0.011 395.53 395.75 0.79 8.05 1.01 1.00 0.96 394.59 0.09 396.53 0.50 0.50 1.01 398.04 2.13 397.88 -1.01 0.00 0.00 0.50 397.53 403.73 6.20 yes Detention SD 1 2.06 125 12 0.011 402.13 400.05 0.79 2.62 0.11 1.00 0.61 401.55 0.30 403.13 0.50 0.05 0.11 403.29 1.00 401.05 -0.11 0.60 0.06 0.00 403.25 405.30 2.05 yes SD 1 EX 7 2.02 10 12 0.011 402.26 402.13 0.79 2.58 0.10 1.00 0.61 403.25 0.02 403.27 0.50 0.05 0.10 403.42 0.99 403.12 -0.10 0.00 0.00 0.16 403.48 404.50 1.02 yes EX 7 EX 8 0.04 34 6 0.011 402.30 402.13 0.20 0.21 0.00 1.00 0.10 402.63 0.00 402.80 0.50 0.00 0.00 402.80 0.29 402.28 0.00 0.00 0.00 0.00 402.80 404.30 1.50 yes EX 7 EX 6 1.96 115 6 0.011 424.70 402.13 0.20 9.96 1.54 1.00 0.50 403.48 9.88 425.20 0.50 0.77 1.54 427.51 4.88 404.57 -1.54 0.00 0.00 0.30 426.27 427.90 1.63 yes EX 6 EX 5 0.33 50 6 0.011 425.30 425.05 0.20 1.68 0.04 1.00 0.29 426.27 0.12 426.39 0.50 0.02 0.04 426.46 0.94 425.52 -0.04 0.00 0.00 0.00 426.41 427.90 1.49 yes EX 5 EX 4 0.25 50 6 0.011 425.55 425.30 0.20 1.25 0.02 1.00 0.25 415.17 0.07 426.05 0.50 0.01 0.02 426.09 0.79 425.70 -0.02 0.00 0.00 0.00 426.06 428.00 1.94 yes EX 4 EX 3 0.17 52 6 0.011 425.81 425.55 0.20 0.88 0.01 1.00 0.21 415.17 0.03 426.31 0.50 0.01 0.01 426.33 0.64 425.87 -0.01 1.00 0.01 0.00 426.33 428.50 2.17 yesEX 3 EX 2 0.10 112 6 0.011 426.37 425.81 0.20 0.52 0.00 1.00 0.16 426.33 0.03 426.87 0.50 0.00 0.00 426.88 0.48 426.05 0.00 0.00 0.00 0.00 426.87 428.70 1.83 yesEX 2 EX 1 0.02 66 6 0.011 426.70 426.37 0.20 0.11 0.00 1.00 0.07 426.87 0.00 427.20 0.50 0.00 0.00 427.20 0.21 426.47 0.00 0.00 0.00 0.00 427.20 428.70 1.50 yes Lindbergh High School Location Lindbergh High School Backwater Analysis - 25-Year 2/19/2025 CONVEYANCE SYSTEM ANALYSIS AND SIZING TABLE USING THE RATIONAL METHOD Location Sub Area C C*A Sum Tc i Q(R) Pipe Typ. Slope Q(F) V V L Tt % d/D Basin (ac)C*A (min.)(cfs)(in.)n (ft.ft.)(pipe (pipe (at (ft.)(min.)From To Number full)full)Q(R)) EX 1 EX 2 EX 1 0.026 0.40 0.01 0.01 6.3 3.03 0.03 6 0.011 0.5%0.47 2.39 8.75 66 0.13 6.84% EX 2 EX 3 EX 2 0.055 0.75 0.04 0.05 6.4 2.99 0.16 6 0.011 0.5%0.47 2.39 2.12 112 0.88 33.12% EX 3 EX 4 EX 3 0.076 0.47 0.04 0.09 7.3 2.76 0.24 6 0.011 0.5%0.47 2.39 2.38 52 0.36 51.57% EX 4 EX 5 EX 4 0.095 0.44 0.04 0.13 7.7 2.68 0.35 12 0.011 0.5%2.99 3.81 23.74 50 0.04 11.66% EX 5 EX 6 EX 5 0.064 0.78 0.05 0.18 7.7 2.67 0.48 12 0.011 0.5%2.99 3.81 32.78 50 0.03 16.10% EX 6 EX 7 EX 6 1.036 0.89 0.92 1.10 7.7 2.66 2.93 6 0.011 20.2%2.98 15.18 17.51 115 0.11 98.38% EX 8 EX 7 EX 8 0.056 0.40 0.02 0.02 6.3 3.03 0.07 6 0.011 0.5%0.47 2.39 18.74 34 0.03 14.63% EX 7 SD 1 EX 7 0.073 0.36 0.03 1.15 7.8 2.66 3.05 12 0.011 1.3%4.81 6.12 6.40 10 0.03 63.50% SD 1 Detention SD 1 0.025 0.87 0.02 1.30 7.8 2.65 3.45 12 0.011 1.7%5.45 6.94 7.31 125 0.29 63.33% SD 2 SD 3 SD 2 3.722 0.85 3.15 3.15 6.3 3.03 9.53 12 0.011 6.6%10.85 13.81 15.63 4 0.00 87.84% SD 3 EX 9 SD 3 3.722 0.85 3.15 3.15 6.3 3.03 9.53 12 0.011 6.6%10.85 13.81 15.62 46 0.05 87.80% Project:Lindbergh High School R=100 yr Calcs by:EMD Job No:C240004-0215 Location:Renton, WA Date:Page 32/19/2025 Lindbergh High School Conveyance Analysis - 100 Year 2/19/2025 Backwater Analysis Table Proposed Site Conditions 100-Yr Backwater Backwater Mannings Coefficient 0.011 Q L Diameter TYP Outlet Inlet Barrel Barrel Velocity Excel Critical TW Friction HGL Entry Entry Exit Outlet Headwater Inlet Approach Bend Bend Junction Headwater Rim Elev. O.K.? Downstream Upstream (cfs) (FT) (in). n Elev Elev Area Velocity Head Check Depth Elev Loss Elev Coef Loss Loss Control Depth Control Head Coefficient Loss Loss Elevation Difference Q L D n ELVO ELVI A V H dc TW Floss HGL Ke ENLoss Eloss Eloc HW/D Elic Hv Kb Bl Junc HW Rim HGL EX 9 SD 3 9.53 46.00 12 0.011 389.15 392.28 0.79 12.13 2.28 1.00 0.99 392.76 2.33 395.09 0.50 1.14 2.28 398.52 3.74 396.02 -2.28 0.0 0.00 0.30 396.53 401.55 5.02 yes SD 3 SD 2 9.53 4.00 12 0.011 395.53 395.75 0.79 12.13 2.29 1.00 0.99 396.53 0.20 396.74 0.50 1.14 2.29 400.17 3.75 399.50 -2.29 0.0 0.00 0.50 398.38 403.73 5.35 yes Detention SD 1 3.45 125.00 12 0.011 402.13 396.08 0.79 4.39 0.30 1.00 0.79 402.03 0.83 403.13 0.50 0.15 0.30 403.58 1.29 397.37 -0.30 0.6 0.18 0.00 403.46 405.5 2.04 yes SD 1 EX 7 3.05 10.00 12 0.011 402.26 402.13 0.79 3.89 0.23 1.00 0.75 403.46 0.05 403.51 0.50 0.12 0.23 403.86 1.29 403.42 -0.23 0.0 0.00 0.16 403.79 404.5 0.71 yes EX 7 EX 8 0.07 34.00 6 0.011 402.30 402.13 0.20 0.35 0.00 1.00 0.13 402.63 0.00 402.80 0.50 0.00 0.00 402.80 0.39 402.32 0.00 0.0 0.00 0.00 402.80 404.3 1.50 yes EX 7 EX 6 2.93 115.00 6 0.011 424.70 402.13 0.20 14.93 3.46 1.00 0.50 403.79 22.20 425.99 0.50 1.73 3.46 431.19 9.73 406.99 -3.46 0.0 0.00 0.30 428.02 428.01 -0.01 no EX 6 EX 5 0.48 50.00 6 0.011 425.30 425.05 0.20 2.45 0.09 1.00 0.35 428.02 0.26 428.29 0.50 0.05 0.09 428.43 1.19 425.65 -0.09 0.0 0.00 0.00 428.33 428.15 -0.18 noEX 5 EX 4 0.35 50.00 6 0.011 425.55 425.30 0.20 1.78 0.05 1.00 0.30 415.79 0.14 426.05 0.50 0.02 0.05 426.12 0.97 425.79 -0.05 0.0 0.00 0.00 426.07 427.98 1.91 yesEX 4 EX 3 0.24 52.00 6 0.011 425.81 425.55 0.20 1.23 0.02 1.00 0.25 426.07 0.07 426.31 0.50 0.01 0.02 426.35 0.78 425.94 -0.02 1.0 0.02 0.00 426.35 428.86 2.51 yes EX 3 EX 2 0.16 112.00 6 0.011 426.37 425.81 0.20 0.79 0.01 1.00 0.20 426.35 0.06 426.87 0.50 0.00 0.01 426.88 0.61 426.11 -0.01 0.0 0.00 0.00 426.87 429.53 2.66 yesEX 2 EX 1 0.03 66.00 6 0.011 426.70 426.37 0.20 0.16 0.00 1.00 0.09 426.87 0.00 427.20 0.50 0.00 0.00 427.20 0.26 426.50 0.00 0.0 0.00 0.00 427.20 429.13 1.93 yes Lindbergh High School Location Lindbergh High School Backwater Analysis - 100-Year 2/19/2025 TESC Sediment Trap Sizing (BMP C240) Total Site: Pervious Area Impervious Area Total Area 0.00 ac 1.08 ac 1.08 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 = 0.425 ft3/s Surface Area Calculation: SA = 2 (0.425 / 0.00096) SA = 886 ft2 VR = SA * 3.5 ft minimum storage depth VR = 886 * 3.5 VR = 3,101 ft3 Storage Volume Required VR = 3,101 ft3 * (7.48 gal/ 1 ft3) VR = 23,196 Gallons Required Volume Provided: (1) 18,900 Gallon & (1) 8,400 Gallon Sediment Storage Tanks V = 18,900 + 8,400 V = 27,300 Gallons Provided ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 12/05/2024 4:43 PM Report Generation Date: 12/05/2024 4:43 PM ————————————————————————————————— Input File Name: Softball Baker Tanks.fld Project Name: Lindbergh High School - Field Improvements Analysis Title: TESC Softball Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 15 Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 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) 1.080 1.080 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.080 1.080 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predeveloped ---------- -------Area (Acres) -------- C, Forest, Flat 1.080 ---------------------------------------------- TESC SEDIMENT SIZING - SOFTBALL FIELD Subbasin Total 1.080 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdeveloped ---------- -------Area (Acres) -------- ROADS/FLAT 1.080 ---------------------------------------------- Subbasin Total 1.080 **********************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 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predeveloped Scenario Postdeveloped Compliance Subbasin: Postdeveloped *** 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 2.293E-02 2-Year 0.425 5-Year 3.637E-02 5-Year 0.544 10-Year 4.701E-02 10-Year 0.629 25-Year 6.110E-02 25-Year 0.810 50-Year 6.741E-02 50-Year 1.014 100-Year 7.690E-02 100-Year 1.212 200-Year 0.106 200-Year 1.282 500-Year 0.145 500-Year 1.372 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals TESC SEDIMENT SIZING - SOFTBALL FIELD TESC Sediment Trap Sizing (BMP C240) Total Site: Pervious Area Impervious Area Total Area 0.00 ac 2.28 ac 2.28 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 = 0.898 ft3/s Surface Area Calculation: SA = 2 (0.898 / 0.00096) SA = 1,871 ft2 VR = SA * 3.5 ft minimum storage depth VR = 2,756.25 * 3.5 VR = 6,549 ft3 Storage Volume Required VR = 9,253 ft3 * (7.48 gal/ 1 ft3) VR = 48,983 Gallons Required Volume Provided: (2) 21,000 Gallon & (1) 8,400 Sediment Storage Tanks V = (2 * 18,900) + 8,400 V = 50,400 Gallons Provided ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 12/05/2024 4:38 PM Report Generation Date: 12/05/2024 4:39 PM ————————————————————————————————— Input File Name: Baseball Baker Tanks.fld Project Name: Lindbergh High School - Field Improvements Analysis Title: TESC Baseball Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 15 Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 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) 2.280 2.280 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.280 2.280 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predeveloped ---------- -------Area (Acres) -------- C, Forest, Flat 2.280 ---------------------------------------------- TESC SEDIMENT SIZING - BASEBALL FIELD Subbasin Total 2.280 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdeveloped ---------- -------Area (Acres) -------- ROADS/FLAT 2.280 ---------------------------------------------- Subbasin Total 2.280 **********************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 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predeveloped Scenario Postdeveloped Compliance Subbasin: Postdeveloped *** 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 4.841E-02 2-Year 0.898 5-Year 7.679E-02 5-Year 1.149 10-Year 9.924E-02 10-Year 1.328 25-Year 0.129 25-Year 1.709 50-Year 0.142 50-Year 2.141 100-Year 0.162 100-Year 2.559 200-Year 0.224 200-Year 2.706 500-Year 0.307 500-Year 2.897 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals TESC SEDIMENT SIZING - BASEBALL FIELD LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS APPENDIX C STORMWATER POLLUTION PREVENTION PLAN (SWPPP) Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan (SWPPP) for Lindbergh High School Field Improvements Prepared for: Renton School District and Project Contractor (TBD) Permittee / Owner Developer Operator / Contractor Renton School District Renton School District TBD 16426 128th Ave SE, Renton, WA, 98058 Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD TBD TBD SWPPP Prepared By Name Organization Contact Phone Number Alan Jacobson Jacobson Consulting Engineers Office: (206) 426-2600 SWPPP Preparation Date June 6, 2025 Project Construction Dates Activity / Phase Start Date End Date Sitework 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: Lindbergh High School Field Improvements Street/Location: 16426 128th Ave SE City: Renton State: WA Zip code: 98058 Subdivision: N/A Receiving waterbody: Ginger Creek/Cedar River 1.1 Existing Conditions Lindbergh High School is a developed campus that is located on one parcel (2823059004), totaling 37.25 acres. The school consists of a single primary school building on the north side of the campus, parking and drive areas on all sides of the building, a baseball field and a softball field to the west, a natatorium to the south, tennis courts south of the natatorium, a track and field to the southeast, and landscaping around the property perimeter and in the parking lots. The main building is surrounded by low landscaping and concrete sidewalks. Total acreage: 37.25 acres Disturbed acreage: 5.73 acres Landscape topography: In general, the site topography of Lindbergh High School around the proposed project work scope is moderate at roughly 1%-3% slopes within the existing baseball and softball fields, and 10%- 20% within the surrounding landscaped areas. Drainage patterns: The TDA consists of the existing baseball field and softball field, which are both underdrained and routed into the existing piped system in the parking lot east of the project site. The conveyance system goes west, entering the municipal system within 128th Ave SE, near the northwest corner of the school property. Stormwater goes north, west, and north again for about 0.6 miles until it ultimately discharges into an existing wetland. Runoff ultimately makes its way to Ginger Creek and then to Cedar River. Existing Vegetation: The site is fully developed with small pockets of native vegetation surrounding the existing tennis courts and football field. These areas of native vegetation are not near the project site. Critical Areas: Sections of the property are considered protected slopes per City of Renton GIS and King County iMap. Additionally, there is a small Seismic Hazard Area on the southeast corner of the overall school site. There are no other critical areas. Page | 5 List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: The project eventually discharges to Ginger Creek and ultimately to the Cedar River, neither of which have any 303(d) listings per the Department of Ecology Water Quality Atlas. Table 1 below includes a list of suspected and/or known contaminants associated with the construction activity. Table 1 – Summary of Site Pollutant Constituents Constituent (Pollutant) Location Depth Concentration pH Newly installed concrete areas Surface N/A 1.2 Proposed Construction Activities Description of site development: Field Improvements are proposed and will consist of replacing the existing baseball and softball fields with synthetic turf fields, installing a detention system and refurbishing the existing subdrainage. New pavement will be installed for walking and access paths. Improvements will also include roofed dugouts, field lighting & striping, batting cages, and access paths. Description of construction activities (example: site preparation, demolition, excavation): The project will consist of site preparation, demolition, and temporary erosion & sedimentation control measures. Then there will be a sizable excavation for the detention system, and for maintenance of the underdrain system for the fields. Pavement and other field amenities will be installed, along with final landscaping measures. Description of site drainage including flow from and onto adjacent properties. Must be consistent with the Site Map in Appendix A: Stormwater will be collected via the field underdrain systems and routed to the proposed detention facility, which will be a StormTech chamber system. From here, runoff will be conveyed to a flow control structure, and then to a water quality facility, prior to connection to the existing on-site pipe system. Stormwater from both fields will be in the same threshold discharge area with stormwater eventually connecting to the existing City system on 128th Ave SE, leaving the site near the northwest corner of the property. Due to slopes around the perimeter of the field areas, as well as perimeter drainage systems to catch any potential run-on, there is no significant upstream area from adjacent areas contributing to the project site. Site drainage from the project will be controlled and will not flow onto adjacent properties. Page | 6 Description of final stabilization (example: extent of revegetation, paving, landscaping): At final stabilization, the project area located on the west side of the school’s campus will include new turf fields and associated paving. Landscaping will be restored around the fields. 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. Each field area can be accessed from their respective driveway areas, using quarry spall stabilized construction access going into the project site. The specific BMPs related to establishing construction access that will be used on this project include: • Stabilized Construction Entrance (BMP C105) Installation Schedules: BMP’s will be installed at the beginning of construction and be inspected and maintained throughout construction. Page | 9 2.1.3 Element 3: Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. The specific BMPs for flow control that shall be used on this project include: Will you construct stormwater retention and/or detention facilities? Yes Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? 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: • Interceptor Dike and Swale (BMP C200) • Check Dams (BMP C207) • Temporary Sediment Settling Tank 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: • Inlet Protection (BMP C220) • Silt Fence (BMP C233) • Temporary Sediment Settling Tank 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 neeed, 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: • 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 (summer 2025) End date: TBD (spring 2026) Will you construct during the wet season? No (for significant earthwork activities) Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. 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 There are steep slopes located between the two fields and north of the baseball field as well. The following specific BMPs will be used to protect slopes for this project: • Temporary and Permanent Seeding (BMP C120) • Mulching (BMP C121) • Nets and Blankets (BMP C122) • Plastic Covering (BMP C123) • Sodding (BMP C124) • Surface Roughening (BMP C130) • Gradient Terraces (BMP C131) • Interceptor Dike and Swale (BMP C200) Page | 13 2.1.7 Element 7: Protect Storm 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: • Inlet Protection (BMP C220) 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, and nor will any channels proposed as part of the redevelopment. 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: • 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 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 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). 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? No Will wheel wash or tire bath system BMPs be used during construction? 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. 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 Page | 17 X New concrete washing or curing waters X Waste streams generated from concrete grinding and sawing X Exposed aggregate processes Dewatering concrete vaults 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? No Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas with appropriate BMPs installed. • Materials on Hand (BMP C150) • Concrete Handling (BMP C151) • Sawcutting and Surfacing Pollution Prevention (BMP C152) • Material Delivery, Storage and Containment (BMP C153) • Concrete Washout Area (BMP C154) • Treating and Disposing of High pH Water (BMP C252) Page | 18 Installation Schedules: BMP’s will be implemented at the beginning of construction and be inspected and maintained throughout construction as required. 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 | 19 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 | 20 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 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 | 21 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 | 22 Table 6 – BMP Implementation Schedule Phase of Construction Project Stormwater BMPs Date Wet/Dry Season Page | 23 Phase of Construction Project Stormwater BMPs Date Wet/Dry Season Page | 24 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 | 25 3.0 Pollution Prevention Team Table 7 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) TBD Resident Engineer Alan Jacobson, Jacobson Consulting Engineers (206) 426-2600 Emergency Ecology Contact Andy Maher, Department of Ecology Pollution Prevention Team (509) 290-7806 Emergency Permittee/ Owner Contact Andrew Hollenback, Renton School District (425) 204-4437 Non-Emergency Owner Contact Matthew Feldmeyer, Renton School District (425) 204-4475 Monitoring Personnel TBD Ecology Regional Office Northwest Regional Office 425-649-7098 Page | 26 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: The receiving waterbody, Cedar River, is not impaired for the discharge point downstream of this project. All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su for pH and/or 25 NTU for turbidity. 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. Page | 27 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. 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). Page | 28 • 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. 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 | 29 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? 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 (Inlet Protection) 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 | 30 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 | 31 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 | 32 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 Appendix A – Site Map Appendix B – BMP Details Preserving Natural Vegetation (BMP C101) High-Visibility Fence (BMP C103) Stabilized Construction Access (BMP C105) Temporary and Permanent Seeding (BMP C120) Mulching (BMP C121) Nets and Blankets (BMP C122) Plastic Covering (BMP C123) Sodding (BMP C124) Surface Roughening (BMP C130) Gradient Terraces (BMP C131) 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) Interceptor Dike and Swale (BMP C200) Check Dams (BMP C207) Storm Drain Inlet Protection (BMP C220) Silt Fence (BMP C233) Straw Wattles (BMP C235) 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 burying and smothering vegetation. l Vegetative buffer zones for streams, lakes or other waterways shall be established by the local permitting authority or other state or federal permits or approvals. Maintenance Standards Inspect the area frequently to make sure flagging remains in place and the area remains undis- turbed. Replace all damaged flagging immediately. Remove all materials located in the buffer area that may impede the ability of the vegetation to act as a filter. BMP C103: High-Visibility Fence Purpose High-visibility fencing is intended to: l Restrict clearing to approved limits. l Prevent disturbance of sensitive areas, their buffers, and other areas required to be left undis- turbed. l Limit construction traffic to designated construction entrances, exits, or internal roads. l Protect areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits plastic, fabric, or metal fence may be used: l At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared. l As necessary to control vehicle access to and on the site. Design and Installation Specifications High-visibility plastic fence shall be composed of a high-density polyethylene material and shall be at least four feet in height. Posts for the fencing shall be steel or wood and placed every 6 feet on center (maximum) or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope shall be used as a top stringer to prevent sagging between posts. The fence color shall be high-visibility orange. The fence tensile strength shall be 360 lbs/ft using the ASTM D4595 testing method. If appropriate install fabric silt fence in accordance with BMP C233: Silt Fence to act as high-visibility fence. Silt fence shall be at least 3 feet high and must be highly visible to meet the requirements of this BMP. Metal fences shall be designed and installed according to the manufacturer's specifications. Metal fences shall be at least 3 feet high and must be highly visible. Fences shall not be wired or stapled to trees. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 274 Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. BMP C105: Stabilized Construction Access Purpose Stabilized construction accesses are established to reduce the amount of sediment transported onto paved roads outside the project site by vehicles or equipment. This is done by constructing a sta- bilized pad of quarry spalls at entrances and exits for project sites. Conditions of Use Construction accesses shall be stabilized wherever traffic will be entering or leaving a construction site if paved roads or other paved areas are within 1,000 feet of the site. For residential subdivision construction sites, provide a stabilized construction access for each res- idence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient length/width to provide vehicle access/parking, based on lot size and configuration. On large commercial, highway, and road projects, the designer should include enough extra mater- ials in the contract to allow for additional stabilized accesses not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and Installation Specifications See Figure II-3.1: Stabilized Construction Access for details. Note: the 100’ minimum length of the access shall be reduced to the maximum practicable size when the size or configuration of the site does not allow the full length (100’). Construct stabilized construction accesses with a 12-inch thick pad of 4-inch to 8-inch quarry spalls, a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed con- crete, cement, or calcium chloride for construction access stabilization because these products raise pH levels in stormwater and concrete discharge to waters of the State is prohibited. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the standards listed in Table II-3.2: Stabilized Con- struction Access Geotextile Standards. Geotextile Property Required Value Grab Tensile Strength (ASTM D4751)200 psi min. Table II-3.2: Stabilized Construction Access Geotextile Standards 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 275 Geotextile Property Required Value Grab Tensile Elongation (ASTM D4632)30% max. Mullen Burst Strength (ASTM D3786-80a)400 psi min. AOS (ASTM D4751)20-45 (U.S. standard sieve size) Table II-3.2: Stabilized Construction Access Geotextile Standards (continued) l Consider early installation of the first lift of asphalt in areas that will be paved; this can be used as a stabilized access. Also consider the installation of excess concrete as a stabilized access. During large concrete pours, excess concrete is often available for this purpose. l Fencing (see BMP C103: High-Visibility Fence) shall be installed as necessary to restrict traffic to the construction access. l Whenever possible, the access shall be constructed on a firm, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. l Construction accesses should avoid crossing existing sidewalks and back of walk drains if at all possible. If a construction access must cross a sidewalk or back of walk drain, the full length of the sidewalk and back of walk drain must be covered and protected from sediment leaving the site. Alternative Material Specification WSDOT has raised safety concerns about the Quarry Spall rock specified above. WSDOT observes that the 4-inch to 8-inch rock sizes can become trapped between Dually truck tires, and then released off-site at highway speeds. WSDOT has chosen to use a modified specification for the rock while continuously verifying that the Stabilized Construction Access remains effective. To remain effective, the BMP must prevent sediment from migrating off site. To date, there has been no per- formance testing to verify operation of this new specification. Jurisdictions may use the alternative specification, but must perform increased off-site inspection if they use, or allow others to use, it. Stabilized Construction Accesses may use material that meets the requirements of WSDOT's Stand- ard Specifications for Road, Bridge, and Municipal Construction Section 9-03.9(1) (WSDOT, 2016) for ballast except for the following special requirements. The grading and quality requirements are listed in Table II-3.3: Stabilized Construction Access Alternative Material Requirements. Sieve Size Percent Passing 2½″99-100 Table II-3.3: Stabilized Construction Access Alternative Material Requirements 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 276 Sieve Size Percent Passing 2″65-100 ¾″40-80 No. 4 5 max. No. 100 0-2 % Fracture 75 min. Table II-3.3: Stabilized Construction Access Alternative Material Requirements (continued) l All percentages are by weight. l The sand equivalent value and dust ratio requirements do not apply. l The fracture requirement shall be at least one fractured face and will apply the combined aggregate retained on the No. 4 sieve in accordance with FOP for AASHTO T 335. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the specifications. l If the access is not preventing sediment from being tracked onto pavement, then alternative measures to keep the streets free of sediment shall be used. This may include replace- ment/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of the access, or the installation of BMP C106: Wheel Wash. l Any sediment that is tracked onto pavement shall be removed by shoveling or street sweep- ing. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is inef- fective and there is a threat to public safety. If it is necessary to wash the streets, the con- struction of a small sump to contain the wash water shall be considered. The sediment would then be washed into the sump where it can be controlled. l Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high effi- ciency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches. l Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. l If vehicles are entering or exiting the site at points other than the construction access(es), BMP C103: High-Visibility Fence shall be installed to control traffic. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 277 l Upon project completion and site stabilization, all construction accesses intended as per- manent access for maintenance shall be permanently stabilized. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 278 Figure II-3.1: Stabilized Construction Access 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 279 NOT TO SCALE \eJSiO« 100' min. Install driveway culvert if there is a roadside ditch present 4" - 8" quarry spalls Geotextile i 15' min.Notes: 1. Driveway shall meet the requirements of the permitting agency. 12" minimum thickness Provide full width of ingress/egress area 2. It is recommended that the access be crowned so that runoff drains off the pad. Stabilized Construction Access Revised June 2018 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 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 C106: Wheel Wash Purpose Wheel washes reduce the amount of sediment transported onto paved roads by washing dirt from the wheels of motor vehicles prior to the motor vehicles leaving the construction site. Conditions of Use l Use a wheel wash when BMP C105: Stabilized Construction Access is not preventing sed- iment from being tracked off site. l Wheel washing is generally an effective BMP when installed with careful attention to topo- graphy. For example, a wheel wash can be detrimental if installed at the top of a slope abut- ting a right-of-way where the water from the dripping truck can run unimpeded into the street. l Pressure washing combined with an adequately sized and surfaced pad with direct drainage to a large 10-foot x 10-foot sump can be very effective. l Wheel wash wastewater is not stormwater. It is commonly called process water, and must be discharged to a separate on-site treatment system that prevents discharge to waters of the State, or to the sanitary sewer with local sewer district approval. l Wheel washes may use closed-loop recirculation systems to conserve water use. l Wheel wash wastewater shall not include wastewater from concrete washout areas. l When practical, the wheel wash should be placed in sequence with BMP C105: Stabilized Construction Access. Locate the wheel wash such that vehicles exiting the wheel wash will enter directly onto BMP C105: Stabilized Construction Access. In order to achieve this, BMP C105: Stabilized Construction Access may need to be extended beyond the standard install- ation to meet the exit of the wheel wash. Design and Installation Specifications Suggested details are shown in Figure II-3.2: Wheel Wash. The Local Permitting Authority may allow other designs. A minimum of 6 inches of asphalt treated base (ATB) over crushed base mater- ial or 8 inches over a good subgrade is recommended to pave the wheel wash. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 280 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 Nets (commonly called matting) are strands of material woven into an open, but high-tensile strength net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or pho- todegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control netting and blankets shall be made of natural plant fibers unaltered by synthetic materials. Erosion control nets and blankets should be used: l To aid permanent vegetated stabilization of slopes 2H:1V or greater and with more than 10 feet of vertical relief. l For drainage ditches and swales (highly recommended). The application of appropriate net- ting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can capture a great deal of sediment due to their open, porous structure. Nets and blankets can be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. Disadvantages of nets and blankets include: l Surface preparation is required. l On slopes steeper than 2.5H:1V, net and blanket installers may need to be roped and har- nessed for safety. l They cost at least $4,000-6,000 per acre installed. Advantages of nets and blankets include: l Installation without mobilizing special equipment. l Installation by anyone with minimal training l Installation in stages or phases as the project progresses. l Installers can hand place seed and fertilizer as they progress down the slope. l Installation in any weather. l There are numerous types of nets and blankets that can be designed with various parameters in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability, cost, and availability. An alternative to nets and blankets in some limited conditions is BMP C202: Riprap Channel Lining. Ensure that BMP C202: Riprap Channel Lining is appropriate before using it as a substitute for nets and blankets. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 293 Design and Installation Specifications l See Figure II-3.3: Channel Installation (Clackamas County et al., 2008) and Figure II-3.4: Slope Installation for typical orientation and installation of nets and blankets used in channels and as slope protection. Note: these are typical only; all nets and blankets must be installed per manufacturer’s installation instructions. l Installation is critical to the effectiveness of these products. If good ground contact is not achieved, runoff can concentrate under the product, resulting in significant erosion. l Installation of nets and blankets on slopes: 1. Complete final grade and track walk up and down the slope. 2. Install hydromulch with seed and fertilizer. 3. Dig a small trench, approximately 12 inches wide by 6 inches deep along the top of the slope. 4. Install the leading edge of the net/blanket into the small trench and staple approximately every 18 inches. NOTE: Staples are metal, “U”-shaped, and a minimum of 6 inches long. Longer staples are used in sandy soils. Biodegradable stakes are also available. 5. Roll the net/blanket slowly down the slope as the installer walks backward. NOTE: The net/blanket rests against the installer’s legs. Staples are installed as the net/blanket is unrolled. It is critical that the proper staple pattern is used for the net/blanket being installed. The net/blanket is not to be allowed to roll down the slope on its own as this stretches the net/blanket, making it impossible to maintain soil contact. In addition, no one is allowed to walk on the net/blanket after it is in place. 6. If the net/blanket is not long enough to cover the entire slope length, the trailing edge of the upper net/blanket should overlap the leading edge of the lower net/blanket and be stapled. On steeper slopes, this overlap should be installed in a small trench, stapled, and covered with soil. l With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the designer consult the manufacturer's inform- ation and that a site visit takes place in order to ensure that the product specified is appro- priate. Information is also available in WSDOT's Standard Specifications for Road, Bridge, and Municipal Construction Division 8-01 and Division 9-14 (WSDOT, 2016). l Use jute matting in conjunction with mulch (BMP C121: Mulching). Excelsior, woven straw blankets and coir (coconut fiber) blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in cer- tain circumstances. l In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. l Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of synthetic blankets, as are riverbanks, beaches and other high-energy environments. If 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 294 synthetic blankets are used, the soil should be hydromulched first. l 100-percent biodegradable blankets are available for use in sensitive areas. These organic blankets are usually held together with a paper or fiber mesh and stitching which may last up to a year. l Most netting used with blankets is photodegradable, meaning it breaks down under sunlight (not UV stabilized). However, this process can take months or years even under bright sun. Once vegetation is established, sunlight does not reach the mesh. It is not uncommon to find non-degraded netting still in place several years after installation. This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and small animals can become trapped in the netting. Maintenance Standards l Maintain good contact with the ground. Erosion must not occur beneath the net or blanket. l Repair and staple any areas of the net or blanket that are damaged or not in close contact with the ground. l Fix and protect eroded areas if erosion occurs due to poorly controlled drainage. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 295 Figure II-3.3: Channel Installation 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 296 NOT TO SCALE f,V- **/ ** z fmmWmv. '?■>12m wm'Sz 6"-~J AV')/Xya'/a// TERMINAL SLOPE AND CHANNELLONGITUDINAL ANCHOR TRENCH ANCHOR TRENCH ij -¥ ■* *-if 574AF AIT J-5' INTERVALS. -V * * Jt f f -tf # ff e CHECK SLOT AT 25’ INTERVALSw-w ISOMETRIC VIEW ft ft a.4^ ffPf*XKm•■:' e>/\X /\ INITIAL CHANNEL ANCHOR TRENCH Z2 INTERMITTENT CHECK SLOT Notes: 1. Check slots to be constructed per manufacturers specifications. 2. Staking or stapling layout per manufacturers specifications.(Clackamas County et al., 2008) Channel Installation Revised July 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-3.4: Slope Installation 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 297 Anchor in 6" x 6" min. trench and staple at 12" intervals s’. IMin. 2" overlap i Min. 6" overlap t'.'.vVr:F'»• "V. Staple overlaps max. 5" spacingtrainIi i—i Bring material down to a level area, turn the end under 4" and staple at 12" intervals Notes: 1.Slope surface shall be smooth before placement for proper soil contact. Stapling pattern as per manufacturer's recommendations. Do not stretch blankets/mattings tight - allow the rolls to mold to any irregularities. For slopes less than 3H:1V, rolls may be placed in horizontal strips. If there is a berm at the top of the slope, anchor upslope of the berm. Lime, fertilize, and seed before installation. Planting of shrubs, trees, etc. should occur after installation. 2. 3. 4. 5. 6. NOT TO SCALE Slope Installation 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 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 Conditions of Use Sodding may be used in the following areas: l Disturbed areas that require short-term or long-term cover. l Disturbed areas that require immediate vegetative cover. l All waterways that require vegetative lining. Waterways may also be seeded rather than sod- ded, and protected with a net or blanket. Design and Installation Specifications Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense root mat for mechanical strength. The following steps are recommended for sod installation: 1. Shape and smooth the surface to final grade in accordance with the approved grading plan. Consider any areas (such as swales) that need to be overexcavated below design elevation to allow room for placing soil amendment and sod. 2. Amend 4 inches (minimum) of compost into the top 8 inches of the soil if the organic content of the soil is less than ten percent or the permeability is less than 0.6 inches per hour. See https://ecology.wa.gov/Waste-Toxics/Reducing-recycling-waste/Organic-mater- ials/Managing-organics-compost for further information. 3. Fertilize according to the sod supplier's recommendations. 4. Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface. 5. Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1V. Staple the upstream edge of each sod strip. 6. Roll the sodded area and irrigate. 7. When sodding is carried out in alternating strips or other patterns, seed the areas between the sod immediately after sodding. Maintenance Standards If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and protected with a net or blanket. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 300 l PAM designated for these uses should be "water soluble" or "linear" or "non-crosslinked". Cross-linked or water absorbent PAM, polymerized in highly acidic (pH<2) conditions, are used to maintain soil moisture content. l The PAM anionic charge density may vary from 2-30 percent; a value of 18 percent is typical. Studies conducted by the United States Department of Agriculture (USDA)/ARS demon- strated that soil stabilization was optimized by using very high molecular weight (12-15 mg/- mole), highly anionic (>20% hydrolysis) PAM. l PAM tackifiers are available and being used in place of guar and alpha plantago. Typically, PAM tackifiers should be used at a mixing rate of no more than 0.5-1 lb. per 1000 gallons of water in a hydromulch machine. Some tackifier product instructions say to use at an applic- ation rate of 3 – 5 lbs per acre, which can be too much. In addition, pump problems can occur at higher application rates due to increased viscosity. Maintenance Standards l PAM may be reapplied on actively worked areas after a 48-hour period. l Reapplication is not required unless PAM treated soil is disturbed or unless turbidity levels show the need for an additional application. If PAM treated soil is left undisturbed, a reapplic- ation may be necessary after two months. More PAM applications may be required for steep slopes, silty and clayey soils (USDA Classification Type "C" and "D" soils), long grades, and high precipitation areas. When PAM is applied first to bare soil and then covered with straw, a reapplication may not be necessary for several months. l Loss of sediment and PAM may be a basis for penalties per RCW 90.48.080. l PAM may affect the treatment efficiency of chitosan flocculent systems. BMP C130: Surface Roughening Purpose Surface roughening aids in the establishment of vegetative cover, reduces runoff velocity, increases infiltration, and provides for sediment trapping through the provision of a rough soil surface. Hori- zontal depressions are created by operating a tiller or other suitable equipment on the contour or by leaving slopes in a roughened condition by not fine grading them. Use this BMP in conjunction with other BMPs such as BMP C120: Temporary and Permanent Seed- ing, BMP C121: Mulching, or BMP C124: Sodding. Conditions for Use l All slopes steeper than 3H:1V and greater than 5 vertical feet require surface roughening to a depth of 2 to 4 inches prior to seeding. l Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until seeding takes place. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 307 l Slopes with a stable rock face do not require roughening. l Slopes where mowing is planned should not be excessively roughened. Design and Installation Specifications There are different methods for achieving a roughened soil surface on a slope, and the selection of an appropriate method depends upon the type of slope. Roughening methods include stair-step grading, grooving, contour furrows, and tracking. See Figure II-3.5: Surface Roughening by Track- ing and Contour Furrows. Factors to be considered in choosing a roughening method are slope steepness, mowing requirements, and whether the slope is formed by cutting or filling. l Disturbed areas that will not require mowing may be stair-step graded, grooved, or left rough after filling. l Stair-step grading is particularly appropriate in soils containing large amounts of soft rock. Each "step" catches material that sloughs from above, and provides a level site where veget- ation can become established. Stairs should be wide enough to work with standard earth mov- ing equipment. Stair steps must be on contour or gullies will form on the slope. l Areas that will be mowed (these areas should have slopes less steep than 3H:1V) may have small furrows left by disking, harrowing, raking, or seed-planting machinery operated on the contour. l Graded areas with slopes steeper than 3H:1V but less than 2H:1V should be roughened before seeding. This can be accomplished in a variety of ways, including "track walking," or driving a crawler tractor up and down the slope, leaving a pattern of cleat imprints parallel to slope contours. l Tracking is done by operating equipment up and down the slope to leave horizontal depres- sions in the soil. Maintenance Standards l Areas that are surface roughened should be seeded as quickly as possible. l Regular inspections should be made of the area. If rills appear, they should be re-roughened and re-seeded immediately. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 308 Figure II-3.5: Surface Roughening by Tracking and Contour Furrows 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 309 o Tracking with machinery up and down the slope provides grooves that will catch seed, rainfall, and reduce runoff. Tracking 16" min (150mm) 50' (15m) 3 Contour Furrows1 Maximum Grooves will catch seed, fertilizer, mulch, rainfall, and decrease runoff. NOT TO SCALE Surface Roughening by Tracking and Contour Furrows Revised June 2016DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington BMP C131: Gradient Terraces Purpose Gradient terraces reduce erosion damage by intercepting surface runoff and conveying it to a stable outlet at a non-erosive velocity. Conditions of Use Gradient terraces are normally limited to bare land having a water erosion problem. They should not be constructed on deep sands or on soils that are too stony, steep, or shallow to permit practical and economical installation and maintenance. Gradient terraces may only be used where suitable outlets are or will be made available. Design and Installation Specifications l The maximum vertical spacing of gradient terraces should be determined by the following method: VI = (0.8)s + y Where: VI = vertical interval in feet s = land rise per 100 feet, expressed in feet y = a soil and cover variable with values from 1.0 to 4.0 Values of “y” are influenced by soil erodibility and cover practices. The lower values are applic- able to erosive soils where little to no residue is left on the surface. The higher value is applic- able only to erosion-resistant soils where a large amount of residue (1½ tons of straw/acre equivalent) is on the surface. l The minimum constructed cross-section should meet the design dimensions. l The top of the constructed ridge should not be lower at any point than the design elevation plus the specified overfill for settlement. The opening at the outlet end of the terrace should have a cross section equal to that specified for the terrace channel. l Channel grades may be either uniform or variable with a maximum grade of 0.6 feet per 100 feet length (0.6%). For short distances, terrace grades may be increased to improve align- ment. The channel velocity should not exceed that which is nonerosive for the soil type. l All gradient terraces should have adequate outlets. Such an outlet may be a grassed water- way, vegetated area, or tile outlet. In all cases the outlet must convey runoff from the terrace or terrace system to a point where the outflow will not cause damage. Vegetative cover and energy dissipators should be used in the outlet channel. l The design elevation of the water surface of the terrace should not be lower than the design elevation of the water surface in the outlet at their junction, when both are operating at design 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 310 flow. l Vertical spacing determined by the above methods may be increased as much as 0.5 feet or 10 percent, whichever is greater, to provide better alignment or location, to avoid obstacles, to adjust for equipment size, or to reach a satisfactory outlet. The drainage area above the ter- race should not exceed the area that would be drained by a terrace with normal spacing. l The terrace should have enough capacity to handle the peak runoff expected from a 2-year, 24-hour design storm without overtopping. l The terrace cross-section should be proportioned to fit the land slope. l The ridge height should include a reasonable settlement factor. l The ridge should have a minimum top width of 3 feet at the design height. l The minimum cross-sectional area of the terrace channel should be 8 square feet for land slopes of 5 percent or less, 7 square feet for slopes from 5 to 8 percent, and 6 square feet for slopes steeper than 8 percent. The terrace can be constructed wide enough to be maintained using a small vehicle. Maintenance Standards Maintenance should be performed as needed. Terraces should be inspected regularly; at least once per year, and after large storm events. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 311 Figure II-3.6: Gradient Terraces 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 312 Slope to adequate outlet ff1 10' min.lsir. & I: I «fS I I I: NOT TO SCALE Gradient Terraces 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 BMP C140: Dust Control Purpose Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage ways, and surface waters. Conditions of Use Use dust control in areas (including roadways) subject to surface and air movement of dust where on-site or off-site impacts to roadways, drainage ways, or surface waters are likely. Design and Installation Specifications l Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching, or paving is impractical, apply gravel or landscaping rock. l Limit dust generation by clearing only those areas where immediate activity will take place, leaving the remaining area(s) in the original condition. Maintain the original ground cover as long as practical. l Construct natural or artificial windbreaks or windscreens. These may be designed as enclos- ures for small dust sources. l Sprinkle the site with water until the surface is wet. Repeat as needed. To prevent carryout of mud onto the street, refer to BMP C105: Stabilized Construction Access and BMP C106: Wheel Wash. l Irrigation water can be used for dust control. Irrigation systems should be installed as a first step on sites where dust control is a concern. l Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and cautions regarding handling and application. Used oil is prohibited from use as a dust sup- pressant. Local governments may approve other dust palliatives such as calcium chloride or PAM. l PAM (BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection) added to water at a rate of 0.5 pounds per 1,000 gallons of water per acre and applied from a water truck is more effect- ive than water alone. This is due to increased infiltration of water into the soil and reduced evaporation. In addition, small soil particles are bonded together and are not as easily trans- ported by wind. Adding PAM may reduce the quantity of water needed for dust control. Note that the application rate specified here applies to this BMP, and is not the same application rate that is specified in BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection, but the downstream protections still apply. Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use. PAM shall not be directly applied to water or allowed to enter a water body. l Contact your local Air Pollution Control Authority for guidance and training on other dust con- trol measures. Compliance with the local Air Pollution Control Authority constitutes 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 313 compliance with this BMP. l Use vacuum street sweepers. l Remove mud and other dirt promptly so it does not dry and then turn into dust. l Techniques that can be used for unpaved roads and lots include: o Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. o Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials. o Add surface gravel to reduce the source of dust emission. Limit the amount of fine particles (those smaller than .075 mm) to 10 to 20 percent. o Use geotextile fabrics to increase the strength of new roads or roads undergoing recon- struction. o Encourage the use of alternate, paved routes, if available. o Apply chemical dust suppressants using the admix method, blending the product with the top few inches of surface material. Suppressants may also be applied as surface treatments. o Limit dust-causing work on windy days. o Pave unpaved permanent roads and other trafficked areas. Maintenance Standards Respray area as necessary to keep dust to a minimum. BMP C150: Materials on Hand Purpose Keep quantities of erosion prevention and sediment control materials on the project site at all times to be used for regular maintenance and emergency situations such as unexpected heavy rains. Hav- ing these materials on-site reduces the time needed to replace existing or implement new BMPs when inspections indicate that existing BMPs are not meeting the Construction SWPPP require- ments. In addition, contractors can save money by buying some materials in bulk and storing them at their office or yard. Conditions of Use l Construction projects of any size or type can benefit from having materials on hand. A small commercial development project could have a roll of plastic and some gravel available for immediate protection of bare soil and temporary berm construction. A large earthwork project, such as highway construction, might have several tons of straw, several rolls of plastic, flexible 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 314 pipe, sandbags, geotextile fabric and steel “T” posts. l Materials should be stockpiled and readily available before any site clearing, grubbing, or earthwork begins. A large contractor or project proponent could keep a stockpile of materials that are available for use on several projects. l If storage space at the project site is at a premium, the contractor could maintain the materials at their office or yard. The office or yard must be less than an hour from the project site. Design and Installation Specifications Depending on project type, size, complexity, and length, materials and quantities will vary. A good minimum list of items that will cover numerous situations includes: l Clear Plastic, 6 mil l Drainpipe, 6 or 8 inch diameter l Sandbags, filled l Straw Bales for mulching l Quarry Spalls l Washed Gravel l Geotextile Fabric l Catch Basin Inserts l Steel "T" Posts l Silt fence material l Straw Wattles Maintenance Standards l All materials with the exception of the quarry spalls, steel “T” posts, and gravel should be kept covered and out of both sun and rain. l Re-stock materials as needed. BMP C151: Concrete Handling Purpose Concrete work can generate process water and slurry that contain fine particles and high pH, both of which can violate water quality standards in the receiving water. Concrete spillage or concrete dis- charge to waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, con- crete process water, and concrete slurry from entering waters of the State. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 315 Conditions of Use Any time concrete is used, utilize these management practices. Concrete construction project com- ponents include, but are not limited to: l Curbs l Sidewalks l Roads l Bridges l Foundations l Floors l Runways Disposal options for concrete, in order of preference are: 1. Off-site disposal 2. Concrete wash-out areas (see BMP C154: Concrete Washout Area) 3. De minimus washout to formed areas awaiting concrete Design and Installation Specifications l Wash concrete truck drums at an approved off-site location or in designated concrete washout areas only. Do not wash out concrete trucks onto the ground (including formed areas awaiting concrete), or into storm drains, open ditches, streets, or streams. Refer to BMP C154: Concrete Washout Area for information on concrete washout areas. o Return unused concrete remaining in the truck and pump to the originating batch plant for recycling. Do not dump excess concrete on site, except in designated concrete washout areas as allowed in BMP C154: Concrete Washout Area. l Wash small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheelbarrows) into designated concrete washout areas or into formed areas awaiting concrete pour. l At no time shall concrete be washed off into the footprint of an area where an infiltration fea- ture will be installed. l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas. l Do not allow washwater from areas, such as concrete aggregate driveways, to drain directly (without detention or treatment) to natural or constructed stormwater conveyances. l Contain washwater and leftover product in a lined container when no designated concrete washout areas (or formed areas, allowed as described above) are available. Dispose of con- tained concrete and concrete washwater (process water) properly. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 316 l Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface waters. l Refer to BMP C252: Treating and Disposing of High pH Water for pH adjustment require- ments. l Refer to the Construction Stormwater General Permit (CSWGP) for pH monitoring require- ments if the project involves one of the following activities: o Significant concrete work (as defined in the CSWGP). o The use of soils amended with (but not limited to) Portland cement-treated base, cement kiln dust or fly ash. o Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for high pH. Maintenance Standards Check containers for holes in the liner daily during concrete pours and repair the same day. BMP C152: Sawcutting and Surfacing Pollution Prevention Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high pH (concrete cutting), both of which can violate the water quality standards in the receiving water. Concrete spillage or concrete discharge to waters of the State is prohibited. Use this BMP to minimize and eliminate process water and slurry created through sawcutting or surfacing from enter- ing waters of the State. Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Saw- cutting and surfacing operations include, but are not limited to: l Sawing l Coring l Grinding l Roughening l Hydro-demolition l Bridge and road surfacing 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 317 Design and Installation Specifications l Vacuum slurry and cuttings during cutting and surfacing operations. l Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight. l Slurry and cuttings shall not drain to any natural or constructed drainage conveyance includ- ing stormwater systems. This may require temporarily blocking catch basins. l Dispose of collected slurry and cuttings in a manner that does not violate ground water or sur- face water quality standards. l Do not allow process water generated during hydro-demolition, surface roughening or similar operations to drain to any natural or constructed drainage conveyance including stormwater systems. Dispose of process water in a manner that does not violate ground water or surface water quality standards. l Handle and dispose of cleaning waste material and demolition debris in a manner that does not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an appropriate disposal site. Maintenance Standards Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters of the state. If inspections show that a violation of water quality standards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and/or vacuum trucks. BMP C153: Material Delivery, Storage, and Containment Purpose Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from material delivery and storage. Minimize the storage of hazardous materials on-site, store mater- ials in a designated area, and install secondary containment. Conditions of Use Use at construction sites with delivery and storage of the following materials: l Petroleum products such as fuel, oil and grease l Soil stabilizers and binders (e.g., Polyacrylamide) l Fertilizers, pesticides and herbicides l Detergents l Asphalt and concrete compounds 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 318 l Hazardous chemicals such as acids, lime, adhesives, paints, solvents, and curing compounds l Any other material that may be detrimental if released to the environment Design and Installation Specifications l The temporary storage area should be located away from vehicular traffic, near the con- struction entrance(s), and away from waterways or storm drains. l Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. l Hazardous material storage on-site should be minimized. l Hazardous materials should be handled as infrequently as possible. l During the wet weather season (Oct 1 – April 30), consider storing materials in a covered area. l Materials should be stored in secondary containments, such as an earthen dike, horse trough, or even a children’s wading pool for non-reactive materials such as detergents, oil, grease, and paints. Small amounts of material may be secondarily contained in “bus boy” trays or con- crete mixing trays. l Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, within secondary containment. l If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums, preventing water from collecting. l Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in approved containers and drums and shall not be overfilled. Containers and drums shall be stored in temporary secondary containment facilities. l Temporary secondary containment facilities shall provide for a spill containment volume able to contain 10% of the total enclosed container volume of all containers, or 110% of the capa- city of the largest container within its boundary, whichever is greater. l Secondary containment facilities shall be impervious to the materials stored therein for a min- imum contact time of 72 hours. l Sufficient separation should be provided between stored containers to allow for spill cleanup and emergency response access. l During the wet weather season (Oct 1 – April 30), each secondary containment facility shall be covered during non-working days, prior to and during rain events. l Keep material storage areas clean, organized and equipped with an ample supply of appro- priate spill clean-up material (spill kit). l The spill kit should include, at a minimum: 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 319 o 1-Water Resistant Nylon Bag o 3-Oil Absorbent Socks 3”x 4’ o 2-Oil Absorbent Socks 3”x 10’ o 12-Oil Absorbent Pads 17”x19” o 1-Pair Splash Resistant Goggles o 3-Pair Nitrile Gloves o 10-Disposable Bags with Ties o Instructions Maintenance Standards l Secondary containment facilities shall be maintained free of accumulated rainwater and spills. In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums. These liquids shall be handled as hazardous waste unless testing determines them to be non-hazardous. l Re-stock spill kit materials as needed. BMP C154: Concrete Washout Area Purpose Prevent or reduce the discharge of pollutants from concrete waste to stormwater by conducting washout off-site, or performing on-site washout in a designated area. Conditions of Use Concrete washout areas are implemented on construction projects where: l Concrete is used as a construction material l It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant, etc.). l Concrete truck drums are washed on-site. Note that auxiliary concrete truck components (e.g. chutes and hoses) and small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheel- barrows) may be washed into formed areas awaiting concrete pour. At no time shall concrete be washed off into the footprint of an area where an infiltration feature will be installed. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 320 Design and Installation Specifications Implementation l Perform washout of concrete truck drums at an approved off-site location or in designated con- crete washout areas only. l Do not wash out concrete onto non-formed areas, or into storm drains, open ditches, streets, or streams. l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas. l Do not allow excess concrete to be dumped on-site, except in designated concrete washout areas as allowed above. l Concrete washout areas may be prefabricated concrete washout containers, or self-installed structures (above-grade or below-grade). l Prefabricated containers are most resistant to damage and protect against spills and leaks. Companies may offer delivery service and provide regular maintenance and disposal of solid and liquid waste. l If self-installed concrete washout areas are used, below-grade structures are preferred over above-grade structures because they are less prone to spills and leaks. l Self-installed above-grade structures should only be used if excavation is not practical. l Concrete washout areas shall be constructed and maintained in sufficient quantity and size to contain all liquid and concrete waste generated by washout operations. Education l Discuss the concrete management techniques described in this BMP with the ready-mix con- crete supplier before any deliveries are made. l Educate employees and subcontractors on the concrete waste management techniques described in this BMP. l Arrange for the contractor’s superintendent or Certified Erosion and Sediment Control Lead (CESCL) to oversee and enforce concrete waste management procedures. l A sign should be installed adjacent to each concrete washout area to inform concrete equip- ment operators to utilize the proper facilities. Contracts Incorporate requirements for concrete waste management into concrete supplier and subcontractor agreements. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 321 Location and Placement l Locate concrete washout areas at least 50 feet from sensitive areas such as storm drains, open ditches, water bodies, or wetlands. l Allow convenient access to the concrete washout area for concrete trucks, preferably near the area where the concrete is being poured. l If trucks need to leave a paved area to access the concrete washout area, prevent track-out with a pad of rock or quarry spalls (see BMP C105: Stabilized Construction Access). These areas should be far enough away from other construction traffic to reduce the likelihood of acci- dental damage and spills. l The number of concrete washout areas you install should depend on the expected demand for storage capacity. l On large sites with extensive concrete work, concrete washout areas should be placed in mul- tiple locations for ease of use by concrete truck drivers. Concrete Truck Washout Procedures l Washout of concrete truck drums shall be performed in designated concrete washout areas only. l Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and discharged into designated concrete washout areas or properly disposed of off-site. Concrete Washout Area Installation l Concrete washout areas should be constructed as shown in the figures below, with a recom- mended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to contain all liquid and concrete waste generated by washout operations. l Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free of holes, tears, or other defects that compromise the impermeability of the material. l Lath and flagging should be commercial type. l Liner seams shall be installed in accordance with manufacturers’ recommendations. l Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic lining material. Maintenance Standards Inspection and Maintenance l Inspect and verify that concrete washout areas are in place prior to the commencement of con- crete work. l Once concrete wastes are washed into the designated washout area and allowed to harden, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 322 the concrete should be broken up, removed, and disposed of per applicable solid waste reg- ulations. Dispose of hardened concrete on a regular basis. l During periods of concrete work, inspect the concrete washout areas daily to verify continued performance. o Check overall condition and performance. o Check remaining capacity (% full). o If using self-installed concrete washout areas, verify plastic liners are intact and side- walls are not damaged. o If using prefabricated containers, check for leaks. l Maintain the concrete washout areas to provide adequate holding capacity with a minimum freeboard of 12 inches. l Concrete washout areas must be cleaned, or new concrete washout areas must be con- structed and ready for use once the concrete washout area is 75% full. l If the concrete washout area is nearing capacity, vacuum and dispose of the waste material in an approved manner. l Do not discharge liquid or slurry to waterways, storm drains or directly onto ground. l Do not discharge to the sanitary sewer without local approval. l Place a secure, non-collapsing, non-water collecting cover over the concrete washout area prior to predicted wet weather to prevent accumulation and overflow of pre- cipitation. l Remove and dispose of hardened concrete and return the structure to a functional con- dition. Concrete may be reused on-site or hauled away for disposal or recycling. l When you remove materials from a self-installed concrete washout area, build a new struc- ture; or, if the previous structure is still intact, inspect for signs of weakening or damage, and make any necessary repairs. Re-line the structure with new plastic after each cleaning. Removal of Concrete Washout Areas l When concrete washout areas are no longer required for the work, the hardened concrete, slurries and liquids shall be removed and properly disposed of. l Materials used to construct concrete washout areas shall be removed from the site of the work and disposed of or recycled. l Holes, depressions or other ground disturbance caused by the removal of the concrete washout areas shall be backfilled, repaired, and stabilized to prevent erosion. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 323 Figure II-3.7: Concrete Washout Area with Wood Planks 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 324 3m Minimum -e- -e-Lath and flagging on 3 sides Sandbag0□ CD □ '>TI SandbagBermc> 10 mil plastic lining□Varies A iAf 'Xo-o-1 m •x Q —I Berm 10 CD CD Section A-A6 10 mil plastic liningPlan Notes: 1.Actual layout determined in the field. A concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. Type "Below Grade ii 2. 3m Minimum JSL JHL T8T Wood frame securely fastened around entire perimeter with two stakes B BtI■s-a ■s-a Varies 10 mil plastic lining S 3 E VStake (typ.) M Section B-Bw 10 mil plastic lining Two-stacked 2x12 rough wood frame Plan Type "Above Grade" with Wood Planks NOT TO SCALE Concrete Washout Area with Wood Planks Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Figure II-3.8: Concrete Washout Area with Straw Bales 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 325 Straw bale 10 mil plastic lining Binding wire Staples (2 per bale)Native material (optional) Wood or metal stakes (2 per bale) Plywood 1200 mm x 610 mm painted white Wood post (89 mm x 89 mm x 2.4 m)Lag screws (12.5 mm)Section B-B Black letters 150 mm heightILCONCRETE WASHOUT' U915 mm f 915 mm T3m Minimum Concrete Washout Sign Detail (or equivalent)Stake (typ)A B Bt1 i 50 mm 3.05 mm dia. steel wire Varies 200 mm f Staple Detail 10 mil plastic lining Notes:Straw bale (typ)1. Actual layout determined in the field. The concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. Plan 2. Type "Above Grade" with Straw Bales NOT TO SCALE Concrete Washout Area with Straw Bales Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Figure II-3.9: Prefabricated Concrete Washout Container w/Ramp 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 326 ■•-0 \riy l-j X - NOT TO SCALE Prefabricated Concrete Washout Container w/Ramp Revised June 2016DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyright.htmMor copyright notice including permissions, limitation of liability, and disclaimer.State of Washington BMP C160: Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of erosion and sediment control (ESC), and water quality protection. The designated person shall be responsible for ensuring compliance with all local, state, and federal erosion and sediment control and water quality requirements. Construction sites one acre or larger that discharge to waters of the State must designate a Certified Erosion and Sediment Control Lead (CESCL) as the responsible representative. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge stormwater to sur- face waters of the state. Sites less than one acre may have a person without CESCL certification conduct inspections. The CESCL shall: l Have a current certificate proving attendance in an erosion and sediment control training course that meets the minimum ESC training and certification requirements established by Ecology. Ecology has provided the minimum requirements for CESCL course training, as well as a list of ESC training and certification providers at: https://ecology.wa.gov/Regulations-Permits/Permits-certifications/Certified-erosion-sed- iment-control OR l Be a Certified Professional in Erosion and Sediment Control (CPESC). For additional inform- ation go to: http://www.envirocertintl.org/cpesc/ Specifications l CESCL certification shall remain valid for three years. l The CESCL shall have authority to act on behalf of the contractor or project proponent and shall be available, or on-call, 24 hours per day throughout the period of construction. l The Construction SWPPP shall include the name, telephone number, fax number, and address of the designated CESCL. See II-2 Construction Stormwater Pollution Prevention Plans (Construction SWPPPs). l A CESCL may provide inspection and compliance services for multiple construction projects in the same geographic region, but must be on site whenever earthwork activities are 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 327 occurring that could generate release of turbid water. l Duties and responsibilities of the CESCL shall include, but are not limited to the following: o Maintaining a permit file on site at all times which includes the Construction SWPPP and any associated permits and plans. o Directing BMP installation, inspection, maintenance, modification, and removal. o Updating all project drawings and the Construction SWPPP with changes made. o Completing any sampling requirements including reporting results using electronic Dis- charge Monitoring Reports (WebDMR). o Facilitate, participate in, and take corrective actions resulting from inspections per- formed by outside agencies or the owner. o Keeping daily logs, and inspection reports. Inspection reports should include: n Inspection date/time. n Weather information; general conditions during inspection and approximate amount of precipitation since the last inspection. n Visual monitoring results, including a description of discharged stormwater. The presence of suspended sediment, turbid water, discoloration, and oil sheen shall be noted, as applicable. n Any water quality monitoring performed during inspection. n General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. n A summary or list of all BMPs implemented, including observations of all erosion/sediment control structures or practices. The following shall be noted: 1. Locations of BMPs inspected. 2. Locations of BMPs that need maintenance. 3. Locations of BMPs that failed to operate as designed or intended. 4. Locations of where additional or different BMPs are required. BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by wind, rain, runoff, and vehicle tracking. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 328 Conditions of Use The construction sequence schedule is an orderly listing of all major land-disturbing activities together with the necessary erosion and sedimentation control measures planned for the project. This type of schedule guides the contractor on work to be done before other work is started so that serious erosion and sedimentation problems can be avoided. Following a specified work schedule that coordinates the timing of land-disturbing activities and the installation of control measures is perhaps the most cost-effective way of controlling erosion during construction. The removal of ground cover leaves a site vulnerable to erosion. Construction sequen- cing that limits land clearing, provides timely installation of erosion and sedimentation controls, and restores protective cover quickly can significantly reduce the erosion potential of a site. Design Considerations l Minimize construction during rainy periods. l Schedule projects to disturb only small portions of the site at any one time. Complete grading as soon as possible. Immediately stabilize the disturbed portion before grading the next por- tion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses. II-3.3 Construction Runoff BMPs BMP C200: Interceptor Dike and Swale Purpose Provide a dike of compacted soil or a swale at the top or base of a disturbed slope or along the peri- meter of a disturbed construction area to convey stormwater. Use the dike and/or swale to intercept the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can prevent storm runoff from entering the work area or sediment-laden runoff from leaving the con- struction site. Conditions of Use Use an interceptor dike or swale where runoff from an exposed site or disturbed slope must be con- veyed to an erosion control BMP which can safely convey the stormwater. l Locate upslope of a construction site to prevent runoff from entering the disturbed area. l When placed horizontally across a disturbed slope, it reduces the amount and velocity of run- off flowing down the slope. l Locate downslope to collect runoff from a disturbed area and direct it to a sediment BMP (e.g. BMP C240: Sediment Trap or BMP C241: Sediment Pond (Temporary)). 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 329 Design and Installation Specifications l Dike and/or swale and channel must be stabilized with temporary or permanent vegetation or other channel protection during construction. l Steep grades require channel protection and check dams. l Review construction for areas where overtopping may occur. l Can be used at the top of new fill before vegetation is established. l May be used as a permanent diversion channel to carry the runoff. l Contributing area for an individual dike or swale should be one acre or less. l Design the dike and/or swale to contain flows calculated by one of the following methods: o Single Event Hydrograph Method: The peak volumetric flow rate calculated using a 10- minute time step from a Type 1A, 10-year, 24-hour frequency storm for the worst-case land cover condition. OR o Continuous Simulation Method: The 10-year peak flow rate, as determined by an approved continuous runoff model with a 15-minute time step for the worst-case land cover condition. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analysis (in most cases, this would be the land cover conditions just prior to final landscaping). Interceptor Dikes Interceptor dikes shall meet the following criteria: l Top Width: 2 feet minimum. l Height: 1.5 feet minimum on berm. l Side Slope: 2H:1V or flatter. l Grade: Depends on topography, however, dike system minimum is 0.5%, and maximum is 1%. l Compaction: Minimum of 90 percent ASTM D698 standard proctor. l Stabilization: Depends on velocity and reach. Inspect regularly to ensure stability. l Ground Slopes <5%: Seed and mulch applied within 5 days of dike construction (see BMP C121: Mulching). l Ground Slopes 5 - 40%: Dependent on runoff velocities and dike materials. Stabilization should be done immediately using either sod or riprap, or other measures to avoid erosion. l The upslope side of the dike shall provide positive drainage to the dike outlet. No erosion shall 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 330 occur at the outlet. Provide energy dissipation measures as necessary. Sediment-laden runoff must be released through a sediment trapping facility. l Minimize construction traffic over temporary dikes. Use temporary cross culverts for channel crossing. l See Table II-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope for recom- mended horizontal spacing between dikes. Average Slope Slope Percent Flowpath Length 20H:1V or less 3-5%300 feet (10 to 20)H:1V 5-10%200 feet (4 to 10)H:1V 10-25%100 feet (2 to 4)H:1V 25-50%50 feet Table II-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope Interceptor Swales Interceptor swales shall meet the following criteria: l Bottom Width: 2 feet minimum; the cross-section bottom shall be level. l Depth: 1-foot minimum. l Side Slope: 2H:1V or flatter. l Grade: Maximum 5 percent, with positive drainage to a suitable outlet (such as BMP C241: Sediment Pond (Temporary)). l Stabilization: Seed as per BMP C120: Temporary and Permanent Seeding, or BMP C202: Riprap Channel Lining, 12 inches thick riprap pressed into the bank and extending at least 8 inches vertical from the bottom. Maintenance Standards l Inspect diversion dikes and interceptor swales once a week and after every rainfall. Imme- diately remove sediment from the flow area. l Damage caused by construction traffic or other activity must be repaired before the end of each working day. l Check outlets and make timely repairs as needed to avoid gully formation. When the area below the temporary diversion dike is permanently stabilized, remove the dike and fill and sta- bilize the channel to blend with the natural surface. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 331 BMP C207: Check Dams Purpose Construction of check dams across a swale or ditch reduces the velocity of concentrated flow and dis- sipates energy at the check dam. Conditions of Use Use check dams where temporary or permanent channels are not yet vegetated, channel lining is infeasible, and/or velocity checks are required. l Check dams may not be placed in streams unless approved by the State Department of Fish and Wildlife. l Check dams may not be placed in wetlands without approval from a permitting agency. l Do not place check dams below the expected backwater from any salmonid bearing water between October 1 and May 31 to ensure that there is no loss of high flow refuge habitat for overwintering juvenile salmonids and emergent salmonid fry. Design and Installation Specifications l Construct rock check dams from appropriately sized rock. The rock used must be large enough to stay in place given the expected design flow through the channel. The rock must be placed by hand or by mechanical means (do not dump the rock to form the dam) to achieve complete coverage of the ditch or swale and to ensure that the center of the dam is lower than the edges. l Check dams may also be constructed of either rock or pea-gravel filled bags. Numerous new products are also available for this purpose. They tend to be re-usable, quick and easy to install, effective, and cost efficient. l Place check dams perpendicular to the flow of water. l The check dam should form a triangle when viewed from the side. This prevents undercutting as water flows over the face of the check dam rather than falling directly onto the ditch bottom. l Before installing check dams, impound and bypass upstream water flow away from the work area. Options for bypassing include pumps, siphons, or temporary channels. l Check dams combined with sumps work more effectively at slowing flow and retaining sed- iment than a check dam alone. A deep sump should be provided immediately upstream of the check dam. l In some cases, if carefully located and designed, check dams can remain as permanent install- ations with very minor regrading. They may be left as either spillways, in which case accu- mulated sediment would be graded and seeded, or as check dams to prevent further sediment from leaving the site. l The maximum spacing between check dams shall be such that the downstream toe of the 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 351 upstream dam is at the same elevation as the top of the downstream dam. l Keep the maximum height at 2 feet at the center of the check dam. l Keep the center of the check dam at least 12 inches lower than the outer edges at natural ground elevation. l Keep the side slopes of the check dam at 2H:1V or flatter. l Key the stone into the ditch banks and extend it beyond the abutments a minimum of 18 inches to avoid washouts from overflow around the dam. l Use filter fabric foundation under a rock or sand bag check dam. If a blanket ditch liner is used, filter fabric is not necessary. A piece of organic or synthetic blanket cut to fit will also work for this purpose. l In the case of grass-lined ditches and swales, all check dams and accumulated sediment shall be removed when the grass has matured sufficiently to protect the ditch or swale - unless the slope of the swale is greater than 4 percent. The area beneath the check dams shall be seeded and mulched immediately after dam removal. l Ensure that channel appurtenances, such as culvert entrances below check dams, are not subject to damage or blockage from displaced stones. l See Figure II-3.16: Rock Check Dam. Maintenance Standards Check dams shall be monitored for performance and sediment accumulation during and after each rainfall that produces runoff. Sediment shall be removed when it reaches one half the sump depth. l Anticipate submergence and deposition above the check dam and erosion from high flows around the edges of the dam. l If significant erosion occurs between dams, install a protective riprap liner in that portion of the channel. See BMP C202: Riprap Channel Lining. 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 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 352 Figure II-3.16: Rock Check Dam 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 353 View Looking Upstream i——A 18' (0.5m)12" f~(150mm) <//&9§>/i 24" (0.6m)%>RpL-ffeNote: Key stone into channel banks and extend it beyond the abutments a minimum of 18" (0.5m) to prevent flow around dam. W fy Section A-A J Flow 24" (0.6m) — 8' (2.4m) -------------' Spacing Between Check Dams 'L' = the distance such that points 'A' and 'B' are of equal elevation. ■L' Point 'B'Point 'A' NOT TO SCALE Rock Check Dam 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 thickness is 2 feet. o For outlets at the base of steep slope pipes (pipe slope greater than 10 percent), use an engineered energy dissipator. o Filter fabric or erosion control blankets should always be used under riprap to prevent scour and channel erosion. See BMP C122: Nets and Blankets. l Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. This work may require a Hydraulic Project Approval (HPA) from the Washington State Depart- ment of Fish and Wildlife. See I-2.11 Hydraulic Project Approvals. Maintenance Standards l Inspect and repair as needed. l Add rock as needed to maintain the intended function. l Clean energy dissipator if sediment builds up. BMP C220: Inlet Protection Purpose Inlet protection prevents coarse sediment from entering drainage systems prior to permanent sta- bilization of the disturbed area. Conditions of Use Use inlet protection at inlets that are operational before permanent stabilization of the disturbed areas that contribute runoff to the inlet. Provide protection for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless those inlets are preceded by a sediment trapping BMP. Also consider inlet protection for lawn and yard drains on new home construction. These small and numerous drains coupled with lack of gutters can add significant amounts of sediment into the roof drain system. If possible, delay installing lawn and yard drains until just before landscaping, or cap these drains to prevent sediment from entering the system until completion of landscaping. Provide 18-inches of sod around each finished lawn and yard drain. Table II-3.10: Storm Drain Inlet Protection lists several options for inlet protection. All of the methods for inlet protection tend to plug and require a high frequency of maintenance. Limit contributing drain- age areas for an individual inlet to one acre or less. If possible, provide emergency overflows with additional end-of-pipe treatment where stormwater ponding would cause a hazard. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 356 Type of Inlet Pro- tection Emergency Overflow Applicable for Paved/ Earthen Sur- faces Conditions of Use Drop Inlet Protection Excavated drop inlet protection Yes, temporary flooding may occur Earthen Applicable for heavy flows. Easy to maintain. Large area requirement: 30'x30'/acre Block and gravel drop inlet pro- tection Yes Paved or Earthen Applicable for heavy concentrated flows. Will not pond. Gravel and wire drop inlet pro- tection No Paved or Earthen Applicable for heavy concentrated flows. Will pond. Can withstand traffic. Catch basin filters Yes Paved or Earthen Frequent maintenance required. Curb Inlet Protection Curb inlet pro- tection with wooden weir Small capacity overflow Paved Used for sturdy, more compact install- ation. Block and gravel curb inlet pro- tection Yes Paved Sturdy, but limited filtration. Culvert Inlet Protection Culvert inlet sed- iment trap N/A N/A 18 month expected life. Table II-3.10: Storm Drain Inlet Protection Design and Installation Specifications Excavated Drop Inlet Protection Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet. Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe- cifications for excavated drop inlet protection include: l Provide a depth of 1-2 ft as measured from the crest of the inlet structure. l Slope sides of excavation should be no steeper than 2H:1V. l Minimum volume of excavation is 35 cubic yards. l Shape the excavation to fit the site, with the longest dimension oriented toward the longest inflow area. l Install provisions for draining to prevent standing water. l Clear the area of all debris. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 357 l Grade the approach to the inlet uniformly. l Drill weep holes into the side of the inlet. l Protect weep holes with screen wire and washed aggregate. l Seal weep holes when removing structure and stabilizing area. l Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass flow. Block and Gravel Filter A block and gravel filter is a barrier formed around the inlet with standard concrete blocks and gravel. See Figure II-3.17: Block and Gravel Filter. Design and installation specifications for block gravel fil- ters include: l Provide a height of 1 to 2 feet above the inlet. l Recess the first row of blocks 2-inches into the ground for stability. l Support subsequent courses by placing a pressure treated wood 2x4 through the block open- ing. l Do not use mortar. l Lay some blocks in the bottom row on their side to allow for dewatering the pool. l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings. l Place gravel to just below the top of blocks on slopes of 2H:1V or flatter. l An alternative design is a gravel berm surrounding the inlet, as follows: o Provide a slope of 3H:1V on the upstream side of the berm. o Provide a slope of 2H:1V on the downstream side of the berm. o Provide a 1-foot wide level stone area between the gravel berm and the inlet. o Use stones 3 inches in diameter or larger on the upstream slope of the berm. o Use gravel ½- to ¾-inch at a minimum thickness of 1-foot on the downstream slope of the berm. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 358 Figure II-3.17: Block and Gravel Filter 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 359 A Drain grate r>Aft> QS, SSL ogjfe Q. ~ _ ?rygioSOso^cy.;Concrete block Sfei A* o• o>cr> °i?o ^•Pa- ■sPc^I? 4 STTO <&', Gravel backfill■osVf\ A-°i ° _?o “■'frvSPP^ •§?° to. gdp> §0-^<S> q® v«r.^4y A Plan View Concrete block Wire screen or filter fabric Overflow water Gravel backfill Ponding height |5»S Water'^n iplllpfls^Drop inlet Section A-A Notes: 1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas, (less than 5%) 2. Excavate a basin of sufficient size adjacent to the drop inlet. 3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent runoff from bypassing the inlet. A temporary dike may be necessary on the downslope side of the structure. NOT TO SCALE Block and Gravel Filter Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Gravel and Wire Mesh Filter Gravel and wire mesh filters are gravel barriers placed over the top of the inlet. This method does not provide an overflow. Design and installation specifications for gravel and wire mesh filters include: l Use a hardware cloth or comparable wire mesh with ½-inch openings. o Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot bey- ond each side of the inlet structure. o Overlap the strips if more than one strip of mesh is necessary. l Place coarse aggregate over the wire mesh. o Provide at least a 12-inch depth of aggregate over the entire inlet opening and extend at least 18-inches on all sides. Catch Basin Filters Catch basin filters are designed by manufacturers for construction sites. The limited sediment stor- age capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. To reduce maintenance requirements, combine a catch basin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights-of-way. Design and install- ation specifications for catch basin filters include: l Provides 5 cubic feet of storage. l Requires dewatering provisions. l Provides a high-flow bypass that will not clog under normal use at a construction site. l Insert the catch basin filter in the catch basin just below the grating. Curb Inlet Protection with Wooden Weir Curb inlet protection with wooden weir is an option that consists of a barrier formed around a curb inlet with a wooden frame and gravel. Design and installation specifications for curb inlet protection with wooden weirs include: l Use wire mesh with ½-inch openings. l Use extra strength filter cloth. l Construct a frame. l Attach the wire and filter fabric to the frame. l Pile coarse washed aggregate against the wire and fabric. l Place weight on the frame anchors. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 360 Block and Gravel Curb Inlet Protection Block and gravel curb inlet protection is a barrier formed around a curb inlet with concrete blocks and gravel. See Figure II-3.18: Block and Gravel Curb Inlet Protection. Design and installation spe- cifications for block and gravel curb inlet protection include: l Use wire mesh with ½-inch openings. l Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks. l Place a 2x4 stud through the outer holes of each spacer block to align the front blocks. l Place blocks on their sides across the front of the inlet and abutting the spacer blocks. l Place wire mesh over the outside vertical face. l Pile coarse aggregate against the wire to the top of the barrier. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 361 Figure II-3.18: Block and Gravel Curb Inlet Protection 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 362 A Catch basin Back of sidewalk 2x4 Wood stud Curb inletBack of curb Concrete block pt < 1'[ ]o a & Wire screen or filter fabric 3c§ i?$C5 3Ko..om,o jOjsQi 0»Wm JS SS A Concrete block% inch (20 mm) Drain gravel Plan View Ponding height % inch (20 mm) Drain gravel Overflow w I□Curb inlet Wire screen or filter fabric r2x4 Wood stud (100x50 Timber stud)/iCatch basin Concrete block Section A-A Notes: 1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff. 2. Barrier shall allow for overflow from severe storm event. 3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately.NOT TO SCALE Block and Gravel Curb Inlet Protection Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Curb and Gutter Sediment Barrier Curb and gutter sediment barrier is a sandbag or rock berm (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure II-3.19: Curb and Gutter Barrier. Design and installation specifications for curb and gutter sediment barrier include: l Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet. l Construct a horseshoe shaped sedimentation trap on the upstream side of the berm. Size the trap to sediment trap standards for protecting a culvert inlet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 363 Figure II-3.19: Curb and Gutter Barrier 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 364 Back of sidewalk Burlap sacks to overlap onto curb Back of curb Curb inletRunoff SpillwayRunoff Catch basin Plan View Gravel filled sandbags stacked tightly Notes: 1. Place curb type sediment barriers on gently sloping street segments, where water can pond and allow sediment to separate from runoff. 2. Sandbags of either burlap or woven 'geotextile' fabric, are filled with gravel, layered and packed tightly. 3. Leave a one sandbag gap in the top row to provide a spillway for overflow. 4. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately.NOT TO SCALE Curb and Gutter Barrier Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Maintenance Standards l Inspect all forms of inlet protection frequently, especially after storm events. Clean and replace clogged catch basin filters. For rock and gravel filters, pull away the rocks from the inlet and clean or replace. An alternative approach would be to use the clogged rock as fill and put fresh rock around the inlet. l Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appropriate. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C231: Brush Barrier Purpose The purpose of brush barriers is to reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use l Brush barriers may be used downslope of disturbed areas that are less than one-quarter acre. l Brush barriers are not intended to treat concentrated flows, nor are they intended to treat sub- stantial amounts of overland flow. Any concentrated flows must be directed to a sediment trap- ping BMP. The only circumstance in which overland flow can be treated solely by a brush barrier, rather than by a sediment trapping BMP, is when the area draining to the barrier is small. l Brush barriers should only be installed on contours. Design and Installation Specifications l Height: 2 feet (minimum) to 5 feet (maximum). l Width: 5 feet at base (minimum) to 15 feet (maximum). l Filter fabric (geotextile) may be anchored over the brush berm to enhance the filtration ability of the barrier. Ten-ounce burlap is an adequate alternative to filter fabric. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 365 BMP C233: Silt Fence Purpose Silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use Silt fence may be used downslope of all disturbed areas. l Silt fence shall prevent sediment carried by runoff from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence. l Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow. Convey any concentrated flows through the drainage system to a sediment trapping BMP. l Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide an adequate method of silt control for anything deeper than sheet or overland flow. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 370 Figure II-3.22: Silt Fence 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 371 Joints in geotextile fabric shall be spliced at posts. Use staples, wire rings or equivalent to attach fabric to posts 2"x2" by 14 Ga. wire or equivalent, if standard strength fabric used x x X VX' XX>0<A xoi Rx Xxx>-X>:X XXXX’1 I EEj-X X I I: ;■;<>'_ >' *X xvwy !>x x ■,x' _n------ i ii i 6' max IMinimum 4''x4'' trench I II Post spacing may be increased to 8' if wire backing is used 2"x2" wood posts, steel fence posts, or equivalent 2''x2" by 14 Ga. wire or equivalent, if standard strength fabric used Geotextile fabric 2' min 7 Backfill trench with native soil or %" - 1.5" washed gravel r 'ToplE -T.\\ Minimum 4''x4'' trench . V 2"x2" wood posts, steel fence posts, or equivalent NOT TO SCALE Silt Fence Revised July 2017 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Design and Installation Specifications l Use in combination with other construction stormwater BMPs. l Maximum slope steepness (perpendicular to the silt fence line) 1H:1V. l Maximum sheet or overland flow path length to the silt fence of 100 feet. l Do not allow flows greater than 0.5 cfs. l Use geotextile fabric that meets the following standards. All geotextile properties listed below are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or exceed the values shown in Table II-3.11: Geotextile Fabric Standards for Silt Fence): Geotextile Property Minimum Average Roll Value Polymeric Mesh AOS (ASTM D4751) 0.60 mm maximum for slit film woven (#30 sieve). 0.30 mm maximum for all other geotextile types (#50 sieve). 0.15 mm minimum for all fabric types (#100 sieve). Water Permittivity (ASTM D4491) 0.02 sec-1 minimum Grab Tensile Strength (ASTM D4632) 180 lbs. Minimum for extra strength fabric. 100 lbs minimum for standard strength fabric. Grab Tensile Strength (ASTM D4632) 30% maximum Ultraviolet Resistance (ASTM D4355) 70% minimum Table II-3.11: Geotextile Fabric Standards for Silt Fence l Support standard strength geotextiles with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the geotextile. Silt fence materials are available that have synthetic mesh backing attached. l Silt fence material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of 0°F to 120°F. l One-hundred percent biodegradable silt fence is available that is strong, long lasting, and can be left in place after the project is completed, if permitted by the local jurisdiction. l Refer to Figure II-3.22: Silt Fence for standard silt fence details. Include the following Stand- ard Notes for silt fence on construction plans and specifications: 1. The Contractor shall install and maintain temporary silt fences at the locations shown in the Plans. 2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those activities. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 372 3. The silt fence shall have a 2-feet min. and a 2½-feet max. height above the original ground surface. 4. The geotextile fabric shall be sewn together at the point of manufacture to form fabric lengths as required. Locate all sewn seams at support posts. Alternatively, two sections of silt fence can be overlapped, provided that the overlap is long enough and that the adjacent silt fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. 5. Attach the geotextile fabric on the up-slope side of the posts and secure with staples, wire, or in accordance with the manufacturer's recommendations. Attach the geotextile fabric to the posts in a manner that reduces the potential for tearing. 6. Support the geotextile fabric with wire or plastic mesh, dependent on the properties of the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely to the up-slope side of the posts with the geotextile fabric up-slope of the mesh. 7. Mesh support, if used, shall consist of steel wire with a maximum mesh spacing of 2- inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh must be as resistant to the same level of ultraviolet radiation as the geotextile fabric it supports. 8. Bury the bottom of the geotextile fabric 4-inches min. below the ground surface. Backfill and tamp soil in place over the buried portion of the geotextile fabric, so that no flow can pass beneath the silt fence and scouring cannot occur. When wire or polymeric back-up support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches min. 9. Drive or place the silt fence posts into the ground 18-inches min. A 12–inch min. depth is allowed if topsoil or other soft subgrade soil is not present and 18-inches cannot be reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of 3H:1V or steeper and the slope is perpendicular to the fence. If required post depths cannot be obtained, the posts shall be adequately secured by bracing or guying to pre- vent overturning of the fence due to sediment loading. 10. Use wood, steel or equivalent posts. The spacing of the support posts shall be a max- imum of 6-feet. Posts shall consist of either: l Wood with minimum dimensions of 2 inches by 2 inches by 3 feet. Wood shall be free of defects such as knots, splits, or gouges. l No. 6 steel rebar or larger. l ASTM A 120 steel pipe with a minimum diameter of 1-inch. l U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft. l Other steel posts having equivalent strength and bending resistance to the post sizes listed above. 11. Locate silt fences on contour as much as possible, except at the ends of the fence, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 373 where the fence shall be turned uphill such that the silt fence captures the runoff water and prevents water from flowing around the end of the fence. 12. If the fence must cross contours, with the exception of the ends of the fence, place check dams perpendicular to the back of the fence to minimize concentrated flow and erosion. The slope of the fence line where contours must be crossed shall not be steeper than 3H:1V. l Check dams shall be approximately 1-foot deep at the back of the fence. Check dams shall be continued perpendicular to the fence at the same elevation until the top of the check dam intercepts the ground surface behind the fence. l Check dams shall consist of crushed surfacing base course, gravel backfill for walls, or shoulder ballast. Check dams shall be located every 10 feet along the fence where the fence must cross contours. l Refer to Figure II-3.23: Silt Fence Installation by Slicing Method for slicing method details. The following are specifications for silt fence installation using the slicing method: 1. The base of both end posts must be at least 2- to 4-inches above the top of the geo- textile fabric on the middle posts for ditch checks to drain properly. Use a hand level or string level, if necessary, to mark base points before installation. 2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard applications. 3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as possible to the geotextile fabric, enabling posts to support the geotextile fabric from upstream water pressure. 4. Install posts with the nipples facing away from the geotextile fabric. 5. Attach the geotextile fabric to each post with three ties, all spaced within the top 8- inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post nipple when tightening to prevent sagging. 6. Wrap approximately 6-inches of the geotextile fabric around the end posts and secure with 3 ties. 7. No more than 24-inches of a 36-inch geotextile fabric is allowed above ground level. 8. Compact the soil immediately next to the geotextile fabric with the front wheel of the tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the upstream side first and then each side twice for a total of four trips. Check and correct the silt fence installation for any deviation before compaction. Use a flat-bladed shovel to tuck the fabric deeper into the ground if necessary. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 374 Figure II-3.23: Silt Fence Installation by Slicing Method 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 375 Ponding height max. 24" \v 3: 3:POST SPACING: 7 max. on open runs 4' max. on pooling areasAttach fabric to upstream side of post Top of Fabric I'////A E'////// Belt * FLOW POST DEPTH: As much below ground as fabric above ground top 8" Drive over each side of silt fence 2 to 4 times with device exerting 60 p.s.i. or greater i Diagonal attachment doubles strength100% compaction100% compaction r33n TT~ J]=I iLE inWo Q.ILEt Attachment Details: • Gather fabric at posts, if needed. • Utilize three ties per post, all within top 8" of fabric. • Position each tie diagonally, puncturing holes vertically a minimum of 1" apart. • Hang each tie on a post nipple and tighten securely. Use cable ties (50 lbs) or soft wire. oQ. Q.31HM1I meii=iii=iii i=in No more than 24" of a 36" fabric is allowed above ground Roll of silt fenceOperation Post installed after compaction Fabric above groundPIo Silt Fence ifJC il==U 200 - jj=ji 300mmIrmssrSlicing blade (18 mm width) Horizontal chisel point (76 mm width) Completed Installation Vibratory plow is not acceptable because of horizontal compaction NOT TO SCALE Silt Fence Installation by Slicing Method Revised June 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Maintenance Standards l Repair any damage immediately. l Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment trap- ping BMP. l Check the uphill side of the silt fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence and remove the trapped sediment. l Remove sediment deposits when the deposit reaches approximately one-third the height of the silt fence, or install a second silt fence. l Replace geotextile fabric that has deteriorated due to ultraviolet breakdown. BMP C234: Vegetated Strip Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use l Vegetated strips may be used downslope of all disturbed areas. l Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to BMP C241: Sediment Pond (Temporary) or other sediment trapping BMP. The only circumstance in which overland flow can be treated solely by a vegetated strip, rather than by a sediment trapping BMP, is when the following criteria are met (see Table II- 3.12: Contributing Drainage Area for Vegetated Strips): Average Contributing Area Slope Average Contributing Area Per- cent Slope Max Contributing area Flowpath Length 1.5H : 1V or flatter 67% or flatter 100 feet 2H : 1V or flatter 50% or flatter 115 feet 4H : 1V or flatter 25% or flatter 150 feet 6H : 1V or flatter 16.7% or flatter 200 feet 10H : 1V or flatter 10% or flatter 250 feet Table II-3.12: Contributing Drainage Area for Vegetated Strips 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 376 Design and Installation Specifications l The vegetated strip shall consist of a continuous strip of dense vegetation with topsoil for a min- imum of a 25-foot length along the flowpath. Grass-covered, landscaped areas are generally not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips shall consist of undisturbed native growth with a well-developed soil that allows for infiltration of runoff. l The slope within the vegetated strip shall not exceed 4H:1V. l The uphill boundary of the vegetated strip shall be delineated with clearing limits. Maintenance Standards l Any areas damaged by erosion or construction activity shall be seeded immediately and pro- tected by mulch. l If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded, sod must be installed. l If there are indications that concentrated flows are traveling across the vegetated strip, storm- water runoff controls must be installed to reduce the flows entering the vegetated strip, or addi- tional perimeter protection must be installed. BMP C235: Wattles Purpose Wattles are temporary erosion and sediment control barriers consisting of straw, compost, or other material that is wrapped in netting made of natural plant fiber or similar encasing material. They reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sed- iment. Conditions of Use l Wattles shall consist of cylinders of plant material such as weed-free straw, coir, wood chips, excelsior, or wood fiber or shavings encased within netting made of natural plant fibers unaltered by synthetic materials. l Use wattles: o In disturbed areas that require immediate erosion protection. o On exposed soils during the period of short construction delays, or over winter months. o On slopes requiring stabilization until permanent vegetation can be established. l The material used dictates the effectiveness period of the wattle. Generally, wattles are effect- ive for one to two seasons. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 377 l Prevent rilling beneath wattles by entrenching and overlapping wattles to prevent water from passing between them. Design Criteria l See Figure II-3.24: Wattles for typical construction details. l Wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length. l Install wattles perpendicular to the flow direction and parallel to the slope contour. l Place wattles in shallow trenches, staked along the contour of disturbed or newly constructed slopes. Dig narrow trenches across the slope (on contour) to a depth of 3- to 5-inches on clay soils and soils with gradual slopes. On loose soils, steep slopes, and areas with high rainfall, the trenches should be dug to a depth of 5- to 7- inches, or 1/2 to 2/3 of the thickness of the wattle. l Start building trenches and installing wattles from the base of the slope and work up. Spread excavated material evenly along the uphill slope and compact it using hand tamping or other methods. l Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches. l Install the wattles snugly into the trenches and overlap the ends of adjacent wattles 12 inches behind one another. l Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle. l If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. l Wooden stakes should be approximately 0.75 x 0.75 x 24 inches min. Willow cuttings or 3/8- inch rebar can also be used for stakes. l Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake pro- truding above the wattle. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 378 Figure II-3.24: Wattles 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 379 3' -4' (1,2 m) jjlSi\fc Viz Overlap adjacent rolls 12" behind one another / /■y \Straw rolls must be placed along slope contours /// \/ \ v-C »S \J/10' - 25' (3-8m)d ■■■ Spacing depends on soil type and slope steepness y. Sediment, organic matter, and native seeds are captured behind the rolls.*3 3"-5" (75-125mm) N\ 8"-10" Dia. (200-250mm)A///-<A.//A Live Stake // // // 1"x1" Stake £/ (25 x 25mm)/ \/ V NOTE:l 1. Straw roll installation requires the placement and secure staking of the roll in a trench, 3" - 5" (75-125mm) deep, dug on contour. Runoff must not be allowed to run under or around roll. A NOT TO SCALE Wattles Revised December 2016 DEPARTMENT OF ECOLOGY Please see http://www.ecy.wa.gov/copyhght.html for copyright notice including permissions, limitation of liability, and disclaimer.State of Washington Maintenance Standards l Wattles may require maintenance to ensure they are in contact with soil and thoroughly entrenched, especially after significant rainfall on steep sandy soils. l Inspect the slope after significant storms and repair any areas where wattles are not tightly abutted or water has scoured beneath the wattles. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C236: Vegetative Filtration Purpose Vegetative filtration as a BMP is used in conjunction with detention storage in the form of portable tanks or BMP C241: Sediment Pond (Temporary), BMP C206: Level Spreader, and a pumping sys- tem with surface intake. Vegetative filtration improves turbidity levels of stormwater discharges by fil- tering runoff through existing vegetation where undisturbed forest floor duff layer or established lawn with thatch layer are present. Vegetative filtration can also be used to infiltrate dewatering waste from foundations, vaults, and trenches as long as runoff does not occur. Conditions of Use l For every five acres of disturbed soil use one acre of grass field, farm pasture, or wooded area. Reduce or increase this area depending on project size, ground water table height, and other site conditions. l Wetlands shall not be used for vegetative filtration. l Do not use this BMP in areas with a high ground water table, or in areas that will have a high seasonal ground water table during the use of this BMP. l This BMP may be less effective on soils that prevent the infiltration of the water, such as hard till. l Using other effective source control measures throughout a construction site will prevent the generation of additional highly turbid water and may reduce the time period or area need for this BMP. l Stop distributing water into the vegetated filtration area if standing water or erosion results. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 380 treatment pond prior to decanting. Compliance with the water quality standards is determined in the receiving water. Operator Training Each project site using chemical treatment must have a trained operator who is certified for oper- ation of an Enhanced Chemical Treatment system. The operator must be trained and certified by an organization approved by Ecology. Organizations approved for operator training are found at the fol- lowing website: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee- guidance-resources/Contaminated-water-on-construction-sites Sediment Removal and Disposal l Sediment shall be removed from the untreated stormwater storage pond and treatment cells as necessary. Typically, sediment removal is required at least once during a wet season and at the decommissioning of the chemical treatment system. Sediment remaining in the cells between batches may enhance the settling process and reduce the required chemical dosage. l Sediment that is known to be non-toxic may be incorporated into the site away from drain- ages. BMP C251: Construction Stormwater Filtration Purpose Filtration removes sediment from runoff originating from disturbed areas of the site. Conditions of Use Traditional Construction Stormwater BMPs used to control soil erosion and sediment loss from con- struction sites may not be adequate to ensure compliance with the water quality standard for tur- bidity in the receiving water. Filtration may be used in conjunction with gravity settling to remove sediment as small as fine silt (0.5 µm). The reduction in turbidity will be dependent on the particle size distribution of the sediment in the stormwater. In some circumstances, sedimentation and fil- tration may achieve compliance with the water quality standard for turbidity. The use of construction stormwater filtration does not require approval from Ecology as long as treat- ment chemicals are not used. Filtration in conjunction with BMP C250: Construction Stormwater Chemical Treatment requires testing under the Chemical Technology Assessment Protocol – Eco- logy (CTAPE) before it can be initiated. Approval from Ecology must be obtained at each site where chemical use is proposed prior to use. See https://- fortress.wa.gov/ecy/publications/SummaryPages/ecy070258.html for a copy of the Request for Chemical Treatment form. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 404 Design and Installation Specifications Two types of filtration systems may be applied to construction stormwater treatment: rapid and slow. Rapid filtration systems are the typical system used for water and wastewater treatment. They can achieve relatively high hydraulic flow rates, on the order of 2 to 20 gpm/sf, because they have auto- matic backwash systems to remove accumulated solids. Slow filtration systems have very low hydraulic rates, on the order of 0.02 gpm/sf, because they do not have backwash systems. Slow filtration systems have generally been used as post construction BMPs to treat stormwater (see V-6 Filtration BMPs). Slow filtration is mechanically simple in com- parison to rapid filtration, but requires a much larger filter area. Filter Types and Efficiencies Sand media filters are available with automatic backwashing features that can filter to 50 µm particle size. Screen or bag filters can filter down to 5 µm. Fiber wound filters can remove particles down to 0.5 µm. Filters should be sequenced from the largest to the smallest pore opening. Sediment removal efficiency will be related to particle size distribution in the stormwater. Treatment Process and Description Stormwater is collected at interception point(s) on the site and diverted to an untreated stormwater sediment pond or tank for removal of large sediment, and storage of the stormwater before it is treated by the filtration system. In a rapid filtration system, the untreated stormwater is pumped from the pond or tank through the filtration media. Slow filtration systems are designed using gravity to convey water from the pond or tank to and through the filtration media. Sizing Filtration treatment systems must be designed to control the velocity and peak volumetric flow rate that is discharged from the system and consequently the project site. See Element 3: Control Flow Rates for further details on this requirement. The untreated stormwater storage pond or tank should be sized to hold 1.5 times the volume of run- off generated from the site during the 10-year, 24-hour storm event, minus the filtration treatment system flowrate for an 8-hour period. For a chitosan-enhanced sand filtration system, the filtration treatment system flowrate should be sized using a hydraulic loading rate between 6-8 gpm/ft2. Other hydraulic loading rates may be more appropriate for other systems. Bypass should be provided around the filtration treatment system to accommodate extreme storm events. Runoff volume shall be calculated using the methods presented in III-2.3 Single Event Hydrograph Method. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases, this would be the land cover conditions just prior to final landscaping). If the filtration treatment system design does not allow you to discharge at the rates as required by Element 3: Control Flow Rates, and if the site has a permanent Flow Control BMP that will serve the planned development, the discharge from the filtration treatment system may be directed to the per- manent Flow Control BMP to comply with Element 3: Control Flow Rates. In this case, all discharge (including water passing through the treatment system and stormwater bypassing the treatment 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 405 system) will be directed into the permanent Flow Control BMP. If site constraints make locating the untreated stormwater storage pond difficult, the permanent Flow Control BMP may be divided to serve as the untreated stormwater storage pond and the post-treatment temporary flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The designer must document in the Construction SWPPP how the per- manent Flow Control BMP is able to attenuate the discharge from the site to meet the requirements of Element 3: Control Flow Rates. If the design of the permanent Flow Control BMP was modified for temporary construction flow control purposes, the construction of the permanent Flow Control BMP must be finalized, as designed for its permanent function, at project completion. Maintenance Standards l Rapid sand filters typically have automatic backwash systems that are triggered by a pre-set pressure drop across the filter. If the backwash water volume is not large or substantially more turbid than the untreated stormwater stored in the holding pond or tank, backwash return to the untreated stormwater pond or tank may be appropriate. However, other means of treat- ment and disposal may be necessary. l Screen, bag, and fiber filters must be cleaned and/or replaced when they become clogged. l Sediment shall be removed from the storage and/or treatment ponds as necessary. Typically, sediment removal is required once or twice during a wet season and at the decommissioning of the ponds. l Disposal of filtration equipment must comply with applicable local, state, and federal reg- ulations. BMP C252: Treating and Disposing of High pH Water Purpose When pH levels in stormwater rise above 8.5, it is necessary to lower the pH levels to the acceptable range of 6.5 to 8.5 prior to discharge to surface or ground water. A pH level range of 6.5 to 8.5 is typ- ical for most natural watercourses, and this neutral pH range is required for the survival of aquatic organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may become stressed and may die. Conditions of Use l The water quality standard for pH in Washington State is in the range of 6.5 to 8.5. Storm- water with pH levels exceeding water quality standards may be either neutralized on site or disposed of to a sanitary sewer or concrete batch plant with pH neutralization capabilities. l Neutralized stormwater may be discharged to surface waters under the Construction Storm- water General permit. l Neutralized process water such as concrete truck wash-out, hydro-demolition, or saw-cutting slurry must be managed to prevent discharge to surface waters. Any stormwater 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 406 contaminated during concrete work is considered process wastewater and must not be dis- charged to waters of the State or stormwater collection systems. l The process used for neutralizing and/or disposing of high pH stormwater from the site must be documented in the Construction Stormwater Pollution Prevention Plan. Causes of High pH High pH at construction sites is most commonly caused by the contact of stormwater with poured or recycled concrete, cement, mortars, and other Portland cement or lime containing construction materials. (See BMP C151: Concrete Handling for more information on concrete handling pro- cedures). The principal caustic agent in cement is calcium hydroxide (free lime). Calcium hardness can contribute to high pH values and cause toxicity that is associated with high pH conditions. A high level of calcium hardness in waters of the state is not allowed. Ground water stand- ard for calcium and other dissolved solids in Washington State is less than 500 mg/l. Treating High pH Stormwater by Carbon Dioxide Sparging Advantages of Carbon Dioxide Sparging l Rapidly neutralizes high pH water. l Cost effective and safer to handle than acid compounds. l CO2 is self-buffering. It is difficult to overdose and create harmfully low pH levels. l Material is readily available. The Chemical Process of Carbon Dioxide Sparging When carbon dioxide (CO2) is added to water (H2O), carbonic acid (H2CO3) is formed which can further dissociate into a proton (H+) and a bicarbonate anion (HCO3-) as shown below: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- The free proton is a weak acid that can lower the pH. Water temperature has an effect on the reac- tion as well. The colder the water temperature is, the slower the reaction occurs. The warmer the water temperature is, the quicker the reaction occurs. Most construction applications in Washington State have water temperatures in the 50°F or higher range so the reaction is almost simultaneous. The Treatment Process of Carbon Dioxide Sparging High pH water may be treated using continuous treatment, continuous discharge systems. These manufactured systems continuously monitor influent and effluent pH to ensure that pH values are within an acceptable range before being discharged. All systems must have fail safe automatic shut off switches in the event that pH is not within the acceptable discharge range. Only trained operators may operate manufactured systems. System manufacturers often provide trained operators or train- ing on their devices. The following procedure may be used when not using a continuous discharge system: 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 407 1. Prior to treatment, the appropriate jurisdiction should be notified in accordance with the reg- ulations set by the jurisdiction. 2. Every effort should be made to isolate the potential high pH water in order to treat it separately from other stormwater on-site. 3. Water should be stored in an acceptable storage facility, detention pond, or containment cell prior to pH treatment. 4. Transfer water to be treated for pH to the pH treatment structure. Ensure that the pH treat- ment structure size is sufficient to hold the amount of water that is to be treated. Do not fill the pH treatment structure completely, allow at least 2 feet of freeboard. 5. The operator samples the water within the pH treatment structure for pH and notes the clarity of the water. As a rule of thumb, less CO2 is necessary for clearer water. The results of the samples and water clarity observations should be recorded. 6. In the pH treatment structure, add CO2 until the pH falls into the range of 6.9-7.1. Adjusting pH to within 0.2 pH units of receiving water (background pH) is recommended. It is unlikely that pH can be adjusted to within 0.2 pH units using dry ice. Compressed carbon dioxide gas should be introduced to the water using a carbon dioxide diffuser located near the bottom of the pH treatment structure, this will allow carbon dioxide to bubble up through the water and diffuse more evenly. 7. Slowly discharge the water, making sure water does not get stirred up in the process. Release about 80% of the water from the pH treatment structure leaving any sludge behind. If turbidity remains above the maximum allowable, consider adding filtration to the treatment train. See BMP C251: Construction Stormwater Filtration. 8. Discharge treated water through a pond or drainage system. 9. Excess sludge needs to be disposed of properly as concrete waste. If several batches of water are undergoing pH treatment, sludge can be left in the treatment structure for the next batch treatment. Dispose of sludge when it fills 50% of the treatment structure volume. 10. Disposal must comply with applicable local, state, and federal regulations. Treating High pH Stormwater by Food Grade Vinegar Food grade vinegar that meets FDA standards may be used to neutralize high pH water. Food grade vinegar is only 4% to 18% acetic acid with the remainder being water. Food grade vinegar may be used if dosed just enough to lower pH sufficiently. Use a treatment process as described above for CO2 sparging, but add food grade vinegar instead of CO2. This treatment option for high pH stormwater does not apply to anything but food grade vinegar. Acetic acid does not equal vinegar. Any other product or waste containing acetic acid must go through the evaluation process in Appendix G of Whole Effluent Toxicity Testing Guidance and Test Review Criteria (Marshall, 2016). 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 408 Disposal of High pH Stormwater Sanitary Sewer Disposal Local sewer authority approval is required prior to disposal via the sanitary sewer. Concrete Batch Plant Disposal l Only permitted facilities may accept high pH water. l Contact the facility to ensure they can accept the high pH water. Maintenance Standards Safety and materials handling: l All equipment should be handled in accordance with OSHA rules and regulations. l Follow manufacturer guidelines for materials handling. Each operator should provide: l A diagram of the monitoring and treatment equipment. l A description of the pumping rates and capacity the treatment equipment is capable of treat- ing. Each operator should keep a written record of the following: l Client name and phone number. l Date of treatment. l Weather conditions. l Project name and location. l Volume of water treated. l pH of untreated water. l Amount of CO2 or food grade vinegar needed to adjust water to a pH range of 6.9-7.1. l pH of treated water. l Discharge point location and description. A copy of this record should be given to the client/contractor who should retain the record for three years. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 409 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: 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. Issuance Date: November 18, 2020 Effective Date: January 1, 2021 Expiration Date: December 31, 2025 CONSTRUCTION STORMWATER GENERAL PERMIT National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge General Permit for Stormwater Discharges Associated with Construction Activity State of Washington Department of Ecology Olympia, Washington 98504 In compliance with the provisions of Chapter 90.48 Revised Code of Washington (State of Washington Water Pollution Control Act) and Title 33 United States Code, Section 1251 et seq. The Federal Water Pollution Control Act (The Clean Water Act) Until this permit expires, is modified, or revoked, Permittees that have properly obtained coverage under this general permit are authorized to discharge in accordance with the special and general conditions that follow. __________________________________ Vincent McGowan, P.E. Water Quality Program Manager Washington State Department of Ecology Construction Stormwater General Permit Page i TABLE OF CONTENTS LIST OF TABLES .................................................................................................................................. ii SUMMARY OF PERMIT REPORT SUBMITTALS ...................................................................................... 1 SPECIAL CONDITIONS ......................................................................................................................... 3 S1. Permit Coverage .............................................................................................................................. 3 S2. Application Requirements ............................................................................................................... 7 S3. Compliance with Standards ............................................................................................................. 9 S4. Monitoring Requirements, Benchmarks, and Reporting Triggers ................................................. 10 S5. Reporting and Recordkeeping Requirements ................................................................................ 17 S6. Permit Fees .................................................................................................................................... 20 S7. Solid and Liquid Waste Disposal .................................................................................................... 20 S8. Discharges to 303(D) or TMDL Waterbodies ................................................................................. 20 S9. Stormwater Pollution Prevention Plan .......................................................................................... 23 S10. Notice Of Termination ................................................................................................................... 32 GENERAL CONDITIONS ..................................................................................................................... 34 G1. Discharge Violations....................................................................................................................... 34 G2. Signatory Requirements ................................................................................................................ 34 G3. Right of Inspection and Entry ......................................................................................................... 35 G4. General Permit Modification and Revocation ............................................................................... 35 G5. Revocation of Coverage Under tPermit ......................................................................................... 35 G6. Reporting a Cause for Modification ............................................................................................... 36 G7. Compliance with Other Laws and Statutes .................................................................................... 36 G8. Duty to Reapply.............................................................................................................................. 36 G9. Removed Substance ....................................................................................................................... 36 G10. Duty to Provide Information .......................................................................................................... 36 G11. Other Requirements of 40 CFR ...................................................................................................... 37 G12. Additional Monitoring .................................................................................................................... 37 G13. Penalties for Violating Permit Conditions ...................................................................................... 37 G14. Upset .............................................................................................................................................. 37 G15. Property Rights .............................................................................................................................. 37 G16. Duty to Comply .............................................................................................................................. 37 G17. Toxic Pollutants .............................................................................................................................. 38 G18. Penalties for Tampering ................................................................................................................. 38 G19. Reporting Planned Changes ........................................................................................................... 38 G20. Reporting Other Information ......................................................................................................... 38 G21. Reporting Anticipated Non-Compliance ........................................................................................ 38 Construction Stormwater General Permit Page ii G22. Requests to Be Excluded From Coverage Under the Permit ......................................................... 39 G23. Appeals........................................................................................................................................... 39 G24. Severability..................................................................................................................................... 39 G25. Bypass Prohibited .......................................................................................................................... 39 APPENDIX A – DEFINITIONS .............................................................................................................. 42 APPENDIX B – ACRONYMS ................................................................................................................ 50 LIST OF TABLES Table 1 Summary of Required Submittals ................................................................................................ 1 Table 2 Summary of Required On-site Documentation ........................................................................... 2 Table 3 Summary of Primary Monitoring Requirements ....................................................................... 12 Table 4 Monitoring and Reporting Requirements ................................................................................. 14 Table 5 Turbidity, Fine Sediment & Phosphorus Sampling and Limits for 303(d)-Listed Waters ................................................................................................................ 22 Table 6 pH Sampling and Limits for 303(d)-Listed Waters ..................................................................... 22 Construction Stormwater General Permit Page 1 SUMMARY OF PERMIT REPORT SUBMITTALS Refer to the Special and General Conditions within this permit for additional submittal requirements. Appendix A provides a list of definitions. Appendix B provides a list of acronyms. Table 1 Summary of Required Submittals Permit Section Submittal Frequency First Submittal Date S5.A and S8 High Turbidity/Transparency Phone Reporting As Necessary Within 24 hours S5.B Discharge Monitoring Report Monthly* Within 15 days following the end of each month S5.F and S8 Noncompliance Notification – Telephone Notification As necessary Within 24 hours S5.F Noncompliance Notification – Written Report As necessary Within 5 Days of non-compliance S9.D Request for Chemical Treatment Form As necessary Written approval from Ecology is required prior to using chemical treatment (with the exception of dry ice, CO2 or food grade vinegar to adjust pH) G2 Notice of Change in Authorization As necessary G6 Permit Application for Substantive Changes to the Discharge As necessary G8 Application for Permit Renewal 1/permit cycle No later than 180 days before expiration S2.A Notice of Permit Transfer As necessary G19 Notice of Planned Changes As necessary G21 Reporting Anticipated Non-compliance As necessary NOTE: *Permittees must submit electronic Discharge Monitoring Reports (DMRs) to the Washington State Department of Ecology monthly, regardless of site discharge, for the full duration of permit coverage. Refer to Section S5.B of this General Permit for more specific information regarding DMRs. Construction Stormwater General Permit Page 2 Table 2 Summary of Required On-site Documentation Document Title Permit Conditions Permit Coverage Letter See Conditions S2, S5 Construction Stormwater General Permit (CSWGP) See Conditions S2, S5 Site Log Book See Conditions S4, S5 Stormwater Pollution Prevention Plan (SWPPP) See Conditions S5, S9 Site Map See Conditions S5, S9 Construction Stormwater General Permit Page 3 SPECIAL CONDITIONS S1. PERMIT COVERAGE A. Permit Area This Construction Stormwater General Permit (CSWGP) covers all areas of Washington State, except for federal operators and Indian Country as specified in Special Condition S1.E.3 and 4. B. Operators Required to Seek Coverage Under this General Permit 1. Operators of the following construction activities are required to seek coverage under this CSWGP: a. Clearing, grading and/or excavation that results in the disturbance of one or more acres (including off-site disturbance acreage related to construction-support activity as authorized in S1.C.2) and discharges stormwater to surface waters of the State; and clearing, grading and/or excavation on sites smaller than one acre that are part of a larger common plan of development or sale, if the common plan of development or sale will ultimately disturb one acre or more and discharge stormwater to surface waters of the State. i. This category includes forest practices (including, but not limited to, class IV conversions) that are part of a construction activity that will result in the disturbance of one or more acres, and discharge to surface waters of the State (that is, forest practices that prepare a site for construction activities); and b. Any size construction activity discharging stormwater to waters of the State that the Washington State Department of Ecology (Ecology): i. Determines to be a significant contributor of pollutants to waters of the State of Washington. ii. Reasonably expects to cause a violation of any water quality standard. 2. Operators of the following activities are not required to seek coverage under this CSWGP (unless specifically required under Special Condition S1.B.1.b, above): a. Construction activities that discharge all stormwater and non-stormwater to groundwater, sanitary sewer, or combined sewer, and have no point source discharge to either surface water or a storm sewer system that drains to surface waters of the State. b. Construction activities covered under an Erosivity Waiver (Special Condition S1.F). c. Routine maintenance that is performed to maintain the original line and grade, hydraulic capacity, or original purpose of a facility. C. Authorized Discharges 1. Stormwater Associated with Construction Activity. Subject to compliance with the terms and conditions of this permit, Permittees are authorized to discharge stormwater associated with construction activity to surface waters of the State or to a storm sewer system that drains to surface waters of the State. (Note that “surface waters of the Construction Stormwater General Permit Page 4 State” may exist on a construction site as well as off site; for example, a creek running through a site.) 2. Stormwater Associated with Construction Support Activity. This permit also authorizes stormwater discharge from support activities related to the permitted construction site (for example, an on-site portable rock crusher, off-site equipment staging yards, material storage areas, borrow areas, etc.) provided: a. The support activity relates directly to the permitted construction site that is required to have an NPDES permit; and b. The support activity is not a commercial operation serving multiple unrelated construction projects, and does not operate beyond the completion of the construction activity; and c. Appropriate controls and measures are identified in the Stormwater Pollution Prevention Plan (SWPPP) for the discharges from the support activity areas. 3. Non-Stormwater Discharges. The categories and sources of non-stormwater discharges identified below are authorized conditionally, provided the discharge is consistent with the terms and conditions of this permit: a. Discharges from fire-fighting activities. b. Fire hydrant system flushing. c. Potable water, including uncontaminated water line flushing. d. Hydrostatic test water. e. Uncontaminated air conditioning or compressor condensate. f. Uncontaminated groundwater or spring water. g. Uncontaminated excavation dewatering water (in accordance with S9.D.10). h. Uncontaminated discharges from foundation or footing drains. i. Uncontaminated or potable water used to control dust. Permittees must minimize the amount of dust control water used. j. Routine external building wash down that does not use detergents. k. Landscape irrigation water. The SWPPP must adequately address all authorized non-stormwater discharges, except for discharges from fire-fighting activities, and must comply with Special Condition S3. At a minimum, discharges from potable water (including water line flushing), fire hydrant system flushing, and pipeline hydrostatic test water must undergo the following: dechlorination to a concentration of 0.1 parts per million (ppm) or less, and pH adjustment to within 6.5 – 8.5 standard units (su), if necessary. D. Prohibited Discharges The following discharges to waters of the State, including groundwater, are prohibited: Construction Stormwater General Permit Page 5 1. Concrete wastewater 2. Wastewater from washout and clean-up of stucco, paint, form release oils, curing compounds and other construction materials. 3. Process wastewater as defined by 40 Code of Federal Regulations (CFR) 122.2 (See Appendix A of this permit). 4. Slurry materials and waste from shaft drilling, including process wastewater from shaft drilling for construction of building, road, and bridge foundations unless managed according to Special Condition S9.D.9.j. 5. Fuels, oils, or other pollutants used in vehicle and equipment operation and maintenance. 6. Soaps or solvents used in vehicle and equipment washing. 7. Wheel wash wastewater, unless managed according to Special Condition S9.D.9. 8. Discharges from dewatering activities, including discharges from dewatering of trenches and excavations, unless managed according to Special Condition S9.D.10. E. Limits on Coverage Ecology may require any discharger to apply for and obtain coverage under an individual permit or another more specific general permit. Such alternative coverage will be required when Ecology determines that this CSWGP does not provide adequate assurance that water quality will be protected, or there is a reasonable potential for the project to cause or contribute to a violation of water quality standards. The following stormwater discharges are not covered by this permit: 1. Post-construction stormwater discharges that originate from the site after completion of construction activities and the site has undergone final stabilization. 2. Non-point source silvicultural activities such as nursery operations, site preparation, reforestation and subsequent cultural treatment, thinning, prescribed burning, pest and fire control, harvesting operations, surface drainage, or road construction and maintenance, from which there is natural runoff as excluded in 40 CFR Subpart 122. 3. Stormwater from any federal operator. 4. Stormwater from facilities located on Indian Country as defined in 18 U.S.C.§1151, except portions of the Puyallup Reservation as noted below. Indian Country includes: a. All land within any Indian Reservation notwithstanding the issuance of any patent, and, including rights-of-way running through the reservation. This includes all federal, tribal, and Indian and non-Indian privately owned land within the reservation. b. All off-reservation Indian allotments, the Indian titles to which have not been extinguished, including rights-of-way running through the same. c. All off-reservation federal trust lands held for Native American Tribes. Construction Stormwater General Permit Page 6 Puyallup Exception: Following the Puyallup Tribes of Indians Land Settlement Act of 1989, 25 U.S.C. §1773; the permit does apply to land within the Puyallup Reservation except for discharges to surface water on land held in trust by the federal government. 5. Stormwater from any site covered under an existing NPDES individual permit in which stormwater management and/or treatment requirements are included for all stormwater discharges associated with construction activity. 6. Stormwater from a site where an applicable Total Maximum Daily Load (TMDL) requirement specifically precludes or prohibits discharges from construction activity. F. Erosivity Waiver Construction site operators may qualify for an Erosivity Waiver from the CSWGP if the following conditions are met: 1. The site will result in the disturbance of fewer than five (5) acres and the site is not a portion of a common plan of development or sale that will disturb five (5) acres or greater. 2. Calculation of Erosivity “R” Factor and Regional Timeframe: a. The project’s calculated rainfall erosivity factor (“R” Factor) must be less than five (5) during the period of construction activity, (See the CSWGP homepage http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html for a link to the EPA’s calculator and step by step instructions on computing the “R” Factor in the EPA Erosivity Waiver Fact Sheet). The period of construction activity starts when the land is first disturbed and ends with final stabilization. In addition: b. The entire period of construction activity must fall within the following timeframes: i. For sites west of the Cascades Crest: June 15 – September 15. ii. For sites east of the Cascades Crest, excluding the Central Basin: June 15 – October 15. iii. For sites east of the Cascades Crest, within the Central Basin: no timeframe restrictions apply. The Central Basin is defined as the portions of Eastern Washington with mean annual precipitation of less than 12 inches. For a map of the Central Basin (Average Annual Precipitation Region 2), refer to: http://www.ecy.wa.gov/programs/wq/stormwater/construction/resourcesguida nce.html. 3. Construction site operators must submit a complete Erosivity Waiver certification form at least one week before disturbing the land. Certification must include statements that the operator will: a. Comply with applicable local stormwater requirements; and b. Implement appropriate erosion and sediment control BMPs to prevent violations of water quality standards. 4. This waiver is not available for facilities declared significant contributors of pollutants as defined in Special Condition S1.B.1.b or for any size construction activity that could Construction Stormwater General Permit Page 7 reasonably expect to cause a violation of any water quality standard as defined in Special Condition S1.B.1.b.ii. 5. This waiver does not apply to construction activities which include non-stormwater discharges listed in Special Condition S1.C.3. 6. If construction activity extends beyond the certified waiver period for any reason, the operator must either: a. Recalculate the rainfall erosivity “R” factor using the original start date and a new projected ending date and, if the “R” factor is still under 5 and the entire project falls within the applicable regional timeframe in Special Condition S1.F.2.b, complete and submit an amended waiver certification form before the original waiver expires; or b. Submit a complete permit application to Ecology in accordance with Special Condition S2.A and B before the end of the certified waiver period. S2. APPLICATION REQUIREMENTS A. Permit Application Forms 1. Notice of Intent Form a. Operators of new or previously unpermitted construction activities must submit a complete and accurate permit application (Notice of Intent, or NOI) to Ecology. b. Operators must apply using the electronic application form (NOI) available on Ecology’s website (http://ecy.wa.gov/programs/wq/stormwater/construction/index.html). Permittees unable to submit electronically (for example, those who do not have an internet connection) must contact Ecology to request a waiver and obtain instructions on how to obtain a paper NOI. Department of Ecology Water Quality Program - Construction Stormwater PO Box 47696 Olympia, Washington 98504-7696 c. The operator must submit the NOI at least 60 days before discharging stormwater from construction activities and must submit it prior to the date of the first public notice (See Special Condition S2.B, below, for details). The 30-day public comment period begins on the publication date of the second public notice. Unless Ecology responds to the complete application in writing, coverage under the general permit will automatically commence on the 31st day following receipt by Ecology of a completed NOI, or the issuance date of this permit, whichever is later; unless Ecology specifies a later date in writing as required by WAC173-226-200(2). See S8.B for Limits on Coverage for New Discharges to TMDL or 303(d)-Listed Waters. d. If an applicant intends to use a Best Management Practice (BMP) selected on the basis of Special Condition S9.C.4 (“demonstrably equivalent” BMPs), the applicant must notify Ecology of its selection as part of the NOI. In the event the applicant selects BMPs after submission of the NOI, the applicant must provide notice of the Construction Stormwater General Permit Page 8 selection of an equivalent BMP to Ecology at least 60 days before intended use of the equivalent BMP. e. Applicants must notify Ecology if they are aware of contaminated soils and/or groundwater associated with the construction activity. Provide detailed information with the NOI (as known and readily available) on the nature and extent of the contamination (concentrations, locations, and depth), as well as pollution prevention and/or treatment BMPs proposed to control the discharge of soil and/or groundwater contaminants in stormwater. Examples of such detail may include, but are not limited to: i. List or table of all known contaminants with laboratory test results showing concentration and depth, ii. Map with sample locations, iii. Related portions of the Stormwater Pollution Prevention Plan (SWPPP) that address the management of contaminated and potentially contaminated construction stormwater and dewatering water, iv. Dewatering plan and/or dewatering contingency plan. 2. Transfer of Coverage Form The Permittee can transfer current coverage under this permit to one or more new operators, including operators of sites within a Common Plan of Development, provided: i. The Permittee submits a complete Transfer of Coverage Form to Ecology, signed by the current and new discharger and containing a specific date for transfer of permit responsibility, coverage and liability (including any Administrative Orders associated with the permit); and ii. Ecology does not notify the current discharger and new discharger of intent to revoke coverage under the general permit. If this notice is not given, the transfer is effective on the date specified in the written agreement. When a current discharger (Permittee) transfers a portion of a permitted site, the current discharger must also indicate the remaining permitted acreage after the transfer. Transfers do not require public notice. 3. Modification of Coverage Form Permittees must notify Ecology regarding any changes to the information provided on the NOI by submitting an Update/Modification of Permit Coverage form in accordance with General Conditions G6 and G19. Examples of such changes include, but are not limited to: i. Changes to the Permittee’s mailing address, ii. Changes to the on-site contact person information, and iii. Changes to the area/acreage affected by construction activity. Construction Stormwater General Permit Page 9 B. Public Notice For new or previously unpermitted construction activities, the applicant must publish a public notice at least one time each week for two consecutive weeks, at least 7 days apart, in a newspaper with general circulation in the county where the construction is to take place. The notice must be run after the NOI has been submitted and must contain: 1. A statement that “The applicant is seeking coverage under the Washington State Department of Ecology’s Construction Stormwater NPDES and State Waste Discharge General Permit.” 2. The name, address, and location of the construction site. 3. The name and address of the applicant. 4. The type of construction activity that will result in a discharge (for example, residential construction, commercial construction, etc.), and the total number of acres to be disturbed over the lifetime of the project. 5. The name of the receiving water(s) (that is, the surface water(s) to which the site will discharge), or, if the discharge is through a storm sewer system, the name of the operator of the system and the receiving water(s) the system discharges to. 6. The statement: Any persons desiring to present their views to the Washington State Department of Ecology regarding this application, or interested in Ecology’s action on this application, may notify Ecology in writing no later than 30 days of the last date of publication of this notice. Ecology reviews public comments and considers whether discharges from this project would cause a measurable change in receiving water quality, and, if so, whether the project is necessary and in the overriding public interest according to Tier II antidegradation requirements under WAC 173-201A-320. Comments can be submitted to: Department of Ecology, PO Box 47696, Olympia, Washington 98504-7696 Attn: Water Quality Program, Construction Stormwater. S3. COMPLIANCE WITH STANDARDS A. Discharges must not cause or contribute to a violation of surface water quality standards (Chapter 173-201A WAC), groundwater quality standards (Chapter 173-200 WAC), sediment management standards (Chapter 173-204 WAC), and human health-based criteria in the Federal water quality criteria applicable to Washington. (40 CFR Part 131.45) Discharges that are not in compliance with these standards are prohibited. B. Prior to the discharge of stormwater and non-stormwater to waters of the State, the Permittee must apply All Known, Available, and Reasonable methods of prevention, control, and Treatment (AKART). This includes the preparation and implementation of an adequate SWPPP, with all appropriate BMPs installed and maintained in accordance with the SWPPP and the terms and conditions of this permit. C. Ecology presumes that a Permittee complies with water quality standards unless discharge monitoring data or other site-specific information demonstrates that a discharge causes or contributes to a violation of water quality standards, when the Permittee complies with the following conditions. The Permittee must fully: Construction Stormwater General Permit Page 10 1. Comply with all permit conditions, including; planning, sampling, monitoring, reporting, and recordkeeping conditions. 2. Implement stormwater BMPs contained in stormwater management manuals published or approved by Ecology, or BMPs that are demonstrably equivalent to BMPs contained in stormwater management manuals published or approved by Ecology, including the proper selection, implementation, and maintenance of all applicable and appropriate BMPs for on-site pollution control. (For purposes of this section, the stormwater manuals listed in Appendix 10 of the Phase I Municipal Stormwater Permit are approved by Ecology.) D. Where construction sites also discharge to groundwater, the groundwater discharges must also meet the terms and conditions of this CSWGP. Permittees who discharge to groundwater through an injection well must also comply with any applicable requirements of the Underground Injection Control (UIC) regulations, Chapter 173-218 WAC. S4. MONITORING REQUIREMENTS, BENCHMARKS, AND REPORTING TRIGGERS A. Site Log Book The Permittee must maintain a site log book that contains a record of the implementation of the SWPPP and other permit requirements, including the installation and maintenance of BMPs, site inspections, and stormwater monitoring. B. Site Inspections Construction sites one (1) acre or larger that discharge stormwater to surface waters of the State must have site inspections conducted by a Certified Erosion and Sediment Control Lead (CESCL). Sites less than one (1) acre may have a person without CESCL certification conduct inspections. (See Special Conditions S4.B.3 and B.4, below, for detailed requirements of the Permittee’s CESCL.) Site inspections must include all areas disturbed by construction activities, all BMPs, and all stormwater discharge points under the Permittee’s operational control. 1. The Permittee must have staff knowledgeable in the principles and practices of erosion and sediment control. The CESCL (sites one acre or more) or inspector (sites less than one acre) must have the skills to assess the: a. Site conditions and construction activities that could impact the quality of stormwater; and b. Effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. The SWPPP must identify the CESCL or inspector, who must be present on site or on-call at all times. The CESCL (sites one (1) acre or more) must obtain this certification through an approved erosion and sediment control training program that meets the minimum training standards established by Ecology. (See BMP C160 in the manual, referred to in Special Condition S9.C.1 and 2.) 2. The CESCL or inspector must examine stormwater visually for the presence of suspended sediment, turbidity, discoloration, and oil sheen. BMP effectiveness must be evaluated to Construction Stormwater General Permit Page 11 determine if it is necessary to install, maintain, or repair BMPs to improve the quality of stormwater discharges. Based on the results of the inspection, the Permittee must correct the problems identified, by: a. Reviewing the SWPPP for compliance with Special Condition S9 and making appropriate revisions within 7 days of the inspection. b. Immediately beginning the process of fully implementing and maintaining appropriate source control and/or treatment BMPs, within 10 days of the inspection. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when an extension is requested by a Permittee within the initial 10-day response period. c. Documenting BMP implementation and maintenance in the site log book. 3. The CESCL or inspector must inspect all areas disturbed by construction activities, all BMPs, and all stormwater discharge points at least once every calendar week and within 24 hours of any discharge from the site. (For purposes of this condition, individual discharge events that last more than one (1) day do not require daily inspections. For example, if a stormwater pond discharges continuously over the course of a week, only one (1) inspection is required that week.) Inspection frequency may be reduced to once every calendar month for inactive sites that are temporarily stabilized. 4. The Permittee must summarize the results of each inspection in an inspection report or checklist and enter the report/checklist into, or attach it to, the site log book. At a minimum, each inspection report or checklist must include: a. Inspection date and time. b. Weather information. c. The general conditions during inspection. d. The approximate amount of precipitation since the last inspection. e. The approximate amount of precipitation within the last 24 hours. f. A summary or list of all implemented BMPs, including observations of all erosion/sediment control structures or practices. g. A description of: i. BMPs inspected (including location). ii. BMPs that need maintenance and why. iii. BMPs that failed to operate as designed or intended, and iv. Where additional or different BMPs are needed, and why. h. A description of stormwater discharged from the site. The Permittee must note the presence of suspended sediment, turbidity, discoloration, and oil sheen, as applicable. Construction Stormwater General Permit Page 12 i. Any water quality monitoring performed during inspection. j. General comments and notes, including a brief description of any BMP repairs, maintenance, or installations made following the inspection. k. An implementation schedule for the remedial actions that the Permittee plans to take if the site inspection indicates that the site is out of compliance. The remedial actions taken must meet the requirements of the SWPPP and the permit. l. A summary report of the inspection. m. The name, title, and signature of the person conducting the site inspection, a phone number or other reliable method to reach this person, and the following statement: I certify that this report is true, accurate, and complete to the best of my knowledge and belief. Table 3 Summary of Primary Monitoring Requirements Size of Soil Disturbance1 Weekly Site Inspections Weekly Sampling w/ Turbidity Meter Weekly Sampling w/ Transparency Tube Weekly pH Sampling2 CESCL Required for Inspections? Sites that disturb less than 1 acre, but are part of a larger Common Plan of Development Required Not Required Not Required Not Required No Sites that disturb 1 acre or more, but fewer than 5 acres Required Sampling Required – either method3 Required Yes Sites that disturb 5 acres or more Required Required Not Required4 Required Yes 1 Soil disturbance is calculated by adding together all areas that will be affected by construction activity. Construction activity means clearing, grading, excavation, and any other activity that disturbs the surface of the land, including ingress/egress from the site. 2 If construction activity results in the disturbance of 1 acre or more, and involves significant concrete work (1,000 cubic yards of concrete or recycled concrete placed or poured over the life of a project) or the use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD], or fly ash), and stormwater from the affected area drains to surface waters of the State or to a storm sewer stormwater collection system that drains to other surface waters of the State, the Permittee must conduct pH sampling in accordance with Special Condition S4.D. 3 Sites with one or more acres, but fewer than 5 acres of soil disturbance, must conduct turbidity or transparency sampling in accordance with Special Condition S4.C.4.a or b. 4 Sites equal to or greater than 5 acres of soil disturbance must conduct turbidity sampling using a turbidity meter in accordance with Special Condition S4.C.4.a. Construction Stormwater General Permit Page 13 C. Turbidity/Transparency Sampling Requirements 1. Sampling Methods a. If construction activity involves the disturbance of five (5) acres or more, the Permittee must conduct turbidity sampling per Special Condition S4.C.4.a, below. b. If construction activity involves one (1) acre or more but fewer than five (5) acres of soil disturbance, the Permittee must conduct either transparency sampling or turbidity sampling per Special Condition S4.C.4.a or b, below. 2. Sampling Frequency a. The Permittee must sample all discharge points at least once every calendar week when stormwater (or authorized non-stormwater) discharges from the site or enters any on-site surface waters of the state (for example, a creek running through a site); sampling is not required on sites that disturb less than an acre. b. Samples must be representative of the flow and characteristics of the discharge. c. Sampling is not required when there is no discharge during a calendar week. d. Sampling is not required outside of normal working hours or during unsafe conditions. e. If the Permittee is unable to sample during a monitoring period, the Permittee must include a brief explanation in the monthly Discharge Monitoring Report (DMR). f. Sampling is not required before construction activity begins. g. The Permittee may reduce the sampling frequency for temporarily stabilized, inactive sites to once every calendar month. 3. Sampling Locations a. Sampling is required at all points where stormwater associated with construction activity (or authorized non-stormwater) is discharged off site, including where it enters any on-site surface waters of the state (for example, a creek running through a site). b. The Permittee may discontinue sampling at discharge points that drain areas of the project that are fully stabilized to prevent erosion. c. The Permittee must identify all sampling point(s) in the SWPPP and on the site map and clearly mark these points in the field with a flag, tape, stake or other visible marker. d. Sampling is not required for discharge that is sent directly to sanitary or combined sewer systems. e. The Permittee may discontinue sampling at discharge points in areas of the project where the Permittee no longer has operational control of the construction activity. Construction Stormwater General Permit Page 14 4. Sampling and Analysis Methods a. The Permittee performs turbidity analysis with a calibrated turbidity meter (turbidimeter) either on site or at an accredited lab. The Permittee must record the results in the site log book in nephelometric turbidity units (NTUs). b. The Permittee performs transparency analysis on site with a 1¾ inch diameter, 60 centimeter (cm)-long transparency tube. The Permittee will record the results in the site log book in centimeters (cm). Table 4 Monitoring and Reporting Requirements Parameter Unit Analytical Method Sampling Frequency Benchmark Value Turbidity NTU SM2130 Weekly, if discharging 25 NTUs Transparency Cm Manufacturer instructions, or Ecology guidance Weekly, if discharging 33 cm 5. Turbidity/Transparency Benchmark Values and Reporting Triggers The benchmark value for turbidity is 25 NTUs. The benchmark value for transparency is 33 centimeters (cm). Note: Benchmark values do not apply to discharges to segments of water bodies on Washington State’s 303(d) list (Category 5) for turbidity, fine sediment, or phosphorus; these discharges are subject to a numeric effluent limit for turbidity. Refer to Special Condition S8 for more information and follow S5.F – Noncompliance Notification for reporting requirements applicable to discharges which exceed the numeric effluent limit for turbidity. a. Turbidity 26 – 249 NTUs, or Transparency 32 – 7 cm: If the discharge turbidity is 26 to 249 NTUs; or if discharge transparency is 32 to 7 cm, the Permittee must: i. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs, and no later than 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. ii. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. iii. Document BMP implementation and maintenance in the site log book. b. Turbidity 250 NTUs or greater, or Transparency 6 cm or less: If a discharge point’s turbidity is 250 NTUs or greater, or if discharge transparency is less than or equal to 6 cm, the Permittee must complete the reporting and adaptive Construction Stormwater General Permit Page 15 management process described below. For discharges which are subject to a numeric effluent limit for turbidity, see S5.F – Noncompliance Notification. i. Within 24 hours, telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number (or through Ecology’s Water Quality Permitting Portal [WQWebPortal] – Permit Submittals when the form is available), in accordance with Special Condition S5.A. • Central Region (Okanogan, Chelan, Douglas, Kittitas, Yakima, Klickitat, Benton): (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 (Kitsap, Snohomish, Island, King, San Juan, Skagit, Whatcom): (425) 649-7000 • Southwest Region (Grays Harbor, Lewis, Mason, Thurston, Pierce, Clark, Cowlitz, Skamania, Wahkiakum, Clallam, Jefferson, Pacific): (360) 407-6300 These numbers and a link to the ERTS reporting page are also listed at the following website: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html. ii. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible, addressing 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. iii. Sample discharges daily until: a) Turbidity is 25 NTUs (or lower); or b) Transparency is 33 cm (or greater); or c) The Permittee has demonstrated compliance with the water quality standard for turbidity: 1) No more than 5 NTUs over background turbidity, if background is less than 50 NTUs, or 2) No more than 10% over background turbidity, if background is 50 NTUs or greater; or *Note: background turbidity in the receiving water must be measured immediately upstream (upgradient) or outside of the area of influence of the discharge. d) The discharge stops or is eliminated. iv. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within seven (7) days of the date the discharge exceeded the benchmark. Construction Stormwater General Permit Page 16 v. Document BMP implementation and maintenance in the site log book. Compliance with these requirements does not relieve the Permittee from responsibility to maintain continuous compliance with permit benchmarks. D. pH Sampling Requirements – Significant Concrete Work or Engineered Soils If construction activity results in the disturbance of 1 acre or more, and involves significant concrete work (significant concrete work means greater than 1000 cubic yards placed or poured concrete or recycled concrete used over the life of a project) or the use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD], or fly ash), and stormwater from the affected area drains to surface waters of the State or to a storm sewer system that drains to surface waters of the State, the Permittee must conduct pH sampling as set forth below. Note: In addition, discharges to segments of water bodies on Washington State’s 303(d) list (Category 5) for high pH are subject to a numeric effluent limit for pH; refer to Special Condition S8. 1. The Permittee must perform pH analysis on site with a calibrated pH meter, pH test kit, or wide range pH indicator paper. The Permittee must record pH sampling results in the site log book. 2. During the applicable pH monitoring period defined below, the Permittee must obtain a representative sample of stormwater and conduct pH analysis at least once per week. a. For sites with significant concrete work, the Permittee must begin the pH sampling period when the concrete is first placed or poured and exposed to precipitation, and continue weekly throughout and after the concrete placement, pour and curing period, until stormwater pH is in the range of 6.5 to 8.5 (su). b. For sites with recycled concrete where monitoring is required, the Permittee must begin the weekly pH sampling period when the recycled concrete is first exposed to precipitation and must continue until the recycled concrete is fully stabilized with the stormwater pH in the range of 6.5 to 8.5 (su). c. For sites with engineered soils, the Permittee must begin the pH sampling period when the soil amendments are first exposed to precipitation and must continue until the area of engineered soils is fully stabilized. 3. The Permittee must sample pH in the sediment trap/pond(s) or other locations that receive stormwater runoff from the area of significant concrete work or engineered soils before the stormwater discharges to surface waters. 4. The benchmark value for pH is 8.5 standard units. Anytime sampling indicates that pH is 8.5 or greater, the Permittee must either: a. Prevent the high pH water (8.5 or above) from entering storm sewer systems or surface waters of the state; or b. If necessary, adjust or neutralize the high pH water until it is in the range of pH 6.5 to 8.5 (su) using an appropriate treatment BMP such as carbon dioxide (CO2) sparging, dry ice or food grade vinegar. The Permittee must obtain written approval from Ecology before using any form of chemical treatment other than CO2 sparging, dry ice or food grade vinegar. Construction Stormwater General Permit Page 17 S5. REPORTING AND RECORDKEEPING REQUIREMENTS A. High Turbidity Reporting Anytime sampling performed in accordance with Special Condition S4.C indicates turbidity has reached the 250 NTUs or more (or transparency less than or equal to 6 cm), high turbidity reporting level, the Permittee must notify Ecology within 24 hours of analysis either by calling the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number by phone or by submitting an electronic ERTS report (through Ecology’s Water Quality Permitting Portal (WQWebPortal) – Permit Submittals when the form is available). See the CSWGP website for links to ERTS and the WQWebPortal. (http://www.ecy.wa.gov/programs/wq/stormwater/ construction/index.html) Also, see phone numbers in Special Condition S4.C.5.b.i. B. Discharge Monitoring Reports (DMRs) Permittees required to conduct water quality sampling in accordance with Special Conditions S4.C (Turbidity/Transparency), S4.D (pH), S8 (303[d]/TMDL sampling), and/or G12 (Additional Sampling) must submit the results to Ecology. Permittees must submit monitoring data using Ecology's WQWebDMR web application accessed through Ecology’s Water Quality Permitting Portal. Permittees unable to submit electronically (for example, those who do not have an internet connection) must contact Ecology to request a waiver and obtain instructions on how to obtain a paper copy DMR at: Department of Ecology Water Quality Program - Construction Stormwater PO Box 47696 Olympia, WA 98504-7696 Permittees who obtain a waiver not to use WQWebDMR must use the forms provided to them by Ecology; submittals must be mailed to the address above. Permittees must submit DMR forms to be received by Ecology within 15 days following the end of each month. If there was no discharge during a given monitoring period, all Permittees must submit a DMR as required with “no discharge” entered in place of the monitoring results. DMRs are required for the full duration of permit coverage (from the first full month following the effective date of permit coverage up until Ecology has approved termination of the coverage). For more information, contact Ecology staff using information provided at the following website: www.ecy.wa.gov/programs/wq/permits/paris/contacts.html. C. Records Retention The Permittee must retain records of all monitoring information (site log book, sampling results, inspection reports/checklists, etc.), Stormwater Pollution Prevention Plan, copy of the permit coverage letter (including Transfer of Coverage documentation) and any other documentation of compliance with permit requirements for the entire life of the construction project and for a minimum of five (5) years following the termination of permit coverage. Such information must include all calibration and maintenance records, and records of all data used to complete the application for this permit. This period of retention must be extended during Construction Stormwater General Permit Page 18 the course of any unresolved litigation regarding the discharge of pollutants by the Permittee or when requested by Ecology. D. Recording Results For each measurement or sample taken, the Permittee must record the following information: 1. Date, place, method, and time of sampling or measurement. 2. The first and last name of the individual who performed the sampling or measurement. 3. The date(s) the analyses were performed. 4. The first and last name of the individual who performed the analyses. 5. The analytical techniques or methods used. 6. The results of all analyses. E. Additional Monitoring by the Permittee If the Permittee samples or monitors any pollutant more frequently than required by this permit using test procedures specified by Special Condition S4 of this permit, the sampling results for this monitoring must be included in the calculation and reporting of the data submitted in the Permittee’s DMR. F. Noncompliance Notification In the event the Permittee is unable to comply with any part of the terms and conditions of this permit, and the resulting noncompliance may cause a threat to human health or the environment (such as but not limited to spills or fuels or other materials, catastrophic pond or slope failure, and discharges that violate water quality standards), or exceed numeric effluent limitations (see S8 – Discharges to 303(d) or TMDL Waterbodies), the Permittee must, upon becoming aware of the circumstance: 1. Notify Ecology within 24 hours of the failure to comply by calling the applicable Regional office ERTS phone number (refer to Special Condition S4.C.5.b.i, or go to https://ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue to find contact information for the regional offices.) 2. Immediately take action to prevent the discharge/pollution, or otherwise stop or correct the noncompliance, and, if applicable, repeat sampling and analysis of any noncompliance immediately and submit the results to Ecology within five (5) days of becoming aware of the violation (See S5.F.3, below, for details on submitting results in a report). 3. Submit a detailed written report to Ecology within five (5) days of the time the Permittee becomes aware of the circumstances, unless requested earlier by Ecology. The report must be submitted using Ecology’s Water Quality Permitting Portal (WQWebPortal) – Permit Submittals, unless a waiver from electronic reporting has been granted according to S5.B. The report must contain a description of the noncompliance, including exact dates and times, and if the noncompliance has not been corrected, the anticipated time it is expected to continue; and the steps taken or planned to reduce, eliminate, and prevent reoccurrence of the noncompliance. Construction Stormwater General Permit Page 19 The Permittee must report any unanticipated bypass and/or upset that exceeds any effluent limit in the permit in accordance with the 24-hour reporting requirement contained in 40 C.F.R. 122.41(l)(6). Compliance with these requirements does not relieve the Permittee from responsibility to maintain continuous compliance with the terms and conditions of this permit or the resulting liability for failure to comply. Upon request of the Permittee, Ecology may waive the requirement for a written report on a case-by-case basis, if the immediate notification is received by Ecology within 24 hours. G. Access to Plans and Records 1. The Permittee must retain the following permit documentation (plans and records) on site, or within reasonable access to the site, for use by the operator or for on-site review by Ecology or the local jurisdiction: a. General Permit b. Permit Coverage Letter c. Stormwater Pollution Prevention Plan (SWPPP) d. Site Log Book e. Erosivity Waiver (if applicable) 2. The Permittee must address written requests for plans and records listed above (Special Condition S5.G.1) as follows: a. The Permittee must provide a copy of plans and records to Ecology within 14 days of receipt of a written request from Ecology. b. The Permittee must provide a copy of plans and records to the public when requested in writing. Upon receiving a written request from the public for the Permittee’s plans and records, the Permittee must either: i. Provide a copy of the plans and records to the requester within 14 days of a receipt of the written request; or ii. Notify the requester within 10 days of receipt of the written request of the location and times within normal business hours when the plans and records may be viewed; and provide access to the plans and records within 14 days of receipt of the written request; or Within 14 days of receipt of the written request, the Permittee may submit a copy of the plans and records to Ecology for viewing and/or copying by the requester at an Ecology office, or a mutually agreed location. If plans and records are viewed and/or copied at a location other than at an Ecology office, the Permittee will provide reasonable access to copying services for which a reasonable fee may be charged. The Permittee must notify the requester within 10 days of receipt of the request where the plans and records may be viewed and/or copied. Construction Stormwater General Permit Page 20 S6. PERMIT FEES The Permittee must pay permit fees assessed by Ecology. Fees for stormwater discharges covered under this permit are established by Chapter 173-224 WAC. Ecology continues to assess permit fees until the permit is terminated in accordance with Special Condition S10 or revoked in accordance with General Condition G5. S7. SOLID AND LIQUID WASTE DISPOSAL The Permittee must handle and dispose of solid and liquid wastes generated by construction activity, such as demolition debris, construction materials, contaminated materials, and waste materials from maintenance activities, including liquids and solids from cleaning catch basins and other stormwater facilities, in accordance with: A. Special Condition S3, Compliance with Standards. B. WAC 173-216-110. C. Other applicable regulations. S8. DISCHARGES TO 303(d) OR TMDL WATERBODIES A. Sampling and Numeric Effluent Limits For Certain Discharges to 303(d)-Listed Water Bodies 1. Permittees who discharge to segments of water bodies listed as impaired by the State of Washington under Section 303(d) of the Clean Water Act for turbidity, fine sediment, high pH, or phosphorus, must conduct water quality sampling according to the requirements of this section, and Special Conditions S4.C.2.b-f and S4.C.3.b-d, and must comply with the applicable numeric effluent limitations in S8.C and S8.D. 2. All references and requirements associated with Section 303(d) of the Clean Water Act mean the most current listing by Ecology of impaired waters (Category 5) that exists on January 1, 2021, or the date when the operator’s complete permit application is received by Ecology, whichever is later. B. Limits on Coverage for New Discharges to TMDL or 303(d)-Listed Waters Construction sites that discharge to a TMDL or 303(d)-listed waterbody are not eligible for coverage under this permit unless the operator: Construction Stormwater General Permit Page 21 1. Prevents exposing stormwater to pollutants for which the waterbody is impaired, and retains documentation in the SWPPP that details procedures taken to prevent exposure on site; or 2. Documents that the pollutants for which the waterbody is impaired are not present at the site, and retains documentation of this finding within the SWPPP; or 3. Provides Ecology with data indicating the discharge is not expected to cause or contribute to an exceedance of a water quality standard, and retains such data on site with the SWPPP. The operator must provide data and other technical information to Ecology that sufficiently demonstrate: a. For discharges to waters without an EPA-approved or -established TMDL, that the discharge of the pollutant for which the water is impaired will meet in-stream water quality criteria at the point of discharge to the waterbody; or b. For discharges to waters with an EPA-approved or -established TMDL, that there is sufficient remaining wasteload allocation in the TMDL to allow construction stormwater discharge and that existing dischargers to the waterbody are subject to compliance schedules designed to bring the waterbody into attainment with water quality standards. Operators of construction sites are eligible for coverage under this permit only after Ecology makes an affirmative determination that the discharge will not cause or contribute to the existing impairment or exceed the TMDL. C. Sampling and Numeric Effluent Limits for Discharges to Water Bodies on the 303(d) List for Turbidity, Fine Sediment, or Phosphorus 1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for turbidity, fine sediment, or phosphorus must conduct turbidity sampling in accordance with Special Condition S4.C.2 and comply with either of the numeric effluent limits noted in Table 5 below. 2. As an alternative to the 25 NTUs effluent limit noted in Table 5 below (applied at the point where stormwater [or authorized non-stormwater] is discharged off-site), Permittees may choose to comply with the surface water quality standard for turbidity. The standard is: no more than 5 NTUs over background turbidity when the background turbidity is 50 NTUs or less, or no more than a 10% increase in turbidity when the background turbidity is more than 50 NTUs. In order to use the water quality standard requirement, the sampling must take place at the following locations: a. Background turbidity in the 303(d)-listed receiving water immediately upstream (upgradient) or outside the area of influence of the discharge. b. Turbidity at the point of discharge into the 303(d)-listed receiving water, inside the area of influence of the discharge. 3. Discharges that exceed the numeric effluent limit for turbidity constitute a violation of this permit. 4. Permittees whose discharges exceed the numeric effluent limit must sample discharges daily until the violation is corrected and comply with the non-compliance notification requirements in Special Condition S5.F. Construction Stormwater General Permit Page 22 Table 5 Turbidity, Fine Sediment & Phosphorus Sampling and Limits for 303(d)-Listed Waters Parameter identified in 303(d) listing Parameter Sampled Unit Analytical Method Sampling Frequency Numeric Effluent Limit1 • Turbidity • Fine Sediment • Phosphorus Turbidity NTU SM2130 Weekly, if discharging 25 NTUs, at the point where stormwater is discharged from the site; OR In compliance with the surface water quality standard for turbidity (S8.C.2.a) 1 Permittees subject to a numeric effluent limit for turbidity may, at their discretion, choose either numeric effluent limitation based on site-specific considerations including, but not limited to, safety, access and convenience. D. Discharges to Water Bodies on the 303(d) List for High pH 1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for high pH must conduct pH sampling in accordance with the table below, and comply with the numeric effluent limit of pH 6.5 to 8.5 su (Table 6). Table 6 pH Sampling and Limits for 303(d)-Listed Waters Parameter identified in 303(d) listing Parameter Sampled/Units Analytical Method Sampling Frequency Numeric Effluent Limit High pH pH /Standard Units pH meter Weekly, if discharging In the range of 6.5 – 8.5 su 2. At the Permittee’s discretion, compliance with the limit shall be assessed at one of the following locations: a. Directly in the 303(d)-listed waterbody segment, inside the immediate area of influence of the discharge; or b. Alternatively, the Permittee may measure pH at the point where the discharge leaves the construction site, rather than in the receiving water. 3. Discharges that exceed the numeric effluent limit for pH (outside the range of 6.5 – 8.5 su) constitute a violation of this permit. 4. Permittees whose discharges exceed the numeric effluent limit must sample discharges daily until the violation is corrected and comply with the non-compliance notification requirements in Special Condition S5.F. E. Sampling and Limits for Sites Discharging to Waters Covered by a TMDL or another Pollution Control Plan Construction Stormwater General Permit Page 23 1. Discharges to a waterbody that is subject to a Total Maximum Daily Load (TMDL) for turbidity, fine sediment, high pH, or phosphorus must be consistent with the TMDL. Refer to http://www.ecy.wa.gov/programs/wq/tmdl/TMDLsbyWria/TMDLbyWria.html for more information on TMDLs. a. Where an applicable TMDL sets specific waste load allocations or requirements for discharges covered by this permit, discharges must be consistent with any specific waste load allocations or requirements established by the applicable TMDL. i. The Permittee must sample discharges weekly, unless otherwise specified by the TMDL, to evaluate compliance with the specific waste load allocations or requirements. ii. Analytical methods used to meet the monitoring requirements must conform to the latest revision of the Guidelines Establishing Test Procedures for the Analysis of Pollutants contained in 40 CFR Part 136. iii. Turbidity and pH methods need not be accredited or registered unless conducted at a laboratory which must otherwise be accredited or registered. b. Where an applicable TMDL has established a general waste load allocation for construction stormwater discharges, but has not identified specific requirements, compliance with Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute compliance with the approved TMDL. c. Where an applicable TMDL has not specified a waste load allocation for construction stormwater discharges, but has not excluded these discharges, compliance with Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute compliance with the approved TMDL. d. Where an applicable TMDL specifically precludes or prohibits discharges from construction activity, the operator is not eligible for coverage under this permit. S9. STORMWATER POLLUTION PREVENTION PLAN The Permittee must prepare and properly implement an adequate Stormwater Pollution Prevention Plan (SWPPP) for construction activity in accordance with the requirements of this permit beginning with initial soil disturbance and until final stabilization. A. The Permittee’s SWPPP must meet the following objectives: 1. To identify best management practices (BMPs) which prevent erosion and sedimentation, and to reduce, eliminate or prevent stormwater contamination and water pollution from construction activity. 2. To prevent violations of surface water quality, groundwater quality, or sediment management standards. 3. To control peak volumetric flow rates and velocities of stormwater discharges. Construction Stormwater General Permit Page 24 B. General Requirements 1. The SWPPP must include a narrative and drawings. All BMPs must be clearly referenced in the narrative and marked on the drawings. The SWPPP narrative must include documentation to explain and justify the pollution prevention decisions made for the project. Documentation must include: a. Information about existing site conditions (topography, drainage, soils, vegetation, etc.). b. Potential erosion problem areas. c. The 13 elements of a SWPPP in Special Condition S9.D.1-13, including BMPs used to address each element. d. Construction phasing/sequence and general BMP implementation schedule. e. The actions to be taken if BMP performance goals are not achieved—for example, a contingency plan for additional treatment and/or storage of stormwater that would violate the water quality standards if discharged. f. Engineering calculations for ponds, treatment systems, and any other designed structures. When a treatment system requires engineering calculations, these calculations must be included in the SWPPP. Engineering calculations do not need to be included in the SWPPP for treatment systems that do not require such calculations. 2. The Permittee must modify the SWPPP if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is, or would be, ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The Permittee must then: a. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within 7 days of the inspection or investigation. b. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible, addressing the problems no later than 10 days from the inspection or investigation. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when an extension is requested by a Permittee within the initial 10-day response period. c. Document BMP implementation and maintenance in the site log book. The Permittee must modify the SWPPP whenever 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. C. Stormwater Best Management Practices (BMPs) BMPs must be consistent with: 1. Stormwater Management Manual for Western Washington (most current approved edition at the time this permit was issued), for sites west of the crest of the Cascade Mountains; or Construction Stormwater General Permit Page 25 2. Stormwater Management Manual for Eastern Washington (most current approved edition at the time this permit was issued), for sites east of the crest of the Cascade Mountains; or 3. Revisions to the manuals listed in Special Condition S9.C.1 & 2, or other stormwater management guidance documents or manuals which provide an equivalent level of pollution prevention, that are approved by Ecology and incorporated into this permit in accordance with the permit modification requirements of WAC 173-226-230; or 4. Documentation in the SWPPP that the BMPs selected provide an equivalent level of pollution prevention, compared to the applicable stormwater management manuals, including: a. The technical basis for the selection of all stormwater BMPs (scientific, technical studies, and/or modeling) that support the performance claims for the BMPs being selected. b. An assessment of how the selected BMP will satisfy AKART requirements and the applicable federal technology-based treatment requirements under 40 CFR part 125.3. D. SWPPP – Narrative Contents and Requirements The Permittee must include each of the 13 elements below in Special Condition S9.D.1-13 in the narrative of the SWPPP and implement them unless site conditions render the element unnecessary and the exemption from that element is clearly justified in the SWPPP. 1. Preserve Vegetation/Mark Clearing Limits a. Before beginning land-disturbing activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area. b. Retain the duff layer, native topsoil, and natural vegetation in an undisturbed state to the maximum degree practicable. 2. Establish Construction Access a. Limit construction vehicle access and exit to one route, if possible. b. Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs, to minimize tracking sediment onto roads. c. Locate wheel wash or tire baths on site, if the stabilized construction entrance is not effective in preventing tracking sediment onto roads. d. If sediment is tracked off site, clean the affected roadway thoroughly at the end of each day, or more frequently as necessary (for example, during wet weather). Remove sediment from roads by shoveling, sweeping, or pickup and transport of the sediment to a controlled sediment disposal area. e. Conduct street washing only after sediment removal in accordance with Special Condition S9.D.2.d. f. Control street wash wastewater by pumping back on site or otherwise preventing it from discharging into systems tributary to waters of the State. Construction Stormwater General Permit Page 26 3. Control Flow Rates a. Protect properties and waterways downstream of construction sites from erosion and the associated discharge of turbid waters due to increases in the velocity and peak volumetric flow rate of stormwater runoff from the project site, as required by local plan approval authority. b. Where necessary to comply with Special Condition S9.D.3.a, construct stormwater infiltration or detention BMPs as one of the first steps in grading. Assure that detention BMPs function properly before constructing site improvements (for example, impervious surfaces). c. If permanent infiltration ponds are used for flow control during construction, protect these facilities from sedimentation during the construction phase. 4. Install Sediment Controls The Permittee must design, install and maintain effective erosion controls and sediment controls to minimize the discharge of pollutants. At a minimum, the Permittee must: a. Construct sediment control BMPs (sediment ponds, traps, filters, infiltration facilities, etc.) as one of the first steps in grading. These BMPs must be functional before other land disturbing activities take place. b. Minimize sediment discharges from the site. The design, installation and maintenance of erosion and sediment controls must address factors such as the amount, frequency, intensity and duration of precipitation, the nature of resulting stormwater runoff, and soil characteristics, including the range of soil particle sizes expected to be present on the site. c. Direct stormwater runoff from disturbed areas through a sediment pond or other appropriate sediment removal BMP, before the runoff leaves a construction site or before discharge to an infiltration facility. Runoff from fully stabilized areas may be discharged without a sediment removal BMP, but must meet the flow control performance standard of Special Condition S9.D.3.a. d. Locate BMPs intended to trap sediment on site in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages. e. Provide and maintain natural buffers around surface waters, direct stormwater to vegetated areas to increase sediment removal and maximize stormwater infiltration, unless infeasible. f. Where feasible, design outlet structures that withdraw impounded stormwater from the surface to avoid discharging sediment that is still suspended lower in the water column. 5. Stabilize Soils a. The Permittee must stabilize exposed and unworked soils by application of effective BMPs that prevent erosion. Applicable BMPs include, but are not limited to: temporary and permanent seeding, sodding, mulching, plastic covering, erosion Construction Stormwater General Permit Page 27 control fabrics and matting, soil application of polyacrylamide (PAM), the early application of gravel base on areas to be paved, and dust control. b. The Permittee must control stormwater volume and velocity within the site to minimize soil erosion. c. The Permittee must control stormwater discharges, including both peak flow rates and total stormwater volume, to minimize erosion at outlets and to minimize downstream channel and stream bank erosion. d. Depending on the geographic location of the project, the Permittee must not allow soils to remain exposed and unworked for more than the time periods set forth below to prevent erosion. West of the Cascade Mountains Crest During the dry season (May 1 - September 30): 7 days During the wet season (October 1 - April 30): 2 days East of the Cascade Mountains Crest, except for Central Basin* During the dry season (July 1 - September 30): 10 days During the wet season (October 1 - June 30): 5 days The Central Basin*, East of the Cascade Mountains Crest During the dry Season (July 1 - September 30): 30 days During the wet season (October 1 - June 30): 15 days *Note: The Central Basin is defined as the portions of Eastern Washington with mean annual precipitation of less than 12 inches. e. The Permittee must stabilize soils at the end of the shift before a holiday or weekend if needed based on the weather forecast. f. The Permittee must stabilize soil stockpiles from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. g. The Permittee must minimize the amount of soil exposed during construction activity. h. The Permittee must minimize the disturbance of steep slopes. i. The Permittee must minimize soil compaction and, unless infeasible, preserve topsoil. 6. Protect Slopes a. The Permittee must design and construct cut-and-fill slopes in a manner to minimize erosion. Applicable practices include, but are not limited to, reducing continuous length of slope with terracing and diversions, reducing slope steepness, and roughening slope surfaces (for example, track walking). b. The Permittee must divert off-site stormwater (run-on) or groundwater away from slopes and disturbed areas with interceptor dikes, pipes, and/or swales. Off-site stormwater should be managed separately from stormwater generated on the site. c. At the top of slopes, collect drainage in pipe slope drains or protected channels to prevent erosion. Construction Stormwater General Permit Page 28 i. West of the Cascade Mountains Crest: Temporary pipe slope drains must handle the peak 10-minute flow rate from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, 1-hour flow rate predicted by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM) to predict flows, bare soil areas should be modeled as "landscaped area.” ii. East of the Cascade Mountains Crest: Temporary pipe slope drains must handle the expected peak flow rate from a 6-month, 3-hour storm for the developed condition, referred to as the short duration storm. d. Place excavated material on the uphill side of trenches, consistent with safety and space considerations. e. Place check dams at regular intervals within constructed channels that are cut down a slope. 7. Protect Drain Inlets a. Protect all storm drain inlets made operable during construction so that stormwater runoff does not enter the conveyance system without first being filtered or treated to remove sediment. b. Clean or remove and replace inlet protection devices when sediment has filled one- third of the available storage (unless a different standard is specified by the product manufacturer). 8. Stabilize Channels and Outlets a. Design, construct and stabilize all on-site conveyance channels to prevent erosion from the following expected peak flows: i. West of the Cascade Mountains Crest: Channels must handle the peak 10- minute flow rate from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, 1-hour flow rate indicated by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the WWHM to predict flows, bare soil areas should be modeled as "landscaped area.” ii. East of the Cascade Mountains Crest: Channels must handle the expected peak flow rate from a 6-month, 3-hour storm for the developed condition, referred to as the short duration storm. b. Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches at the outlets of all conveyance systems. Construction Stormwater General Permit Page 29 9. Control Pollutants Design, install, implement and maintain effective pollution prevention measures to minimize the discharge of pollutants. The Permittee must: a. Handle and dispose of all pollutants, including waste materials and demolition debris that occur on site in a manner that does not cause contamination of stormwater. b. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other materials that have the potential to pose a threat to human health or the environment. Minimize storage of hazardous materials on-site. Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. On-site fueling tanks must include secondary containment. Secondary containment means placing tanks or containers within an impervious structure capable of containing 110% of the volume of the largest tank within the containment structure. Double-walled tanks do not require additional secondary containment. c. Conduct maintenance, fueling, and repair of heavy equipment and vehicles using spill prevention and control measures. Clean contaminated surfaces immediately following any spill incident. d. Discharge wheel wash or tire bath wastewater to a separate on-site treatment system that prevents discharge to surface water, such as closed-loop recirculation or upland land application, or to the sanitary sewer with local sewer district approval. e. Apply fertilizers and pesticides in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Follow manufacturers’ label requirements for application rates and procedures. f. Use BMPs to prevent contamination of stormwater runoff by pH-modifying sources. The sources for this contamination include, but are not limited to: bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, recycled concrete stockpiles, waste streams generated from concrete grinding and sawing, exposed aggregate processes, dewatering concrete vaults, concrete pumping and mixer washout waters. (Also refer to the definition for "concrete wastewater" in Appendix A – Definitions.) g. Adjust the pH of stormwater or authorized non-stormwater if necessary to prevent an exceedance of groundwater and/or surface water quality standards. h. Assure that washout of concrete trucks is performed off-site or in designated concrete washout areas only. Do not wash out concrete truck drums onto the ground, or into storm drains, open ditches, streets, or streams. Washout of small concrete handling equipment may be disposed of in a formed area awaiting concrete where it will not contaminate surface or groundwater. Do not dump excess concrete on site, except in designated concrete washout areas. Concrete spillage or concrete discharge directly to groundwater or surface waters of the State is Construction Stormwater General Permit Page 30 prohibited. At no time shall concrete be washed off into the footprint of an area where an infiltration BMP will be installed. i. Obtain written approval from Ecology before using any chemical treatment, with the exception of CO2, dry ice or food grade vinegar, to adjust pH. j. Uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations may be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters. Prior to infiltration, water from water-only based shaft drilling that comes into contact with curing concrete must be neutralized until pH is in the range of 6.5 to 8.5 (su). 10. Control Dewatering a. Permittees must discharge foundation, vault, and trench dewatering water, which have characteristics similar to stormwater runoff at the site, in conjunction with BMPs to reduce sedimentation before discharge to a sediment trap or sediment pond. b. Permittees may discharge clean, non-turbid dewatering water, such as well-point groundwater, to systems tributary to, or directly into surface waters of the State, as specified in Special Condition S9.D.8, provided the dewatering flow does not cause erosion or flooding of receiving waters. Do not route clean dewatering water through stormwater sediment ponds. Note that “surface waters of the State” may exist on a construction site as well as off site; for example, a creek running through a site. c. Other dewatering treatment or disposal options may include: i. Infiltration ii. Transport off site in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters. iii. Ecology-approved on-site chemical treatment or other suitable treatment technologies (See S9.D.9.i, regarding chemical treatment written approval). iv. Sanitary or combined sewer discharge with local sewer district approval, if there is no other option. v. Use of a sedimentation bag with discharge to a ditch or swale for small volumes of localized dewatering. d. Permittees must handle highly turbid or contaminated dewatering water separately from stormwater. 11. Maintain BMPs a. Permittees must maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to assure continued performance of their intended function in accordance with BMP specifications. b. Permittees must remove all temporary erosion and sediment control BMPs within 30 days after achieving final site stabilization or after the temporary BMPs are no longer needed. Construction Stormwater General Permit Page 31 12. Manage the Project a. Phase development projects to the maximum degree practicable and take into account seasonal work limitations. b. Inspect, maintain and repair all BMPs as needed to assure continued performance of their intended function. Conduct site inspections and monitoring in accordance with Special Condition S4. c. Maintain, update, and implement the SWPPP in accordance with Special Conditions S3, S4, and S9. 13. Protect Low Impact Development (LID) BMPs The primary purpose of on-site LID Stormwater Management is to reduce the disruption of the natural site hydrology through infiltration. LID BMPs are permanent facilities. a. Permittees must protect all LID BMPs (including, but not limited to, Bioretention and Rain Garden facilities) from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the Bioretention and/or Rain Garden facilities. Restore the BMPs to their fully functioning condition if they accumulate sediment during construction. Restoring the facility must include removal of sediment and any sediment-laden bioretention/ rain garden soils, and replacing the removed soils with soils meeting the design specification. b. Permittees must maintain the infiltration capabilities of LID BMPs by protecting against compaction by construction equipment and foot traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment. c. Permittees must control erosion and avoid introducing sediment from surrounding land uses onto permeable pavements. Do not allow muddy construction equipment on the base material or pavement. Do not allow sediment-laden runoff onto permeable pavements or base materials. d. Permittees must clean permeable pavements fouled with sediments or no longer passing an initial infiltration test using local stormwater manual methodology or the manufacturer’s procedures. e. Permittees must keep all heavy equipment off existing soils under LID BMPs that have been excavated to final grade to retain the infiltration rate of the soils. E. SWPPP – Map Contents and Requirements The Permittee’s SWPPP must also include a vicinity map or general location map (for example, a USGS quadrangle map, a portion of a county or city map, or other appropriate map) with enough detail to identify the location of the construction site and receiving waters within one mile of the site. The SWPPP must also include a legible site map (or maps) showing the entire construction site. The following features must be identified, unless not applicable due to site conditions. 1. The direction of north, property lines, and existing structures and roads. 2. Cut and fill slopes indicating the top and bottom of slope catch lines. Construction Stormwater General Permit Page 32 3. Approximate slopes, contours, and direction of stormwater flow before and after major grading activities. 4. Areas of soil disturbance and areas that will not be disturbed. 5. Locations of structural and nonstructural controls (BMPs) identified in the SWPPP. 6. Locations of off-site material, stockpiles, waste storage, borrow areas, and vehicle/equipment storage areas. 7. Locations of all surface water bodies, including wetlands. 8. Locations where stormwater or non-stormwater discharges off-site and/or to a surface waterbody, including wetlands. 9. Location of water quality sampling station(s), if sampling is required by state or local permitting authority. 10. Areas where final stabilization has been accomplished and no further construction-phase permit requirements apply. 11. Location or proposed location of LID facilities. S10. NOTICE OF TERMINATION Partial terminations of permit coverage are not authorized. A. The site is eligible for termination of coverage when it has met any of the following conditions: 1. The site has undergone final stabilization, the Permittee has removed all temporary BMPs (except biodegradable BMPs clearly manufactured with the intention for the material to be left in place and not interfere with maintenance or land use), and all stormwater discharges associated with construction activity have been eliminated; or 2. All portions of the site that have not undergone final stabilization per Special Condition S10.A.1 have been sold and/or transferred (per Special Condition S2.A), and the Permittee no longer has operational control of the construction activity; or 3. For residential construction only, the Permittee has completed temporary stabilization and the homeowners have taken possession of the residences. B. When the site is eligible for termination, the Permittee must submit a complete and accurate Notice of Termination (NOT) form, signed in accordance with General Condition G2, to: Department of Ecology Water Quality Program - Construction Stormwater PO Box 47696 Olympia, WA 98504-7696 Construction Stormwater General Permit Page 33 When an electronic termination form is available, the Permittee may choose to submit a complete and accurate Notice of Termination (NOT) form through the Water Quality Permitting Portal rather than mailing a hardcopy as noted above. The termination is effective on the 31st calendar day following the date Ecology receives a complete NOT form, unless Ecology notifies the Permittee that termination request is denied because the Permittee has not met the eligibility requirements in Special Condition S10.A. Permittees are required to comply with all conditions and effluent limitations in the permit until the permit has been terminated. Permittees transferring the property to a new property owner or operator/Permittee are required to complete and submit the Notice of Transfer form to Ecology, but are not required to submit a Notice of Termination form for this type of transaction. Construction Stormwater General Permit Page 34 GENERAL CONDITIONS G1. DISCHARGE VIOLATIONS All discharges and activities authorized by this general permit must be consistent with the terms and conditions of this general permit. Any discharge of any pollutant more frequent than or at a level in excess of that identified and authorized by the general permit must constitute a violation of the terms and conditions of this permit. G2. SIGNATORY REQUIREMENTS A. All permit applications must bear a certification of correctness to be signed: 1. In the case of corporations, by a responsible corporate officer. 2. In the case of a partnership, by a general partner of a partnership. 3. In the case of sole proprietorship, by the proprietor. 4. In the case of a municipal, state, or other public facility, by either a principal executive officer or ranking elected official. B. All reports required by this permit and other information requested by Ecology (including NOIs, NOTs, and Transfer of Coverage forms) must be signed by a person described above or by a duly authorized representative of that person. A person is a duly authorized representative only if: 1. The authorization is made in writing by a person described above and submitted to Ecology. 2. The authorization specifies either an individual or a position having responsibility for the overall operation of the regulated facility, such as the position of plant manager, superintendent, position of equivalent responsibility, or an individual or position having overall responsibility for environmental matters. C. Changes to authorization. If an authorization under paragraph G2.B.2 above is no longer accurate because a different individual or position has responsibility for the overall operation of the facility, a new authorization satisfying the requirements of paragraph G2.B.2 above must be submitted to Ecology prior to or together with any reports, information, or applications to be signed by an authorized representative. D. Certification. Any person signing a document under this section must make the following certification: I certify under penalty of law, that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations. Construction Stormwater General Permit Page 35 G3. RIGHT OF INSPECTION AND ENTRY The Permittee must allow an authorized representative of Ecology, upon the presentation of credentials and such other documents as may be required by law: A. To enter upon the premises where a discharge is located or where any records are kept under the terms and conditions of this permit. B. To have access to and copy, at reasonable times and at reasonable cost, any records required to be kept under the terms and conditions of this permit. C. To inspect, at reasonable times, any facilities, equipment (including monitoring and control equipment), practices, methods, or operations regulated or required under this permit. D. To sample or monitor, at reasonable times, any substances or parameters at any location for purposes of assuring permit compliance or as otherwise authorized by the Clean Water Act. G4. GENERAL PERMIT MODIFICATION AND REVOCATION This permit may be modified, revoked and reissued, or terminated in accordance with the provisions of Chapter 173-226 WAC. Grounds for modification, revocation and reissuance, or termination include, but are not limited to, the following: A. When a change occurs in the technology or practices for control or abatement of pollutants applicable to the category of dischargers covered under this permit. B. When effluent limitation guidelines or standards are promulgated pursuant to the CWA or Chapter 90.48 RCW, for the category of dischargers covered under this permit. C. When a water quality management plan containing requirements applicable to the category of dischargers covered under this permit is approved, or D. When information is obtained that indicates cumulative effects on the environment from dischargers covered under this permit are unacceptable. G5. REVOCATION OF COVERAGE UNDER THE PERMIT Pursuant to Chapter 43.21B RCW and Chapter 173-226 WAC, the Director may terminate coverage for any discharger under this permit for cause. Cases where coverage may be terminated include, but are not limited to, the following: A. Violation of any term or condition of this permit. B. Obtaining coverage under this permit by misrepresentation or failure to disclose fully all relevant facts. C. A change in any condition that requires either a temporary or permanent reduction or elimination of the permitted discharge. D. Failure or refusal of the Permittee to allow entry as required in RCW 90.48.090. E. A determination that the permitted activity endangers human health or the environment, or contributes to water quality standards violations. F. Nonpayment of permit fees or penalties assessed pursuant to RCW 90.48.465 and Chapter 173-224 WAC. Construction Stormwater General Permit Page 36 G. Failure of the Permittee to satisfy the public notice requirements of WAC 173-226-130(5), when applicable. The Director may require any discharger under this permit to apply for and obtain coverage under an individual permit or another more specific general permit. Permittees who have their coverage revoked for cause according to WAC 173-226-240 may request temporary coverage under this permit during the time an individual permit is being developed, provided the request is made within ninety (90) days from the time of revocation and is submitted along with a complete individual permit application form. G6. REPORTING A CAUSE FOR MODIFICATION The Permittee must submit a new application, or a supplement to the previous application, whenever a material change to the construction activity or in the quantity or type of discharge is anticipated which is not specifically authorized by this permit. This application must be submitted at least sixty (60) days prior to any proposed changes. Filing a request for a permit modification, revocation and reissuance, or termination, or a notification of planned changes or anticipated noncompliance does not relieve the Permittee of the duty to comply with the existing permit until it is modified or reissued. G7. COMPLIANCE WITH OTHER LAWS AND STATUTES Nothing in this permit will be construed as excusing the Permittee from compliance with any applicable federal, state, or local statutes, ordinances, or regulations. G8. DUTY TO REAPPLY The Permittee must apply for permit renewal at least 180 days prior to the specified expiration date of this permit. The Permittee must reapply using the electronic application form (NOI) available on Ecology’s website. Permittees unable to submit electronically (for example, those who do not have an internet connection) must contact Ecology to request a waiver and obtain instructions on how to obtain a paper NOI. Department of Ecology Water Quality Program - Construction Stormwater PO Box 47696 Olympia, WA 98504-7696 G9. REMOVED SUBSTANCE The Permittee must not re-suspend or reintroduce collected screenings, grit, solids, sludges, filter backwash, or other pollutants removed in the course of treatment or control of stormwater to the final effluent stream for discharge to state waters. G10. DUTY TO PROVIDE INFORMATION The Permittee must submit to Ecology, within a reasonable time, all information that Ecology may request to determine whether cause exists for modifying, revoking and reissuing, or terminating this permit or to determine compliance with this permit. The Permittee must also submit to Ecology, upon request, copies of records required to be kept by this permit [40 CFR 122.41(h)]. Construction Stormwater General Permit Page 37 G11. OTHER REQUIREMENTS OF 40 CFR All other requirements of 40 CFR 122.41 and 122.42 are incorporated in this permit by reference. G12. ADDITIONAL MONITORING Ecology may establish specific monitoring requirements in addition to those contained in this permit by administrative order or permit modification. G13. PENALTIES FOR VIOLATING PERMIT CONDITIONS Any person who is found guilty of willfully violating the terms and conditions of this permit shall be deemed guilty of a crime, and upon conviction thereof shall be punished by a fine of up to ten thousand dollars ($10,000) and costs of prosecution, or by imprisonment at the discretion of the court. Each day upon which a willful violation occurs may be deemed a separate and additional violation. Any person who violates the terms and conditions of a waste discharge permit shall incur, in addition to any other penalty as provided by law, a civil penalty in the amount of up to ten thousand dollars ($10,000) for every such violation. Each and every such violation shall be a separate and distinct offense, and in case of a continuing violation, every day’s continuance shall be deemed to be a separate and distinct violation. G14. UPSET Definition – “Upset” means an exceptional incident in which there is unintentional and temporary noncompliance with technology-based permit effluent limitations because of factors beyond the reasonable control of the Permittee. An upset does not include noncompliance to the extent caused by operational error, improperly designed treatment facilities, inadequate treatment facilities, lack of preventive maintenance, or careless or improper operation. An upset constitutes an affirmative defense to an action brought for noncompliance with such technology-based permit effluent limitations if the requirements of the following paragraph are met. A Permittee who wishes to establish the affirmative defense of upset must demonstrate, through properly signed, contemporaneous operating logs or other relevant evidence that: 1) an upset occurred and that the Permittee can identify the cause(s) of the upset; 2) the permitted facility was being properly operated at the time of the upset; 3) the Permittee submitted notice of the upset as required in Special Condition S5.F, and; 4) the Permittee complied with any remedial measures required under this permit. In any enforcement proceeding, the Permittee seeking to establish the occurrence of an upset has the burden of proof. G15. PROPERTY RIGHTS This permit does not convey any property rights of any sort, or any exclusive privilege. G16. DUTY TO COMPLY The Permittee must comply with all conditions of this permit. Any permit noncompliance constitutes a violation of the Clean Water Act and is grounds for enforcement action; for permit termination, revocation and reissuance, or modification; or denial of a permit renewal application. Construction Stormwater General Permit Page 38 G17. TOXIC POLLUTANTS The Permittee must comply with effluent standards or prohibitions established under Section 307(a) of the Clean Water Act for toxic pollutants within the time provided in the regulations that establish those standards or prohibitions, even if this permit has not yet been modified to incorporate the requirement. G18. PENALTIES FOR TAMPERING The Clean Water Act provides that any person who falsifies, tampers with, or knowingly renders inaccurate any monitoring device or method required to be maintained under this permit shall, upon conviction, be punished by a fine of not more than $10,000 per violation, or by imprisonment for not more than two years per violation, or by both. If a conviction of a person is for a violation committed after a first conviction of such person under this condition, punishment shall be a fine of not more than $20,000 per day of violation, or imprisonment of not more than four (4) years, or both. G19. REPORTING PLANNED CHANGES The Permittee must, as soon as possible, give notice to Ecology of planned physical alterations, modifications or additions to the permitted construction activity. The Permittee should be aware that, depending on the nature and size of the changes to the original permit, a new public notice and other permit process requirements may be required. Changes in activities that require reporting to Ecology include those that will result in: A. The permitted facility being determined to be a new source pursuant to 40 CFR 122.29(b). B. A significant change in the nature or an increase in quantity of pollutants discharged, including but not limited to: a 20% or greater increase in acreage disturbed by construction activity. C. A change in or addition of surface water(s) receiving stormwater or non-stormwater from the construction activity. D. A change in the construction plans and/or activity that affects the Permittee’s monitoring requirements in Special Condition S4. Following such notice, permit coverage may be modified, or revoked and reissued pursuant to 40 CFR 122.62(a) to specify and limit any pollutants not previously limited. Until such modification is effective, any new or increased discharge in excess of permit limits or not specifically authorized by this permit constitutes a violation. G20. REPORTING OTHER INFORMATION Where the Permittee becomes aware that it failed to submit any relevant facts in a permit application, or submitted incorrect information in a permit application or in any report to Ecology, it must promptly submit such facts or information. G21. REPORTING ANTICIPATED NON-COMPLIANCE The Permittee must give advance notice to Ecology by submission of a new application or supplement thereto at least forty-five (45) days prior to commencement of such discharges, of any facility expansions, production increases, or other planned changes, such as process modifications, in the permitted facility or activity which may result in noncompliance with permit limits or conditions. Any maintenance of facilities, which might necessitate unavoidable interruption of Construction Stormwater General Permit Page 39 operation and degradation of effluent quality, must be scheduled during non-critical water quality periods and carried out in a manner approved by Ecology. G22. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT Any discharger authorized by this permit may request to be excluded from coverage under the general permit by applying for an individual permit. The discharger must submit to the Director an application as described in WAC 173-220-040 or WAC 173-216-070, whichever is applicable, with reasons supporting the request. These reasons will fully document how an individual permit will apply to the applicant in a way that the general permit cannot. Ecology may make specific requests for information to support the request. The Director will either issue an individual permit or deny the request with a statement explaining the reason for the denial. When an individual permit is issued to a discharger otherwise subject to the construction stormwater general permit, the applicability of the construction stormwater general permit to that Permittee is automatically terminated on the effective date of the individual permit. G23. APPEALS A. The terms and conditions of this general permit, as they apply to the appropriate class of dischargers, are subject to appeal by any person within 30 days of issuance of this general permit, in accordance with Chapter 43.21B RCW, and Chapter 173-226 WAC. B. The terms and conditions of this general permit, as they apply to an individual discharger, are appealable in accordance with Chapter 43.21B RCW within 30 days of the effective date of coverage of that discharger. Consideration of an appeal of general permit coverage of an individual discharger is limited to the general permit’s applicability or nonapplicability to that individual discharger. C. The appeal of general permit coverage of an individual discharger does not affect any other dischargers covered under this general permit. If the terms and conditions of this general permit are found to be inapplicable to any individual discharger(s), the matter shall be remanded to Ecology for consideration of issuance of an individual permit or permits. G24. SEVERABILITY The provisions of this permit are severable, and if any provision of this permit, or application of any provision of this permit to any circumstance, is held invalid, the application of such provision to other circumstances, and the remainder of this permit shall not be affected thereby. G25. BYPASS PROHIBITED A. Bypass Procedures Bypass, which is the intentional diversion of waste streams from any portion of a treatment facility, is prohibited for stormwater events below the design criteria for stormwater management. Ecology may take enforcement action against a Permittee for bypass unless one of the following circumstances (1, 2, 3 or 4) is applicable. 1. Bypass of stormwater is consistent with the design criteria and part of an approved management practice in the applicable stormwater management manual. 2. Bypass for essential maintenance without the potential to cause violation of permit limits or conditions. Construction Stormwater General Permit Page 40 Bypass is authorized if it is for essential maintenance and does not have the potential to cause violations of limitations or other conditions of this permit, or adversely impact public health. 3. Bypass of stormwater is unavoidable, unanticipated, and results in noncompliance of this permit. This bypass is permitted only if: a. Bypass is unavoidable to prevent loss of life, personal injury, or severe property damage. “Severe property damage” means substantial physical damage to property, damage to the treatment facilities which would cause them to become inoperable, or substantial and permanent loss of natural resources which can reasonably be expected to occur in the absence of a bypass. b. There are no feasible alternatives to the bypass, such as the use of auxiliary treatment facilities, retention of untreated wastes, maintenance during normal periods of equipment downtime (but not if adequate backup equipment should have been installed in the exercise of reasonable engineering judgment to prevent a bypass which occurred during normal periods of equipment downtime or preventative maintenance), or transport of untreated wastes to another treatment facility. c. Ecology is properly notified of the bypass as required in Special Condition S5.F of this permit. 4. A planned action that would cause bypass of stormwater and has the potential to result in noncompliance of this permit during a storm event. The Permittee must notify Ecology at least thirty (30) days before the planned date of bypass. The notice must contain: a. A description of the bypass and its cause b. An analysis of all known alternatives which would eliminate, reduce, or mitigate the need for bypassing. c. A cost-effectiveness analysis of alternatives including comparative resource damage assessment. d. The minimum and maximum duration of bypass under each alternative. e. A recommendation as to the preferred alternative for conducting the bypass. f. The projected date of bypass initiation. g. A statement of compliance with SEPA. h. A request for modification of water quality standards as provided for in WAC 173- 201A-110, if an exceedance of any water quality standard is anticipated. i. Steps taken or planned to reduce, eliminate, and prevent reoccurrence of the bypass. 5. For probable construction bypasses, the need to bypass is to be identified as early in the planning process as possible. The analysis required above must be considered during Construction Stormwater General Permit Page 41 preparation of the Stormwater Pollution Prevention Plan (SWPPP) and must be included to the extent practical. In cases where the probable need to bypass is determined early, continued analysis is necessary up to and including the construction period in an effort to minimize or eliminate the bypass. Ecology will consider the following before issuing an administrative order for this type bypass: a. If the bypass is necessary to perform construction or maintenance-related activities essential to meet the requirements of this permit. b. If there are feasible alternatives to bypass, such as the use of auxiliary treatment facilities, retention of untreated wastes, stopping production, maintenance during normal periods of equipment down time, or transport of untreated wastes to another treatment facility. c. If the bypass is planned and scheduled to minimize adverse effects on the public and the environment. After consideration of the above and the adverse effects of the proposed bypass and any other relevant factors, Ecology will approve, conditionally approve, or deny the request. The public must be notified and given an opportunity to comment on bypass incidents of significant duration, to the extent feasible. Approval of a request to bypass will be by administrative order issued by Ecology under RCW 90.48.120. B. Duty to Mitigate The Permittee is required to take all reasonable steps to minimize or prevent any discharge or sludge use or disposal in violation of this permit that has a reasonable likelihood of adversely affecting human health or the environment. Construction Stormwater General Permit Page 42 APPENDIX A – DEFINITIONS AKART is an acronym for “All Known, Available, and Reasonable methods of prevention, control, and Treatment.” AKART represents the most current methodology that can be reasonably required for preventing, controlling, or abating the pollutants and controlling pollution associated with a discharge. Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or phosphorus, which was completed and approved by EPA before January 1, 2021, or before the date the operator’s complete permit application is received by Ecology, whichever is later. TMDLs completed after a complete permit application is received by Ecology become applicable to the Permittee only if they are imposed through an administrative order by Ecology, or through a modification of permit coverage. Applicant means an operator seeking coverage under this permit. Benchmark means a pollutant concentration used as a permit threshold, below which a pollutant is considered unlikely to cause a water quality violation, and above which it may. When pollutant concentrations exceed benchmarks, corrective action requirements take effect. Benchmark values are not water quality standards and are not numeric effluent limitations; they are indicator values. Best Management Practices (BMPs) means schedules of activities, prohibitions of practices, maintenance procedures, and other physical, structural and/or managerial practices to prevent or reduce the pollution of waters of the State. BMPs include treatment systems, operating procedures, and practices to control stormwater associated with construction activity, spillage or leaks, sludge or waste disposal, or drainage from raw material storage. Buffer means an area designated by a local jurisdiction that is contiguous to and intended to protect a sensitive area. Bypass means the intentional diversion of waste streams from any portion of a treatment facility. Calendar Day A period of 24 consecutive hours starting at 12:00 midnight and ending the following 12:00 midnight. Calendar Week (same as Week) means a period of seven consecutive days starting at 12:01 a.m. (0:01 hours) on Sunday. Certified Erosion and Sediment Control Lead (CESCL) means a person who has current certification through an approved erosion and sediment control training program that meets the minimum training standards established by Ecology (See BMP C160 in the SWMM). Chemical Treatment means the addition of chemicals to stormwater and/or authorized non-stormwater prior to filtration and discharge to surface waters. Clean Water Act (CWA) means the Federal Water Pollution Control Act enacted by Public Law 92-500, as amended by Public Laws 95-217, 95-576, 96-483, and 97-117; USC 1251 et seq. Combined Sewer means a sewer which has been designed to serve as a sanitary sewer and a storm sewer, and into which inflow is allowed by local ordinance. Construction Stormwater General Permit Page 43 Common Plan of Development or Sale means a site where multiple separate and distinct construction activities may be taking place at different times on different schedules and/or by different contractors, but still under a single plan. Examples include: 1) phased projects and projects with multiple filings or lots, even if the separate phases or filings/lots will be constructed under separate contract or by separate owners (e.g., a development where lots are sold to separate builders); 2) a development plan that may be phased over multiple years, but is still under a consistent plan for long-term development; 3) projects in a contiguous area that may be unrelated but still under the same contract, such as construction of a building extension and a new parking lot at the same facility; and 4) linear projects such as roads, pipelines, or utilities. If the project is part of a common plan of development or sale, the disturbed area of the entire plan must be used in determining permit requirements. Composite Sample means a mixture of grab samples collected at the same sampling point at different times, formed either by continuous sampling or by mixing discrete samples. May be "time-composite" (collected at constant time intervals) or "flow-proportional" (collected either as a constant sample volume at time intervals proportional to stream flow, or collected by increasing the volume of each aliquot as the flow increases while maintaining a constant time interval between the aliquots. Concrete Wastewater means any water used in the production, pouring and/or clean-up of concrete or concrete products, and any water used to cut, grind, wash, or otherwise modify concrete or concrete products. Examples include water used for or resulting from concrete truck/mixer/pumper/tool/chute rinsing or washing, concrete saw cutting and surfacing (sawing, coring, grinding, roughening, hydro- demolition, bridge and road surfacing). When stormwater comingles with concrete wastewater, the resulting water is considered concrete wastewater and must be managed to prevent discharge to waters of the State, including groundwater. Construction Activity means land disturbing operations including clearing, grading or excavation which disturbs the surface of the land (including off-site disturbance acreage related to construction-support activity). Such activities may include road construction, construction of residential houses, office buildings, or industrial buildings, site preparation, soil compaction, movement and stockpiling of topsoils, and demolition activity. Construction Support Activity means off-site acreage that will be disturbed as a direct result of the construction project and will discharge stormwater. For example, off-site equipment staging yards, material storage areas, borrow areas, and parking areas. Contaminant means any hazardous substance that does not occur naturally or occurs at greater than natural background levels. See definition of “hazardous substance” and WAC 173-340-200. Contaminated soil means soil which contains contaminants, pollutants, or hazardous substances that do not occur naturally or occur at levels greater than natural background. Contaminated groundwater means groundwater which contains contaminants, pollutants, or hazardous substances that do not occur naturally or occur at levels greater than natural background. Demonstrably Equivalent means that the technical basis for the selection of all stormwater BMPs is documented within a SWPPP, including: 1. The method and reasons for choosing the stormwater BMPs selected. 2. The pollutant removal performance expected from the BMPs selected. Construction Stormwater General Permit Page 44 3. The technical basis supporting the performance claims for the BMPs selected, including any available data concerning field performance of the BMPs selected. 4. An assessment of how the selected BMPs will comply with state water quality standards. 5. An assessment of how the selected BMPs will satisfy both applicable federal technology-based treatment requirements and state requirements to use all known, available, and reasonable methods of prevention, control, and treatment (AKART). Department means the Washington State Department of Ecology. Detention means the temporary storage of stormwater to improve quality and/or to reduce the mass flow rate of discharge. Dewatering means the act of pumping groundwater or stormwater away from an active construction site. Director means the Director of the Washington State Department of Ecology or his/her authorized representative. Discharger means an owner or operator of any facility or activity subject to regulation under Chapter 90.48 RCW or the Federal Clean Water Act. Domestic Wastewater means water carrying human wastes, including kitchen, bath, and laundry wastes from residences, buildings, industrial establishments, or other places, together with such groundwater infiltration or surface waters as may be present. Ecology means the Washington State Department of Ecology. Engineered Soils means the use of soil amendments including, but not limited, to Portland cement treated base (CTB), cement kiln dust (CKD), or fly ash to achieve certain desirable soil characteristics. Equivalent BMPs means operational, source control, treatment, or innovative BMPs which result in equal or better quality of stormwater discharge to surface water or to groundwater than BMPs selected from the SWMM. Erosion means the wearing away of the land surface by running water, wind, ice, or other geological agents, including such processes as gravitational creep. Erosion and Sediment Control BMPs means BMPs intended to prevent erosion and sedimentation, such as preserving natural vegetation, seeding, mulching and matting, plastic covering, filter fences, sediment traps, and ponds. Erosion and sediment control BMPs are synonymous with stabilization and structural BMPs. Federal Operator is an entity that meets the definition of “Operator” in this permit and is either any department, agency or instrumentality of the executive, legislative, and judicial branches of the Federal government of the United States, or another entity, such as a private contractor, performing construction activity for any such department, agency, or instrumentality. Final Stabilization (same as fully stabilized or full stabilization) means the completion of all soil disturbing activities at the site and the establishment of permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent erosion. See the applicable Stormwater Management Manual for more information on vegetative cover expectations and equivalent permanent stabilization measures. Construction Stormwater General Permit Page 45 Groundwater means water in a saturated zone or stratum beneath the land surface or a surface waterbody. Hazardous Substance means any dangerous or extremely hazardous waste as defined in RCW 70.105.010 (5) and (6), or any dangerous or extremely dangerous waste as designated by rule under chapter 70.105 RCW; any hazardous sub-stance as defined in RCW 70.105.010(14) or any hazardous substance as defined by rule under chapter 70.105 RCW; any substance that, on the effective date of this section, is a hazardous substance under section 101(14) of the federal cleanup law, 42U.S.C., Sec. 9601(14); petroleum or petroleum products; and any substance or category of substances, including solid waste decomposition products, determined by the director by rule to present a threat to human health or the environment if released into the environment. The term hazardous substance does not include any of the following when contained in an underground storage tank from which there is not a release: crude oil or any fraction thereof or petroleum, if the tank is in compliance with all applicable federal, state, and local law. Injection Well means a well that is used for the subsurface emplacement of fluids. (See Well.) Jurisdiction means a political unit such as a city, town or county; incorporated for local self-government. National Pollutant Discharge Elimination System (NPDES) means the national program for issuing, modifying, revoking and reissuing, terminating, monitoring, and enforcing permits, and imposing and enforcing pretreatment requirements, under sections 307, 402, 318, and 405 of the Federal Clean Water Act, for the discharge of pollutants to surface waters of the State from point sources. These permits are referred to as NPDES permits and, in Washington State, are administered by the Washington State Department of Ecology. Notice of Intent (NOI) means the application for, or a request for coverage under this general permit pursuant to WAC 173-226-200. Notice of Termination (NOT) means a request for termination of coverage under this general permit as specified by Special Condition S10 of this permit. Operator means any party associated with a construction project that meets either of the following two criteria: • The party has operational control over construction plans and specifications, including the ability to make modifications to those plans and specifications; or • The party has day-to-day operational control of those activities at a project that are necessary to ensure compliance with a SWPPP for the site or other permit conditions (e.g., they are authorized to direct workers at a site to carry out activities required by the SWPPP or comply with other permit conditions). Permittee means individual or entity that receives notice of coverage under this general permit. pH means a liquid’s measure of acidity or alkalinity. A pH of 7 is defined as neutral. Large variations above or below this value are considered harmful to most aquatic life. pH Monitoring Period means the time period in which the pH of stormwater runoff from a site must be tested a minimum of once every seven days to determine if stormwater pH is between 6.5 and 8.5. Construction Stormwater General Permit Page 46 Point Source means any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, and container from which pollutants are or may be discharged to surface waters of the State. This term does not include return flows from irrigated agriculture. (See the Fact Sheet for further explanation) Pollutant means dredged spoil, solid waste, incinerator residue, filter backwash, sewage, garbage, domestic sewage sludge (biosolids), munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt, and industrial, municipal, and agricultural waste. This term does not include sewage from vessels within the meaning of section 312 of the CWA, nor does it include dredged or fill material discharged in accordance with a permit issued under section 404 of the CWA. Pollution means contamination or other alteration of the physical, chemical, or biological properties of waters of the State; including change in temperature, taste, color, turbidity, or odor of the waters; or such discharge of any liquid, gaseous, solid, radioactive or other substance into any waters of the State as will or is likely to create a nuisance or render such waters harmful, detrimental or injurious to the public health, safety or welfare; or to domestic, commercial, industrial, agricultural, recreational, or other legitimate beneficial uses; or to livestock, wild animals, birds, fish or other aquatic life. Process Wastewater means any non-stormwater which, during manufacturing or processing, comes into direct contact with or results from the production or use of any raw material, intermediate product, finished product, byproduct, or waste product. If stormwater commingles with process wastewater, the commingled water is considered process wastewater. Receiving Water means the waterbody at the point of discharge. If the discharge is to a storm sewer system, either surface or subsurface, the receiving water is the waterbody to which the storm system discharges. Systems designed primarily for other purposes such as for groundwater drainage, redirecting stream natural flows, or for conveyance of irrigation water/return flows that coincidentally convey stormwater are considered the receiving water. Representative means a stormwater or wastewater sample which represents the flow and characteristics of the discharge. Representative samples may be a grab sample, a time-proportionate composite sample, or a flow proportionate sample. Ecology’s Construction Stormwater Monitoring Manual provides guidance on representative sampling. Responsible Corporate Officer for the purpose of signatory authority means: (i) a president, secretary, treasurer, or vice-president of the corporation in charge of a principal business function, or any other person who performs similar policy- or decision-making functions for the corporation, or (ii) the manager of one or more manufacturing, production, or operating facilities, provided, the manager is authorized to make management decisions which govern the operation of the regulated facility including having the explicit or implicit duty of making major capital investment recommendations, and initiating and directing other comprehensive measures to assure long term environmental compliance with environmental laws and regulations; the manager can ensure that the necessary systems are established or actions taken to gather complete and accurate information for permit application requirements; and where authority to sign documents has been assigned or delegated to the manager in accordance with corporate procedures (40 CFR 122.22). Sanitary Sewer means a sewer which is designed to convey domestic wastewater. Construction Stormwater General Permit Page 47 Sediment means the fragmented material that originates from the weathering and erosion of rocks or unconsolidated deposits, and is transported by, suspended in, or deposited by water. Sedimentation means the depositing or formation of sediment. Sensitive Area means a waterbody, wetland, stream, aquifer recharge area, or channel migration zone. SEPA (State Environmental Policy Act) means the Washington State Law, RCW 43.21C.020, intended to prevent or eliminate damage to the environment. Significant Amount means an amount of a pollutant in a discharge that is amenable to available and reasonable methods of prevention or treatment; or an amount of a pollutant that has a reasonable potential to cause a violation of surface or groundwater quality or sediment management standards. Significant Concrete Work means greater than 1000 cubic yards placed or poured concrete or recycled concrete used over the life of a project. Significant Contributor of Pollutants means a facility determined by Ecology to be a contributor of a significant amount(s) of a pollutant(s) to waters of the State of Washington. Site means the land or water area where any "facility or activity" is physically located or conducted. Source Control BMPs means physical, structural or mechanical devices or facilities that are intended to prevent pollutants from entering stormwater. A few examples of source control BMPs are erosion control practices, maintenance of stormwater facilities, constructing roofs over storage and working areas, and directing wash water and similar discharges to the sanitary sewer or a dead end sump. Stabilization means the application of appropriate BMPs to prevent the erosion of soils, such as, temporary and permanent seeding, vegetative covers, mulching and matting, plastic covering and sodding. See also the definition of Erosion and Sediment Control BMPs. Storm Drain means any drain which drains directly into a storm sewer system, usually found along roadways or in parking lots. Storm Sewer System means a means a conveyance, or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm drains designed or used for collecting or conveying stormwater. This does not include systems which are part of a combined sewer or Publicly Owned Treatment Works (POTW), as defined at 40 CFR 122.2. Stormwater means that portion of precipitation that does not naturally percolate into the ground or evaporate, but flows via overland flow, interflow, pipes, and other features of a stormwater drainage system into a defined surface waterbody, or a constructed infiltration facility. Stormwater Management Manual (SWMM) or Manual means the technical Manual published by Ecology for use by local governments that contain descriptions of and design criteria for BMPs to prevent, control, or treat pollutants in stormwater. Stormwater Pollution Prevention Plan (SWPPP) means a documented plan to implement measures to identify, prevent, and control the contamination of point source discharges of stormwater. Construction Stormwater General Permit Page 48 Surface Waters of the State includes lakes, rivers, ponds, streams, inland waters, salt waters, and all other surface waters and water courses within the jurisdiction of the state of Washington. Temporary Stabilization means the exposed ground surface has been covered with appropriate materials to provide temporary stabilization of the surface from water or wind erosion. Materials include, but are not limited to, mulch, riprap, erosion control mats or blankets and temporary cover crops. Seeding alone is not considered stabilization. Temporary stabilization is not a substitute for the more permanent “final stabilization.” Total Maximum Daily Load (TMDL) means a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet state water quality standards. Percentages of the total maximum daily load are allocated to the various pollutant sources. A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The TMDL calculations must include a "margin of safety" to ensure that the waterbody can be protected in case there are unforeseen events or unknown sources of the pollutant. The calculation must also account for seasonable variation in water quality. Transfer of Coverage (TOC) means a request for transfer of coverage under this general permit as specified by Special Condition S2.A of this permit. Treatment BMPs means BMPs that are intended to remove pollutants from stormwater. A few examples of treatment BMPs are detention ponds, oil/water separators, biofiltration, and constructed wetlands. Transparency means a measurement of water clarity in centimeters (cm), using a 60 cm transparency tube. The transparency tube is used to estimate the relative clarity or transparency of water by noting the depth at which a black and white Secchi disc becomes visible when water is released from a value in the bottom of the tube. A transparency tube is sometimes referred to as a “turbidity tube.” Turbidity means the clarity of water expressed as nephelometric turbidity units (NTUs) and measured with a calibrated turbidimeter. Uncontaminated means free from any contaminant. See definition of “contaminant” and WAC 173-340-200. Upset means an exceptional incident in which there is unintentional and temporary noncompliance with technology-based permit effluent limitations because of factors beyond the reasonable control of the Permittee. An upset does not include noncompliance to the extent caused by operational error, improperly designed treatment facilities, inadequate treatment facilities, lack of preventive maintenance, or careless or improper operation. Waste Load Allocation (WLA) means the portion of a receiving water’s loading capacity that is allocated to one of its existing or future point sources of pollution. WLAs constitute a type of water quality based effluent limitation (40 CFR 130.2[h]). Water-Only Based Shaft Drilling is a shaft drilling process that uses water only and no additives are involved in the drilling of shafts for construction of building, road, or bridge foundations. Water Quality means the chemical, physical, and biological characteristics of water, usually with respect to its suitability for a particular purpose. Waters of the State includes those waters as defined as "waters of the United States" in 40 CFR Subpart 122.2 within the geographic boundaries of Washington State and "waters of the State" as defined in Chapter 90.48 RCW, which include lakes, rivers, ponds, streams, inland waters, underground waters, salt Construction Stormwater General Permit Page 49 waters, and all other surface waters and water courses within the jurisdiction of the state of Washington. Well means a bored, drilled or driven shaft, or dug hole whose depth is greater than the largest surface dimension. (See Injection Well.) Wheel Wash Wastewater means any water used in, or resulting from the operation of, a tire bath or wheel wash (BMP C106: Wheel Wash), or other structure or practice that uses water to physically remove mud and debris from vehicles leaving a construction site and prevent track-out onto roads. When stormwater comingles with wheel wash wastewater, the resulting water is considered wheel wash wastewater and must be managed according to Special Condition S9.D.9. Construction Stormwater General Permit Page 50 APPENDIX B – ACRONYMS AKART All Known, Available, and Reasonable Methods of Prevention, Control, and Treatment BMP Best Management Practice CESCL Certified Erosion and Sediment Control Lead CFR Code of Federal Regulations CKD Cement Kiln Dust cm Centimeters CPD Common Plan of Development CTB Cement-Treated Base CWA Clean Water Act DMR Discharge Monitoring Report EPA Environmental Protection Agency ERTS Environmental Report Tracking System ESC Erosion and Sediment Control FR Federal Register LID Low Impact Development NOI Notice of Intent NOT Notice of Termination NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Unit RCW Revised Code of Washington SEPA State Environmental Policy Act SWMM Stormwater Management Manual SWPPP Stormwater Pollution Prevention Plan TMDL Total Maximum Daily Load UIC Underground Injection Control USC United States Code USEPA United States Environmental Protection Agency WAC Washington Administrative Code WQ Water Quality WWHM Western Washington Hydrology Model Appendix H – Engineering Calculations TESC Sediment Trap Sizing (BMP C240) Total Site: Pervious Area Impervious Area Total Area 0.00 ac 1.08 ac 1.08 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 = 0.425 ft3/s Surface Area Calculation: SA = 2 (0.425 / 0.00096) SA = 886 ft2 VR = SA * 3.5 ft minimum storage depth VR = 886 * 3.5 VR = 3,101 ft3 Storage Volume Required VR = 3,101 ft3 * (7.48 gal/ 1 ft3) VR = 23,196 Gallons Required Volume Provided: (1) 18,900 Gallon & (1) 8,400 Gallon Sediment Storage Tanks V = 18,900 + 8,400 V = 27,300 Gallons Provided ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 12/05/2024 4:43 PM Report Generation Date: 12/05/2024 4:43 PM ————————————————————————————————— Input File Name: Softball Baker Tanks.fld Project Name: Lindbergh High School - Field Improvements Analysis Title: TESC Softball Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 15 Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 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) 1.080 1.080 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.080 1.080 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predeveloped ---------- -------Area (Acres) -------- C, Forest, Flat 1.080 ---------------------------------------------- TESC SEDIMENT SIZING - SOFTBALL FIELD Subbasin Total 1.080 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdeveloped ---------- -------Area (Acres) -------- ROADS/FLAT 1.080 ---------------------------------------------- Subbasin Total 1.080 **********************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 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predeveloped Scenario Postdeveloped Compliance Subbasin: Postdeveloped *** 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 2.293E-02 2-Year 0.425 5-Year 3.637E-02 5-Year 0.544 10-Year 4.701E-02 10-Year 0.629 25-Year 6.110E-02 25-Year 0.810 50-Year 6.741E-02 50-Year 1.014 100-Year 7.690E-02 100-Year 1.212 200-Year 0.106 200-Year 1.282 500-Year 0.145 500-Year 1.372 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals TESC SEDIMENT SIZING - SOFTBALL FIELD TESC Sediment Trap Sizing (BMP C240) Total Site: Pervious Area Impervious Area Total Area 0.00 ac 2.28 ac 2.28 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 = 0.898 ft3/s Surface Area Calculation: SA = 2 (0.898 / 0.00096) SA = 1,871 ft2 VR = SA * 3.5 ft minimum storage depth VR = 2,756.25 * 3.5 VR = 6,549 ft3 Storage Volume Required VR = 9,253 ft3 * (7.48 gal/ 1 ft3) VR = 48,983 Gallons Required Volume Provided: (2) 21,000 Gallon & (1) 8,400 Sediment Storage Tanks V = (2 * 18,900) + 8,400 V = 50,400 Gallons Provided ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.64 Program License Number: 201910001 Project Simulation Performed on: 12/05/2024 4:38 PM Report Generation Date: 12/05/2024 4:39 PM ————————————————————————————————— Input File Name: Baseball Baker Tanks.fld Project Name: Lindbergh High School - Field Improvements Analysis Title: TESC Baseball Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Full Period of Record Available used for Routing Climatic Region Number: 15 Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 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) 2.280 2.280 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.280 2.280 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predeveloped ---------- -------Area (Acres) -------- C, Forest, Flat 2.280 ---------------------------------------------- TESC SEDIMENT SIZING - BASEBALL FIELD Subbasin Total 2.280 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdeveloped ---------- -------Area (Acres) -------- ROADS/FLAT 2.280 ---------------------------------------------- Subbasin Total 2.280 **********************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 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predeveloped Scenario Postdeveloped Compliance Subbasin: Postdeveloped *** 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 4.841E-02 2-Year 0.898 5-Year 7.679E-02 5-Year 1.149 10-Year 9.924E-02 10-Year 1.328 25-Year 0.129 25-Year 1.709 50-Year 0.142 50-Year 2.141 100-Year 0.162 100-Year 2.559 200-Year 0.224 200-Year 2.706 500-Year 0.307 500-Year 2.897 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals TESC SEDIMENT SIZING - BASEBALL FIELD LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS APPENDIX D OPERATIONS AND MAINTENANCE MANUAL 255 S. King Street, Suite #800, Seattle, WA 98104 | 206.426.2600 | JACOBSONENGINEERS.COM OPERATIONS AND MAINTENANCE MANUAL Lindbergh High School Field Improvements 16426 128th Ave SE, Renton, WA 98058 June 6, 2025 _______________________________________________ Party Responsible for Maintenance and Operations: Renton School District Maintenance Department Contact: Todd Simanton (425) 204-4406 Todd.simanton@rentonschools.us _____________________________________________ Prepared by: Jacobson Consulting Engineers Contact: Alan Jacobson (206) 426-2600 alan@jacobsonengineers.com 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. 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-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 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. ENGINEERED SOLUTIONS Modular Wetlands® Linear Operatons & Maintenance Manual 2 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR OOPPEERRAATTIIOONN && MMAAIINNTTEENNAANNCCEE MMAANNUUAALL TTAABBLLEE OOFF CCOONNTTEENNTTSS OOvveerrvviieeww ........................................................................................................................................................................ 3 SSaaffeettyy NNoottiiccee && PPeerrssoonnaall SSaaffeettyy EEqquuiippmmeenntt ................................................................................................................. 4 MMoodduullaarr WWeettllaannddss LLiinneeaarr CCoommppoonneennttss LLiisstt ................................................................................................................. 5 IInnssppeeccttiioonn SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt ......................................................................................................................... 6 IInnssppeeccttiioonn && MMaaiinntteennaannccee NNootteess .................................................................................................................................. 7 IInnssppeeccttiioonn PPrroocceessss ......................................................................................................................................................... 7 MMaaiinntteennaannccee IInnddiiccaattoorrss ................................................................................................................................................. 9 MMaaiinntteennaannccee SSuummmmaarryy && EEqquuiippmmeenntt LLiisstt..................................................................................................................... 9 MMaaiinntteennaannccee IInnssttrruuccttiioonnss .............................................................................................................................................11 RReeppllaacciinngg BBiiooffiillttrraattiioonn MMeeddiiaa iiff RReeqquuiirreedd ....................................................................................................................14 RReeppllaacciinngg DDrraaiinn DDoowwnn FFiilltteerr MMeeddiiaa ((OOnnllyy oonn OOllddeerr CCaalliiffoorrnniiaa MMooddeellss)) .....................................................................16 NNootteess .............................................................................................................................................................................17 IInnssppeeccttiioonn RReeppoorrtt .........................................................................................................................................................18 CClleeaanniinngg && MMaaiinntteennaannccee RReeppoorrtt ..................................................................................................................................19 3 OOVVEERRVVIIEEWW This operation and maintenance (O&M) manual is for the Modular Wetlands Linear Biofilter (MWL). Please read the instructions and equipment lists closely prior to starting. It is important to follow all necessary safety procedures associated with state and local regulations. Please contact Contech for more information on pre-authorized third-party service providers who can provide inspection and maintenance services in your area. For a list of service providers in your area, please visit www.conteches.com/maintenance. PPLLAACCEEHHOOLLDDEERR FFOORR MMAARRKKEETTIINNGG PPHHOOTTOO WWAARRNNIINNGG Confined space entry may be required. Contractor to obtain all equipment and training to meet applicable local and OSHA regulations regarding confined space entry. It is the Contractor’s or entry personnel’s responsibility to always proceed safely. 4 SSAAFFEETTYY NNOOTTIICCEE && PPEERRSSOONNAALL SSAAFFEETTYY EEQQUUIIPPMMEENNTT Job site safety is a topic and a practice addressed comprehensively by others. The inclusions here are merely reminders to whole areas of Safety Practice that are the responsibility of the Owner(s), Manager(s), and Service Provider(s). OSHA and Canadian OSH, Federal, State/Provincial, and Local Jurisdiction Safety Standards apply on any given site or project. The knowledge and applicability of those responsibilities is the Service Provider’s responsibility and outside the scope of Contech Engineered Solutions. Safety Boots Gloves Hard Hat Eye Protection Maintenance and Protection of Traffic Plan 5 MMOODDUULLAARR WWEETTLLAANNDDSS LLIINNEEAARR CCOOMMPPOONNEENNTTSS LLIISSTT The MWL system comes in multiple sizes and configurations, including side by side or end to end layouts, both as open planters or underground systems. See shop drawings (plans) for project specific details. The standard MWL system is comprised of the following components: 6 IINNSSPPEECCTTIIOONN SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT Stormwater regulations require BMPs be inspected and maintained to ensure they are operating as designed to allow for effective pollutant removal and provide protection to receiving water bodies. It is recommended that inspections be performed multiple times during the first year to assess the site-specific loading conditions. The first year of inspections can be used to set inspection and maintenance intervals for subsequent years to ensure appropriate maintenance is provided. Inspect pre-treatment, biofiltration, and discharge chambers an average of once every six to twelve months. Varies based on site specific and local conditions. Average inspection time is approximately 15 minutes. Always ensure appropriate safety protocol and procedures are followed. The following is a list of equipment required to allow for simple and effective inspection of the MWL: Modular Wetlands Linear Inspection Form Flashlight Tape Measure Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) 7 IINNSSPPEECCTTIIOONN && MMAAIINNTTEENNAANNCCEE NNOOTTEESS 1.Following maintenance and/or inspection, it is recommended that the maintenance operator prepare a maintenance/inspection record. The record should include any maintenance activities performed, amount and description of debris collected, and condition of the system and its various filter mechanisms. 2.The owner should keep maintenance/inspection record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspection upon request at any time. 3.Transport all debris, trash, organics, and sediments to approved facility for disposal in accordance with local and state requirements. 4.Entry into chambers may require confined space training based on state and local regulations. 5.No fertilizer shall be used in the biofiltration chamber. 6.Irrigation should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigation required is dependent on plant species. Some plants may not require irrigation after initial establishment. IINNSSPPEECCTTIIOONN PPRROOCCEESSSS 1.Prepare the inspection form by writing in the necessary information including project name, location, date & time, unit number and other information (see inspection form). 2.Observe the inside of the system through the access covers. If minimal light is available and vision into the unit is impaired, utilize a flashlight to see inside the system and all chambers. 3.Look for any out of the ordinary obstructions in the inflow pipe, pre-treatment chamber, biofiltration chamber, discharge chamber or outflow pipe. Write down any observations on the inspection form. 4.Through observation and/or digital photographs, estimate the amount of trash, debris accumulated in the pre- treatment chamber. Utilizing a tape measure or measuring stick, estimate the amount of sediment in this chamber. Record this depth on the inspection form. 5.Through visual observation, inspect the condition of the pre-filter cartridges. Look for excessive build-up of sediment on the cartridges, any build-up on the tops of the cartridges, or clogging of the holes. Record this information on the inspection form. The pre-filter cartridges can be further inspected by removing the cartridge tops and assessing the color of the BioMediaGREEN filter cubes (requires entry into pre-treatment chamber - see notes previous notes regarding confined space entry). Record the color of the material. New material is a light green color. As the media becomes clogged, it will turn darker in color, eventually becoming dark brown or black. The closer to black the media is the higher percentage that the media is exhausted and in need of replacement. 8 6.The biofiltration chamber is generally maintenance-free due to the system’s advanced pre-treatment chamber. For units which have open planters with vegetation, it is recommended that the vegetation be inspected. Look for any plants that are dead or showing signs of disease or other negative stressors. Record the general health of the plants on the inspection form and indicate through visual observation or digital photographs if trimming of the vegetation is required. 7.The discharge chamber houses the control riser (if applicable), drain down filter (only in California - older models), and is connected to the outflow pipe. It is important to check to ensure the orifice is in proper operating condition and free of any obstructions. It is also important to assess the condition of the drain down filter media which utilizes a block form of the BioMediaGREEN. Assess in the same manner as the cubes in the pre-filter cartridge as mentioned above. 8.Finalize the inspection report for analysis by the maintenance manager to determine if maintenance is required. 9 MMAAIINNTTEENNAANNCCEE IINNDDIICCAATTOORRSS Based upon the observations made during inspection, maintenance of the system may be required based on the following indicators: Missing or damaged internal components or cartridges. Obstructions in the system or its inlet and/or outlet pipes. Excessive accumulation of floatables in the pre-treatment chamber in which the length and width of the chamber is fully impacted more than 18”. Excessive accumulation of sediment in the pre-treatment chamber of more than 6” in depth. Excessive accumulation of sediment on the BioMediaGREEN media housed within the pretreatment cartridges. When media is more than 85% clogged, replacement is required. The darker the BioMediaGREEN, the more clogged it is and in need of replacement. Excessive accumulation of sediment on the BioMediaGREEN media housed within the drain down filter (California only - older models). Overgrown vegetation. MMAAIINNTTEENNAANNCCEE SSUUMMMMAARRYY && EEQQUUIIPPMMEENNTT LLIISSTT The time has come to maintain your MWL. All necessary pre-maintenance steps must be carried out before maintenance occurs. Once traffic control has been set up per local and state regulations and access covers have been safely opened, the maintenance process can begin. It should be noted that some maintenance activities require confined space entry. All confined space requirements must be strictly followed before entry into the system. In addition, the following is recommended: Prepare the maintenance form by writing in the necessary information including project name, location, date & time, unit number and other info (see maintenance form). Set up all appropriate safety and maintenance equipment. Ensure traffic control is set up and properly positioned. Prepared pre-checks (OSHA, safety, confined space entry) are performed. o A gas meter should be used to detect the presence of any hazardous gases prior to entering the system. If hazardous gases are present, do not enter the vault. Following appropriate confined space procedures, take steps such as utilizing a venting system to address the hazard. Once it is determined to be safe, enter the system utilizing appropriate entry equipment such as a ladder and tripod with harness. 10 The following is a list of equipment required for maintenance of the MWL: Modular Wetlands Linear Maintenance Form Flashlight Access Cover Hook Ratchet & 7/16” Socket (if required for older pre-filter cartridges that have two bolts holding the lids on) Vacuum Assisted Truck with Pressure Washer Replacement BioMediaGREEN (If Required) (order BioMediaGREEN from Contech’s Maintenance Team members at https://www.conteches.com/maintenance) 11 MMAAIINNTTEENNAANNCCEE IINNSSTTRRUUCCTTIIOONNSS 11..AACCCCEESSSS CCOOVVEERR RREEMMOOVVAALL Upon determining that the vault is safe for entry, remove all access cover(s) and position the vacuum truck accordingly. 22..PPRREESSSSUURREE WWAASSHH SSYYSSTTEEMM CCHHAAMMBBEERRSS With the pressure washer, spray down pollutants accumulated on the walls and floors of the pre- treatment and discharge chambers. Then wash any accumulated sediment from the pre-filter cartridge(s). 33..VVAACCUUUUMM SSYYSSTTEEMM CCHHAAMMBBEERRSS Vacuum out pre-treatment and discharge chambers and remove all accumulated pollutants including trash, debris, and sediments. Be sure to vacuum the pre- treatment floor until the pervious pavers are visible and clean.((MMWWLL ssyysstteemmss oouuttssiiddee ooff CCaalliiffoorrnniiaa mmaayy oorr mmaayy nnoott hhaavvee ppeerrvviioouuss ppaavveerrss oonn tthhee fflloooorr iinn tthhee pprree-- ttrreeaattmmeenntt cchhaammbbeerr)) If pre-filter cartridges require media replacement, proceed to SStteepp 44. If not, replace the access cover(s) and proceed to SStteepp 77. 12 44..PPRREE--FFIILLTTEERR CCAARRTTRRIIDDGGEE LLIIDD RREEMMOOVVAALL After successfully cleaning out the pre-treatment chamber, enter the chamber and remove the lid(s) from the pre-filter cartridge(s) by removing the two thumb screws. (Older pre-filter cartridges have two bolts holding the lids on that require a 7/16” socket to remove) 55..VVAACCUUUUMM EEXXIISSTTIINNGG PPRREE--FFIILLTTEERR MMEEDDIIAA Utilize the vacuum truck hose or hose extension to remove the filter media from each of the individual media cages. Once filter media has been sucked out, use a pressure washer to spray down the inside of the cartridge and its media cages. Remove cleaned media cages and place to the side. Once removed, the vacuum hose can be inserted into the cartridge to vacuum out any remaining material near the bottom of the cartridge. 66..PPRREE--FFIILLTTEERR MMEEDDIIAA RREEPPLLAACCEEMMEENNTT Reinstall media cages and fill with new media from the manufacturer or outside supplier. Manufacturer will provide specification of media and sources to purchase. The easiest way to fill the media cages is to utilize a refilling tray that can also be sourced from the manufacturer. Place the refilling tray on top of the cartridge and fill with new bulk media shaking it down into the cages. Using your hands, lightly compact the media into each filter cage. Once the cages are full (each cartridge will hold five heaping 5gal buckets of bulk media),remove the refilling tray and replace the cartridge top, ensuring fasteners are properly tightened. 13 77..MMAAIINNTTAAIINNIINNGG VVEEGGEETTAATTIIOONN In general, the biofiltration chamber is maintenance-free with the exception of maintaining the vegetation. The MWL utilizes vegetation similar to surrounding landscape areas, therefore, trim vegetation to match surrounding vegetation. If any plants have died, replace them with new ones. 88..IINNSSPPEECCTT UUNNDDEERRDDRRAAIINN SSYYSSTTEEMM Each vertical under drain on the biofiltration chamber has a removable threaded cap that can be taken off to check for any blockages or root growth. Once removed, a jetting attachment to the pressure washer can be used to clean out the under drain and orifice riser if needed. 99..RREEPPLLAACCEE AACCCCEESSSS CCOOVVEERRSS Once maintenance is complete, replace all access cover(s) 14 RREEPPLLAACCIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA IIFF RREEQQUUIIRREEDD As with all biofilter systems, at some point the biofiltration media will need to be replaced, either due to physical clogging or sorptive exhaustion (for dissolved pollutants) of the media ion exchange capacity (to remove dissolved metals and phosphorous). The general life of this media is 10 to 20 years based on site specific conditions and pollutant loading, so replacing the biofiltration media should not be a common occurrence. In the event that the biofiltration media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new biofiltration media. The quantity of media needed can be determined by providing the model number and unit depth. Media will be provided in super sacks for easy installation. Each sack will weigh between 1,000 and 2,000 lbs. Biofiltration media replacement can be done following the steps below: 11..VVAACCUUUUMM EEXXIISSTTIINNGG BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Remove the mulch and vegetation to access the biofiltration media, and then position the vacuum truck accordingly. Utilize the vacuum truck to vacuum out all the media. Once all media is removed, use the pressure washer to spray down all the netting and underdrain systems on the inside of the media containment cage. Vacuum out any remaining debris after spraying down netting. Inspect the netting for any damage or holes. If the netting is damaged, it can be repaired or replaced with guidance by the manufacturer. 22..IINNSSTTAALLLLIINNGG NNEEWW BBIIOOFFIILLTTRRAATTIIOONN MMEEDDIIAA Ensure that the chamber is fully cleaned prior to installation of new media into the media containment cage(s). Media will be provided in super sacks for easy installation. A lifting apparatus (forklift, backhoe, boom truck, or other) is recommended to position the super sack over the biofiltration chamber. Add media in lifts to ensure that the riser pipes remain vertical. Be sure to only fill the media cage(s) up to the same level as the old media. 15 33..RREEPPLLAANNTT VVEEGGEETTAATTIIOONN Once the media has been replaced, replant the vegetation and cover biofiltration chamber with approved mulch (if applicable). If the existing vegetation is not being reused, and new vegetation is being planted, you will need to acquire new plant establishment media that will be installed just below the mulch layer at each plant location. (see plan drawings for details). Contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new plant establishment media. 16 RREEPPLLAACCIINNGG DDRRAAIINN DDOOWWNN FFIILLTTEERR MMEEDDIIAA ((OONNLLYY OONN OOLLDDEERR CCAALLIIFFOORRNNIIAA MMOODDEELLSS)) NOTE: The drain down filter is only found on units installed in California prior to 2023 If during inspection it was determined that the drain down filter media requires replacement, contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new media. 11..RREEMMOOVVEE EEXXIISSTTIINNGG DDRRAAIINN DDOOWWNN MMEEDDIIAA Pull knob back to unlock the locking mechanism and lift the drain down filter housing to remove the used BioMediaGREEN filter block. 22..IINNSSTTAALLLL NNEEWW DDRRAAIINN DDOOWWNN MMEEDDIIAA Ensure that the chamber and housing are fully cleaned prior to installation of new media, and then insert the new BioMediaGREEN filter block. The media filter block should fit snugly between the chamber walls and be centered under the filter housing. Lower the housing over the filter block and secure the locking mechanism. 17 NOTES _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ _______________________________________________________________________________________________________ 18 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No YesType of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. Inspection Report Modular Wetlands Linear Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging the unit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance ENGINEERED SOLUTIONS 19 For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date //Time AM / PM Weather Condition Additional Notes Site Map # Comments: Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed@ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands LinearENGINEERED SOLUTIONS SUPPORT DRAWINGS AND SPECIFICATIONS ARE AVAILABLE AT WWW.CONTECHES.COM © 2024 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 WWW.CONTECHES.COM ALL RIGHTS RESERVED. PRINTED IN THE USA. CONTECH ENGINEERED SOLUTIONS LLC PROVIDES SITE SOLUTIONS FOR THE CIVIL ENGINEERING INDUSTRY. CONTECH’S PORTFOLIO INCLUDES BRIDGES, DRAINAGE, SANITARY SEWER, STORMWATER AND EARTH STABILIZATION PRODUCTS. FOR INFORMATION ON OTHER CONTECH DIVISION OFFERINGS, VISIT CONTECHES.COM OR CALL 800-338-1122. ModWetLinear OM Manual 03/24 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. ENGINEERED SOLUTIONS Isolator® Row Plus O&M Manual 2 Looking down the Isolator Row Plus from the manhole opening, ADS Plus Fabric is shown between the chamber and stone base. StormTech Isolator Row Plus with Overflow Structure (not to scale) The Isolator® Row Plus Introduction An important component of any Stormwater Pollution Prevention Plan is inspection and maintenance. The StormTech Isolator Row Plus is a technique to inexpensively enhance Total Suspended Solids (TSS), Total Phosphorus (TP), Total Petroluem Hydrocarbons (TPH) and Total Nitrogen (TN) removal with easy access for inspection and maintenance. The Isolator Row Plus The Isolator Row Plus is a row of StormTech chambers, either SC-160, SC-310, SC-310-3, SC-740, DC-780, SC-800, MC-3500, MC-4500 or MC- 7200 models, are lined with filter fabric and connected to a closely located manhole for easy access. The fabric lined chambers provide for sediment settling and filtration as stormwater rises in the Isolator Row Plus and passes through the filter fabric. The open bottom chambers allow stormwater to flow vertically out of the chambers. Sediments are captured in the Isolator Row Plus protecting the adjacent stone and chambers storage areas from sediment accumulation. ADS Isolator Row and Plus fabric are placed between the stone and the Isolator Row Plus chambers. The woven geotextile provides a media for stormwater filtration, a durable surface for maintenance, prevents scour of the underlying stone and remains intact during high pressure jetting. The Isolator Row Plus is designed to capture the “first flush” runoff and offers the versatility to be sized on a volume basis or a flow-rate basis. An upstream manhole provides access to the Isolator Row Plus and includes a high/low concept such that stormwater flow rates or volumes that exceed the capacity of the Isolator Row Plus bypass through a manifold to the other chambers. This is achieved with an elevated bypass manifold or a high-flow weir. This creates a differential between the Isolator Row Plus row of chambers and the manifold to the rest of the system, thus allowing for settlement time in the Isolator Row Plus. After Stormwater flows through the Isolator Row Plus and into the rest of the chamber system it is either exfiltrated into the soils below or passed at a controlled rate through an outlet manifold and outlet control structure. The Isolator Row Plus FlampTM is a flared end ramp apparatus attached to the inlet pipe on the inside of the chamber end cap. The FLAMP provides a smooth transition from pipe invert to fabric bottom. It is configured to improve chamber function performance by enhancing outflow of solid debris that would otherwise collect at the chamber's end, or more difficult to remove and require confined space entry into the chamber area. It also serves to improve the fluid and solid flow into the access pipe during maintenance and cleaning and to guide cleaning and inspection equipment back into the inlet pipe when complete. The Isolator Row Plus may be part of a treatment train system. The treatment train design and pretreatment device selection by the design engineer is often driven by regulatory requirements. Whether pretreatment is used or not, StormTech recommend using the Isolator Row Plus to minimize maintenance requirements and maintenance costs. Note: See the StormTech Design Manual for detailed information on designing inlets for a StormTech system, including the Isolator Row Plus. 3 Inspection The frequency of inspection and maintenance varies by location. A routine inspection schedule needs to be established for each individual location based upon site specific variables. The type of land use (i.e. industrial, commercial, residential), anticipated pollutant load, percent imperviousness, climate, etc. all play a critical role in determining the actual frequency of inspection and maintenance practices. At a minimum, StormTech recommends annual inspections. Initially, the Isolator Row Plus should be inspected every 6 months for the first year of operation. For subsequent years, the inspection should be adjusted based upon previous observation of sediment deposition. The Isolator Row Plus incorporates a combination of standard manhole(s) and strategically located inspection ports (as needed). The inspection ports allow for easy access to the system from the surface, eliminating the need to perform a confined space entry for inspection purposes. If upon visual inspection it is found that sediment has accumulated, a stadia rod should be inserted to determine the depth of sediment. When the average depth of sediment exceeds 3" (75 mm) throughout the length of the Isolator Row Plus, clean-out should be performed. Maintenance The Isolator Row Plus was designed to reduce the cost of periodic maintenance. By “isolating” sediments to just one row, costs are dramatically reduced by eliminating the need to clean out each row of the entire storage bed. If inspection indicates the potential need for maintenance, access is provided via a manhole(s) located on the end(s) of the row for cleanout. If entry into the manhole is required, please follow local and OSHA rules for a confined space entry. Maintenance is accomplished with the JetVac process. The JetVac process utilizes a high pressure water nozzle to propel itself down the Isolator Row Plus while scouring and suspending sediments. As the nozzle is retrieved, the captured pollutants are flushed back into the manhole for vacuuming. Most sewer and pipe maintenance companies have vacuum/JetVac combination vehicles. Selection of an appropriate JetVac nozzle will improve maintenance efficiency. Fixed nozzles designed for culverts or large diameter pipe cleaning are preferable. Rear facing jets with an effective spread of at least 45” are best. StormTech recommends a maximum nozzle pressure of 2000 psi be utilized during cleaning. JetVac reels can vary in length. For ease of maintenance, ADS recommends Isolator Row Plus lengths up to 200' (61 m). The JetVac process shall only be performed on StormTech Isolator Row Plus that have ADS Plus Fabric (as specified by StormTech) over their angular base stone. Isolator Row Plus Inspection/Maintenance StormTech Isolator Row Plus (not to scale) Isolator Row Plus Step By Step Maintenance Procedures Step 1 Inspect Isolator Row Plus for sediment. A) Inspection ports (if present) i. Remove lid from floor box frame ii. Remove cap from inspection riser iii. Using a flashlight and stadia rod,measure depth of sediment and record results on maintenance log. iv. If sediment is at or above 3 inch depth, proceed to Step 2. If not, proceed to Step 3. B) All Isolator Row Plus i. Remove cover from manhole at upstream end of Isolator Row Plus ii. Using a flashlight, inspect down Isolator Row Plus through outlet pipe 1. Mirrors on poles or cameras may be used to avoid a confined space entry 2. Follow OSHA regulations for confined space entry if entering manhole iii. If sediment is at or above the lower row of sidewall holes (approximately 3 inches), proceed to Step 2. If not, proceed to Step 3. Step 2 Clean out Isolator Row Plus using the JetVac process. A) A fixed floor cleaning nozzle with rear facing nozzle spread of 45 inches or more is preferable B) Apply multiple passes of JetVac until backflush water is clean C) Vacuum manhole sump as required Step 3 Replace all caps, lids and covers, record observations and actions. Step 4 Inspect & clean catch basins and manholes upstream of the StormTech system. ADS “Terms and Conditions of Sale” are available on the ADS website, www.adspipe.com The ADS logo and the Green Stripe are registered trademarks of Advanced Drainage Systems, Inc. StormTech® and the Isolator® Row Plus are registered trademarks of StormTech, Inc. © 2024 Advanced Drainage Systems, Inc. #11081 7/24 CS 4 21) B)1) A) Sample Maintenance Log Date Stadia Rod Readings Sedi- ment Depth (1)–(2) Observations/Actions InspectorFixed point to chamber bottom (1) Fixed point to top of sediment (2) 3/15/11 6.3 ft none New installation. Fixed point is CI frame at grade DJM 9/24/11 6.2 0.1 ft Some grit felt SM 6/20/13 5.8 0.5 ft Mucky feel, debris visible in manhole and in Isolator Row Plus, maintenance due NV 7/7/13 6.3 ft 0 System jetted and vacuumed DJM adspipe.com 800-821-6710 LINDBERGH HIGH SCHOOL FIELD IMPROVEMENTS APPENDIX E BOND QUANTITIES WORKSHEET FACILITY SUMMARY SHEET DECLARATION OF COVENANT 1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200 Date Prepared: Name: PE Registration No: Firm Name: Firm Address: Phone No. Email Address: Project Name: Project Owner: CED Plan # (LUA): Phone: CED Permit # (C):Address: Site Address: Street Intersection: Addt'l Project Owner: Parcel #(s): Phone: Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NO Water Service Provided by: If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: 10.3% Roadway (Erosion Control + Transportation)D 421,009.25$ 2 All prices include labor, equipment, materials, overhead, profit, and taxes. City of Renton Sales Tax is: SITE IMPROVEMENT BOND QUANTITY WORKSHEET PROJECT INFORMATION CITY OF RENTON CITY OF RENTON 1 Select the current project status/phase from the following options: Engineer Stamp Required (all cost estimates must have original wet stamp and signature) Clearing and Grading Utility Providers N/A Project Location and Description Project Owner Information Lindbergh High School Field Improvements Seattle, WA 98178 2823059004 Matt Feldmeyer c/o Renton School District LUA25-000051 (425) 204-4475 16426 128th Ave SE, Renton, WA 98058 7812 South 124th Street 128th Ave SE & SE 167th St C25000977 6/6/2025 Prepared by: FOR APPROVALProject Phase 1 alan@jacobsonengineers.com Alan Jacobson 43667 Jacobson Consulting Engineers 255 S King St, Suite 800, Seattle, WA 98104 (206) 426-2600 -$ Abbreviated Legal Description: SE 1/4 OF NE 1/4 STR 28-23-05 LESS S 250 FT OF E 523 FT OF W 553 FT LESS CO RD PER RENTON DECLARATION OF LOT COMBINATION LUA 22- 000106 REC #20240507000960 Total Estimated Construction Costs A + B + C + D 1,497,440.19$ Estimated Civil Construction Permit - Construction Costs2 Stormwater (Drainage) & Misc. Utilities C 1,076,430.94$ As outlined in City Ordinance No. 4345, 50% of the plan review and inspection fees are to be paid at Permit Submittal. The balance is due at Permit Issuance. Significant changes or additional review cycles (beyond 3 cycles) during the review process may result in adjustments to the final review fees. Water A -$ Wastewater (Sanitary Sewer)B Page 2 of 15 Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION Version 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Unit Reference #Price Unit Quantity CostBackfill & compaction-embankment ESC-1 7.50$ CY Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 90.00$ Each 11 990.00Catch Basin Protection ESC-3 145.00$ Each 35 5,075.00Crushed surfacing 1 1/4" minus ESC-4 WSDOT 9-03.9(3)110.00$ CY Ditching ESC-5 10.50$ CY Excavation-bulk ESC-6 2.30$ CY Fence, silt ESC-7 SWDM 5.4.3.1 5.00$ LF 1733 8,665.00 Fence, Temporary (NGPE)ESC-8 1.75$ LF Geotextile Fabric ESC-9 3.00$ SY Hay Bale Silt Trap ESC-10 0.60$ Each Hydroseeding ESC-11 SWDM 5.4.2.4 0.90$ SY Interceptor Swale / Dike ESC-12 1.15$ LF 988 1,136.20Jute Mesh ESC-13 SWDM 5.4.2.2 4.00$ SY Level Spreader ESC-14 2.00$ LF Mulch, by hand, straw, 3" deep ESC-15 SWDM 5.4.2.1 2.90$ SY Mulch, by machine, straw, 2" deep ESC-16 SWDM 5.4.2.1 2.30$ SY Piping, temporary, CPP, 6"ESC-17 13.75$ LF 16 220.00Piping, temporary, CPP, 8"ESC-18 16.00$ LF 195 3,120.00 Piping, temporary, CPP, 12"ESC-19 20.50$ LF Plastic covering, 6mm thick, sandbagged ESC-20 SWDM 5.4.2.3 4.60$ SY Rip Rap, machine placed; slopes ESC-21 WSDOT 9-13.1(2)51.00$ CY Rock Construction Entrance, 50'x15'x1'ESC-22 SWDM 5.4.4.1 2,050.00$ Each 2 4,100.00 Rock Construction Entrance, 100'x15'x1'ESC-23 SWDM 5.4.4.1 3,675.00$ Each Sediment pond riser assembly ESC-24 SWDM 5.4.5.2 2,525.00$ Each Sediment trap, 5' high berm ESC-25 SWDM 5.4.5.1 22.00$ LF Sed. trap, 5' high, riprapped spillway berm section ESC-26 SWDM 5.4.5.1 80.00$ LF Seeding, by hand ESC-27 SWDM 5.4.2.4 1.15$ SY Sodding, 1" deep, level ground ESC-28 SWDM 5.4.2.5 9.20$ SY Sodding, 1" deep, sloped ground ESC-29 SWDM 5.4.2.5 11.50$ SY TESC Supervisor ESC-30 125.00$ HR Water truck, dust control ESC-31 SWDM 5.4.7 160.00$ HR Unit Reference #Price Unit Quantity Cost SWDM D.2.1.2.5 6,000.00$ Each 2 12,000.00 36,000.00$ LS 1 36,000.00 100.00$ Each 5 500.00 EROSION/SEDIMENT SUBTOTAL:71,806.20 SALES TAX @ 10.3%7,396.04 EROSION/SEDIMENT TOTAL:79,202.24 (A) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR EROSION & SEDIMENT CONTROL Description No. (A) Tree Protection Sump Pump Baker Tank WRITE-IN-ITEMS Page 3 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.a EROSION_CONTROL Version: 4/01/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.CostGENERAL ITEMS Backfill & Compaction- embankment GI-1 7.00$ CY Backfill & Compaction- trench GI-2 10.25$ CY Clear/Remove Brush, by hand (SY)GI-3 1.15$ SY Bollards - fixed GI-4 275.00$ Each Bollards - removable GI-5 520.00$ Each Clearing/Grubbing/Tree Removal GI-6 11,475.00$ Acre Excavation - bulk GI-7 2.30$ CY 10190 23,437.00 Excavation - Trench GI-8 5.75$ CY Fencing, cedar, 6' high GI-9 23.00$ LF Fencing, chain link, 4'GI-10 44.00$ LF Fencing, chain link, vinyl coated, 6' high GI-11 23.00$ LF Fencing, chain link, gate, vinyl coated, 20' GI-12 1,600.00$ Each Fill & compact - common barrow GI-13 28.75$ CY Fill & compact - gravel base GI-14 31.00$ CY 2000 62,000.00 Fill & compact - screened topsoil GI-15 44.75$ CY Gabion, 12" deep, stone filled mesh GI-16 74.50$ SY Gabion, 18" deep, stone filled mesh GI-17 103.25$ SY Gabion, 36" deep, stone filled mesh GI-18 172.00$ SY Grading, fine, by hand GI-19 2.90$ SY Grading, fine, with grader GI-20 2.30$ SY Monuments, 3' Long GI-21 1,025.00$ Each Sensitive Areas Sign GI-22 8.00$ Each Sodding, 1" deep, sloped ground GI-23 9.25$ SY Surveying, line & grade GI-24 975.00$ Day Surveying, lot location/lines GI-25 2,050.00$ Acre Topsoil Type A (imported)GI-26 32.75$ CY 5,610 183,727.50 Traffic control crew ( 2 flaggers )GI-27 137.75$ HR Trail, 4" chipped wood GI-28 9.15$ SY Trail, 4" crushed cinder GI-29 10.25$ SY Trail, 4" top course GI-30 13.75$ SY Conduit, 2"GI-31 5.75$ LF Wall, retaining, concrete GI-32 63.00$ SF 70 4,410.00 Wall, rockery GI-33 17.25$ SF SUBTOTAL THIS PAGE:273,574.50 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) Page 4 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000sy RI-1 34.50$ SY AC Grinding, 4' wide machine 1000-2000sy RI-2 18.25$ SY AC Grinding, 4' wide machine > 2000sy RI-3 11.50$ SY AC Removal/Disposal RI-4 40.00$ SY Barricade, Type III ( Permanent )RI-5 64.25$ LF Guard Rail RI-6 34.50$ LF Curb & Gutter, rolled RI-7 19.50$ LF Curb & Gutter, vertical RI-8 14.25$ LF Curb and Gutter, demolition and disposal RI-9 20.50$ LF Curb, extruded asphalt RI-10 6.25$ LF Curb, extruded concrete RI-11 8.00$ LF Sawcut, asphalt, 3" depth RI-12 3.00$ LF Sawcut, concrete, per 1" depth RI-13 5.00$ LF 50 250.00 Sealant, asphalt RI-14 2.25$ LF Shoulder, gravel, 4" thick RI-15 17.25$ SY Sidewalk, 4" thick RI-16 43.50$ SY Sidewalk, 4" thick, demolition and disposal RI-17 37.00$ SY Sidewalk, 5" thick RI-18 47.00$ SY Sidewalk, 5" thick, demolition and disposal RI-19 46.00$ SY 784 36,064.00 Sign, Handicap RI-20 97.00$ Each Striping, per stall RI-21 8.00$ Each Striping, thermoplastic, ( for crosswalk )RI-22 3.50$ SF Striping, 4" reflectorized line RI-23 0.55$ LF Additional 2.5" Crushed Surfacing RI-24 4.15$ SY HMA 1/2" Overlay 1.5" RI-25 16.00$ SY HMA 1/2" Overlay 2"RI-26 20.75$ SY HMA Road, 2", 4" rock, First 2500 SY RI-27 32.25$ SY HMA Road, 2", 4" rock, Qty. over 2500SY RI-28 24.00$ SY HMA Road, 4", 6" rock, First 2500 SY RI-29 51.75$ SY HMA Road, 4", 6" rock, Qty. over 2500 SY RI-30 42.50$ SY HMA Road, 4", 4.5" ATB RI-31 43.50$ SY Gravel Road, 4" rock, First 2500 SY RI-32 17.25$ SY Gravel Road, 4" rock, Qty. over 2500 SY RI-33 11.50$ SY Thickened Edge RI-34 10.00$ LF SUBTOTAL THIS PAGE:36,314.00 (B)(C)(D)(E) Page 5 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) PARKING LOT SURFACING No.2" AC, 2" top course rock & 4" borrow PL-1 24.00$ SY 2" AC, 1.5" top course & 2.5" base course PL-2 32.00$ SY 4" select borrow PL-3 5.75$ SY 1.5" top course rock & 2.5" base course PL-4 16.00$ SY SUBTOTAL PARKING LOT SURFACING: (B)(C)(D)(E) LANDSCAPING & VEGETATION No.Street Trees LA-1 Median Landscaping LA-2 Right-of-Way Landscaping LA-3 Wetland Landscaping LA-4 SUBTOTAL LANDSCAPING & VEGETATION: (B)(C)(D)(E) TRAFFIC & LIGHTING No.Signs TR-1 3,000.00$ Each Street Light System ( # of Poles)TR-2 Traffic Signal TR-3 Traffic Signal Modification TR-4 SUBTOTAL TRAFFIC & LIGHTING: (B)(C)(D)(E) WRITE-IN-ITEMS SUBTOTAL WRITE-IN ITEMS: STREET AND SITE IMPROVEMENTS SUBTOTAL:309,888.50 SALES TAX @ 10.3%31,918.52 STREET AND SITE IMPROVEMENTS TOTAL:341,807.02 (B)(C)(D)(E) Page 6 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost DRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/D D-1 30.00$ SY * (CBs include frame and lid) Beehive D-2 103.00$ Each Through-curb Inlet Framework D-3 460.00$ Each CB Type I D-4 1,725.00$ Each 2 3,450.00 CB Type IL D-5 2,000.00$ Each CB Type II, 48" diameter D-6 3,500.00$ Each for additional depth over 4' D-7 550.00$ FT CB Type II, 54" diameter D-8 4,075.00$ Each 1 4,075.00 for additional depth over 4'D-9 570.00$ FTCB Type II, 60" diameter D-10 4,225.00$ Each for additional depth over 4'D-11 690.00$ FT CB Type II, 72" diameter D-12 6,900.00$ Each for additional depth over 4'D-13 975.00$ FT CB Type II, 96" diameter D-14 16,000.00$ Each for additional depth over 4'D-15 1,050.00$ FT Trash Rack, 12"D-16 400.00$ Each Trash Rack, 15"D-17 470.00$ Each Trash Rack, 18"D-18 550.00$ Each Trash Rack, 21"D-19 630.00$ Each Cleanout, PVC, 4"D-20 170.00$ Each Cleanout, PVC, 6"D-21 195.00$ Each 2 390.00 Cleanout, PVC, 8"D-22 230.00$ Each 1 230.00 Culvert, PVC, 4" D-23 11.50$ LF Culvert, PVC, 6" D-24 15.00$ LF 250 3,750.00 Culvert, PVC, 8" D-25 17.00$ LF Culvert, PVC, 12" D-26 26.00$ LF 196 5,096.00 Culvert, PVC, 15" D-27 40.00$ LF Culvert, PVC, 18" D-28 47.00$ LF Culvert, PVC, 24"D-29 65.00$ LF Culvert, PVC, 30" D-30 90.00$ LF Culvert, PVC, 36" D-31 150.00$ LF Culvert, CMP, 8"D-32 22.00$ LF Culvert, CMP, 12"D-33 33.00$ LF SUBTOTAL THIS PAGE:16,991.00 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Page 7 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued)Culvert, CMP, 15"D-34 40.00$ LF Culvert, CMP, 18"D-35 47.00$ LF Culvert, CMP, 24"D-36 64.00$ LF Culvert, CMP, 30"D-37 90.00$ LF Culvert, CMP, 36"D-38 150.00$ LF Culvert, CMP, 48"D-39 218.00$ LFCulvert, CMP, 60"D-40 310.00$ LF Culvert, CMP, 72"D-41 400.00$ LF Culvert, Concrete, 8"D-42 48.00$ LF Culvert, Concrete, 12"D-43 55.00$ LF Culvert, Concrete, 15"D-44 89.00$ LF Culvert, Concrete, 18"D-45 100.00$ LF Culvert, Concrete, 24"D-46 120.00$ LF Culvert, Concrete, 30"D-47 145.00$ LF Culvert, Concrete, 36"D-48 175.00$ LF Culvert, Concrete, 42"D-49 200.00$ LF Culvert, Concrete, 48"D-50 235.00$ LF Culvert, CPE Triple Wall, 6" D-51 16.00$ LF Culvert, CPE Triple Wall, 8" D-52 18.00$ LF Culvert, CPE Triple Wall, 12" D-53 27.00$ LF Culvert, CPE Triple Wall, 15" D-54 40.00$ LF Culvert, CPE Triple Wall, 18" D-55 47.00$ LF Culvert, CPE Triple Wall, 24" D-56 64.00$ LF Culvert, CPE Triple Wall, 30" D-57 90.00$ LF Culvert, CPE Triple Wall, 36" D-58 149.00$ LF Culvert, LCPE, 6"D-59 69.00$ LF Culvert, LCPE, 8"D-60 83.00$ LF Culvert, LCPE, 12"D-61 96.00$ LF Culvert, LCPE, 15"D-62 110.00$ LF Culvert, LCPE, 18"D-63 124.00$ LF Culvert, LCPE, 24"D-64 138.00$ LFCulvert, LCPE, 30"D-65 151.00$ LF Culvert, LCPE, 36"D-66 165.00$ LF Culvert, LCPE, 48"D-67 179.00$ LF Culvert, LCPE, 54"D-68 193.00$ LF SUBTOTAL THIS PAGE: (B)(C)(D)(E) Page 8 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued)Culvert, LCPE, 60"D-69 206.00$ LF Culvert, LCPE, 72"D-70 220.00$ LF Culvert, HDPE, 6"D-71 48.00$ LF Culvert, HDPE, 8"D-72 60.00$ LF Culvert, HDPE, 12"D-73 85.00$ LF Culvert, HDPE, 15"D-74 122.00$ LF Culvert, HDPE, 18"D-75 158.00$ LF Culvert, HDPE, 24"D-76 254.00$ LF Culvert, HDPE, 30"D-77 317.00$ LF Culvert, HDPE, 36"D-78 380.00$ LF Culvert, HDPE, 48"D-79 443.00$ LF Culvert, HDPE, 54"D-80 506.00$ LF Culvert, HDPE, 60"D-81 570.00$ LF Culvert, HDPE, 72"D-82 632.00$ LF Pipe, Polypropylene, 6"D-83 96.00$ LF Pipe, Polypropylene, 8"D-84 100.00$ LFPipe, Polypropylene, 12"D-85 100.00$ LF Pipe, Polypropylene, 15"D-86 103.00$ LF Pipe, Polypropylene, 18"D-87 106.00$ LF Pipe, Polypropylene, 24"D-88 119.00$ LF Pipe, Polypropylene, 30"D-89 136.00$ LF Pipe, Polypropylene, 36"D-90 185.00$ LF Pipe, Polypropylene, 48"D-91 260.00$ LF Pipe, Polypropylene, 54"D-92 381.00$ LF Pipe, Polypropylene, 60"D-93 504.00$ LF Pipe, Polypropylene, 72"D-94 625.00$ LF Culvert, DI, 6"D-95 70.00$ LF Culvert, DI, 8"D-96 101.00$ LF Culvert, DI, 12"D-97 121.00$ LF Culvert, DI, 15"D-98 148.00$ LF Culvert, DI, 18"D-99 175.00$ LF Culvert, DI, 24"D-100 200.00$ LF Culvert, DI, 30"D-101 227.00$ LF Culvert, DI, 36"D-102 252.00$ LF Culvert, DI, 48"D-103 279.00$ LF Culvert, DI, 54"D-104 305.00$ LF Culvert, DI, 60"D-105 331.00$ LF Culvert, DI, 72"D-106 357.00$ LF SUBTOTAL THIS PAGE: Page 9 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) (B)(C)(D)(E) Page 10 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Specialty Drainage ItemsDitching SD-1 10.90$ CY Flow Dispersal Trench (1,436 base+)SD-3 32.00$ LF French Drain (3' depth)SD-4 30.00$ LF Geotextile, laid in trench, polypropylene SD-5 3.40$ SY Mid-tank Access Riser, 48" dia, 6' deep SD-6 2,300.00$ Each Pond Overflow Spillway SD-7 18.25$ SY Restrictor/Oil Separator, 12"SD-8 1,320.00$ Each Restrictor/Oil Separator, 15"SD-9 1,550.00$ Each Restrictor/Oil Separator, 18"SD-10 1,950.00$ Each Riprap, placed SD-11 48.20$ CY Tank End Reducer (36" diameter)SD-12 1,375.00$ Each Infiltration pond testing SD-13 143.00$ HR Permeable Pavement SD-14 Permeable Concrete Sidewalk SD-15 10.50$ SF Culvert, Box __ ft x __ ft SD-16 SUBTOTAL SPECIALTY DRAINAGE ITEMS: (B)(C)(D)(E)STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)Detention Pond SF-1 Each Detention Tank SF-2 1.00$ Each Detention Vault SF-3 ###########Each Infiltration Pond SF-4 Each Infiltration Tank SF-5 Each Infiltration Vault SF-6 Each Infiltration Trenches SF-7 Each Basic Biofiltration Swale SF-8 Each Wet Biofiltration Swale SF-9 Each Wetpond SF-10 Each Wetvault SF-11 Each Sand Filter SF-12 Each Sand Filter Vault SF-13 Each Linear Sand Filter SF-14 Each Proprietary Facility SF-15 Each Bioretention Facility SF-16 Each SUBTOTAL STORMWATER FACILITIES: (B)(C)(D)(E) Page 11 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs)Modular Wetland (Water Quality) WI-1 30,000.00$ Each 1 30,000.00 Control Structure WI-2 3,600.00$ Each 1 3,600.00 Connect to Existing System WI-3 3,600.00$ Each 1 3,600.00 StormTech Chamber Detention System WI-4 920,000.00$ Each 1 920,000.00 Removal of Existing Storm Pipe WI-5 1.00$ LF 1721 1,721.00 WI-6 WI-7 WI-8 WI-9 WI-10 WI-11 WI-12 WI-13 WI-14 WI-15 SUBTOTAL WRITE-IN ITEMS:958,921.00 DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:975,912.00 SALES TAX @ 10.3%100,518.94 DRAINAGE AND STORMWATER FACILITIES TOTAL:1,076,430.94 (B) (C) (D) (E) Page 12 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Connection to Existing Watermain W-1 3,400.00$ Each Ductile Iron Watermain, CL 52, 4 Inch Diameter W-2 58.00$ LF Ductile Iron Watermain, CL 52, 6 Inch Diameter W-3 65.00$ LF Ductile Iron Watermain, CL 52, 8 Inch Diameter W-4 75.00$ LF Ductile Iron Watermain, CL 52, 10 Inch Diameter W-5 80.00$ LF Ductile Iron Watermain, CL 52, 12 Inch Diameter W-6 145.00$ LF Gate Valve, 4 inch Diameter W-7 1,225.00$ Each Gate Valve, 6 inch Diameter W-8 1,350.00$ Each Gate Valve, 8 Inch Diameter W-9 1,550.00$ Each Gate Valve, 10 Inch Diameter W-10 2,100.00$ Each Gate Valve, 12 Inch Diameter W-11 2,500.00$ Each Fire Hydrant Assembly W-12 5,000.00$ Each Permanent Blow-Off Assembly W-13 1,950.00$ Each Air-Vac Assembly, 2-Inch Diameter W-14 3,050.00$ Each Air-Vac Assembly, 1-Inch Diameter W-15 1,725.00$ Each Compound Meter Assembly 3-inch Diameter W-16 9,200.00$ Each Compound Meter Assembly 4-inch Diameter W-17 10,500.00$ Each Compound Meter Assembly 6-inch Diameter W-18 11,500.00$ Each Pressure Reducing Valve Station 8-inch to 10-inch W-19 23,000.00$ Each WATER SUBTOTAL: SALES TAX @ 10.3% WATER TOTAL: (B) (C) (D) (E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR WATER Quantity Remaining (Bond Reduction) (B)(C) Page 13 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.d WATER Version: 4/1/2024 Printed 6/6/2025 CED Permit #:C25000977 Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Clean Outs SS-1 1,150.00$ Each Grease Interceptor, 500 gallon SS-2 9,200.00$ Each Grease Interceptor, 1000 gallon SS-3 11,500.00$ Each Grease Interceptor, 1500 gallon SS-4 17,200.00$ Each Side Sewer Pipe, PVC. 4 Inch Diameter SS-5 92.00$ LF Side Sewer Pipe, PP. 6 Inch Diameter SS-6 150.00$ LF Sewer Pipe, PVC, 8 inch Diameter SS-7 120.00$ LF Sewer Pipe, PVC, 12 Inch Diameter SS-8 144.00$ LF Sewer Pipe, DI, 8 inch Diameter SS-9 130.00$ LF Sewer Pipe, DI, 12 Inch Diameter SS-10 150.00$ LF Manhole, 48 Inch Diameter SS-11 6,900.00$ Each Manhole, 54 Inch Diameter SS-13 6,800.00$ Each Manhole, 60 Inch Diameter SS-15 7,600.00$ Each Manhole, 72 Inch Diameter SS-17 10,600.00$ Each Manhole, 96 Inch Diameter SS-19 16,000.00$ Each Pipe, C-900, 12 Inch Diameter SS-21 205.00$ LF Outside Drop SS-24 1,700.00$ LS Inside Drop SS-25 1,150.00$ LS Sewer Pipe, PVC, ____ Inch Diameter SS-26Lift Station (Entire System)SS-27 LS SANITARY SEWER SUBTOTAL: SALES TAX @ 10.3% SANITARY SEWER TOTAL: (B) (C) (D) (E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR SANITARY SEWER Quantity Remaining (Bond Reduction) (B)(C) Page 14 of 15 Ref 8-H Bond Quantity Worksheet SECTION II.e SANITARY SEWER Version: 4/1/2024 Printed 6/6/2025 1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200 Date: Name: Project Name: PE Registration No: CED Plan # (LUA): Firm Name:CED Permit # (C): Firm Address: Site Address: Phone No. Parcel #(s): Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a) Existing Right-of-Way Improvements Subtotal (b) (b)-$ Future Public Improvements Subtotal (c)-$ Stormwater & Drainage Facilities (Public & Private) Subtotal (d) (d)1,076,430.94$ (e) (f) Site Restoration Existing Right-of-Way and Storm Drainage Improvements Maintenance Bond 215,286.19$ Bond Reduction2 Construction Permit Bond Amount 3 Minimum Bond Amount is $10,000.00 1 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering. 2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% will cover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering. * Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton. ** Note: All prices include labor, equipment, materials, overhead, profit, and taxes. (206) 426-2600 alan@jacobsonengineers.com Lindbergh High School Field Improvements LUA25-000051 16426 128th Ave SE, Renton, WA 98058 2823059004 FOR APPROVAL C25000977 255 S King St, Suite 800, Seattle, WA 98104 1,155,633.17$ P (a) x 100% SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS 6/6/2025 Alan Jacobson 43667 Jacobson Consulting Engineers R ((b x 150%) + (d x 100%)) S (e) x 150% + (f) x 100% Bond Reduction: Existing Right-of-Way Improvements (Quantity Remaining)2 Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2 T (P +R - S) Prepared by: Project Information CONSTRUCTION BOND AMOUNT */** (prior to permit issuance) EST1 ((b) + (c) + (d)) x 20% -$ MAINTENANCE BOND */** (after final acceptance of construction) 79,202.24$ -$ 1,076,430.94$ 79,202.24$ -$ 1,076,430.94$ -$ Page 15 of 15 Ref 8-H Bond Quantity Worksheet SECTION III. BOND WORKSHEET Version: 4/1/2024 Printed 6/6/2025 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 Lindbergh High School Field Improvements 16426 128th Ave SE, Renton WA, 98058 12823059004 Ginger Creek Cedar River N/A 5.05 3.59 71% 148,625 6.75% 0 ----- N/A TBD 148,625 67.5% 148,625 67.5% 1 1 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 Lindbergh High School Field Improvements 16426 128th Ave SE, Renton WA, 98058 Ginger Creek Cedar River StormTech MC-7200 Chamber Detention East side of baseball field 75,140 6.25'N/A 3.588 71.0% 1 East of baseball field 2 N/A School NW drainage basin 1.0 0.25 0.067 N/A N/A 1 Modular Wetland (Manufacturer: Contech) 12 8 T H A V E N U E S E H SD SD SD SD SD SD SD SD SD EXHIBIT A - SITE PLAN NYOPLAST BASIN (TYP OF 6) FLOW CONTROL STRUCTURETYPE 1 CB CONNECTION TO EXISTING STORM SYSTEM MODULAR WETLAND (WATERQUALITY) INTERCEPT UPSTREAM SOFTBALL DRAINAGE SYSTEM STORMTECH MC-7200 CHAMBER DETENTION SYSTEM Page 1 of ___ Return Address: City Clerk’s Office City of Renton 1055 S Grady Way Renton, WA 98057 DECLARATION OF COVENANT FOR INSPECTION AND MAINTENANCE OF DRAINAGE FACILITIES AND ON-SITE BMPS Grantor: Grantee: City of Renton, a Washington municipal corporation Legal Description: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved City of Renton (check one of the following) Residential Building Permit Commercial Building Permit Clearing and Grading Permit Civil Construction or Utility Permit for Permit(s)_____________________ (Construction/Building/Utility Permit #) relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covenants (covenant) with the City of Renton (“City of Renton” or “City”), a municipal corporation of the state of Washington, that he/she (they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs 1 through 9 below with regard to the Property, and hereby grants (grant) an easement as described in Paragraphs 2 and 3. Grantor(s) hereby grants (grant), covenants (covenant), and agrees (agree) as follows: 1.The Grantor(s) or his/her (their) successors in interest and assigns ("Owners ") shall at their own cost, operate, maintain, and keep in good repair, the Property's drainage facilities constructed as required in the approved construction plans and specifications __________________ (Project Plan #) on file with the City of Renton and submitted to the City of Renton for the review and approval of permit(s) _____________________________ (Construction/Building/Utility Permit #). The Property's drainage facilities are shown and/or listed on Exhibit A – Site Plan. The Property’s drainage facilities shall be maintained in compliance with the operation and maintenance schedule included and attached herein as Exhibit B – Operations and Maintenance. Drainage facilities include pipes, channels, flow control facilities, water quality facilities, on-site best management practices (BMPs) and other engineered structures designed to manage and/or Page 2 of ___ treat stormwater on the Property. On-site BMPs include dispersion and infiltration devices, bioretention, permeable pavements, rainwater harvesting systems, tree retention credit, reduced impervious surface footprint, vegetated roofs and other measures designed to mimic pre-developed hydrology and minimize stormwater runoff on the Property. 2.City of Renton shall have the right to ingress and egress over those portions of the Property necessary to perform inspections of the stormwater facilities and BMPs and conduct maintenance activities specified in this Declaration of Covenant and in accordance with the Renton Municipal Code. City of Renton shall provide at least thirty (30) days’ written notice to the Owners that entry on the Property is planned for the inspection of drainage facilities. After the thirty (30) days, the Owners shall allow the City of Renton to enter for the sole purpose of inspecting drainage facilities. In lieu of inspection by the City, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the drainage facilities and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the City of Renton within fifteen (15) days of receiving the City’s notice of inspection. Within thirty (30) days of giving this notice, the Owners, or engineer on behalf of the Owners, shall provide the engineer’s report to the City of Renton. If the report is not provided in a timely manner as specified above, the City of Renton may inspect the drainage facilities without further notice. 3.If City of Renton determines from its inspection, or from an engineer’s report provided in accordance with Paragraph 2, that maintenance, repair, restoration, and/or mitigation work is required to be done to any of the drainage facilities, City of Renton shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (“Work”) required pursuant to the Renton Municipal Code. The City shall also set a reasonable deadline for the Owners to complete the Work, or to provide an engineer’s report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the City access to re-inspect the drainage facilities unless an engineer’s report has been provided verifying completion of the Work. If the Work is not completed within the time frame set by the City, the City may initiate an enforcement action and/or perform the Work and hereby is given access to the Property for such purposes. Written notice will be sent to the Owners stating the City’s intention to perform such Work. This Work will not commence until at least seven (7) days after such notice is mailed. If, within the sole discretion of the City, there exists an imminent or present danger, the seven (7) day notice period will be waived and Work will begin immediately. 4.The Owners shall assume all responsibility for the cost of any Work, or any measures taken by the City to address conditions as described in Paragraph 3. Such responsibility shall include reimbursement to the City within thirty (30) days of the receipt of the invoice for any such Work performed. Overdue payments will require payment of interest at the maximum legal rate allowed by RCW 19.52.020 (currently twelve percent (12%)). If the City initiates legal action to enforce this agreement, the prevailing party in such action is entitled to recover reasonable litigation costs and attorney’s fees. 5.The Owners are required to obtain written approval from City of Renton prior to filling, piping, cutting, or removing vegetation (except in routine landscape maintenance) in open vegetated stormwater facilities (such as swales, channels, ditches, ponds, etc.), or performing any alterations or modifications to the drainage facilities referenced in this Declaration of Covenant. Page 3 of ___ 6.Any notice or consent required to be given or otherwise provided for by the provisions of this Agreement shall be effective upon personal delivery, or three (3) days after mailing by Certified Mail, return receipt requested. 7.With regard to the matters addressed herein, this agreement constitutes the entire agreement between the parties, and supersedes all prior discussions, negotiations, and all agreements whatsoever whether oral or written. 8.This Declaration of Covenant is intended to protect the value and desirability and promote efficient and effective management of surface water drainage of the real property described above, and shall inure to the benefit of all the citizens of the City of Renton and its successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest, and assigns. 9.This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and the City that is recorded by King County in its real property records. IN WITNESS WHEREOF, this Declaration of Covenant for the Inspection and Maintenance of Drainage Facilities is executed this _____ day of ____________________, 20_____. GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this _____ day of ___________________, 20_____. Printed name Notary Public in and for the State of Washington, residing at My appointment expires Damien Pattenaude Renton School District Superintendent 12 8 T H A V E N U E S E H SD SD SD SD SD SD SD SD SD EXHIBIT A - SITE PLAN NYOPLAST BASIN (TYP OF 6) FLOW CONTROL STRUCTURE TYPE 1 CATCH BASIN CONNECTION TO EXISTING STORM SYSTEM MODULAR WETLAND (WATERQUALITY) INTERCEPT UPSTREAM SOFTBALL DRAINAGE SYSTEM STORMTECH MC-7200 CHAMBER DETENTION SYSTEM Page 4 of 26 MAINTENANCE INSTRUCTIONS FOR SOIL AMENDMENT Your property contains an on-site BMP (best management practice) called “soil amendment,” which was installed to mitigate the stormwater quantity and quality impacts of some or all of the pervious surfaces on your property. Soil amendment is a method of regaining greater stormwater functions in the post development landscape by increasing treatment of pollutants and sediments, and minimizing the need for some landscaping chemicals. To be successful, the soil condition must be able to soak water into the ground for a reasonable number of years. This on-site BMP shall be maintained per Appendix A of the City of Renton’s Surface Water Design Manual. MAINTENANCE RESTRICTIONS The size, placement, and composition of these devices as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES To be successful, the soil must be able to soak water into the ground for a reasonable number of years. • Return leaf fall and shredded woody materials from the landscape to the site when possible in order to replenish soil nutrients and structure. • On turf areas, “grasscycle” (mulch-mow or leave the clippings) to build turf health. • Maintain 2 to 3 inches of mulch over bare areas in landscape beds. • Re-seed bare turf areas until the vegetation fully covers the ground surface. • Avoid using pesticides (bug and weed killers) which damage the soil. • Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers, or slow-release synthetic balanced fertilizers. RECORDING REQUIREMENT These on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. 26Page 5 of EXHIBIT B - OPERATIONS AND MAINTENANCE 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 fiush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting fiush 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. Page 6 of 26 Structure (cont.) 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 fllm. 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. 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. Oriflce Plate Damaged or missing oriflce plate Control device is not working properly due to missing, out of place, or bent oriflce plate. Plate is in place and works as designed. Obstructions to oriflce plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overfiow Pipe Obstruction to overfiow pipe Any trash or debris blocking (or having the potential of blocking) the overfiow pipe. Pipe is free of all obstructions and works as designed. Page 7 of 26 Overfiow Pipe (cont.) Deformed or damaged lip of overfiow pipe Lip of overfiow pipe is bent or deformed. Overfiow pipe does not allow overfiow at an elevation lower than design. Inlet/Outlet Pipe Sediment accumulation Sediment fllling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes fioatables and non-fioatables). 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. Page 8 of 26 No. 5 – Catch Basins and Manholes Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Sediment 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 without 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 fiush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting fiush 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 No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Page 9 of 26 any evidence of soil particles entering catch basin through cracks. Structure (cont.) 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 fllm. Inlet/Outlet Pipe Sediment accumulation Sediment fllling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes fioatables and non-fioatables). 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 (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. Page 10 of 26 Manhole Cover/Lid (cont.) 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. Page 11 of 26 No. 6 – Conveyance Pipes and Ditches Maintenance Component Defect or Problem Condition 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 fiows freely through pipes. Vegetation/root growth in pipe Vegetation/roots that reduce free movement of water through pipes. Water fiows 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 fllm. 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/fiushed 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 fllm. Excessive vegetation growth Vegetation that reduces free movement of water through ditches. Water fiows freely through ditches. Page 12 of 26 Ditches (cont.) 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. Page 13 of 26 No. 11 – Grounds (Landscaping) Maintenance Component Defect or Problem Condition 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 flll up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris is 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 fllm. 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 identifled Any tree or limb of a tree identifled 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 identifled 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. Page 14 of 26 1 MODULAR WETLANDS® LINEAR OPERATION & MAINTENANCE MANUAL OVERVIEW The Modular Wetlands Linear Biofilter is designed to remove high levels of trash, debris, sediments, nutrients, metals, and hydrocarbons. Its simple design allows for quick and easy installatfon. The system is housed in a standard precast structure and can be installed at various depths to meet site-specific conditfons. INTRODUCTION This is the Modular Wetlands Linear Biofilter operatfon and maintenance manual. Before startfng, read the instructfons and equipment lists closely. It is important to follow all necessary safety procedures associated with state and local regulatfons. Some steps required confined space entry. Please contact Contech for more informatfon on pre-authorized third-party contractors who can provide installatfon services in your area. For a list of service providers in your area please visit: www.conteches.com/maintenance. INSTRUCTIONS INSPECTION SUMMARY Stormwater regulatfons require BMPs be inspected and maintained to ensure they are operatfng as designed to allow for effectfve pollutant removal and provide protectfon to receiving water bodies. It is recommended that inspectfons be performed multfple tfmes during the first year to assess the site specific loading conditfons. The first year of inspectfons can be used to set inspectfon and maintenance intervals for subsequent years to ensure appropriate maintenance is provided. • Inspect pre-treatment, biofiltratfon, and discharge chambers an average of once every six to twelve months. Varies based on site specific and local conditfons. • Average inspectfon tfme is approximately 15 minutes. Always ensure appropriate safety protocol and procedures are followed. • The following is a list of equipment required to allow for simple and effectfve inspectfon of the Modular Wetlands Linear: • Modular Wetlands Linear Inspectfon Form • Flashlight • Manhole hook or appropriate tools to remove access hatches and covers • Appropriate traffic control signage and procedures • Measuring pole and/or tape measure • Protectfve clothing and eye protectfon • 7/16” open or closed ended wrench • Large permanent black marker (initfal inspectfons only - first year) Page 15 of 26 2 Note: entering a confined space requires appropriate safety and certfficatfon. It is generally not required for routfne inspectfons of the system. INSPECTION AND MAINTENANCE NOTES 1. Following maintenance and/or inspectfon, it is recommended that the maintenance operator prepare a maintenance/inspectfon record. The record should include any maintenance actfvitfes performed, amount and descriptfon of debris collected, and conditfon of the system and its various filter mechanisms. 2. The owner should keep maintenance/inspectfon record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspectfon upon request at any tfme. 3. Transport all debris, trash, organics, and sediments to approved facility for disposal in accordance with local and state requirements. 4. Entry into chambers may require confined space training based on state and local regulatfons. 5. No fertflizer shall be used in the biofiltratfon chamber. 6. Irrigatfon should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigatfon required is dependent on plant species. Some plants may not require irrigatfon after initfal establishment. INSPECTION PROCESS 1. Prepare the inspectfon form by writfng in the necessary informatfon including project name, locatfon, date & tfme, unit number and other informatfon (see inspectfon form). 2. Observe the inside of the system through the access covers. If minimal light is available and vision into the unit is impaired, utflize a flashlight to see inside the system and all of its chambers. 3. Look for any out of the ordinary obstructfons in the inflow pipe, pre-treatment chamber, biofiltratfon chamber, discharge chamber or outilow pipe. Write down any observatfons on the inspectfon form. 4. Through observatfon and/or digital photographs, estfmate the amount of trash, debris accumulated in the pre-treatment chamber. Utflizing a tape measure or measuring stfck, estfmate the amount of sediment in this chamber. Record this depth on the inspectfon form. 5. Through visual observatfon, inspect the conditfon of the pre-filter cartridges. Look for excessive build-up of sediment on the cartridges, any build-up on the tops of the cartridges, or clogging of the holes. Record this informatfon on the inspectfon form. The prefilter cartridges can be further inspected by removing the cartridge tops and assessing the color of the BioMediaGREEN filter cubes (requires entry into pre-treatment chamber - see notes previous notes regarding confined space entry). Record the color of the material. New material is a light green color. As the media becomes clogged, it will turn darker in color, eventually becoming dark brown or black. The closer to black the media is the higher percentage that the media is exhausted and is in need of replacement. Page 16 of 26 3 6. The biofiltratfon chamber is generally maintenance-free due to the system’s advanced pre- treatment chamber. For units which have open planters with vegetatfon, it is recommended that the vegetatfon be inspected. Look for any plants that are dead or showing signs of disease or other negatfve stressors. Record the general health of the plants on the inspectfon form and indicate through visual observatfon or digital photographs if trimming of the vegetatfon is required. 7. The discharge chamber houses the orifice control structure, drain down filter (only in California - older models), and is connected to the outilow pipe. It is important to check to ensure the orifice is in proper operatfng conditfons and free of any obstructfons. It is also important to assess the conditfon of the drain down filter media which utflizes a block form of the BioMediaGREEN. Assess in the same manner as the cubes in the pre- filter cartridge as mentfoned above. Generally, the discharge chamber will be clean and free of debris. Inspect the water marks on the side walls. If possible, inspect the discharge chamber during a rain event to assess the amount of flow leaving the system while it is at 100% capacity (pre-treatment chamber water level at peak HGL - top of bypass weir). The water level of the flowing water should be compared to the watermark level on the side walls, which is an indicator of the highest discharge rate the system achieved when initfally installed. Record on the form if there is any difference in level from the watermark in inches. NOTE: During the first few storms, the water level in the outilow chamber should be observed and a 6” long horizontal watermark line drawn (using a large permanent marker) at the water level in the discharge chamber while the system is operatfng at 100% capacity. The diagram below illustrates where the line should be drawn. This line is a reference point for future inspectfons of the system. Water level in the discharge chamber is a functfon of flow rate and pipe size. Observatfon of the water level during the first few months of operatfon can be used as a benchmark level for future inspectfons. The initfal mark and all future observatfons shall be made when the system is at 100% capacity (water level at maximum level in the pre-treatment chamber). If future water levels are below this mark when the system is at 100% capacity, this is an indicator that maintenance to the pre-filter cartridges may be needed. 8. Finalize the inspectfon report for analysis by the maintenance manager to determine if maintenance is required. MAINTENANCE INDICATORS Based upon the observatfons made during inspectfon, maintenance of the system may be required based on the following indicators: • Missing or damaged internal components or cartridges Page 17 of 26 4 • Obstructfons in the system or its inlet and/or outlet pipes • Excessive accumulatfon of floatables in the pretreatment chamber in which the length and width of the chamber is fully impacted more than 18”. See photo below. • Excessive accumulatfon of sediment in the pretreatment chamber of more than 6” in depth. • Excessive accumulatfon of sediment on the BioMediaGREEN media housed within the pretreatment cartridges. The following chart shows photos of the conditfon of the BioMediaGREEN contained within the pre-filter cartridges. When media is more than 85% clogged, replacement is required. • Excessive accumulatfon of sediment on the BioMediaGREEN media housed within the pretreatment cartridges. When media is more than 85% clogged, replacement is required. The darker the BioMediaGREEN, the more clogged it is and in need of replacement. INSPECTION PROCESS • Excessive accumulatfon of sediment on the BioMediaGREEN media housed within the drain down filter (California only - older models). The following photos show the conditfon of the BioMediaGREEN contained within the drain down filter. When media is more than 85% clogged, replacement is required. • Overgrown vegetatfon. • Water level in the discharge chamber during 100% operatfng capacity (pretreatment chamber water level at max height) is lower than the water mark by 20%. MAINTENANCE SUMMARY The tfme has come to maintain your Modular Wetlands Linear. All necessary pre-maintenance steps must be carried out before maintenance occurs. Once traffic control has been set up per local and state regulatfons and access covers have been safely opened, the maintenance process can begin. It should be noted that some maintenance actfvitfes require confined space entry. All confined space requirements must be strictly followed before entry into the system. In additfon, the following is recommended: • Prepare the maintenance form by writfng in the necessary informatfon including project name, locatfon, date & tfme, unit number and other info. • Set up all appropriate safety and cleaning equipment. • Ensure traffic control is set up and properly positfoned. • Prepared pre-checks (OSHA, safety, confined space entry) are performed. • The following is a list of equipment to required for maintenance of the Modular Wetlands Linear: • Modular Wetlands Linear Maintenance Form • Manhole hook or appropriate tools to access hatches and covers • Protectfve clothing, flashlight, and eye protectfon • 7/16” open or closed ended wrench • Vacuum assisted truck with pressure washer • Replacement BioMediaGREEN for pre-filter cartridges if required (order from one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance). Page 18 of 26 5 MAINTENANCE | PRETREATMENT CHAMBER 1. Remove access cover over pre-treatment chamber and positfon vacuum truck accordingly. 2. With a pressure washer, spray down pollutants accumulated on walls and pre-filter cartridges. 3. Vacuum out pre-treatment chamber and remove all accumulated pollutants including trash, debris, and sediments. Be sure to vacuum the floor untfl the pervious pavers are visible and clean. 9. If pre-filter cartridges require media replacement, contfnue to step 5. If not, replace access cover and move to step 11. MAINTENANCE | PREFILTER CARTRIDGES 4. After successfully cleaning out the pre-treatment chamber enter the pre-treatment chamber. 5. Unscrew the two bolts holding the lid on each cartridge filter and remove lid. 6. Place the vacuum hose over each individual media filter to suck out filter media. 7. Once filter media has been sucked out, use a pressure washer to spray down the inside of the cartridge and it’s media cages. Remove cleaned media cages and place to the side. Once removed, the vacuum hose can be inserted into the cartridge to vacuum out any remaining material near the bottom of the cartridge. 8. Reinstall media cages and fill with new media from the manufacturer or outside supplier. Manufacturer will provide specificatfon of media and sources to purchase. Utflize the manufacture-provided refilling tray and place on top of the cartridge. Fill the tray with new bulk media and shake down into place. Using your hands, lightly compact the media into each filter cage. Once the cages are full, remove the refilling tray and replace the cartridge top, ensuring bolts are properly tfghtened. 9. Exit the pre-treatment chamber. Replace access hatch or manhole cover. MAINTENANCE | BIOFILTRATION CHAMBER 10. In general, the biofiltratfon chamber is maintenance-free with the exceptfon of maintaining the vegetatfon. The Modular Wetlands Linear utflizes vegetatfon similar to surrounding landscape areas, therefore trim vegetatfon to match surrounding vegetatfon. If any plants have died, replace them with new ones. 11. Each vertfcal under drain on the biofiltratfon chamber has a removable (threaded cap) that can be taken off to check any blockages or root growth. Once removed, a jetting attachment can be used to clean out the under drain and orifice riser. 12. As with all biofilter systems, at some point the biofiltratfon media (WetlandMedia) will need to be replaced. Either because of physical clogging of sorptfve exhaustfon of the media ion exchange capacity (to remove dissolved metals and phosphorous). The general life of this media is 10 to 20 years based on site specific conditfons and pollutant loading. Utflize the vacuum truck to vacuum out the media by placing the hose into the chamber. Once all the media is removed Page 19 of 26 6 use the power washer to spray down all the netting on the outer metal cage. Inspect the netting for any damage or holes. If the netting is damaged it can be repaired or replaced with guidance by the manufacturer. 13. Contact one of Contech’s Maintenance Team members at https://www.conteches.com/maintenance to order new WetlandMedia. The quantfty of media needed can be determined by providing the model number and unit depth. Media will be provided in super sacks for easy installatfon. Each sack will weigh between 1000 and 2000 lbs. A lifting apparatus (backhoe, boom truck, or other) is recommended to positfon the super sack over the biofiltratfon chamber. Fill the media cages up to the same level as the old media. Replant with vegetatfon. MAINTENANCE | DISCHARGE CHAMBER 14. Remove access hatch or manhole cover over discharge chamber. 15. Enter chamber to gain access to the drain down filter. Unlock the locking mechanism and lift up drain down filter housing to remove used BioMediaGREEN filter block as shown below. NOTE: Drain down filter is only found on units installed in California prior to 2023. If no drain down filter is present, skip steps 16 and 17. 16. Insert a new BioMediaGREEN filter block and lock drain down filter housing back in place. 17. Replace access hatch or manhole cover over discharge chamber. Page 20 of 26 8 © 2023 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 WWW.CONTECHES.COM ALL RIGHTS RESERVED. PRINTED IN THE USA. CONTECH ENGINEERED SOLUTIONS LLC PROVIDES SITE SOLUTIONS FOR THE CIVIL ENGINEERING INDUSTRY. CONTECH’S PORTFOLIO INCLUDES BRIDGES, DRAINAGE, SANITARY SEWER, STORMWATER AND EARTH STABILIZATION PRODUCTS. FOR INFORMATION ON OTHER CONTECH DIVISION OFFERINGS, VISIT CONTECHES.COM OR CALL 800-338-1122. NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. DRAWINGS AND SPECIFICATIONS ARE AVAILABLE AT WWW.CONTECHES.COM Modular Wetlands Maintenance Guide 1/2023 Page 21 of 26 Page 22 of 26 Page 23 of 26 Page 24 of 26 Page 25 of 26 Exhibit C – Legal Description Page 5 of ___ 66 THE SOUTHEAST QUARTER OF THE NORTHEAST QUARTER OF SECTION 28, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON; EXCEPT THE SOUTH 250 FEET OF THE EAST 523 FEET OF THE WEST 553 FEET; AND EXCEPT THE WEST 30 FEET FOR THE COUNTY ROAD, PURSUANT TO CITY OF RENTON DECLARATION OF LOT COMBINATION NO. LUA22-000106, RECORDED UNDER KING COUNTY RECORDING NO. 20240507000960, KING COUNTY, WASHINGTON. Page 26 of 26