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DRAFT TECHNICAL INFORMATION REPORT Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Renton Municipal Airport | City of Renton PRE24-000055 JUNE 2024 Prepared for: City of Renton Renton Municipal Airport 616 W Perimeter Rd, Unit A Renton, WA 98057 Contact: William Adams, PE Phone: (425) 430-7473 Email: wadams@rentonwa.gov Prepared by: DOWL, LLC 15325 SE 30th Pl, Suite 300 Bellevue, WA 98007 Contact: Jason Shrope, PE Phone: (425) 869-2670 Email: jshrope@dowl.com Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page ii PROJECT ENGINEER’S CERTIFICATION I hereby state that this Drainage Control Plan for the Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Project has been prepared by me or under my supervision and meets the standards of care and expertise which is usual and customary in this community for professional engineers. I understand that the City of Renton does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page iii TABLE OF CONTENTS PROJECT ENGINEER’S CERTIFICATION ............................................................II 1.0 PROJECT OVERVIEW .......................................................................................1 2.0 CONDITIONS AND REQUIREMENTS SUMMARY ..................................2 2.1 Conditions of Approval.............................................................................................2 2.2 Core and Special Requirements ..............................................................................2 2.2.1 Core Requirement #1: Discharge at Natural Location..................................2 2.2.2 Core Requirement #2: Offsite Analysis ........................................................2 2.2.3 Core Requirement #3: Flow Control Facilities..............................................2 2.2.4 Core Requirement #4: Conveyance System ................................................2 2.2.5 Core Requirement #5: Construction Stormwater Pollution Prevention ................................................................................................................2 2.2.6 Core Requirement #6: Maintenance & Operations.......................................2 2.2.7 Core Requirement #7: Financial Guarantees & Liability...............................2 2.2.8 Core Requirement #8: Water Quality Facilities ............................................3 2.2.9 Core Requirement #9: On-Site BMPs ..........................................................3 2.2.10 Special Requirement #1: Other Adopted Area-Specific Requirements...........................................................................................................3 2.2.11 Special Requirement #2: Flood Hazard Area Delineation............................3 2.2.12 Special Requirement #3: Flood Protection Facilities....................................3 2.2.13 Special Requirement #4: Source Control .....................................................3 2.2.14 Special Requirement #5: Oil Control ............................................................3 2.2.15 Special Requirement #6: Aquifer Protection Areas ......................................3 3.0 OFFSITE ANALYSIS ...........................................................................................4 4.0 FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALSYIS AND DESIGN ....................................................................................................................5 4.1 Existing Site Hydrology ............................................................................................5 4.2 Developed Site Hydrology........................................................................................6 4.3 Performance Standards ...........................................................................................6 4.4 Water Quality............................................................................................................8 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..............................9 6.0 SPECIAL REPORTS AND STUDIES ..........................................................10 7.0 OTHER PERMITS ...............................................................................................11 8.0 CWSPPP ANALYSIS AND DESIGN ............................................................12 8.1 ESC Plan Analysis and Design..............................................................................12 8.1.1 Scope of Work............................................................................................12 8.1.2 Clearing Limits............................................................................................12 8.1.3 Cover Measures .........................................................................................12 8.1.4 Perimeter Protection...................................................................................12 8.1.5 Traffic Area Stabilization.............................................................................12 8.1.6 Sediment Retention....................................................................................12 8.1.7 Surface Water Collection............................................................................12 8.1.8 Dewatering Control.....................................................................................13 8.1.9 Dust Control................................................................................................13 Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page iv 8.1.10 Flow Control ...............................................................................................13 8.2 CSWPPP Plan Design ...........................................................................................13 9.0 BOND QUANTITIES, FACILITIY SUMMARIES, AND DECLARATION OF COVNENANT...............................................................17 9.1 Bond Quantities......................................................................................................17 9.2 Flow Control and Water Quality Facility Summary Sheet and Sketch ...................17 9.3 Declaration of Covenant for Privately Maintained Flow Control and Water Quality Facilities...............................................................................................................17 10.0 OPERATIONS & MAINTENANCE MANUAL............................................18 TABLES Table 1 – Existing Area Summary.................................................................................................5 Table 2 – Developed Area Summary ............................................................................................6 FIGURES & APPENDECIES Figure 1: TIR Worksheet Figure 2: Vicinity Map Figure 3: USGS Soil Survey Figure 4: Table for Determining Drainage Review Type Figure 5: Basin Map Figure 6: Storm Drain Map Figure 7: Geological Hazards Map Figure 8: Steep Slopes Map Figure 9: Flood Map Figure 10: Aquifer Protection Map Appendix A: 243 Building WWHM Appendix B: HWA Geotechnical Report Appendix C: SWPPP Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page I EXECUTIVE SUMMARY The proposed Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Project is located at 749 E Perimeter Road, Renton, Washington 98055 and 243 W Perimeter Road, Renton, Washington 98055, respectively (See Figure 2). The proposed project consists of the rehabilitation of the existing Windsock Apron, the rehabilitation of the existing 243 Building Apron, the reconstruction of the 243 Building parking lot, and the installation of proposed aircraft tiedowns. All existing stormwater structures and associated conveyance pipes will be protected in place and one landscape island curb cut at the 243 Building parking lot is proposed to ensure runoff characteristics remain unchanged. A list of improvements can be seen in Section 1.0. The purpose of this report is to show that the proposed improvements follow the standards and regulations developed by the City of Renton and the Washington Department of Ecology (DOE). These regulations are identified in the 2022 City of Renton Surface Water Design Manual (RSWDM). Water quantity calculations were performed in the Western Washington Hydrology Model 2012 (WWHM), an approved model by the DOE and City of Renton. WWHM uses the EPA Hydrologic Simulation Program Fortran (HSPF), which is a calibrated continuous simulation hydrologic model. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 1 1.0 PROJECT OVERVIEW The Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Project is located at 749 E Perimeter Road, Renton, Washington 98055 and 243 W Perimeter Road, Renton, Washington 98055, respectively. The site is located within Township 23 North, Range 5 East, Section 7 W.M.; the King County Parcel Number is: 0723059007. Refer to Figure 2, for a general location of both proposed work areas. This Technical Information Report (TIR) has been prepared in accordance with the 2022 City of Renton Surface Water Design Manual (RSWDM) and the DOE SWMMWW. The report describes how the project’s site improvements comply with the City of Renton regulations for stormwater and drainage. The project consists of the following improvements within the Renton Municipal Airport property: •Full depth pavement rehabilitation at the Windsock Apron •Full depth pavement rehabilitation at the 243 Building Apron •243 Building parking lot reconstruction and reconfiguration •Relocation of existing fence and vehicle gate V7 Since the intent of this project is to provide full depth pavement rehabilitation for both work areas, no adjustments to the existing stormwater system are proposed. Existing catch basins and conveyance pipes will be protected in place. For additional information on drainage requirements and how each applies see Section 2.2 and Figure 1. A majority of the stormwater runoff from the windsock apron is collected via existing catch basins located within the apron and is routed to an existing detention pond located between Runway 16-34 and Taxiway B, just west of the work area. A small northeastern portion of this work area sheet flows east and is collected in a catch basin northeast of the work area and discharges directly into the Cedar River. Stormwater runoff from the 243 Building apron and parking lot is collected via existing catch basins and routed west into an existing 60-inch pipe which conveys runoff north and ultimately discharges into Lake Washington (See Figure 6). The USDA soil map defines the soil as urban land (see Figure 3). A geotechnical report was completed by HWA Geosciences for the Wind Sock apron project that included subsurface borings. This geotechnical report describes the site soils as consisting of artificial fill, modified land and Quaternary Alluvium deposited by the Cedar and Black Rivers (see Appendix B). Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 2 2.0 CONDITIONS & REQUIREMENTS SUMMARY 2.1 Conditions of Approval This project and any proposed storm drain improvements will comply with the 2022 City of Renton Surface Water Design Manual (RSWDM). 2.2 Core & Special Requirements Both work areas are proposing more than 2,000 square feet of new plus replaced impervious surfaces but are not subject to Simplified Drainage Review, Directed Drainage Review, or Large Project Drainage Review per Table 1.1.2.A of the RSWDM, as seen in Figure 4. Therefore, the project will require a Full Drainage Review and will need to adhere to Core Requirements #1-9 and Special Requirements #1-6. Below is a list of all required Core and Special Requirements, per the RSWDM, and a description of how each will be met: 2.2.1 Core Requirement #1: Discharge at Natural Location The existing conveyance system and associated structures will be protected in place and the existing drainage patterns and discharge locations will be maintained. 2.2.2 Core Requirement #2: Offsite Analysis The 243 Building apron and parking lot is adding a small amount of new impervious surface which doesn’t substantially increase flows and the windsock apron is adding no new impervious surface. No downstream impacts are anticipated based on the proposed project improvements. See Section 3.0 for additional information. 2.2.3 Core Requirement #3: Flow Control Facilities Both work areas are considered flow control exempt. See Section 4.0 for additional information explaining why this project is flow control exempt. 2.2.4 Core Requirement #4: Conveyance System The existing conveyance system for both work areas will be protected in place. See Section 5.0 for additional information on the existing conveyance system. 2.2.5 Core Requirement #5: Construction Stormwater Pollution Prevention A Construction Stormwater Pollution Prevention Plan (CSWPPP) has been provided in Appendix C. 2.2.6 Core Requirement #6: Maintenance & Operations No new storm drainage structures are proposed and therefore no O&M Manual is provided. 2.2.7 Core Requirement #7: Financial Guarantees & Liability This project will comply with financial guarantees as required by the City of Renton. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 3 2.2.8 Core Requirement #8: Water Quality Facilities This project is considered exempt from implementing new water quality facilities. See Section 4.4 for additional information as to why this project is exempt from adding water quality facilities. 2.2.9 Core Requirement #9: On-Site BMPs Both work areas have been evaluated for feasibility of Low Impact Development (LID) design. See section 4.3 for additional information on the feasibility of these Best Management Practices (BMPs). 2.2.10 Special Requirement #1: Other Adopted Area-Specific Requirements This project is not located within an area having specific requirements above and beyond the core and special requirements listed herein. 2.2.11 Special Requirement #2: Flood Hazard Area Delineation Both project sites are outside of the 100-year floodplain or the FEMA floodway, but both project areas are within Zone X Other Flood Areas, 500-year floodplain, per the City of Renton COR Mapping. 2.2.12 Special Requirement #3: Flood Protection Facilities The existing windsock apron is located near an existing Cedar River levee. The existing levee will be protected in place and no adjustments to this levee will be made. 2.2.13 Special Requirement #4: Source Control This project does not warrant source controls. Each proposed apron and the 243 Building parking lot are considered transient parking areas and will be only used for a few hours at a time. 2.2.14 Special Requirement #5: Oil Control This project does not warrant oil controls. Each proposed apron and the 243 Building parking lot are considered transient parking areas and will be only used for a few hours at a time. 2.2.15 Special Requirement #6: Aquifer Protection Areas The 243 Building apron and parking lot is located within Zone 2 of the Aquifer Protection Areas. A fill source statement will be provided for any offsite soils brought to the site. No infiltration facilities are proposed. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 4 3.0 OFFSITE ANALYSIS Both work areas are deemed to be exempt per Section 1.2.2 of the RSWDM. An explanation of the exemption is provided below. Windsock Apron: The windsock apron proposes no new impervious surface. Therefore, there is no increase in flow between the existing and developed conditions. 243 Building Apron and Parking Lot: The 243 Building apron and parking lot proposes 4,369 square feet of new impervious surface but also proposes 2,405 square feet of new landscape area resulting in 1,964 square feet of effective impervious surface area. The addition of this new impervious surface increases flows between the existing and developed conditions by approximately 0.03 cfs during the 100-year storm event, as seen in Appendix A. Runoff from this work area is collected in catch basins and routed to an existing 60-inch conveyance pipe which runs along W Perimeter Road. Runoff ultimately discharges into Lake Washington, north of the work area. This minor increase in flows for the 100-year storm event is deemed inconsequential for the downstream conveyance system. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 5 4.0 FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) & WATER QUALITY FACILITY ANALSYIS & DESIGN 4.1 Existing Site Hydrology Windsock Apron: The windsock apron consists of asphalt pavement surfacing and is generally flat with slopes ranging between 0.5% and 2.0%. Site drainage consists of multiple catch basins and conveyance pipes which convey runoff underneath Taxiway B and discharges to an onsite detention pond west of the windsock apron. The existing detention pond only receives flows from the existing windsock apron. After flows have been mitigated, stormwater combines with flows from Runway 16/34 and discharges into the Cedar River. 243 Building Apron and Parking Lot: The 243 Building apron and parking lot areas are also generally flat with slopes ranging between 0.5% and 3.0%. The existing groundcover is a mix of existing asphalt and concrete pavements, along with some landscaped and grassed areas. Runoff generated from the 243 Building apron is captured in existing catch basins and is routed west to structures within W Perimeter Road. Runoff generated from the 243 Building parking lot is routed south and connects to structures located within the Airport Way right of way. Both the apron and parking lot discharge into a 60-inch conveyance pipe which runs parallel to W Perimeter Road. Flows continue north and ultimately discharge into Lake Washington. Below is a summary of all impervious and pervious areas for the existing conditions: Table 1 – Existing Area Summary Existing Areas Contributing Area Total Area, Square Foot Windsock Apron Pervious Area 0 Impervious Area 66,725 Total 66,725 243 Building Apron and Parking Lot Pervious Area 5,710 Impervious Area 43,381 Total 59,091 Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 6 4.2 Developed Site Hydrology Windsock Apron: The windsock apron is located within the Peak Rate Flow Control Standard Area, as seen in the City of Renton (COR) Maps. Per Section 1.2.3.1 of the RSWDM, the windsock apron is flow control exempt since no new impervious surfaces are proposed and there will be no increase in flows for the 100-year storm event between the existing and developed conditions. 243 Building Apron and Parking Lot: The 243 Building apron and parking lot is located within the Peak Rate Flow Control Standard Area, as seen in the City of Renton (COR) Maps. Per Section 1.2.3.1 of the RSWDM, the 243 Building apron and parking lot is flow control exempt since flows increase less than 0.15 cfs (approximately 0.03 cfs) between the existing and developed conditions for the 100-year storm event. Below is a summary of all impervious and pervious areas for the developed conditions: Table 2 – Developed Area Summary Developed Areas Contributing Area Total Area, Square Foot Windsock Apron Pervious Area (with Removed Impervious)0 New Impervious Area 0 Replaced Impervious Area 66,725 Total 66,725 243 Building Apron and Parking Lot Pervious Area (with Removed Impervious)3,746 New Impervious Area 4,369 Replaced Impervious Area 40,976 Total 59,091 4.3 Performance Standards As seen in Section 4.2 above, both work areas are considered flow control exempt. Although no performance standard needs to be met, on-site best management practices (BMPs) need to be evaluated for applicability per Section 1.2.9.2.2 and Appendix C.2 of the RSWDM. Below is a list of each evaluated BMP and its applicability to this project: Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 7 •Full Dispersion – Infeasible o The existing site is largely developed with no native vegetation. Full Dispersion is therefore deemed infeasible. •Full Infiltration – Infeasible o The existing site consists of high groundwater and since the site is largely developed there is little room for a surface infiltration facility. Full infiltration is therefore deemed infeasible. •Limited Infiltration – Infeasible o Infiltration on a limited basis will still require the removal of existing impervious surfaces to a pervious surface. This would result in inefficient infiltration facility with the concern of groundwater seepage. Limited infiltration is therefore deemed infeasible. •Basic Dispersion – Infeasible o The proposed project sites are considered fully developed. A minimum 50-foot flow path for treatment is not feasible and therefore basic dispersion is deemed infeasible. •Bioretention – Infeasible o Aside from shallow groundwater, surface infiltration facilities may attract birds which is a safety concern at airport properties. Bioretention facilities are therefore deemed infeasible. •Permeable Pavement – Infeasible o Permeable pavements are not acceptable at airports due to the heavy aircraft wheel load as well as the potential for aggregates to become dislodged causing unnecessary foreign object debris (FOD) hazards. Permeable pavement is therefore deemed infeasible. •Reduced Impervious Surface Credit – Infeasible o The reduced impervious surface credit conflicts with the need to maximize usable apron or parking lot space for aircraft and vehicle parking. Reduced impervious surface credit is therefore deemed infeasible. •Native Growth Retention Credit – Infeasible o Since the project site is fully developed there is no native growth available to retain. The native growth retention credit is therefore deemed infeasible. •Perforated Pipe Connection – Infeasible o The proposed conditions have little landscape cover and is intended to be used for aircraft and vehicle parking. Heavy aircraft wheel loads located on the proposed pavement may cause damage to these perforated pipes. A perforated pipe connection is therefore deemed infeasible. •Soil Amendment – Feasible o Amended Soils will be placed in all disturbed vegetated areas. •Tree Retention Credit – Infeasible o There are no existing trees located within either work areas. Tree retention is therefore deemed infeasible. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 8 4.4 Water Quality This project is exempt from Core Requirement #8: Water Quality Facilities per Section 1.2.8 of the RSWDM. The project falls under the “Cost Exemption of Parcel Redevelopment Projects” since the total valuation of the project’s proposed improvements is less than 50% of the assessed value of the existing project site, the project adds less than 5,000 square feet of new PGIS, and the project adds less than 3/4 acre of new PGPS. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 9 5.0 CONVEYANCE SYSTEM ANALYSIS & DESIGN Windsock Apron: The windsock apron proposes no new impervious surface. Since no new impervious surface is proposed at the windsock apron, there is no increase in flow for the 100-year storm event, between existing and developed conditions. There are no changes proposed to the existing storm drain conveyance system and no anticipated impacts as a result of the proposed improvements. 243 Building Apron and Parking Lot: The proposed improvements at the 243 Building apron and parking lot site result in a 0.03 cfs increase in runoff for the 100-year storm event between the existing and developed conditions. Since increase is considered insignificant and there is no concern regarding the downstream pipe capacity. There are no changes proposed to the existing storm drain conveyance system and no anticipated impacts as a result of the proposed improvements. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 10 6.0 SPECIAL REPORTS & STUDIES •The project geotechnical report prepared by HWA GeoSciences Inc. is provided in Appendix B. •A Construction Stormwater Pollution Prevention Plan (SWPPP) is provided in Appendix C. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 11 7.0 OTHER PERMITS •A National Pollutant Discharge Elimination System (NPDES) permit will be required since the project area is over an acre. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 12 8.0 SWPPP ANALYSIS & DESIGN 8.1 ESC Plan Analysis & Design 8.1.1 Scope of Work The disturbed area of the project is 2.66 acres for 243 Building apron and parking lot and the windsock apron combined. The 243 Building apron and parking lot is surrounded by W Perimeter Road to the west and south, Taxiway A and an access road to the east, and an existing hangar to the north. The windsock apron is surrounded by two hangars to the north, Taxiway B to the west, landscaped areas to the south, and E Perimeter Road to the east. Earthwork for this project will be limited to the excavation necessary for the removal of the existing pavement section and subsequent installation of the proposed pavement section. 8.1.2 Clearing Limits The clearing limits will be spray painted with white paint along the edges of existing asphalt pavement to be removed. 8.1.3 Cover Measures Any exposed disturbed soil areas that are left un-worked for more than 12 hours shall be covered with plastic covering. 8.1.4 Perimeter Protection For perimeter protection this project will use a combination of silt fences, triangular silt dikes and FAA approved low profile barricades. 8.1.5 Traffic Area Stabilization Access to the sites will be done via W Perimeter Road for the 243 Building work area and E Perimeter Road for the Windsock work area. Once existing asphalt has been removed, a temporary construction entrance shall be installed. If the construction entrance is not providing enough protection, then a wheel wash shall be installed as well. 8.1.6 Sediment Retention Due to the work areas being considered fully developed and the high groundwater present sediment ponds or traps have been deemed infeasible. Commercial settling tanks will be employed at both work areas to pump any collected runoff from the work areas for sediment retention and dewatering purposes. Stormwater will be subsequently discharged from the site via the existing stormwater system located onsite or will discharge directly into the Cedar River 8.1.7 Surface Water Collection An existing downstream conveyance system is in place. Stormwater from the construction area will pass through a filtration tank and subsequently discharged into the existing downstream system. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 13 8.1.8 Dewatering Control Dewatering is not anticipated to be necessary on this project. 8.1.9 Dust Control It is anticipated that dust will not be a major concern during construction since minimal grading is proposed. In the event dust control is required, water shall be utilized for dust control. 8.1.10 Flow Control Flow control is not provided. Stormwater will be collected in settling and filtration tanks and discharged into the existing downstream conveyance system. 8.2 SWPPP Plan Design The Stormwater Pollution Prevention Plan (SWPPP) is a stand-alone document that describes the Construction BMPs. The SWPPP has been prepared and will be submitted to the City of Renton concurrently with this TIR (See Appendix C). The project Certified Erosion and Sedimentation Control Lead (CESCL) will be selected at a later date but shall be a member of the site general contractor. A construction activity NPDES permit shall also be obtained prior to construction commencement.h The 13 elements and BMPs recommended for both project areas have been identified below: 8.2.1 Element #1 – Preserve Vegetation/Mark Clearing Limits Silt fences and triangular silt dikes shall be employed along the work area perimeter. White paint shall be utilized along the edges of pavement removal areas. Additionally, FAA approved barricades shall be used per the Construction Safety Phasing Plan (CSPP) in Appendix C. Below is a list of applicable BMPs for this Element: •BMP C208 – Triangular Silt Dike •BMP C233 – Silt Fence 8.2.2 Element #2 – Establish Construction Access Upon removal of existing asphalt and concrete pavements, a construction entrance shall be installed per City of Renton standard detail 215.10, unless the contractor deems it to be unnecessary. Wheel washing, street sweeping, and street cleaning shall be employed as necessary to prevent sediment from tracking onto E or W Perimeter Roads. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 14 Below is a list of applicable BMPs for this Element: •BMP C105 – Stabilized Construction Access •BMP C106 – Wheel Wash •BMP C107 – Construction Road / Parking Area Stabilization 8.2.3 Element #3 – Control Flow Rates Flow control is not provided. 8.2.4 Element #4 – Install Sediment Controls Stormwater runoff from the disturbed areas shall pass through a catch basin insert per City of Renton standard detail 216.30 or captured in a Triangular Silt Dike. Below is a list of applicable BMPs for this Element: •BMP C208 – Triangular Silt Dike •BMP C233 – Silt Fence 8.2.5 Element #5 – Stabilize Soils Exposed and unworked soils shall be stabilized with plastic coverings per City of Renton standard detail 213.30 or an equivalent protection. Water shall be used for dust control as needed. Any proposed landscape areas shall employ temporary/permanent seeding. Below is a list of applicable BMPs for this Element: •BMP C120 – Temporary and Permanent Seeding •BMP C123 – Plastic Covering •BMP C140 – Dust Control •BMP C150 – Materials on Hand 8.2.6 Element #6 – Protect Slopes There are no steep slopes present within the disturbed areas. No slope protection is required. 8.2.7 Element #7 – Protect Drain Inlets Catch basin filters shall be employed per City of Renton standard detail 216.30. Each catch basin within the project’s vicinity or downstream of the project area shall have a catch basin filter installed. Below is a list of applicable BMPs for this Element: •BMP C220 – Inlet Protection 8.2.8 Element #8 – Stabilize Channels and Outlets There are no channels or outlets impacted by the project. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 15 8.2.9 Element #9 – Control Pollutants The following measures will be taken: •All vehicles, equipment and petroleum product storage/dispensing areas will be inspected daily to detect any leaks or spills and to identify any required maintenance. •Fueling will be conducted on hard pavement. •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 onsite, temporary plastic will be placed beneath and, if raining, over the vehicle. •Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. •Process water and slurry resulting from concrete work will be prevented from entering waters of the state by implementing Concrete Handling measures, pH neutralization will be employed at the contractor’s discretion. Below is a list of applicable BMPs for this Element: •BMP C106 – Wheel Wash •BMP C151 – Concrete Handling •BMP C152 – Sawcutting and Surfacing Pollution Prevention •BMP C153 – Material Delivery, Storage and Containment •BMP C154 – Concrete Washout Area 8.2.10 Element #10 – Control Dewatering Dewatering is not anticipated for this project. 8.2.11 Element #11 – Maintain BMPs All Temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be inspected, maintained and repaired as needed to ensure continued performance of their intended function. Below is a list of applicable BMPs for this Element: •BMP C150 – Materials on Hand •BMP C160 – Certified Erosion and Sediment Control Lead 8.2.12 Element #12 – Manage the Project During construction consideration shall be given to removing and replacing the pavement in stages. Site inspections and monitoring will be conducted in accordance with the Special Conditions S4 of the CSWGP. The contractor will update the SWPPP, as necessary, and keep a copy onsite at all times. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 16 Below is a list of applicable BMPs for this Element: •BMP C150 – Materials on Hand •BMP C160 – Certified Erosion and Sediment Control Lead •BMP C162 – Scheduling 8.2.13 Element #13 – Protect LID BMPs No LID BMPs are proposed and there are none within the project’s vicinity. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 17 9.0 BOND QUANTITIES, FACILITIY SUMMARIES, & DECLARATION OF COVNENANT 9.1 Bond Quantities The standard King County bond quantity worksheet is provided in the appendices. The scope of work includes all erosion and sediment control devices required for both project areas. 9.2 Flow Control & Water Quality Facility Summary Sheet and Sketch No new flow control or water quality facilities are proposed as part of this project. 9.3 Declaration of Covenant for Privately Maintained Flow Control & Water Quality Facilities No new flow control or water quality facilities are proposed as part of this project. Draft Technical Information Report | Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Page 18 10.0 OPERATIONS & MAINTENANCE MANUAL There are no new stormwater facilities proposed as part of this project and therefore no O&M Manual is provided. FIGURE 1: TIR WORKSHEET CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Land Use (e.g., Subdivision / Short Subd.) Building (e.g., M/F / Commercial / SFR) Grading Right-of-Way Use Other _______________________ DFW HPA COE 404 DOE Dam Safety FEMA Floodplain COE Wetlands Other ________ Shoreline Management Structural Rockery/Vault/_____ ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final: Full Targeted Simplified Large Project Directed __________________ __________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final: Full Modified Simplified __________________ __________________ __________________ REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: _____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream ________________________ Lake ______________________________ Wetlands ____________________________ Closed Depression ____________________ Floodplain ___________________________ Other _______________________________ _______________________________ Steep Slope __________________________ Erosion Hazard _______________________ Landslide Hazard ______________________ Coal Mine Hazard ______________________ Seismic Hazard _______________________ Habitat Protection ______________________ _____________________________________ REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas__________________ SEPA________________________________ LID Infeasibility________________________ Other________________________________ _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas__________________ SEPA________________________________ LID Infeasibility________________________ Other________________________________ _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas__________________ SEPA________________________________ LID Infeasibility________________________ Other________________________________ _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-5 Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust Control Flow Control Control Pollutants Protect Existing and Proposed BMPs/Facilities Maintain Protective BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize exposed surfaces Remove and restore Temporary ESC Facilities Clean and remove all silt and debris, ensure operation of Permanent BMPs/Facilities, restore operation of BMPs/Facilities as necessary Flag limits of sensitive areas and open space preservation areas Other _______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Description Water Quality Description On-site BMPs Description Detention Infiltration Regional Facility Shared Facility Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Full Dispersion Full Infiltration Limited Infiltration Rain Gardens Bioretention Permeable Pavement Basic Dispersion Soil Amendment Perforated Pipe Connection Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-6 Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other ____________________________ Cast in Place Vault Retaining Wall Rockery > 4′ High Structural on Steep Slope Other _______________________________ Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. ____________________________________________________________________________________ Signed/Date FIGURE 2: VICINITY MAP 72,224 6,019 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 3/15/2024 Legend 4,09302,046 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 4,093 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Renton <all other values> 2021.sid Red: Band_1 Green: Band_2 Blue: Band_3 FIGURE 3: USGS SOIL SURVEY United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for King County Area, Washington Natural Resources Conservation Service February 26, 2024 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 How Soil Surveys Are Made..................................................................................5 Soil Map..................................................................................................................8 Soil Map................................................................................................................9 Legend................................................................................................................10 Map Unit Legend................................................................................................11 Map Unit Descriptions.........................................................................................11 King County Area, Washington.......................................................................13 AgD—Alderwood gravelly sandy loam, 15 to 30 percent slopes.................13 InC—Indianola loamy sand, 5 to 15 percent slopes....................................14 Ur—Urban land...........................................................................................16 References............................................................................................................17 4 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and Custom Soil Resource Report 6 identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. Custom Soil Resource Report 7 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 8 9 Custom Soil Resource Report Soil Map 525930052594005259500525960052597005259800525990052600005260100526020052603005260400525930052594005259500525960052597005259800525990052600005260100526020052603005260400558800 558900 559000 559100 559200 559300 559400 559500 558800 558900 559000 559100 559200 559300 559400 559500 47° 29' 40'' N 122° 13' 12'' W47° 29' 40'' N122° 12' 32'' W47° 29' 3'' N 122° 13' 12'' W47° 29' 3'' N 122° 12' 32'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 250 500 1000 1500 Feet 0 50 100 200 300 Meters Map Scale: 1:5,520 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. 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 19, Aug 29, 2023 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. Custom Soil Resource Report 10 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI AgD Alderwood gravelly sandy loam, 15 to 30 percent slopes 5.7 6.1% InC Indianola loamy sand, 5 to 15 percent slopes 3.6 3.8% Ur Urban land 84.7 90.1% Totals for Area of Interest 94.0 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The Custom Soil Resource Report 11 delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 12 King County Area, Washington AgD—Alderwood gravelly sandy loam, 15 to 30 percent slopes Map Unit Setting National map unit symbol: 2t627 Elevation: 0 to 1,000 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 46 to 52 degrees F Frost-free period: 160 to 240 days Farmland classification: Farmland of statewide importance Map Unit Composition Alderwood and similar soils:85 percent Minor components:15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting Landform:Hills, ridges Landform position (two-dimensional):Backslope Landform position (three-dimensional):Nose slope, side slope, talf Down-slope shape:Convex, linear Across-slope shape:Convex Parent material:Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile A - 0 to 7 inches: gravelly sandy loam Bw1 - 7 to 21 inches: very gravelly sandy loam Bw2 - 21 to 30 inches: very gravelly sandy loam Bg - 30 to 35 inches: very gravelly sandy loam 2Cd1 - 35 to 43 inches: very gravelly sandy loam 2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities Slope:15 to 30 percent Depth to restrictive feature:20 to 39 inches to densic material Drainage class:Moderately well drained Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table:About 18 to 37 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Very low (about 2.7 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: B Ecological site: F002XA004WA - Puget Lowlands Forest Forage suitability group: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XF303WA), Limited Depth Soils (G002XS301WA) Custom Soil Resource Report 13 Other vegetative classification: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XF303WA), Limited Depth Soils (G002XS301WA) Hydric soil rating: No Minor Components Everett Percent of map unit:5 percent Landform:Moraines, eskers, kames Landform position (two-dimensional):Backslope Landform position (three-dimensional):Side slope Down-slope shape:Convex Across-slope shape:Convex Hydric soil rating: No Indianola Percent of map unit:5 percent Landform:Terraces, kames, eskers Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Hydric soil rating: No Shalcar Percent of map unit:3 percent Landform:Depressions Landform position (three-dimensional):Dip Down-slope shape:Concave Across-slope shape:Concave Hydric soil rating: Yes Norma Percent of map unit:2 percent Landform:Drainageways, depressions Landform position (three-dimensional):Dip Down-slope shape:Linear, concave Across-slope shape:Concave Hydric soil rating: Yes InC—Indianola loamy sand, 5 to 15 percent slopes Map Unit Setting National map unit symbol: 2t635 Elevation: 0 to 980 feet Mean annual precipitation: 30 to 81 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 170 to 210 days Farmland classification: Prime farmland if irrigated Map Unit Composition Indianola and similar soils:85 percent Custom Soil Resource Report 14 Minor components:15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Indianola Setting Landform:Terraces, kames, eskers Landform position (three-dimensional):Riser Down-slope shape:Linear Across-slope shape:Linear Parent material:Sandy glacial outwash Typical profile Oi - 0 to 1 inches: slightly decomposed plant material A - 1 to 6 inches: loamy sand Bw1 - 6 to 17 inches: loamy sand Bw2 - 17 to 27 inches: sand BC - 27 to 37 inches: sand C - 37 to 60 inches: sand Properties and qualities Slope:5 to 15 percent Depth to restrictive feature:More than 80 inches Drainage class:Somewhat excessively drained Capacity of the most limiting layer to transmit water (Ksat):High to very high (5.95 to 99.90 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 3.9 inches) Interpretive groups Land capability classification (irrigated): 4e Land capability classification (nonirrigated): 4s Hydrologic Soil Group: A Ecological site: F002XA004WA - Puget Lowlands Forest Forage suitability group: Droughty Soils (G002XN402WA), Droughty Soils (G002XS401WA) Other vegetative classification: Droughty Soils (G002XN402WA), Droughty Soils (G002XS401WA) Hydric soil rating: No Minor Components Alderwood Percent of map unit:8 percent Landform:Hills, ridges Landform position (two-dimensional):Shoulder Landform position (three-dimensional):Nose slope, talf Down-slope shape:Convex, linear Across-slope shape:Convex Hydric soil rating: No Everett Percent of map unit:5 percent Landform:Moraines, eskers, kames Landform position (two-dimensional):Shoulder, footslope Custom Soil Resource Report 15 Landform position (three-dimensional):Base slope, crest Down-slope shape:Convex Across-slope shape:Convex Hydric soil rating: No Norma Percent of map unit:2 percent Landform:Drainageways, depressions Landform position (three-dimensional):Dip Down-slope shape:Linear, concave Across-slope shape:Concave Hydric soil rating: Yes Ur—Urban land Map Unit Composition Urban land:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Urban Land Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8 Hydric soil rating: No Custom Soil Resource Report 16 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 17 United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report 18 FIGURE 4: TABLE FOR DETERMINING DRAINAGE REVIEW TYPE FIGURE 5: BASIN MAP RENTON MUNICIPAL AIRPORT (RNT) - RENTON, WA WWW.DOWL.COM WINDSOCK GA APRON, 243 BLDG APRON & PARKING LOT REHAB.C20EX-1 RENTON MUNICIPAL AIRPORT (RNT) - RENTON, WA WWW.DOWL.COM WINDSOCK GA APRON, 243 BLDG APRON & PARKING LOT REHAB.C20EX-2 FIGURE 6: STORM DRAIN MAP 18,056 1,505 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 3/19/2024 Legend 1,0230512 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 1,023 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Renton <all other values> Pipe Public Pipe Private Pipe Public Culvert Private Culvert Public Roofdrain Private Roofdrain Streets Parks Waterbodies Designated Neighborhoods 2021.sid Red: Band_1 Green: Band_2 Blue: Band_3 FIGURE 7: GEOLOGICAL HAZARDS MAP 7,943 662 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 3/19/2024 Legend 4500225 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 450 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Renton <all other values> Erosion Hazard - High Landslide Very High High Moderate Unclassified Seismic Hazard Areas Faults Streets Parks Waterbodies 2021.sid Red: Band_1 Green: Band_2 Blue: Band_3 FIGURE 8: STEEP SLOPES MAP 7,943 662 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 3/19/2024 Legend 4500225 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 450 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Renton <all other values> Slope City of Renton >15% & <=25% >25% & <=40% (Sensitive) >40% & <=90% (Protected) >90% (Protected) Streets Parks Waterbodies 2021.sid Red: Band_1 Green: Band_2 Blue: Band_3 FIGURE 9: FLOOD MAP 7,943 662 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 3/19/2024 Legend 4500225 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 450 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov Floodway Special Flood Hazard Areas (100 year flood) Other Flood Areas (Zone X - 500 year flood) Streets Parks Waterbodies 2021.sid Red: Band_1 Green: Band_2 Blue: Band_3 FIGURE 10: AQUIFER PROTECTION MAP 7,943 662 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 3/19/2024 Legend 4500225 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 450 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Renton <all other values> Wellhead Protection Area Zones Zone 1 Zone 1 Modified Zone 2 Streets Parks Waterbodies 2021.sid Red: Band_1 Green: Band_2 Blue: Band_3 APPENDIX A: 243 BUILDING WWHM EXISTING VS DEVELOPED WWHM2012 PROJECT REPORT ___________________________________________________________________ Project Name: RNT BLDG 243 WWHM Site Name: Site Address: City : Report Date: 3/18/2024 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2021/08/18 Version : 4.2.18 ___________________________________________________________________ Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ___________________________________________________________________ High Flow Threshold for POC 1: 50 year ___________________________________________________________________ EXISTING LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat .131 Pervious Total 0.131 Impervious Land Use acre ROADS FLAT 0.996 Impervious Total 0.996 Basin Total 1.127 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater ___________________________________________________________________ DEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre A B, Lawn, Flat .086 Pervious Total 0.086 Impervious Land Use acre ROADS FLAT 1.041 Impervious Total 1.041 Basin Total 1.127 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater ___________________________________________________________________ ___________________________________________________________________ ANALYSIS RESULTS Stream Protection Duration ___________________________________________________________________ Existing Landuse Totals for POC #1 Total Pervious Area:0.131 Total Impervious Area:0.996 ___________________________________________________________________ Developed Landuse Totals for POC #1 Total Pervious Area:0.086 Total Impervious Area:1.041 ___________________________________________________________________ Flow Frequency Return Periods for Existing. POC #1 Return Period Flow(cfs) 2 year 0.380595 5 year 0.481325 10 year 0.549828 25 year 0.638753 50 year 0.706857 100 year 0.776651 Flow Frequency Return Periods for Developed. POC #1 Return Period Flow(cfs) 2 year 0.397459 5 year 0.502418 10 year 0.573773 25 year 0.666373 50 year 0.737275 100 year 0.809921 ___________________________________________________________________ Stream Protection Duration Annual Peaks for Existing and Developed. POC #1 Year Existing Developed 1949 0.492 0.514 1950 0.531 0.555 1951 0.311 0.324 1952 0.273 0.286 1953 0.295 0.308 1954 0.310 0.324 1955 0.350 0.366 1956 0.345 0.360 1957 0.391 0.409 1958 0.315 0.330 1959 0.322 0.336 1960 0.316 0.330 1961 0.334 0.349 1962 0.291 0.304 1963 0.324 0.338 1964 0.317 0.331 1965 0.404 0.421 1966 0.269 0.281 1967 0.464 0.485 1968 0.527 0.551 1969 0.367 0.383 1970 0.354 0.370 1971 0.422 0.441 1972 0.444 0.461 1973 0.264 0.276 1974 0.385 0.402 1975 0.443 0.463 1976 0.298 0.312 1977 0.323 0.338 1978 0.395 0.413 1979 0.541 0.565 1980 0.485 0.507 1981 0.397 0.415 1982 0.560 0.585 1983 0.455 0.476 1984 0.287 0.300 1985 0.396 0.414 1986 0.343 0.359 1987 0.529 0.553 1988 0.321 0.336 1989 0.402 0.420 1990 0.703 0.725 1991 0.548 0.570 1992 0.285 0.297 1993 0.246 0.258 1994 0.268 0.280 1995 0.352 0.368 1996 0.381 0.396 1997 0.367 0.382 1998 0.369 0.385 1999 0.754 0.788 2000 0.376 0.392 2001 0.412 0.431 2002 0.481 0.503 2003 0.375 0.391 2004 0.706 0.737 2005 0.323 0.337 2006 0.288 0.300 2007 0.659 0.689 2008 0.535 0.557 2009 0.491 0.513 ___________________________________________________________________ Stream Protection Duration Ranked Annual Peaks for Existing and Developed. POC #1 Rank Existing Developed 1 0.7541 0.7881 2 0.7056 0.7374 3 0.7031 0.7246 4 0.6595 0.6892 5 0.5596 0.5849 6 0.5475 0.5696 7 0.5407 0.5652 8 0.5346 0.5574 9 0.5315 0.5555 10 0.5295 0.5534 11 0.5275 0.5513 12 0.4924 0.5144 13 0.4908 0.5130 14 0.4851 0.5070 15 0.4811 0.5028 16 0.4639 0.4848 17 0.4554 0.4760 18 0.4439 0.4635 19 0.4434 0.4607 20 0.4219 0.4410 21 0.4124 0.4310 22 0.4036 0.4214 23 0.4017 0.4199 24 0.3968 0.4148 25 0.3959 0.4138 26 0.3950 0.4129 27 0.3909 0.4085 28 0.3849 0.4023 29 0.3809 0.3955 30 0.3755 0.3924 31 0.3746 0.3912 32 0.3686 0.3852 33 0.3668 0.3832 34 0.3666 0.3821 35 0.3538 0.3697 36 0.3519 0.3678 37 0.3501 0.3660 38 0.3445 0.3601 39 0.3432 0.3587 40 0.3339 0.3490 41 0.3239 0.3383 42 0.3229 0.3375 43 0.3225 0.3370 44 0.3217 0.3362 45 0.3213 0.3358 46 0.3169 0.3312 47 0.3159 0.3301 48 0.3154 0.3296 49 0.3111 0.3237 50 0.3103 0.3236 51 0.2985 0.3118 52 0.2951 0.3085 53 0.2909 0.3041 54 0.2878 0.3003 55 0.2874 0.2996 56 0.2845 0.2974 57 0.2734 0.2857 58 0.2693 0.2814 59 0.2682 0.2802 60 0.2638 0.2757 61 0.2464 0.2576 ___________________________________________________________________ Stream Protection Duration POC #1 The Facility FAILED Facility FAILED duration standard for 1+ flows. Flow(cfs) Exist Dev Percentage Pass/Fail 0.1903 1797 2116 117 Fail 0.1955 1641 1928 117 Fail 0.2007 1485 1757 118 Fail 0.2060 1356 1612 118 Fail 0.2112 1219 1431 117 Fail 0.2164 1107 1315 118 Fail 0.2216 1008 1206 119 Fail 0.2268 926 1099 118 Fail 0.2320 850 993 116 Fail 0.2373 785 915 116 Fail 0.2425 725 854 117 Fail 0.2477 668 795 119 Fail 0.2529 614 732 119 Fail 0.2581 564 669 118 Fail 0.2633 534 614 114 Fail 0.2686 490 583 118 Fail 0.2738 454 545 120 Fail 0.2790 415 499 120 Fail 0.2842 389 456 117 Fail 0.2894 366 426 116 Fail 0.2947 341 403 118 Fail 0.2999 317 378 119 Fail 0.3051 293 348 118 Fail 0.3103 274 323 117 Fail 0.3155 256 306 119 Fail 0.3207 240 288 120 Fail 0.3260 222 268 120 Fail 0.3312 207 250 120 Fail 0.3364 192 234 121 Fail 0.3416 181 217 119 Fail 0.3468 172 206 119 Fail 0.3520 156 192 123 Fail 0.3573 146 180 123 Fail 0.3625 140 172 122 Fail 0.3677 133 158 118 Fail 0.3729 123 147 119 Fail 0.3781 115 139 120 Fail 0.3834 108 135 125 Fail 0.3886 104 124 119 Fail 0.3938 100 116 116 Fail 0.3990 90 108 120 Fail 0.4042 87 105 120 Fail 0.4094 84 100 119 Fail 0.4147 75 94 125 Fail 0.4199 72 89 123 Fail 0.4251 66 86 130 Fail 0.4303 64 79 123 Fail 0.4355 63 74 117 Fail 0.4408 59 69 116 Fail 0.4460 54 65 120 Fail 0.4512 53 64 120 Fail 0.4564 51 61 119 Fail 0.4616 50 57 114 Fail 0.4668 46 54 117 Fail 0.4721 44 53 120 Fail 0.4773 41 51 124 Fail 0.4825 36 50 138 Fail 0.4877 33 46 139 Fail 0.4929 31 45 145 Fail 0.4981 29 40 137 Fail 0.5034 29 36 124 Fail 0.5086 25 33 132 Fail 0.5138 23 31 134 Fail 0.5190 21 29 138 Fail 0.5242 20 28 140 Fail 0.5295 18 25 138 Fail 0.5347 15 23 153 Fail 0.5399 13 21 161 Fail 0.5451 11 21 190 Fail 0.5503 9 19 211 Fail 0.5555 9 17 188 Fail 0.5608 8 12 150 Fail 0.5660 8 12 150 Fail 0.5712 8 9 112 Fail 0.5764 8 9 112 Fail 0.5816 8 9 112 Fail 0.5868 8 8 100 Pass 0.5921 8 8 100 Pass 0.5973 8 8 100 Pass 0.6025 8 8 100 Pass 0.6077 8 8 100 Pass 0.6129 8 8 100 Pass 0.6182 8 8 100 Pass 0.6234 8 8 100 Pass 0.6286 8 8 100 Pass 0.6338 6 8 133 Fail 0.6390 6 8 133 Fail 0.6442 6 8 133 Fail 0.6495 6 7 116 Fail 0.6547 6 7 116 Fail 0.6599 6 6 100 Pass 0.6651 5 6 120 Fail 0.6703 5 6 120 Fail 0.6756 4 6 150 Fail 0.6808 4 6 150 Fail 0.6860 4 6 150 Fail 0.6912 3 5 166 Fail 0.6964 3 5 166 Fail 0.7016 3 5 166 Fail 0.7069 1 4 400 Fail _____________________________________________________ The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. ___________________________________________________________________ Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. ___________________________________________________________________ LID Report LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Total Volume Infiltrated 0.00 0.00 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Failed ___________________________________________________________________ Perlnd and Implnd Changes No changes have been made. ___________________________________________________________________ This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2024; All Rights Reserved. APPENDIX B: HWA GEOTECHNICAL REPORT GEOTECHNICAL REPORT RENTON MUNICIPAL AIRPORT GA APRON REHABILITATION RENTON, WASHINGTON HWA Project No. 2023-055-21 November 2, 2023 Prepared for DOWL Engineering 21312 30th Dr. SE, STE. 110, Bothell, WA 98021 | 425.774.0106 | hwageo.com November 2, 2023 HWA Project No. 2023-055-21 DOWL Engineering 8410 154th Avenue NE, Suite 120 Redmond, Washington 98052 Attention: Wes Holden, P.E. Subject: GEOTECHNICAL REPORT Renton Municipal Airport GA Apron Rehabilitation Renton, Washington Mr. Holden: As authorized, HWA GeoSciences Inc. (HWA) has completed a geotechnical and pavement engineering study for the GA Apron Rehabilitation project at the Renton Municipal Airport in Renton, Washington. Our scope of work included logging the drilling of 7 geotechnical borings, performing pavement coring at 7 locations, performing Falling Weight Deflectometer (FWD) testing, laboratory testing, engineering analyses, and preparation of the attached report summarizing the investigation results and our recommendations. The work was performed to provide recommendations for rehabilitation of the GA Apron at Renton Municipal Airport. We appreciate the opportunity to provide geotechnical services on this project. Sincerely, HWA GEOSCIENCES INC. Seth Pemble, L.G. Bryan K. Hawkins, P.E. Geologist Senior Geotechnical Engineer Renton Municipal Airport – GA Apron Rehabilitation i HWA GEOSCIENCES INC. TABLE OF CONTENTS 1.0 INTRODUCTION ..........................................................................................................1 1.1 GENERAL .......................................................................................................1 1.2 PROJECT UNDERSTANDING ............................................................................1 2.0 FIELD INVESTIGATION AND LABORATORY TESTING ..................................................2 2.1 DRILLED BORINGS .........................................................................................2 2.2 PAVEMENT CORING .......................................................................................2 2.3 FALLING WEIGHT DEFLECTOMETER TESTING ...............................................4 2.4 LABORATORY TESTING .................................................................................5 3.0 SITE CONDITIONS ......................................................................................................6 3.1 SITE DESCRIPTION .........................................................................................6 3.2 GENERAL GEOLOGY ......................................................................................6 3.3 SUBSURFACE CONDITIONS ............................................................................7 3.4 GROUNDWATER CONDITIONS ........................................................................7 4.0 CONCLUSIONS AND RECOMMENDATIONS ..................................................................8 4.1 GENERAL .......................................................................................................8 4.2 FROST CONDITIONS .......................................................................................8 4.3 DRAINAGE .....................................................................................................8 4.4 WET WEATHER EARTHWORK ........................................................................8 4.5 TEMPORARY EXCAVATIONS ..........................................................................9 5.0 CONDITIONS AND LIMITATIONS .................................................................................9 REFERENCES .........................................................................................................11 Renton Municipal Airport – GA Apron Rehabilitation ii HWA GEOSCIENCES INC. LIST OF FIGURES (FOLLOWING TEXT) Figure 1 Site & Vicinity Map Figures 2A & 2B Site and Exploration Plans Figure 3 FWD Test Results – GA Apron Maximum Deflections Figure 4 FWD Test Results – GA Apron Subgrade Resilient Moduli APPENDICES Appendix A: Field Exploration Figure A-1 Legend of Terms and Symbols Used on Exploration Logs Figures A-2 – A-8 Logs of Pavement Cores Core-1 through Core-6 Figure A-9 – A-15 Logs of Borings BH-1 through BH-7 Appendix B: Laboratory Test Results Figures B-1 Summary of Material Properties Figures B-2 – B-5 Particle Size Analysis of Soils Figures B-6 Liquid Limit, Plastic Limit, and Plasticity Index of Soils GEOTECHNICAL REPORT RENTON MUNICIPAL AIRPORT GA APRON REHABILITATION RENTON, WASHINGTON 1.0 INTRODUCTION 1.1 GENERAL This report summarizes the results of a geotechnical investigation undertaken by HWA GeoSciences at Renton Municipal Airport in Renton, Washington, in support of the design and construction of the GA Apron Rehabilitation project. Our scope of work included: • Logging the drilling of 7 geotechnical borings to a depth of about 11.5 feet each. • Performing pavement coring at 7 locations along with shallow excavations through each core hole using hand digging equipment. • Performing Falling Weight Deflectometer testing at GA Apron. • Performing laboratory testing consisting of natural moisture content testing, grain size analyses, Atterberg Limits, and organic content. • Performing engineering analyses pertaining to the proposed improvements and development of this report. The general project location is shown on the Site & Vicinity Map, Figure 1. The locations of our drilled boring and pavement core explorations are shown on the Site and Exploration Plans, Figures 2A and 2B. 1.2 PROJECT UNDERSTANDING We understand that Renton Municipal Airport plans to rehabilitate/reconstruct the pavement at the GA Apron, covering an area of approximately 7,200 square yards. Existing pavement demolition, subgrade stabilization, various drainage improvements, and new pavement consisting of either Portland Cement Concrete (PCC), or Hot Mix Asphalt (HMA) are proposed for this project. November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 2 HWA GEOSCIENCES INC. 2.0 FIELD INVESTIGATION AND LABORATORY TESTING 2.1 DRILLED BORINGS On August 28, 2023, HWA logged the drilling of 4 geotechnical borings at the GA Apron (Figure 2A) and 3 geotechnical borings in parking areas southwest of Taxiway A (Figure 2B) to assess pavement layer thicknesses and subsurface soil and groundwater conditions. The borings were drilled by Holocene Drilling, of Puyallup, Washington, under subcontract to HWA, using a Mobile B-58 truck-mounted drill rig using hollow stem auger drilling techniques. Standard Penetration Test (SPT) sampling was performed directly below the pavement and at depths of approximately 2.5, 5, 7.5 and 10 feet below pavement surface in each of the borings. The SPT resistance (“N-value”) of the soil was logged during each test. Standard Penetration Testing (SPT) was performed using a 2-inch outside diameter split-spoon sampler driven by a 140-pound hammer with an automatic hammer. During the tests, samples were obtained by driving the sampler 18 inches into the soil with the hammer free-falling 30 inches. The number of blows required for each 6-inches of penetration was recorded. This resistance, or N-value, provides an indication of relative density of granular soils and the relative consistency of cohesive soils. A geologist from HWA logged the explorations and recorded pertinent information, including sample depths, stratigraphy, soil descriptions, and groundwater occurrence. Soil samples obtained from the explorations were classified in the field and representative portions were placed in plastic bags. These soil samples were then taken to our Bothell, Washington, laboratory for further examination and testing. Soils were classified in general accordance with the American Society for Testing and Materials (ASTM) classification system. The summary boring logs are presented in Appendix A, Figures A-9 through A-15. The stratigraphic contacts shown on the exploration logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The soil and groundwater conditions depicted are only for the specific date and location reported and, therefore, are not necessarily representative of other locations and times. 2.2 PAVEMENT CORING Pavement coring was performed on August 21, 2023, at 7 locations on the GA Apron. Pavement core locations are shown in Figure 2A. Pavement coring was performed using a 6-inch diameter, trailer hitch mounted, electric core drill to evaluate HMA pavement thickness, HMA lift thickness and depth of cracking. Shallow excavations to depths of about 0.6 to 5 feet below pavement surface were completed below each pavement core, using hand digging equipment, to assess crushed aggregate base thickness and shallow subgrade support conditions. Two geologists and a geotechnical engineer from HWA completed the pavement coring and shallow November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 3 HWA GEOSCIENCES INC. excavations. Samples of the crushed aggregate base and subgrade soils were collected during excavations. Pavement core holes were backfilled with material that was excavated from the hole and compacted in lifts. Pavement patching at the surface was completed by compacting water activated Aquaphalt 6.0 permanent pavement repair material. The thickness of the pavement patch material matched or exceeded the thickness of the existing HMA layer. Table 1 summarizes the pavement structure encountered at the location of pavement cores and drilled borings. Table 1. Summary of Pavement Structure Core Designation HMA Thickness (in.) Crushed Aggregate Base Thickness (in.) PCC Thickness (in.) Granular Fill Thickness (in.) Notes Core-1 3 4 - 6 Loose sand subgrade. Core-2 2.75 4.25 - - Vertical steel embedded in PCC below CSBC. Core-2A 2.5 4 4 - Terminated in CSBC below PCC at a depth of 13 inches. Core-3 2.25 4.25 - 5 Medium stiff to soft silt subgrade with peat and organics. Core-4 2 2 - - Medium stiff to soft silt subgrade. Core-5 2 1 - 7 Old asphalt material encountered from 10 to 13.25 inches above a 0.75-inch- thick layer of cementitious silt with dense gravel below. Core-6 2.25 5.25 - 12.5+ Excavation terminated in dense gravel fill at a depth of 20 inches. BH-1 2.75 - - 5 Soft, gray silt with sand subgrade. November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 4 HWA GEOSCIENCES INC. BH-2 3.25 - 4.25 - Very soft, organic silt subgrade. BH-3 2.5 - - 9.5 Very soft silt subgrade. BH-4 2.5 - - - Loose to very loose silty sand subgrade. BH-5 - - 6 - Loose, clean to silty sand subgrade. BH-6 1.5 - - - Loose sand with silt subgrade. BH-7 1.5 - - - Loose gravel and silty sand subgrade. 2.3 FALLING WEIGHT DEFLECTOMETER TESTING Falling Weight Deflectometer (FWD) testing was conducted on the GA Apron on August 21, 2023, within the project limits. Testing along the GA Apron was completed at approximate spacings of 20 feet in an approximately grid pattern where access between parked aircraft was available. Global Positioning System (GPS) readings were taken at each test location. Figure 3 presents color contoured maximum deflections (immediately under the applied load), normalized to a load of 9,000 pounds, for each test location. Figure 4 presents color contoured subgrade resilient modulus values for each test location. The FWD testing was undertaken using a Dynatest Model 8012 Fast Falling Weight Deflectometer. This FWD allows the pavement to be tested under a wide range of loading conditions (6,500 to 27,000 pounds) to simulate a variety of traffic loads. For this project, pulse loads of approximately 6,000, 9,000 and 12,000 pounds were applied to the pavement surface at each test location. The corresponding pavement surface deflections were measured with velocity transducers located directly under the loaded area, and at 8,12, 18, 24, 36, 48, 60, and 72 inches from the center of the loaded area. Table 2 summarizes the FWD deflection data for the GA Apron. Table 2. Maximum Deflection Normalized to 9,000-pound Load – GA Apron Location Number of Tests Average Maximum Deflection, mils Standard Deviation, mils Highest Deflection in Segment, mils Lowest Deflection in Segment, mils GA Apron 131 47.6 17.8 95.2 12.5 November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 5 HWA GEOSCIENCES INC. Table 3 summarizes the backcalculated subgrade resilient moduli values for the GA Apron. The program BAKFAA was used for backcalculation of the surface layer, base layer and subgrade resilient moduli. Backcalculation was performed by inputting pavement layer thickness obtained from pavement coring. Table 3. Backcalculated Subgrade Resilient Modulus – GA Apron Location Number of Tests Average Subgrade Resilient Modulus, ksi Standard Deviation, ksi Highest Value, ksi Lowest Value, ksi GA Apron 131 8.0 3.8 38.5 3.3 The subgrade resilient moduli values are consistent with very soft to soft silt and very loose to loose, silty sand. Most of the highest subgrade resilient moduli values are located near the access road to the east where additional granular fill may have been placed during past improvements. 2.4 LABORATORY TESTING Representative soil samples obtained from the drilled borings and pavement core explorations were taken to the HWA laboratory for examination and testing. Laboratory tests were conducted on selected soil samples from the drilled borings to characterize engineering properties of the soils. Laboratory tests, as described below, included moisture and visual description, grain size distribution, Atterberg limits and organic content. The results of the laboratory testing are presented in Appendix B. Moisture Content of Soil: The moisture content (percent by dry mass) of selected soil samples was determined in general accordance with ASTM D2216. The results are shown at the sampled intervals on the appropriate exploration logs in Appendix A and on the Summary of Materials Properties report, Figure B-1. Particle Size Analysis of Soils: The particle size distribution of selected soil samples from the drilled borings were determined in general accordance with ASTM D6913. The results are summarized on the attached Particle Size Analysis of Soils reports, Figures B-2 through B-5, which also provide information regarding the classification of the samples and the moisture content at the time of testing. Liquid Limit, Plastic Limit, and Plasticity Index of Soils (Atterberg Limits): Four samples were tested using method ASTM D4318, multi-point method. The results are reported on the attached Liquid Limit, Plastic Limit, and Plasticity Index of Soils report, Figure B-6 along with the classification of the samples and the moisture content at the time of testing. November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 6 HWA GEOSCIENCES INC. Organic Content – Loss on Ignition: One sample was selected to determine organic content per ASTM D2974. The results are shown at the sampled intervals on the appropriate exploration log in Appendix A and on the Summary of Materials Properties report, Appendix B, Figure B-1. 3.0 SITE CONDITIONS 3.1 SITE DESCRIPTION The GA Apron is located at the eastern side of Renton Municipal Airport and adjoins the middle portion of Taxiway B. The Cedar River flows north immediately east of GA Apron and into Lake Washington at the northeast corner of the airport. The site is generally flat aside from minor sloping for surface water drainage. Pavement surfacing consists of HMA. Areas of high severity pavement distress, consisting of alligator cracking, exist near the middle and western half of the GA Apron. Other areas of HMA pavement near the existing hangars to the north and near the Cedar River Levee to the east exhibit low to medium severity longitudinal and transverse cracking. In addition to our investigations at the GA Apron site, we were requested to perform 3 additional borings (BH-5 through BH-7) at a second site located in the southwest corner of Renton Municipal Airport southwest of Taxiway A. The pavement surfacing consists mostly of HMA, with an area of PCC panels south of the hangar. We understand that drainage improvements were installed within the last few years to alleviate ponding water in the area paved with PCC pavement. The GA Apron is in a historic wetland and floodplain of the Cedar and Black Rivers that has been used as agricultural land, lumber mills, and more recently an airport. The second site included in this project is located where the Cedar River historically flowed into the Black River. The Black River is now filled in and/or diverted into underground culverts. The Cedar River was rerouted to flow north along the eastern edge of the Renton Municipal Airport into the southern end of Lake Washington. 3.2 GENERAL GEOLOGY The project site is located within the Puget Lowland. The Puget Lowland has repeatedly been occupied by a portion of the continental glaciers that developed during the ice ages of the Quaternary period. During at least four periods, portions of the ice sheet advanced south from British Columbia into the lowlands of Western Washington. The southern extent of these glacial advances was near Olympia, Washington. Each major advance included numerous local advances and retreats, and each advance and retreat resulted in its own sequence of erosion and deposition of glacial lacustrine, outwash, till, and drift deposits. Between and following these glacial advances, sediments from the Olympic and Cascade Mountains accumulated in the Puget November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 7 HWA GEOSCIENCES INC. Lowland. As the most recent glacier retreated, it uncovered a sculpted landscape of elongated, north-south trending hills and valleys between the Cascade and Olympic Mountain ranges, composed of a complex sequence of glacial and interglacial deposits. Geologic information for the project area was obtained from the Washington State Department of Natural Resources Geologic Information Portal. According to this map, the project site soils are mapped as artificial fill, modified land, and Quaternary alluvium deposited by the Cedar River and Black River. 3.3 SUBSURFACE CONDITIONS Subsurface conditions encountered in the explorations were different at the two sites evaluated. The GA Apron site is primarily underlain by subgrade soils consisting of soft to very soft silt and loose to very loose, silty sand. The HMA thickness varied from about 2 to 3 inches in thickness with varying layers below, as indicated on the exploration logs. Portland Cement Concrete (PCC) was encountered immediately below the HMA at the location of BH-2. PCC was encountered below an approximately 4-inch-thick layer of CSBC below the HMA surface at the locations of Core-2 and Core-2A. All three of these explorations are located in the northwest corner of the site. Subsurface conditions near the southwest corner of Taxiway A encountered loose, silty sand and gravel below the existing pavement section. 3.4 GROUNDWATER CONDITIONS At the GA Apron site, groundwater seepage was encountered in the alluvium at the locations of Core-1 and Core-3 at depths of 4.5 and 3.9 feet below ground surface, respectively. At the locations of borings BH-1 through BH-4, groundwater seepage was encountered at depths of 5 to 6 feet below ground surface. Borings located at the southwest corner of the airport, BH-5 through BH-7, encountered groundwater seepage at depths of 8 to 10 feet below ground surface. We anticipate the groundwater levels are highest near the end of the wet winter months and lower during the dry summer months. Lake Washington water levels are monitored by the Lake Observations by Citizen Scientists & Satellites (LOCSS) at the Juanita Beach Park in Kirkland, Washington. Data from the LOCSS website suggests that water levels fluctuate about 2 feet annually with a low water level of 16.5 feet elevation. Surface water runoff, groundwater recharge, and lake water levels likely all affect groundwater levels at the airport. November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 8 HWA GEOSCIENCES INC. 4.0 CONCLUSIONS AND RECOMMENDATIONS 4.1 GENERAL The results of the explorations and FWD testing indicate the presence of soft to very soft, fine- grained soils, including layers of peat and organic silt, that will likely require stabilization before new pavement is constructed. Site 2, near the southwest corner of Taxiway A has loose, but mostly granular, subsurface conditions. The loose soils will require thorough compaction before pavement reconstruction. 4.2 FROST CONDITIONS A frost depth penetration analysis was performed as part of the project. The alluvial soils encountered at GA Apron are considered frost susceptible and are classified as Frost Group FG-4, per the Airport Pavement Design and Evaluation Advisory Circular (FAA, 2021), based on grain size analyses. Contour maps of maximum frost penetration depth for this area indicate a depth of 12 inches for fine-grained soils (Pavement Interactive website). At the site near the southwest corner of Taxiway A, the soil is classified as Frost Group FG-2. Contour maps of maximum frost penetration depth for this area indicate a depth of about 20 inches for coarse-grained soils (Pavement Interactive Website). 4.3 DRAINAGE It is essential to the satisfactory performance of the pavement that good drainage is provided to prevent water ponding on or alongside, or accumulating beneath, the pavement. Water ponding can cause saturation of the pavement and subgrade layers and lead to premature failure. The base layers and subgrade surface should be graded to prevent water being trapped within the layer. The surface of the pavement should be sloped to convey water away from the pavement to appropriate drainage facilities. 4.4 WET WEATHER EARTHWORK The fine-grained subgrade soils encountered at the GA Apron are highly moisture sensitive and will be unworkable and pump heavily when wet, and possibly even during dry weather as these soils tend to hold moisture and dry slowly, especially with the presence of peat and organic silt. We recommend that earthwork and paving operations occur in periods of dry summer weather. Stabilization techniques may be required prior to operation of construction equipment. If earthwork is to be performed, or fill is to be placed in wet weather or under wet conditions when soil moisture content is difficult to control, the following recommendations should apply: • The on-site, native soils will not be suitable for use as structural fill or backfill. November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 9 HWA GEOSCIENCES INC. • Earthwork should be accomplished in small sections to minimize exposure to wet weather. Excavation or the removal of unsuitable soil should be followed promptly by the placement and compaction of a suitable thickness of clean structural fill. The size and type of construction equipment used may have to be limited to prevent soil disturbance. • The ground surface within the construction area should be sloped and sealed with a smooth drum vibratory roller to promote rapid runoff of precipitation, to prevent surface water from flowing into excavations, and to prevent ponding of water. • No soil should be left uncompacted, so it can absorb water. Soils that become too wet for compaction should be removed and replaced with clean granular materials. • Excavation and placement of fill should be observed on a full-time basis by a person experienced in wet weather earthwork to verify that all unsuitable materials are removed, and suitable compaction and site drainage is achieved. 4.5 TEMPORARY EXCAVATIONS Any excavations deeper than 4 feet should be sloped or shored in accordance with current State of Washington Labor and Industries Safety and Health guidelines. Per these guidelines, all soils encountered are classified as Type C Soil. Temporary unsupported excavations within Type C Soil should be sloped no steeper than 1½H:1V (horizontal: vertical). Flatter side slopes could be required for excavations below the water table or where groundwater seepage is present. The contractor should monitor the stability of the temporary excavations and adjust the construction schedule and slope inclination accordingly. The contractor should be responsible for control of ground and surface water and should employ sloping, slope protection, ditching, sumps, dewatering, and other measures, as necessary, to prevent sloughing of soils and heave of the bottom of the excavation. 5.0 CONDITIONS AND LIMITATIONS We have prepared this report for DOWL Engineering for use in design of this project. This report should be provided in its entirety to prospective contractors for bidding and estimating purposes; however, the conclusions and interpretations presented herein should not be construed as a warranty of the subsurface conditions. Experience shows that soil and ground water conditions can vary significantly over small distances. Inconsistent conditions may occur between explorations that may not be detected by a geotechnical study of this nature. If, during future site operations, subsurface conditions are encountered which vary appreciably from those described herein, HWA should be notified to review the recommendations made in this report, and revise, if necessary. If there is a substantial lapse of time between submission of this report November 2, 2023 HWA Project No. 2023-055-21 Renton Municipal Airport – GA Apron Rehabilitation 10 HWA GEOSCIENCES INC. and the start of construction, or if conditions change due to construction operations, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations considering the changed conditions and time lapse. This report is issued with the understanding that it is the responsibility of the owner, or the owners’ representative, to ensure that the information and recommendations are brought to the attention of the appropriate design team personnel and incorporated into the project plans and specifications, and the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field. We recommend HWA be retained to monitor construction, evaluate subgrade soil conditions as they are exposed, and verify that subgrade preparation, backfilling, and compaction are accomplished in accordance with the specifications. Within the limitations of scope, schedule and budget, HWA attempted to execute these services in accordance with generally accepted professional principles and practices in the fields of geotechnical and pavement engineering at the time the report was prepared. No warranty, express or implied, is made. The scope of our work did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous or toxic substances in the soil, surface water, or ground water at this site. ◆ We appreciate this opportunity to be of service. If you have questions or require additional services, please contact either of the undersigned below. Sincerely, HWA GEOSCIENCES INC. Seth Pemble, L.G. Bryan K. Hawkins, P.E. Geologist Senior Geotechnical Engineer REFERENCES Federal Aviation Administration (FAA), 2016, Advisory Circular No. 150/5320-6G, Airport Pavement Design and Evaluation, dated 6/7/2021. Project Location - Figure 2B Project Location - Figure 2A BH-1 BH-3 BH-2 BH-4 Core-1 Core-5 Core-3 Core-4 Core-6 Core-2 Core-2A Legend Pavement Core Designation & Approximate LocationCore-3 Borehole Designation & Approximate LocationBH-1 BH-5 BH-6 BH-7 Legend Borehole Designation & Approximate LocationBH-5 FIGURE NO.: DRAWN BY.: CHECK BY.: PROJECT # FWD TEST RESULTS - GA APRON MAXIMUM DEFLECTIONS Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington 2023-055 RM BKH 3 City of Renton, County of King, Bureau of Land Management, Esri Canada, Esri, HERE, Garmin, INCREMENT P, USGS, EPA, USDA, King County, EagleView Technologies, Inc.0 60 120 18030 Feet ¯ Legend Maximum Deflections Deflections (Mils) 0 – 10 > 10 – 20 > 20 – 30 > 30 – 40 > 40 – 50 > 50 – 60 > 60 – 70 > 70 – 80 > 80 – 140 FIGURE NO.: DRAWN BY.: CHECK BY.: PROJECT # FWD TEST RESULTS - GA APRON SUBGRADE RESILIENT MODULI Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington 2023-055 RM BKH 4 Map data © OpenStreetMap contributors, Microsoft, Facebook, Inc. and its affiliates, Esri Community Maps contributors, Map layer by Esri, City of Renton, County of King, Bureau of Land Management, Esri Canada, Esri, HERE, Garmin, INCREMENT P, USGS, EPA, USDA, EagleView Technologies, Inc., Esri, USDA FSA06012018030 Feet ¯ Legend Subgrade Resilient Modulus ksi 2 – 4 > 4 – 8 > 8 – 12 > 12 – 16 > 16 – 24 > 24 – 36 APPENDIX A FIELD EXPLORATIONS A-12023-055 Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington SYMBOLS USED ON EXPLORATION LOGS LEGEND OF TERMS AND Clean Gravel (little or no fines) More than 50% of Coarse Fraction Retained on No. 4 Sieve Gravel with SM SC ML MH CH OH RELATIVE DENSITY OR CONSISTENCY VERSUS SPT N-VALUE Very Loose Loose Medium Dense Very Dense Dense N (blows/ft) 0 to 4 4 to 10 10 to 30 30 to 50 over 50 Approximate Relative Density(%) 0 - 15 15 - 35 35 - 65 65 - 85 85 - 100 COHESIVE SOILS Consistency Very Soft Soft Medium Stiff Stiff Very Stiff Hard N (blows/ft) 0 to 2 2 to 4 4 to 8 8 to 15 15 to 30 over 30 Approximate Undrained Shear Strength (psf) <250 250 - No. 4 Sieve Sand with Fines (appreciable amount of fines) amount of fines) More than 50% Retained on No. 200 Sieve Size Sand and Sandy Soils Clean Sand (little or no fines) 50% or More of Coarse Fraction Passing Fine Grained Soils Silt and Clay Liquid Limit Less than 50% 50% or More Passing No. 200 Sieve Size Silt and Clay Liquid Limit 50% or More 500 500 - 1000 1000 - 2000 2000 - 4000 >4000 DensityDensity USCS SOIL CLASSIFICATION SYSTEM Coarse Grained Soils Gravel and Gravelly Soils Highly Organic Soils GROUP DESCRIPTIONS Well-graded GRAVEL Poorly-graded GRAVEL Silty GRAVEL Clayey GRAVEL Well-graded SAND Poorly-graded SAND Silty SAND Clayey SAND SILT Lean CLAY Organic SILT/Organic CLAY Elastic SILT Fat CLAY Organic SILT/Organic CLAY PEAT MAJOR DIVISIONS GW SP CL OL PT GP GM GC SW COHESIONLESS SOILS Fines (appreciable LEGEND 2023-055.GPJ 8/29/23 PROJECT NO.:FIGURE: Coarse sand Medium sand SIZE RANGE Larger than 12 in Smaller than No. 200 (0.074mm) Gravel 3 in to 12 in 3 in to No 4 (4.5mm) No. 4 (4.5 mm) to No. 200 (0.074 mm) COMPONENT DRY Absence of moisture, dusty, dry to the touch. MOIST COMPONENT DEFINITIONS time of drilling) Groundwater Level (measured in well or open hole after water level stabilized) Groundwater Level (measured at TEST SYMBOLS GROUNDWATER SYMBOLS AL Atterberg Limits: California Bearing Ratio CN Consolidation DD OC Organic Content pH pH of Soils 12 - 30% Clayey, Silty, Sandy, Gravelly 3 in to 3/4 in 3/4 in to No 4 (4.5mm) No. 4 (4.5 mm) to No. 10 (2.0 mm) No. 10 (2.0 mm) to No. 40 (0.42 mm) No. 40 (0.42 mm) to No. 200 (0.074 mm) NOTES: Soil classifications presented on exploration logs are based on visual and laboratory observation. Density/consistency, color, modifier (if any) GROUP NAME, additions to group name (if any), moisture content. Proportion, gradation, and angularity of constituents, additional comments. (GEOLOGIC INTERPRETATION) Please refer to the discussion in the report text as well as the exploration logs for a more complete description of subsurface conditions. Soil descriptions are presented in the following general order: < 5% Damp but no visible water. WET Visible free water, usually soil is below water table. Boulders Cobbles Coarse gravel Fine gravel Sand MOISTURE CONTENT COMPONENT PROPORTIONS Fine sand Silt and Clay 5 - 12% PROPORTION RANGE DESCRIPTIVE TERMS Clean Slightly (Clayey, Silty, Sandy) 30 - 50% Components are arranged in order of increasing quantities. Very (Clayey, Silty, Sandy, Gravelly) PID PP CBR DS Direct Shear GS Grain Size Distribution K Permeability Moisture/Density Relationship (Proctor) Resilient Modulus Photoionization Device Reading Res. Resistivity SG Percent Fines%F MD MR Specific Gravity CD Consolidated Drained Triaxial Torvane (Approx. Shear Strength, tsf) Dry Density (pcf) CU Consolidated Undrained Triaxial TV UU Unconsolidated Undrained Triaxial UC Unconfined Compression SAMPLE TYPE SYMBOLS Non-standard Penetration Test (3.0" OD Split Spoon with Brass Rings) (140 lb. hammer with 30 in. drop) Shelby Tube Small Bag Sample Large Bag (Bulk) Sample Core Run 2.0" OD Split Spoon (SPT) PL = Plastic Limit, LL = Liquid Limit Pocket Penetrometer (Approx. Comp. Strength, tsf) 3-1/4" OD Split Spoon GW SP SM ML 3 inches Hot Mix Asphalt. 1 lift. Cored on medium severity sealed longitudinal crack. Crack filled with organics below sealant. 4 inches Crushed Surfacing Base Course. Dense, brown, sandy, coarse, crushed GRAVEL with silt, moist. (CSBC) 6 inches Gravel Borrow. Medium dense, brown, sandy, fine to coarse, rounded GRAVEL, moist. (GRAVEL BORROW) Loose, brown, fine to medium SAND, moist. Very loose, dark gray, very silty SAND to sandy SILT, wet. Corehole was terminated at 60 inches below ground surface. Groundwater seepage was observed at 54 inches below ground surface. S-1 LOGGED BY: B. Hawkins and therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTIONSYMBOL PAGE: 1 of 1 Core-1 EXCAVATING EQUIPMENT: 6-inch Diameter Core Barrel PROJECT NO.:MOISTURECONTENT(%)Geotechnical Services STREET: PAVEMENT CORE EXCAVATION COMPANY: HWA GeoSciences Inc.SAMPLE NUMBERSAMPLE TYPEOTHER TESTSDATE COMPLETED: 8/21/23 FIGURE:USCS SOIL CLASS.2023-055 PAVEMENT CORE PHOTO 2023-055.GPJ 11/2/23 Renton Municipal Airport GA Apron Rehabilitation Renton, Washington A-2DEPTH (feet)PAVEMENT CORE PHOTO GA Apron LOCATION: See Figure 2A 0 1 2 3 4 5 6 2.75 inches Hot Mix Asphalt. No cracking at core location. (HMA) 4.25 inches Crushed Surfacing Base Course. Dense, brownish gray, sandy, coarse, crushed GRAVEL with silt, moist. (CSBC) Corehole was terminated at 7 inches below ground surface due to encountering a vertical steel plate embedded in PCC below the CSBC. Core-2A was drilled 4 feet South and 1.5 feet east of Core-2. LOGGED BY: B. Hawkins and therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTIONSYMBOL PAGE: 1 of 1 Core-2 EXCAVATING EQUIPMENT: 6-inch Diameter Core Barrel PROJECT NO.:MOISTURECONTENT(%)Geotechnical Services STREET: PAVEMENT CORE EXCAVATION COMPANY: HWA GeoSciences Inc.SAMPLE NUMBERSAMPLE TYPEOTHER TESTSDATE COMPLETED: 8/21/23 FIGURE:USCS SOIL CLASS.2023-055 PAVEMENT CORE PHOTO 2023-055.GPJ 11/2/23 Renton Municipal Airport GA Apron Rehabilitation Renton, Washington A-3DEPTH (feet)PAVEMENT CORE PHOTO GA Apron LOCATION: See Figure 2A 0 1 2 2.5 inches Hot Mix Asphalt. 1 lift. No cracking in this location. 4 inches Crushed Surfacing Base Course. Dense, brownish gray, sandy, coarse, crushed GRAVEL with silt, moist. (CSBC) 4 inches Portland Cement Concrete. Cored with 4-inch diameter barrel. (PCC) Dense, gray, sandy, coarse, crushed GRAVEL with silt, moist. (CSBC) Corehole was terminated at 13 inches below ground surface. No groundwater seepage was observed during the exploration. S-1 LOGGED BY: B. Hawkins and therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTIONSYMBOL PAGE: 1 of 1 Core-2A EXCAVATING EQUIPMENT: 6-inch Diameter Core Barrel PROJECT NO.:MOISTURECONTENT(%)Geotechnical Services STREET: PAVEMENT CORE EXCAVATION COMPANY: HWA GeoSciences Inc.SAMPLE NUMBERSAMPLE TYPEOTHER TESTSDATE COMPLETED: 8/21/23 FIGURE:USCS SOIL CLASS.2023-055 PAVEMENT CORE PHOTO 2023-055.GPJ 11/2/23 Renton Municipal Airport GA Apron Rehabilitation Renton, Washington A-4DEPTH (feet)PAVEMENT CORE PHOTO GA Apron LOCATION: See Figure 2A 0 1 2 GW ML ML ML PT ML SP SM 2.25 inches Hot Mix Asphalt. 1 lift. Cored on medium to high severity alligator cracking. Core cracked through full depth and broken into 3 pieces. (HMA) 4.25 inches Crushed Surfacing Base Course. Dense, brown, sandy, coarse, crushed GRAVEL with silt, moist. (CSBC) 5 inches Gravel Borrow. Medium dense, dark gray, silty, sandy, fine to coarse, rounded GRAVEL, moist. (GRAVEL BORROW) Medium stiff, dark gray SILT with sand, moist. Medium stiff, dark brown SILT with organics, moist. Soft, dark brown SILT with peat lenses, moist. Soft, dark gray, clayey silt to silty clay, moist. Loose, dark gray, clean, fine to medium SAND with lenses of silty, fine SAND, wet. Corehole was terminated at 51 inches below ground surface. Groundwater seepage was observed at 47 inches below ground surface. S-1 S-2 LOGGED BY: B. Hawkins and therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTIONSYMBOL PAGE: 1 of 1 Core-3 EXCAVATING EQUIPMENT: 6-inch Diameter Core Barrel PROJECT NO.:MOISTURECONTENT(%)Geotechnical Services STREET: PAVEMENT CORE EXCAVATION COMPANY: HWA GeoSciences Inc.SAMPLE NUMBERSAMPLE TYPEOTHER TESTSDATE COMPLETED: 8/21/23 FIGURE:USCS SOIL CLASS.2023-055 PAVEMENT CORE PHOTO 2023-055.GPJ 11/2/23 Renton Municipal Airport GA Apron Rehabilitation Renton, Washington A-5DEPTH (feet)PAVEMENT CORE PHOTO GA Apron LOCATION: See Figure 2A 0 1 2 3 4 5 ML ML SP SP SM 2 inches Hot Mix Asphalt. 1 lift. Cored on medium to high severity alligator cracking. Cracked through full depth. (HMA) 2 inches Crushed Surfacing Base Course. Dense, brown, sandy, coarse, crushed GRAVEL with silt, moist. (CSBC) Medium stiff, dark gray SILT with sand and occassional fine to coarse gravel, moist. 4-inch cobble at 5 to 9-inches below ground surface. Medium stiff to soft, dark gray SILT with fine sand, moist. Loose, dark gray, fine to medium SAND, moist. Loose, dark gray, fine to medium SAND with silt, moist. Corehole was terminated at 36 inches below ground surface. No groundwater seepage was observed during the exploration. S-1 S-2 S-3 LOGGED BY: B. Hawkins and therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTIONSYMBOL PAGE: 1 of 1 Core-4 EXCAVATING EQUIPMENT: 6-inch Diameter Core Barrel PROJECT NO.:MOISTURECONTENT(%)Geotechnical Services STREET: PAVEMENT CORE EXCAVATION COMPANY: HWA GeoSciences Inc.SAMPLE NUMBERSAMPLE TYPEOTHER TESTSDATE COMPLETED: 8/21/23 FIGURE:USCS SOIL CLASS.2023-055 PAVEMENT CORE PHOTO 2023-055.GPJ 11/2/23 Renton Municipal Airport GA Apron Rehabilitation Renton, Washington A-6DEPTH (feet)PAVEMENT CORE PHOTO GA Apron LOCATION: See Figure 2A 0 1 2 3 4 GW GP 2 inches Hot Mix Asphalt. 1 lift. Cored on sealed, medium severity longitudinal crack. Core cracked through full depth with sealant holding core together and vegetation in crack below sealant. (HMA) 1 inch Crushed Surfacing Base Course. Medium dense, brown, sandy, coarse, mostly crushed with some rounded GRAVEL with silt, moist. (CSBC) 7 inches Gravel Borrow. Medium dense, brown, sandy, fine to coarse, rounded GRAVEL, moist. (GRAVEL BORROW) 3.25 inches Asphaltic Material. Cored using 4-inch diameter core barrel. Very soft. Crumbles easily. High oil content. (OLD ASPHALT LAYER) 0.75 inches Cement. Gray cement with silt. Dense, dark gray GRAVEL with silth and sand, moist. Corehole was terminated at 16 inches below ground surface. No groundwater seepage was observed during the exploration. LOGGED BY: B. Hawkins and therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTIONSYMBOL PAGE: 1 of 1 Core-5 EXCAVATING EQUIPMENT: 6-inch Diameter Core Barrel PROJECT NO.:MOISTURECONTENT(%)Geotechnical Services STREET: PAVEMENT CORE EXCAVATION COMPANY: HWA GeoSciences Inc.SAMPLE NUMBERSAMPLE TYPEOTHER TESTSDATE COMPLETED: 8/21/23 FIGURE:USCS SOIL CLASS.2023-055 PAVEMENT CORE PHOTO 2023-055.GPJ 11/2/23 Renton Municipal Airport GA Apron Rehabilitation Renton, Washington A-7DEPTH (feet)PAVEMENT CORE PHOTO GA Apron LOCATION: See Figure 2A 0 1 2 GP 2.25 inches Hot Mix Asphalt. 1 Lift. Cored on medium severity sealed crack. Cracked through full depth. Sealant holding pieces together with silt and organics in joint below sealant. (HMA) 5.25 inches Crushed Surfacing Base Course. Dense, grayish brown, sandy, crushed, coarse GRAVEL with silt, moist. (CSBC) Dense, brown, sandy, fine to coarse GRAVEL with silt, moist. (FILL) Becomes dark gray at 17 inches below ground surface. Corehole was terminated at 20 inches below ground surface. No groundwater seepage was observed during the exploration. S-1 LOGGED BY: B. Hawkins and therefore may not necessarily be indicative of other times and/or locations. NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTIONSYMBOL PAGE: 1 of 1 Core-6 EXCAVATING EQUIPMENT: 6-inch Diameter Core Barrel PROJECT NO.:MOISTURECONTENT(%)Geotechnical Services STREET: PAVEMENT CORE EXCAVATION COMPANY: HWA GeoSciences Inc.SAMPLE NUMBERSAMPLE TYPEOTHER TESTSDATE COMPLETED: 8/21/23 FIGURE:USCS SOIL CLASS.2023-055 PAVEMENT CORE PHOTO 2023-055.GPJ 11/2/23 Renton Municipal Airport GA Apron Rehabilitation Renton, Washington A-8DEPTH (feet)PAVEMENT CORE PHOTO GA Apron LOCATION: See Figure 2A 0 1 2 3 GS GS AL OC S-1 S-2A S-2B S-3 S-4 S-5 2.75 inches Hot Mix Asphalt. (HMA) Very loose, brown, sandy GRAVEL with silt, moist. (GRAVEL BORROW FILL) Soft, gray, SILT with sand, moist. (ALLUVIUM) Very loose, gray, poorly graded SAND with silt, moist. Very loose, gray, poorly graded SAND with silt, moist to wet. Very soft, dark grayish brown, organic SILT with thin sand lenses, moist. Decomposing wood in tip of sampler. Becomes brown with fine peaty organics, moist. Organic content = 16.4% Borehole was terminated at 11.5 feet below ground surface. Groundwater seepage was observed at 6 feet below ground surface. 2-1-2 1-2-2 1-2-2 0/18" 0/18" GP GM ML SP SM SP SM OH BORING-DSM 2023-055.GPJ 11/2/23 FIGURE:PROJECT NO.:2023-055 Renton, Washington Geotechnical Services Renton Municipal Airport GA Apron Rehabilitation Natural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION BH-1 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBEROTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot Standard Penetration Test A-9DEPTH(feet)0 5 10 15 ELEVATION(feet)DATE COMPLETED: 8/28/2023 DRILLING COMPANY: Holocene Drilling DRILLING METHOD: HSA w/Mobile B-58 Truck Rig LOCATION: See Figure 2A DATE STARTED: 8/28/2023 SAMPLING METHOD: SPT w/Autohammer LOGGED BY: S. Pemble >>>>243 AL AL S-1 S-2 S-3 S-4A S-4B S-5 3.25 inches Hot Mix Asphalt. (HMA) 4.25 inches Portland Cement Concrete. (PCC) Very soft, dark grayish brown, SILT with fine organics, moist. (ALLUVIUM) Very soft, dark grayish brown and gray, organic SILT with fine peaty organics, moist. Very soft, gray, interlayered, fine sandy SILT and silty, fine SAND, moist to wet. Very loose, gray, silty, fine SAND with scattered fine organics, moist to wet. Very soft, dark grayish brown, fine, sandy SILT with scattered fine organics, moist. Becomes brown with peaty organics, moist. Borehole was terminated at 11.5 feet below ground surface. Slow groundwater seepage was observed at 5 feet below ground surface. 0/18" 0/18" 0/18" 0/18" 0/18" OH OH ML SM ML BORING-DSM 2023-055.GPJ 11/2/23 FIGURE:PROJECT NO.:2023-055 Renton, Washington Geotechnical Services Renton Municipal Airport GA Apron Rehabilitation Natural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION BH-2 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBEROTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot Standard Penetration Test A-10DEPTH(feet)0 5 10 15 ELEVATION(feet)DATE COMPLETED: 8/28/2023 DRILLING COMPANY: Holocene Drilling DRILLING METHOD: HSA w/Mobile B-58 Truck Rig LOCATION: See Figure 2A DATE STARTED: 8/28/2023 SAMPLING METHOD: SPT w/Autohammer LOGGED BY: S. Pemble >> >>195 AL GS S-1 S-2A S-2B S-3 S-4 S-5 2.5 inches Hot Mix Asphalt. (HMA) Loose, brown and gray, sandy GRAVEL with silt, moist. (FILL) Very soft, greenish gray, SILT, moist. (ALLUVIUM) Very soft, dark gray, SILT, moist. Very loose, gray, SAND with silt and fine silty SAND laminations, wet. Very soft, dark grayish brown, fine sandy SILT with charcoal and interlayered organic SILT, moist. Very soft, dark grayish brown, organic SILT with scattered fine peaty organics, moist. Borehole was terminated at 11.5 feet below ground surface. Groundwater seepage was observed at 5 feet below ground surface. 6-3-2 1-0-1 1-2-1 0/18" 0/18" GP GM ML ML SP SM ML OL BORING-DSM 2023-055.GPJ 11/2/23 FIGURE:PROJECT NO.:2023-055 Renton, Washington Geotechnical Services Renton Municipal Airport GA Apron Rehabilitation Natural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION BH-3 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBEROTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot Standard Penetration Test A-11DEPTH(feet)0 5 10 15 ELEVATION(feet)DATE COMPLETED: 8/28/2023 DRILLING COMPANY: Holocene Drilling DRILLING METHOD: HSA w/Mobile B-58 Truck Rig LOCATION: See Figure 2A DATE STARTED: 8/28/2023 SAMPLING METHOD: SPT w/Autohammer LOGGED BY: S. Pemble GS GS S-1 S-2 S-3 S-4 S-5 2.5 inches Hot Mix Asphalt. (HMA) Loose, brown, silty SAND with gravel, moist. (FILL) Very loose, dark gray, silty SAND with gravel and a small white shell fragment, moist. (ALLUVIUM) Very loose, gray, poorly graded SAND with silt and 2 inch thick interlayered silty fine SAND, wet. Very soft, gray, fine sandy SILT with scattered fine organics, wet. Very soft, dark grayish brown, fine sandy SILT with fine organics and thin interlayered silty SAND, wet. Organic silt in tip of sampler. Borehole was terminated at 11.5 feet below ground surface. Groundwater seepage was observed at 5.5 feet below ground surface. 5-3-2 1-1-2 1-1-1 0-0-1 0/18" SM SM SP SM ML ML BORING-DSM 2023-055.GPJ 11/2/23 FIGURE:PROJECT NO.:2023-055 Renton, Washington Geotechnical Services Renton Municipal Airport GA Apron Rehabilitation Natural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION BH-4 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBEROTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot Standard Penetration Test A-12DEPTH(feet)0 5 10 15 ELEVATION(feet)DATE COMPLETED: 8/28/2023 DRILLING COMPANY: Holocene Drilling DRILLING METHOD: HSA w/Mobile B-58 Truck Rig LOCATION: See Figure 2A DATE STARTED: 8/28/2023 SAMPLING METHOD: SPT w/Autohammer LOGGED BY: S. Pemble GS GS S-1 S-2 S-3 S-4 S-5 6 inches Portland Cement Concrete. (PCC) Loose, brown, poorly graded SAND with gravel, moist. (REWORKED/REGRADED ALLUVIUM) Loose, gray, silty SAND with gravel and scattered organics, moist. Becomes very loose with fine gravel, moist. Very loose, gray, silty SAND with scattered fine gravel, wet. Interlayered SAND with silt and fine organics. (ALLUVIUM) Becomes loose, gray, gravelly, silty SAND, wet. Borehole was terminated at 11.5 feet below ground surface. Groundwater seepage was observed at 8 feet below ground surface. 3-4-2 3-4-2 1-1-1 0-1-1 1-3-2 SP SM SM BORING-DSM 2023-055.GPJ 11/2/23 FIGURE:PROJECT NO.:2023-055 Renton, Washington Geotechnical Services Renton Municipal Airport GA Apron Rehabilitation Natural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION BH-5 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBEROTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot Standard Penetration Test A-13DEPTH(feet)0 5 10 15 ELEVATION(feet)DATE COMPLETED: 8/28/2023 DRILLING COMPANY: Holocene Drilling DRILLING METHOD: HSA w/Mobile B-58 Truck Rig LOCATION: See Figure 2B DATE STARTED: 8/28/2023 SAMPLING METHOD: SPT w/Autohammer LOGGED BY: S. Pemble GS GS S-1 S-2 S-3 S-4 S-5 1.5 inches Hot Mix Asphalt. (HMA) Loose, brown, gravelly, SAND with silt, moist. (FILL) Loose, brown and gray mottled, gravelly, silty SAND, moist. Loose, gray, interlayered, poorly graded SAND and silty SAND with gravel, moist. (REWORKED/REGRADED ALLUVIUM) Loose, gray, sandy, poorly graded GRAVEL, moist. Loose, gray, sandy, fine GRAVEL, moist. Poor recovery. Loose, gray, sandy, poorly graded GRAVEL with silt, wet. Poor recovery. (ALLUVIUM) Borehole was terminated at 11.5 feet below ground surface. Groundwater seepage was observed at 10 feet below ground surface. 7-3-3 1-2-7 2-3-5 3-4-3 3-3-4 SP SM SM SP SM GP GP GP GM BORING-DSM 2023-055.GPJ 11/2/23 FIGURE:PROJECT NO.:2023-055 Renton, Washington Geotechnical Services Renton Municipal Airport GA Apron Rehabilitation Natural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION BH-6 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBEROTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot Standard Penetration Test A-14DEPTH(feet)0 5 10 15 ELEVATION(feet)DATE COMPLETED: 8/28/2023 DRILLING COMPANY: Holocene Drilling DRILLING METHOD: HSA w/Mobile B-58 Truck Rig LOCATION: See Figure 2B DATE STARTED: 8/28/2023 SAMPLING METHOD: SPT w/Autohammer LOGGED BY: S. Pemble GS GS S-1 S-2 S-3 S-4 S-5 1.5 inches Hot Mix Asphalt. (HMA) Loose, brown, silty, sandy, poorly graded GRAVEL, moist. (FILL) Loose, gray, silty SAND with scattered gravel, moist. (REWORKED/REGRADED ALLUVIUM) With scattered fine gravel, dark brown organics and wood, moist. Loose, gray, silty SAND with scattered fine gravel and medium SAND interlayers, moist. (ALLUVIUM) Loose, gray, sandy, poorly graded GRAVEL, moist. Loose, dark gray, poorly graded SAND with silt and gravel, wet. Drove rock, poor recovery. Borehole was terminated at 11.5 feet below ground surface. Groundwater seepage was observed at 10 feet below ground surface. 4-3-4 2-2-2 1-2-4 5-3-3 1-2-3 GM SM SM GP SP SM BORING-DSM 2023-055.GPJ 11/2/23 FIGURE:PROJECT NO.:2023-055 Renton, Washington Geotechnical Services Renton Municipal Airport GA Apron Rehabilitation Natural Water ContentUSCS SOIL CLASSWater Content (%) NOTE: This log of subsurface conditions applies only at the specified location and on the date indicated DESCRIPTION BH-7 PAGE: 1 of 1(blows/6 inches)GROUNDWATERPEN. RESISTANCELiquid LimitSYMBOL0 10 20 30 40 50 0 20 40 60 80 100SAMPLE TYPESAMPLE NUMBEROTHER TESTSPlastic Limit BORING: and therefore may not necessarily be indicative of other times and/or locations. (140 lb. weight, 30" drop) Blows per foot Standard Penetration Test A-15DEPTH(feet)0 5 10 15 ELEVATION(feet)DATE COMPLETED: 8/28/2023 DRILLING COMPANY: Holocene Drilling DRILLING METHOD: HSA w/Mobile B-58 Truck Rig LOCATION: See Figure 2B DATE STARTED: 8/28/2023 SAMPLING METHOD: SPT w/Autohammer LOGGED BY: S. Pemble APPENDIX B LABORATORY TEST RESULTS BH-1,S-2A 2.5 3.0 29.5 1.2 14.6 84.2 ML Very dark gray, SILT with sand BH-1,S-2B 3.0 4.0 11.2 0.1 90.2 9.7 SP-SM Very dark gray, poorly graded SAND with silt BH-1,S-5 10.0 11.5 242.8 16.4 246 183 63 OH Very dark brown, organic SILT BH-2,S-1 1.0 2.5 92.9 121 78 43 OH Very dark gray, organic SILT BH-2,S-2 2.5 4.0 195.2 117 84 33 OH Dark grayish-brown, organic SILT BH-3,S-2B 3.5 4.0 39.5 39 30 9 ML Very dark gray, SILT BH-3,S-3 5.0 6.5 26.9 93.2 6.8 SP-SM Very dark gray, poorly graded SAND with silt BH-4,S-1 0.4 1.9 7.6 35.2 50.8 14.0 SM Very dark grayish-brown, silty SAND with gravel BH-4,S-3 5.0 6.5 29.9 0.4 79.2 20.4 SM Very dark gray, silty SAND BH-5,S-1 0.5 2.0 4.1 40.0 55.6 4.4 SP Dark yellowish-brown, poorly graded SAND with gravel BH-5,S-2 2.5 4.0 8.7 40.0 42.3 17.7 SM Very dark gray, silty SAND with gravel BH-6,S-2 2.5 4.0 9.2 34.2 43.6 22.2 SM Very dark gray, silty SAND with gravel BH-6,S-3 5.0 6.5 2.4 58.2 38.4 3.4 GP Very dark gray, poorly graded GRAVEL with sand BH-7,S-2 2.5 4.0 12.5 6.6 51.9 41.4 SM Very dark gray, silty SAND BH-7,S-4 7.5 9.0 3.1 53.2 43.2 3.6 GP Very dark gray, poorly graded GRAVEL with sand(feet)TOP DEPTHSAMPLE DESCRIPTION Notes:ASTM SOILMOISTURECONTENT (%)ORGANIC% FINESSPECIFIC GRAVITYEXPLORATIONDESIGNATION1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES B-1 PAGE: 1 of 1 SUMMARY OF LIMITS (%) ATTERBERG BOTTOM DEPTHCONTENT (%)% SAND% GRAVELPIPLLL CLASSIFICATION(feet)2023-055PROJECT NO.: INDEX MATSUM 2 2023-055.GPJ 9/7/23 FIGURE: Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-2A S-2B S-3 2.5 - 3.0 3.0 - 4.0 5.0 - 6.5 #10 14.6 90.2 93.2 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-2 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 1.2 0.1 Sand % (ML) Very dark gray, SILT with sand (SP-SM) Very dark gray, poorly graded SAND with silt (SP-SM) Very dark gray, poorly graded SAND with silt Fines % 0.00050.005 CLAY BH-1 BH-1 BH-3 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 30 11 27 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 84.2 9.7 6.8 2023-055PROJECT NO.: HWAGRSZ 2023-055.GPJ 9/7/23 FIGURE: Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-1 S-3 S-1 0.4 - 1.9 5.0 - 6.5 0.5 - 2.0 #10 50.8 79.2 55.6 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-3 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 35.2 0.4 40.0 Sand % (SM) Very dark grayish-brown, silty SAND with gravel (SM) Very dark gray, silty SAND (SP) Dark yellowish-brown, poorly graded SAND with gravel Fines % 0.00050.005 CLAY BH-4 BH-4 BH-5 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 8 30 4 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 14.0 20.4 4.4 2023-055PROJECT NO.: HWAGRSZ 2023-055.GPJ 9/7/23 FIGURE: Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-2 S-2 S-3 2.5 - 4.0 2.5 - 4.0 5.0 - 6.5 #10 42.3 43.6 38.4 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-4 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 40.0 34.2 58.2 Sand % (SM) Very dark gray, silty SAND with gravel (SM) Very dark gray, silty SAND with gravel (GP) Very dark gray, poorly graded GRAVEL with sand Fines % 0.00050.005 CLAY BH-5 BH-6 BH-6 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 9 9 2 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 17.7 22.2 3.4 2023-055PROJECT NO.: HWAGRSZ 2023-055.GPJ 9/7/23 FIGURE: Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110 GRAIN SIZE IN MILLIMETERS 50 SAMPLE S-2 S-4 2.5 - 4.0 7.5 - 9.0 #10 51.9 43.2 30 CLASSIFICATION OF SOIL- ASTM D2487 Group Symbol and Name U.S. STANDARD SIEVE SIZES SAND B-5 Coarse #60#40#20 Fine Coarse SYMBOL Gravel % 3"1-1/2"PERCENT FINER BY WEIGHT#4 #200 6.6 53.2 Sand % (SM) Very dark gray, silty SAND (GP) Very dark gray, poorly graded GRAVEL with sand Fines % 0.00050.005 CLAY BH-7 BH-7 SILT 3/4" GRAVEL 0.05 5/8" 70 #100 0.5 12 3 50 Medium Fine 3/8" 5 PI 90 10 % MC LL PLDEPTH ( ft.) PARTICLE-SIZE ANALYSIS OF SOILS METHOD ASTM D6913 41.4 3.6 2023-055PROJECT NO.: HWAGRSZ 2023-055.GPJ 9/7/23 FIGURE: Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington 0 10 20 30 40 50 60 70 80 90 100 0 40 80 120 160 200 240 10.0 - 11.5 1.0 - 2.5 2.5 - 4.0 3.5 - 4.0 (OH) Very dark brown, organic SILT (OH) Very dark gray, organic SILT (OH) Dark grayish-brown, organic SILT (ML)Very dark gray, SILT LIQUID LIMIT (LL) 246 121 117 39 % MC LL BH-1 BH-2 BH-2 BH-3 243 93 195 40 LIQUID LIMIT, PLASTIC LIMIT AND PLASTICITY INDEX OF SOILS METHOD ASTM D4318 B-6 63 43 33 9 CL-ML % FinesSAMPLE ML CLASSIFICATION MHPLASTICITY INDEX (PI)SYMBOL PL PI 183 78 84 30 S-5 S-1 S-2 S-2B DEPTH (ft) CL CH 2023-055PROJECT NO.: HWAATTB EXPANDED SAMPLE COLUMN (HIGH LL) 2023-055.GPJ 9/7/23 FIGURE: Renton Municipal Airport GA Apron Rehabilitation Geotechnical Services Renton, Washington APPENDIX C: SWPPP Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan (SWPPP) for City of Renton – Renton Municipal Airport Windsock Apron and 243 Building Apron and Parking Lot Rehabilitaiton Project Prepared for: Department of Ecology Northwest Region Permittee / Owner Developer Operator / Contractor City of Renton TBD TBD Renton Municipal Airport 616 W Perimeter Rd, Unit A Renton, WA 98057 Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD TBD TBD SWPPP Prepared By Name Organization Contact Phone Number Alex Lange DOWL 602-732-7280 SWPPP Preparation Date 04/03/2024 Project Construction Dates Activity / Phase Start Date End Date TBD TBD TBD ii | P a g e GENERAL INSTRUCTIONS AND CAVEATS This template presents the recommended structure and content for preparation of a Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan (SWPPP). The Department of Ecology’s (Ecology) CSWGP requirements inform the structure and content of this SWPPP template; however, you must customize this template to reflect the conditions of your site. A Construction Stormwater Site Inspection Form can be found on Ecology’s website. https://www.ecology.wa.gov/Regulations-Permits/Permits-certifications/Stormwater-general- permits/Construction-stormwater-permit Using the SWPPP Template Each section will include instructions and space for information specific to your project. Please read the instructions for each section and provide the necessary information when prompted. This Word template can be modified electronically. You may add/delete text, copy and paste, edit tables, etc. Some sections may be completed with brief answers while others may require several pages of explanation. Follow this link to a copy of the Construction Stormwater General Permit: https://www.ecology.wa.gov/Regulations-Permits/Permits-certifications/Stormwater-general- permits/Construction-stormwater-permit iii | P a g e Table of Contents Project Information (1.0) ............................................................................................................................................ 2 Existing Conditions (1.1) ........................................................................................................................................ 2 Proposed Construction Activities (1.2) ................................................................................................................ 3 Construction Stormwater Best Management Practices (BMPs) (2.0) ................................................................. 5 The 13 Elements (2.1) ........................................................................................................................................... 5 Element 1: Preserve Vegetation / Mark Clearing Limits (2.1.1) .................................................................. 5 Element 2: Establish Construction Access (2.1.2) ........................................................................................ 5 Element 3: Control Flow Rates (2.1.3) ............................................................................................................ 6 Element 4: Install Sediment Controls (2.1.4).................................................................................................. 6 Element 5: Stabilize Soils (2.1.5) ..................................................................................................................... 6 Element 6: Protect Slopes (2.1.6) .................................................................................................................... 7 Element 7: Protect Drain Inlets (2.1.7) ............................................................................................................ 8 Element 8: Stabilize Channels and Outlets (2.1.8) ....................................................................................... 8 Element 9: Control Pollutants (2.1.9) .............................................................................................................. 8 Element 10: Control Dewatering (2.1.10) ..................................................................................................... 10 Element 11: Maintain BMPs (2.1.11) ............................................................................................................ 11 Element 12: Manage the Project (2.1.12) ..................................................................................................... 12 Element 13: Protect Low Impact Development (LID) BMPs (2.1.13) ....................................................... 13 Pollution Prevention Team (3.0) ............................................................................................................................. 14 Monitoring and Sampling Requirements (4.0) ...................................................................................................... 15 Site Inspection (4.1) ............................................................................................................................................. 15 Stormwater Quality Sampling (4.2) .................................................................................................................... 15 Turbidity Sampling (4.2.1) ............................................................................................................................... 15 pH Sampling (4.2.2) ......................................................................................................................................... 16 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies (5.0) ............................................ 18 303(d) Listed Waterbodies (5.1) ......................................................................................................................... 18 TMDL Waterbodies (5.2) ..................................................................................................................................... 18 Reporting and Record Keeping (6.0) ..................................................................................................................... 19 Record Keeping (6.1) ........................................................................................................................................... 19 Site Log Book (6.1.1) ....................................................................................................................................... 19 Records Retention (6.1.2) ............................................................................................................................... 19 Updating the SWPPP (6.1.3) .......................................................................................................................... 19 Reporting (6.2) ...................................................................................................................................................... 20 Discharge Monitoring Reports (6.2.1) ........................................................................................................... 20 Notification of Noncompliance (6.2.2) ........................................................................................................... 20 7.0 Appendix/Glossary ............................................................................................................................................. 21 iv | P a g e List of Tables Table 1 – List of Acronyms and Abbreviations ....................................................................................................... 1 Table 3 – Pollutants .................................................................................................................................................... 8 Table 4 – pH-Modifying Sources ............................................................................................................................ 10 Table 5 – Dewatering BMPs.................................................................................................................................... 10 Table 6 – Management ............................................................................................................................................ 12 Table 7 – BMP Implementation Schedule ............................................................................................................. 13 Table 8 – Team Information .................................................................................................................................... 14 Table 9 – Turbidity Sampling Method .................................................................................................................... 15 Table 10 – pH Sampling Method ............................................................................................................................ 17 List of Appendices Appendix A – Engineering Plans ............................................................................................................................ 22 Appendix B – BMP Details ...................................................................................................................................... 23 Appendix C – Correspondence ............................................................................................................................... 24 Appendix D – City of Renton ESC and SWPPS Maintenance Report .............................................................. 25 Appendix E – Construction Stormwater General Permit (CSWGP) .................................................................. 26 1 | P a g e Table 1 – 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 2 | P a g e Project Information (1.0) Project/Site Name: Windsock Apron and 243 Building Apron and Parking Lot Rehabilitation Street/Location: 749 E Perimeter Rd (Windsock) and 243 W Perimeter Rd (243 Building) City: Renton State: WA Zip code: 98057 Subdivision: N/A Receiving waterbody: Cedar River and Lake Washington Existing Conditions (1.1) Total acreage (including support activities such as off-site equipment staging yards, material storage areas, borrow areas). Total acreage: 3.00 acres Disturbed acreage: 2.89 acres Existing structures: The site is located at the Renton Municipal Airport located at 749 E Perimeter Road (Windsock) and 243 W Perimeter Rd (243 Building) in Renton, Washington 98057. The existing site consists of Runway 16/34, Taxiways A and B and numerous connector taxiways, aprons, hangers and offices. The proposed area of disturbance is limited to the Windsock apron and the 243 Building apron and parking lot. Landscape topography: Both work areas are relatively flat with slopes ranging from 1% to 3%.The highest and lowest elevations for the Windsock apron is approximately 23.7 feet, located at the southwestern portion of the apron. and 22.3 feet, located in the center of the apron, respectively. The highest and lowest elevations for the 243 Building is approximately 30.7 feet, located in the southeastern portion of the site, and 28.2 feet located in the western portion of the site, respectively. Drainage patterns: Stormwater runoff for the Windsock apron is captured in catch basins and is either routed to an onsite detention pond located west of the apron or discharges directly into the Cedar River. Stormwater runoff from the 243 Building is captured in catch basins and is routed to an offsite City of Renton owned conveyance system and eventually outfalls into Lake Washington. Existing Vegetation: The existing site is fully developed and consists of hardscape and landscape areas. Critical Areas (wetlands, streams, high erosion risk, steep or difficult to stabilize slopes): 3 | P a g e The Windsock apron is located adjacent to the Cedar River. There are no critical areas present at the 243 Building site. List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: According to EPA’s Stormwater Discharge Mapping Tool, the project will discharge into the Cedar River and Lake Washington. The Cedar River has the following imparements: • Dissolved Oxygen • Temperature • Bacteria – Escherichia Coli (E. Coli) • Bacteria – Fecal Coliform • High Molecular Weight Polycyclic Aromatic Hydrocarbons (HPAH) in Sediment • Low Molecular Weight Polycyclic Aromatic Hydrocarbons (LPAH) in Sediment • Polychlorinated Biphenyls (PCBs) in Sediment There are no listed impairments for Lake Washington. Proposed Construction Activities (1.2) Description of site development (example: subdivision): The proposed project wil consist of the pavement reconstruction for the Windsock apron, and the reconstruction of the 243 Building apron and parking lot. Description of construction activities (example: site preparation, demolition, excavation): Construction activites for this project will include site preparation, site clearing, excavation, grading, compaction and paving. Description of site drainage including flow from and onto adjacent properties. Must be consistent with Site Map in Appendix A: Stormwater runoff gerenated from the Windsock apron either flows east to an existing catch basin and eventually outfalls into the Cedar River or is captured in catch basins centered on the apron and is routed to an on-site detention pond for storage. Stormwater runoff gerenated from the 243 Building is captured in catch basins and is routed to a City of Renton owned conveyance system which ultimately outfalls into Lake Washington. Description of final stabilization (example: extent of revegetation, paving, landscaping): The final stabilization of the project site will include pavement and revegetation of the disturbed soil up to the marked clearing limits of construction. All tempoarary erosion and sediment control BMPs wil be removed once the project site has been stabilized. 4 | P a g e Contaminated Site Information: Proposed activities regarding contaminated soils or groundwater (example: on-site treatment system, authorized sanitary sewer discharge): There are no known contaminated soils at the site. Groundwater is relatively high, but no construction activities will impact groundwater. 5 | P a g e Construction Stormwater Best Management Practices (BMPs) (2.0) The SWPPP is a living document reflecting current conditions and changes throughout the life of the project. These changes may be informal (i.e. hand-written notes and deletions). Update the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design. The 13 Elements (2.1) Element 1: Preserve Vegetation / Mark Clearing Limits (2.1.1) There are no existing natural features within the area of disturbance. BMPs C208 (Triangular Silt Dike) and C233 (Silt Fence) shall be utilized onsite. Silt fence will be installed along the vegetated areas of disturbance, while Triangular Silt Dikes will be installed along the paved areas of disturbance. List and describe BMPs: C208: Triangular Silt Dike C233: Silt Fence Installation Schedules: The clearing limits shall be marked prior to any construction activites. Inspection and Maintenance plan:The clearing limits shalled be maintained by the Contractor the duration of construction. Responsible Staff: Contractor Element 2: Establish Construction Access (2.1.2) Existing paved roadways provide access to the work area. A stablized construction access and employee parking area is therefore not anticipated, unless deemed necessary by the contractor. C106 (Wheel Wash) shall be utilized onsite to prevent sediment tracking and foreign object debris (FOD) from entering any paved areas still active for aircrafts. List and describe BMPs: C105: Stabilized Construction Access C106: Wheel Wash C107: Construction Road / Parking Area Stabilization Installation Schedules: A wheel wash shall be installed prior to any construction activites. Inspection and Maintenance plan: Wheel washing, street sweeping, and street cleaning will be implemented as necessary to prevent sediment from tracking onto surrounding hardscape areas. Any hardscape areas that may be impacted by sediment tracking shall be street sweeped/cleaned when possible. Responsible Staff: Contractor 6 | P a g e Element 3: Control Flow Rates (2.1.3) Will you construct stormwater retention and/or detention facilities? No Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? No No flow control facilities are proposed as part of this project. List and describe BMPs: N/A Installation Schedules: N/A Inspection and Maintenance plan: N/A Responsible Staff: Contractor as Neccessary Element 4: Install Sediment Controls (2.1.4) BMPs C208 (Triangular Silt Dikes) and C233 (Silt Fence) will be utilized onsite. Silt fencing shall be installed on existing vegetated areas and triangular silt dikes shall be installed on exisitng hardscape area to protect downstream areas from sediment laden runoff as well as protect open runways, taxiways and taxilanes from sediment. List and describe BMPs: C208: Triangular Silt Dikes C233: Silt Fence Installation Schedules: Silt fence and triangular silt dikes shall be installed prior to any construction activities. Inspection and Maintenance plan: The Contractor shall inspect and maintain silt fencing and triangular silt dikes during construction. Responsible Staff: Contractor Element 5: Stabilize Soils (2.1.5) BMPs C120 (Temporary and Permanent Seeding), C123 (Plastic Covering), C140 (Dust Control) C150 (Materials on Hand) will be utilized onsite. During stockpile operations, plastic covering shall be utilized to protect sediment laden runoff from entering the airport operations area. Check weather reports, and ensure that stockpiled soils are properly covered prior to storm events. Dust control may be required during construction. Materials shall be readily available to adequately protect erosion sensitive areas. Upon completion of final grading activities all disturbed landscape areas shall be restablized using temporary and permanent seeding. BMPs shall be monitored daily and repaired as needed. 7 | P a g e West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Anticipated project dates: Start date: TBD End date: TBD Will you construct during the wet season? No List and describe BMPs: C120: Tempoary and Permanent Seeding C123: Plastic Covering C140: Dust Control C150: Materials on Hand Installation Schedules: Plastic covering shall be used to limit exposed soils, as needed throughout construction. Dust control as well as on-hand materials shall be implemented as needed throughout construction. Tempoary and permanent seeding shall be implemented upon completion of final grading activities. Inspection and Maintenance plan: The Contractor shall be responsible for inspecting and maintaining plastic coverings and control throughout construction. The Contractor will also be responsible for utilizing materials on hand as needed throughout construction. Responsible Staff: Contractor Element 6: Protect Slopes (2.1.6) Will steep slopes be present at the site during construction? No No steep slopes will be present at the site during construction. BMP C123 (Plastic Covering) will be utilized onsite. During stockpile operations, plastic covering shall be utilized to protect sediment laden runoff from entering paved areas within the airport property. Check weather reports, and ensure that stockpiled soils are properly covered prior to storm events. List and describe BMPs: C123: Plastic Covering Installation Schedules: Plastic covering shall be implemented on a by need basis. 8 | P a g e Inspection and Maintenance plan: The Contractor is responsible for inspecting and maintaining these BMPs during construction. Responsible Staff: Contractor Element 7: Protect Drain Inlets (2.1.7) BMP C220 (Inlet Protection) will be utilized onsite. All catch basins within the immediate vicinity of the project shall be fitted with inlet protection inserts to protect catch basins and associated pipes from sediment laden runoff. Inlet protection devices shall be cleaned or replaced when sediments has filled the device by one third, or as specified by the manufacturer. Straw wattles may also be utilized per the discresion of the CESCL. List and describe BMPs: C220: Inlet Protection Installation Schedules: Storm drain inlet protection shall be installed on all existing catch basins prior to any construction activities. Inspection and Maintenance plan: The Contractor is responsible for inspecting and maintaining the storm drain inlet protections on all catch basins. Responsible Staff: Contractor Element 8: Stabilize Channels and Outlets (2.1.8) 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. There are no proposed channels or outlets proposed as part of this project. List and describe BMPs: N/A Installation Schedules: N/A Inspection and Maintenance plan: N/A Responsible Staff: Contractor as Neccessary Element 9: Control Pollutants (2.1.9) The following pollutants are anticipated to be present on-site: Table 3 – Pollutants Pollutant (and source, if applicable) Gasoline – Fuel for Vehicles Hydraulic Oil – Operator’s Equipment 9 | P a g e All vehicle and equipment will be inspected regularly to detect if there are any leaks or spills and to identify if any maintenance is needed. Contaminated surfaces will be cleaned immediately in the event of a discharge or spill. Slurry and cuttings from sawcutting existing pavement will be prevented from entering waters by implementing Sawcutting and Surfacing Pollution Prevention measures. Contaminated water shall be disposed of off-site. BMPs C106 (Wheel Wash), C151 (Concrete Handling), C154 (Concrete Washout Area), C153 (Material Delivery, Storage and Continment), and C152 (Sawcutting and Surfacing Pollution Prevention) will be utilized onsite. Wheel wash and concrete washout areas shall be staged near haul routes to protect Renton Airport hardscape areas. BMPs shall be monitored daily and repaired as needed. A spill prevention kit shall be maintained onsite at all times. List and describe BMPs: C106: Wheel Wash C151: Concrete Handling C152: Sawcutting and Surfacing Pollution Prevention C153: Material Delivery, Storage, and Continment C154: Concrete Washout Area Installation Schedules: BMPs will be implemented as necessary throughout construction. Inspection and Maintenance plan: The Contractor shall provide sawcutting pollution prevention during sawcutting on the project site. All vehicles and equipment shall be inspected regularly throughout construction by the Contractor to detect if there are any leaks or spills and to identify any maintenance needs. Responsible Staff: Contractor Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? Maintenance and/or repair of heavy equipment and vehicles may occur onsite if necessary. Spill prevention measures, such as drip pans, will be used when conducting maintenance and/or repairs on vehicles and equipment. Will wheel wash or tire bath system BMPs be used during construction? Wheel wash will occur on site as necessary. Contaminated water shall be disposed of off-site. Will pH-modifying sources be present on-site? Yes 10 | P a g e Table 4 – pH-Modifying Sources None Bulk cement Cement kiln dust Fly ash Other cementitious materials X New concrete washing or curing waters Waste streams generated from concrete grinding and sawing Exposed aggregate processes Dewatering concrete vaults X Concrete pumping and mixer washout waters X Recycled concrete Other (i.e. calcium lignosulfate) [please describe] List and describe BMPs: C151: Concrete Handling C152: Sawcutting and Surfacing Pollution Prevention C154: Concrete Washout Area Installation Schedules: High pH water (pH greater than 8.5) shall be treated and disposed of as necessary. Inspection and Maintenance plan: The Contractor shall be responsible for ensuring high pH water is treated and disposed of as necessary throughout construction. Responsible Staff: 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. Element 10: Control Dewatering (2.1.10) Dewatering is not anticipated for this project. Table 5 – 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) 11 | P a g e Element 11: Maintain BMPs (2.1.11) 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 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. 12 | P a g e Element 12: Manage the Project (2.1.12) 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 6 – Management X Design the project to fit the existing topography, soils, and drainage patterns X Emphasize erosion control rather than sediment control X Minimize the extent and duration of the area exposed X Keep runoff velocities low X Retain sediment on-site X Thoroughly monitor site and maintain all ESC measures X Schedule major earthwork during the dry season Other (please describe) 13 | P a g e Table 7 – BMP Implementation Schedule Phase of Construction Project Stormwater BMPs Date Wet/Dry Season Start of Project Stabilized Construction Access (BMP C105) As Required Wet/Dry Start of Project Wheel Wash (BMP C106) Start Wet/Dry Start of Project Construction Road / Parking Area Stabilization As Required Wet/Dry Completion of Grading Tempoarary and Permanent Seeding (BMP C120) Start Wet/Dry Start of Project Plastic Covering (BMP C123) As Required Wet/Dry Start of Project Topsoiling/Composting (BMP C125) As Required Wet/Dry Start of Project Dust Control (BMP C140) As Required Dry Start of Project Materials on Hand (BMP C150) Start Wet/Dry Completion of Grading Concrete Handling (BMP C151) Start Wet/Dry Start of Project Sawcutting and Surfacing Pollution Prevention (BMP C152) Start Wet/Dry Start of Project Material Delivery, Storage and Containment (BMP C153) Start Wet/Dry Completion of Grading Concrete Washout Area (BMP C154) Start Wet/Dry Start of Project Triangular Silt Dikes (BMP C208) Start Wet/Dry Start of Project Storm Drain Inlet Protection (BMP C220) Start Wet/Dry Start of Project Silt Fence (BMP C233) Start Wet/Dry Element 13: Protect Low Impact Development (LID) BMPs (2.1.13) No LID BMPs will be utilized onsite for this project. 14 | P a g e Pollution Prevention Team (3.0) Table 8 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) TBD TBD Resident Engineer Wes Holden, PE (425) 869-2670 Emergency Ecology Contact Stacey Britton (360) 764-3727 Emergency Permittee/ Owner Contact TBD TBD Non-Emergency Owner Contact TBD TBD Monitoring Personnel N/A N/A Ecology Regional Office Northwest Regional Office (206) 594-0000 15 | P a g e Monitoring and Sampling Requirements (4.0) Monitoring includes visual inspection, sampling for water quality parameters of concern, and documentation of the inspection and sampling findings in a site log book. A site log book 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 ESC and SWPPS Maintenance Report under Appendix D. The site log book 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: Site runoff from the windsock apron discharges into the Cedar River. Site Inspection (4.1) 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. Stormwater Quality Sampling (4.2) Turbidity Sampling (4.2.1) Requirements include calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: Table 9 – Turbidity Sampling Method Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) X 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 less than 33 centimeters. 16 | P a g e 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 log book. 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 • Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 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 log book. 4. Continue to sample discharges daily until one of the following is true: • Turbidity is 25 NTU (or lower). • Transparency is 33 cm (or greater). • Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater • The discharge stops or is eliminated. pH Sampling (4.2.2) 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. 17 | P a g e 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 10 – pH Sampling Method X pH meter pH test kit Wide range pH indicator paper 18 | P a g e Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies (5.0) 303(d) Listed Waterbodies (5.1) Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? Yes, Cedar River List the impairment(s): • Dissolved Oxygen • Temperature • Bacteria – Escherichia Coli (E. Coli) • Bacteria – Fecal Coliform • High Molecular Weight Polycyclic Aromatic Hydrocarbons (HPAH) in Sediment • Low Molecular Weight Polycyclic Aromatic Hydrocarbons (LPAH) in Sediment • Polychlorinated Biphenyls (PCBs) in Sediment TMDL Waterbodies (5.2) Waste Load Allocation for CWSGP discharges: There are no TMDL waterbodies within the project vicinity. Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point of discharge. 19 | P a g e Reporting and Record Keeping (6.0) Record Keeping (6.1) Site Log Book (6.1.1) A site log book 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 Records Retention (6.1.2) 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 Log Book 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. Updating the SWPPP (6.1.3) 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. 20 | P a g e Reporting (6.2) Discharge Monitoring Reports (6.2.1) 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: https://www.ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Water-quality- permits-guidance/WQWebPortal-guidance Notification of Noncompliance (6.2.2) If any of the terms and conditions of the permit is 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. 21 | P a g e 7.0 Appendix/Glossary 22 | P a g e Appendix A – Engineering Plans (Provided Separately) 23 | P a g e Appendix B – BMP Details 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 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 Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. Midpoint spray nozzles are only needed in extremely muddy conditions. Wheel wash systems should be designed with a small grade change, 6- to 12-inches for a 10-foot- wide pond, to allow sediment to flow to the low side of pond to help prevent re-suspension of sed- iment. A drainpipe with a 2- to 3-foot riser should be installed on the low side of the pond to allow for easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a closed-loop system. Polyacrylamide (PAM) added to the wheel wash water at a rate of 0.25 - 0.5 pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is already being used for dust or erosion control and is being applied by a water truck, the same truck can be used to change the wash water. Maintenance Standards The wheel wash should start out each day with fresh water. The wheel wash water should be changed a minimum of once per day. On large earthwork jobs where more than 10-20 trucks per hour are expected, the wheel wash water will need to be changed more often. 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 281 Figure II-3.2: Wheel Wash 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 282 BMP C107: Construction Road / Parking Area Stabilization Purpose Stabilizing roads, parking areas, and other on-site vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or stormwater runoff. Conditions of Use Roads and parking areas shall be stabilized wherever they are constructed, whether permanent or temporary, for use by construction traffic. BMP C103: High-Visibility Fence shall be installed, if necessary, to limit the access of vehicles to only those roads and parking areas that are stabilized. Design and Installation Specifications l On areas that will receive asphalt as part of the project, install the first lift as soon as possible. l A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course shall be applied immediately after grading or utility installation. A 4-inch course of asphalt treated base (ATB) may also be used, or the road/parking area may be paved. It may also be possible to use cement or calcium chloride for soil stabilization. If cement or cement kiln dust is used for roadbase stabilization, pH monitoring and BMP C252: Treating and Disposing of High pH Water is necessary to evaluate and minimize the effects on stormwater. If the area will not be used for permanent roads, parking areas, or structures, a 6-inch depth of hog fuel may also be used, but this is likely to require more maintenance. Whenever possible, con- struction roads and parking areas shall be placed on a firm, compacted subgrade. l Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain. Drainage ditches shall be provided on each side of the roadway in the case of a crowned section, or on one side in the case of a super-elevated section. Drainage ditches shall be directed to a sediment control BMP. l Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet- flows into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not adequate. If this area has at least 50 feet of vegetation that water can flow through, then it is generally preferable to use the vegetation to treat runoff, rather than a sediment pond or trap. The 50 feet shall not include wetlands or their buffers. If runoff is allowed to sheetflow through adjacent vegetated areas, it is vital to design the roadways and parking areas so that no con- centrated runoff is created. l Storm drain inlets shall be protected to prevent sediment-laden water entering the drainage system (see BMP C220: Inlet Protection). Maintenance Standards Inspect stabilized areas regularly, especially after large storm events. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 283 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 BMP C123: Plastic Covering Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. Conditions of Use Plastic covering may be used on disturbed areas that require cover measures for less than 30 days, except as stated below. l Plastic is particularly useful for protecting cut and fill slopes and stockpiles. However, the rel- atively rapid breakdown of most polyethylene sheeting makes it unsuitable for applications greater than six months. l Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. l Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on- site measures to counteract the increases. Creating a trough with wattles or other material can convey clean water away from these areas. l To prevent undercutting, trench and backfill rolled plastic covering products. l Although the plastic material is inexpensive to purchase, the cost of installation, maintenance, removal, and disposal add to the total costs of this BMP. l Whenever plastic is used to protect slopes, install water collection measures at the base of the slope. These measures include plastic-covered berms, channels, and pipes used to convey clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a plastic covered slope with dirty runoff from a project. l Other uses for plastic include: o Temporary ditch liner. o Pond liner in temporary sediment pond. o Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored. o Emergency slope protection during heavy rains. o Temporary drainpipe (“elephant trunk”) used to direct water. Design and Installation Specifications l Plastic slope cover must be installed as follows: 1. Run plastic up and down the slope, not across the slope. 2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 298 3. Provide a minimum of 8-inch overlap at the seams. 4. On long or wide slopes, or slopes subject to wind, tape all seams. 5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope and backfill with soil to keep water from flowing underneath. 6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them together with twine to hold them in place. 7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This prevents high velocity runoff from contacting bare soil, which causes extreme erosion. 8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be staked in place. l Plastic sheeting shall have a minimum thickness of 0.06 millimeters. l If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be installed at the toe of the slope in order to reduce the velocity of runoff. Maintenance Standards l Torn sheets must be replaced and open seams repaired. l Completely remove and replace the plastic if it begins to deteriorate due to ultraviolet radi- ation. l Completely remove plastic when no longer needed. l Dispose of old tires used to weight down plastic sheeting appropriately. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C124: Sodding Purpose The purpose of sodding is to establish turf for immediate erosion protection and to stabilize drainage paths where concentrated overland flow will occur. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 299 BMP C125: Topsoiling / Composting Purpose Topsoiling and composting provide a suitable growth medium for final site stabilization with veget- ation. While not a permanent cover practice in itself, topsoiling and composting are an integral com- ponent of providing permanent cover in those areas where there is an unsuitable soil surface for plant growth. Use this BMP in conjunction with other BMPs such as BMP C120: Temporary and Per- manent Seeding, BMP C121: Mulching, or BMP C124: Sodding. Implementation of this BMP may meet the post-construction requirements of BMP T5.13: Post-Construction Soil Quality and Depth. Native soils and disturbed soils that have been organically amended not only retain much more stormwater, but also serve as effective biofilters for urban pollutants and, by supporting more vig- orous plant growth, reduce the water, fertilizer and pesticides needed to support installed land- scapes. Topsoil does not include any subsoils but only the material from the top several inches including organic debris. Conditions of Use l Permanent landscaped areas shall contain healthy topsoil that reduces the need for fertilizers, improves overall topsoil quality, provides for better vegetative health and vitality, improves hydrologic characteristics, and reduces the need for irrigation. l Leave native soils and the duff layer undisturbed to the maximum extent practicable. Stripping of existing, properly functioning soil system and vegetation for the purpose of topsoiling during construction is not acceptable. Preserve existing soil systems in undisturbed and uncom- pacted conditions if functioning properly. l Areas that already have good topsoil, such as undisturbed areas, do not require soil amend- ments. l Restore, to the maximum extent practical, native soils disturbed during clearing and grading to a condition equal to or better than the original site condition’s moisture-holding capacity. Use on-site native topsoil, incorporate amendments into on-site soil, or import blended topsoil to meet this requirement. l Topsoiling is a required procedure when establishing vegetation on shallow soils, and soils of critically low pH (high acid) levels. l Beware of where the topsoil comes from, and what vegetation was on site before disturbance. Invasive plant seeds may be included and could cause problems for establishing native plants, landscaped areas, or grasses. l Topsoil from the site will contain mycorrhizal bacteria that are necessary for healthy root growth and nutrient transfer. These native mycorrhiza are acclimated to the site and will provide optimum conditions for establishing grasses. Use commercially available mycorrhiza products when using off-site topsoil. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 301 Design and Installation Specifications Meet the following requirements for disturbed areas that will be developed as lawn or landscaped areas at the completed project site: l Maximize the depth of the topsoil wherever possible to provide the maximum possible infilt- ration capacity and beneficial growth medium. Topsoil shall have: o A minimum depth of 8-inches. Scarify subsoils below the topsoil layer at least 4-inches with some incorporation of the upper material to avoid stratified layers, where feasible. Ripping or re-structuring the subgrade may also provide additional benefits regarding the overall infiltration and interflow dynamics of the soil system. o A minimum organic content of 10% dry weight in planting beds, and 5% organic matter content in turf areas. Incorporate organic amendments to a minimum 8-inch depth except where tree roots or other natural features limit the depth of incorporation. o A pH between 6.0 and 8.0 or matching the pH of the undisturbed soil. o If blended topsoil is imported, then fines should be limited to 25 percent passing through a 200 sieve. l Mulch planting beds with 2 inches of organic material l Accomplish the required organic content, depth, and pH by returning native topsoil to the site, importing topsoil of sufficient organic content, and/or incorporating organic amendments. When using the option of incorporating amendments to meet the organic content requirement, use compost that meets the compost specification for Bioretention (See BMP T7.30: Biore- tention), with the exception that the compost may have up to 35% biosolids or manure. l Sections 3 through 7 of Building Soil: Guidelines and Resources for Implementing Soil Quality and Depth BMP T5.13 in WDOE Stormwater Management Manual for Western Washington (Stenn et al., 2016), provides useful guidance for implementing whichever option is chosen. It includes guidance for pre-approved default strategies and guidance for custom strategies. Check with your local jurisdiction concerning its acceptance of this guidance. l The final composition and construction of the soil system will result in a natural selection or favoring of certain plant species over time. For example, incorporation of topsoil may favor grasses, while layering with mildly acidic, high-carbon amendments may favor more woody vegetation. l Allow sufficient time in scheduling for topsoil spreading prior to seeding, sodding, or planting. l Take care when applying top soil to subsoils with contrasting textures. Sandy topsoil over clayey subsoil is a particularly poor combination, as water creeps along the junction between the soil layers and causes the topsoil to slough. If topsoil and subsoil are not properly bonded, water will not infiltrate the soil profile evenly and it will be difficult to establish vegetation. The best method to promote bonding is to actually work the topsoil into the layer below for a depth of at least 6 inches. l Field exploration of the site shall be made to determine if there is surface soil of sufficient quantity and quality to justify stripping. Topsoil shall be friable and loamy (loam, sandy loam, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 302 silt loam, sandy clay loam, and clay loam). Avoid areas of natural ground water recharge. l Stripping shall be confined to the immediate construction area. A 4-inch to 6-inch stripping depth is common, but depth may vary depending on the particular soil. All surface runoff con- trol structures shall be in place prior to stripping. l Do not place topsoil while in a frozen or muddy condition, when the subgrade is excessively wet, or when conditions exist that may otherwise be detrimental to proper grading or pro- posed sodding or seeding. l In any areas requiring grading, remove and stockpile the duff layer and topsoil on site in a des- ignated, controlled area, not adjacent to public resources and critical areas. Reapply stock- piled topsoil to other portions of the site where feasible. l Locate the topsoil stockpile so that it meets specifications and does not interfere with work on the site. It may be possible to locate more than one pile in proximity to areas where topsoil will be used. l Stockpiling of topsoil shall occur in the following manner: o Side slopes of the stockpile shall not exceed 2H:1V. o Between October 1 and April 30: n An interceptor dike with gravel outlet and silt fence shall surround all topsoil. n Within 2 days complete erosion control seeding, or covering stockpiles with clear plastic, or other mulching materials. o Between May 1 and September 30: n An interceptor dike with gravel outlet and silt fence shall surround all topsoil if the stockpile will remain in place for a longer period of time than active construction grading. n Within 7 days complete erosion control seeding, or covering stockpiles with clear plastic, or other mulching materials. l When native topsoil is to be stockpiled and reused the following should apply to ensure that the mycorrhizal bacterial, earthworms, and other beneficial organisms will not be destroyed: o Re-install topsoil within 4 to 6 weeks. o Do not allow the saturation of topsoil with water. o Do not use plastic covering. Maintenance Standards l Inspect stockpiles regularly, especially after large storm events. Stabilize any areas that have eroded. l Establish soil quality and depth toward the end of construction and once established, protect from compaction, such as from large machinery use, and from erosion. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 303 l Plant and mulch soil after installation. l Leave plant debris or its equivalent on the soil surface to replenish organic matter. l Reduce and adjust, where possible, the use of irrigation, fertilizers, herbicides and pesticides, rather than continuing to implement formerly established practices. BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection Purpose Polyacrylamide (PAM) is used on construction sites to prevent soil erosion. Applying PAM to bare soil in advance of a rain event significantly reduces erosion and controls sed- iment in two ways. First, PAM increases the soil’s available pore volume, thus increasing infiltration and reducing the quantity of stormwater runoff. Second, it increases flocculation of suspended particles and aids in their deposition, thus reducing stormwater runoff turbidity and improving water quality. Conditions of Use PAM shall not be directly applied to water or allowed to enter a water body. Stormwater runoff shall pass through a sediment pond prior to discharging to surface waters. PAM can be applied to bare soil under the following conditions: l During rough grading operations. l In Staging areas. l Balanced cut and fill earthwork. l Haul roads prior to placement of crushed rock surfacing. l Compacted soil roadbase. l Stockpiles. l After final grade and before paving or final seeding and planting. l Pit sites. l Sites having a winter shut down. In the case of winter shut down, or where soil will remain unworked for several months, PAM should be used together with mulch. Design and Installation Specifications l Do not use PAM on a slope that flows directly into a stream or wetland. l Do not add PAM to water discharging from the site. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 304 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 Figure II-3.8: Concrete Washout Area with Straw Bales 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 325 Figure II-3.9: Prefabricated Concrete Washout Container w/Ramp 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 326 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 BMP C208: Triangular Silt Dike (TSD) Purpose Triangular silt dikes (TSDs) may be used as check dams, for perimeter protection, for temporary soil stockpile protection, for drop inlet protection, or as a temporary interceptor dike. Conditions of Use l TSDs may be used on soil or pavement with adhesive or staples. l TSDs have been used to build temporary: o BMP C241: Sediment Pond (Temporary); o BMP C200: Interceptor Dike and Swale; o BMP C154: Concrete Washout Area; o BMP C203: Water Bars; o BMP C206: Level Spreader; o BMP C220: Inlet Protection; o BMP C207: Check Dams o curbing; and o berms. Design and Installation Specifications l TSDs are made of urethane foam sewn into a woven geosynthetic fabric. l TSDs are triangular, 10 inches to 14 inches high in the center, with a 20-inch to 28-inch base. A 2 foot apron extends beyond both sides of the triangle along its standard section of 7 feet. A sleeve at one end allows attachment of additional sections as needed. l Install with ends curved up to prevent water from flowing around the ends. l The fabric flaps and check dam units are attached to the ground with wire staples. Wire staples should be No. 11 gauge wire and should be 200 mm to 300 mm in length. l When multiple units are installed, the sleeve of fabric at the end of the unit shall overlap the abutting unit and be stapled. l When used as check dams: o TSDs should be located and installed as soon as construction will allow. o TSDs should be placed perpendicular to the flow of water. o The leading edge of the TSD must be secured with rocks, sandbags, or a small key slot 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 354 and staples. o In the case of grass-lined ditches and swales, 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. Maintenance Standards l Inspect TSDs for performance and sediment accumulation during and after each rainfall that produces runoff. Remove sediment when it reaches one half the height of the TSD. l Anticipate submergence and deposition above the TSD and erosion from high flows around the edges of the TSD. Immediately repair any damage or any undercutting of the TSD. BMP C209: Outlet Protection Purpose Outlet protection prevents scour at conveyance outlets and minimizes the potential for downstream erosion by reducing the velocity of concentrated stormwater flows. Conditions of Use Use outlet protection at the outlets of all ponds, pipes, ditches, or other conveyances that discharge to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch. Design and Installation Specifications l The receiving channel at the outlet of a pipe shall be protected from erosion by lining a min- imum of 6 feet downstream and extending up the channel sides a minimum of 1–foot above the maximum tailwater elevation, or 1-foot above the crown, whichever is higher. For pipes lar- ger than 18 inches in diameter, the outlet protection lining of the channel shall be four times the diameter of the outlet pipe. l Standard wingwalls, tapered outlets, and paved channels should also be considered when appropriate for permanent culvert outlet protection (WSDOT, 2015). l BMP C122: Nets and Blankets or BMP C202: Riprap Channel Lining provide suitable options for lining materials. l With low flows, BMP C201: Grass-Lined Channels can be an effective alternative for lining material. l The following guidelines shall be used for outlet protection with riprap: o If the discharge velocity at the outlet is less than 5 fps, use 2-inch to 8-inch riprap. Min- imum thickness is 1-foot. o For 5 to 10 fps discharge velocity at the outlet, use 24-inch to 48-inch riprap. Minimum 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 355 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 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 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 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 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 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 24 | P a g e Appendix C – Correspondence (Not Applicable) 25 | P a g e Appendix D – City of Renton ESC and SWPPS Maintenance Report CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 8-E-1 REFERENCE 8-E CSWPP WORKSHEET FORMS E S C M A I N T E N A N C E R E P O R T Performed By: ___________________________ Date: ___________________________ Project Name: ___________________________ CED Permit #: ___________________________ Clearing Limits Damage OK Problem Visible OK Problem Intrusions OK Problem Other OK Problem Mulch Rills/Gullies OK Problem Thickness OK Problem Other OK Problem Nets/Blankets Rills/Gullies OK Problem Ground Contact OK Problem Other OK Problem Plastic Tears/Gaps OK Problem Other OK Problem Seeding Percent Cover OK Problem Rills/Gullies OK Problem Mulch OK Problem Other OK Problem Sodding Grass Health OK Problem Rills/Gullies OK Problem Other OK Problem Perimeter Protection including Silt Fence Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual Ref 8-E-2 Flow Control, Treatment, and On-site BMP/Facility Protection Damage OK Problem Sedimentation OK Problem Concentrated Flow OK Problem Rills/Gullies OK Problem Intrusions OK Problem Other OK Problem Brush Barrier Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Vegetated Strip Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Construction Entrance Dimensions OK Problem Sediment Tracking OK Problem Vehicle Avoidance OK Problem Other OK Problem Wheel Wash Dimensions OK Problem Sed build up or tracking OK Problem Other OK Problem Construction Road Stable Driving Surf. OK Problem Vehicle Avoidance OK Problem Other OK Problem Sediment Trap/Pond Sed. Accumulation OK Problem Overtopping OK Problem Inlet/Outlet Erosion OK Problem Other OK Problem Catch Basin/Inlet Protection Sed. Accumulation OK Problem Damage OK Problem Clogged Filter OK Problem Other OK Problem Interceptor Dike/Swale Damage OK Problem Sed. Accumulation OK Problem Overtopping OK Problem Other OK Problem REFERENCE 8-E: CSWPP WORKSHEET FORMS 2022 City of Renton Surface Water Design Manual 6/22/2022 8-E-3 Pipe Slope Drain Damage OK Problem Inlet/Outlet OK Problem Secure Fittings OK Problem Other OK Problem Ditches Damage OK Problem Sed. Accumulation OK Problem Overtopping OK Problem Other OK Problem Outlet Protection Scour OK Problem Other OK Problem Level Spreader Damage OK Problem Concentrated Flow OK Problem Rills/Gullies OK Problem Sed. Accumulation OK Problem Other OK Problem Dewatering Controls Sediment OK Problem Dust Control Palliative applied OK Problem Miscellaneous Wet Season Stockpile OK Problem Other OK Problem Comments: Actions Taken: Problems Unresolved: REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual Ref 8-E-4 BMP Implementation Completed by: Title: Date: Develop a plan for implementing each BMP. Describe the steps necessary to implement the BMP (i.e., any construction or design), the schedule for completing those steps (list dates), and the person(s) responsible for implementation. BMPs Description of Action(s) Required for Implementation Scheduled Milestone and Completion Date(s) Person Responsible for Action Good Housekeeping 1. 2. 3 Preventive Maintenance 1. 2. 3. 4. Spill Prevention and Emergency Cleanup 1. 2. 3. Inspections 1. 2. 3. REFERENCE 8-E: CSWPP WORKSHEET FORMS 2022 City of Renton Surface Water Design Manual 6/22/2022 8-E-5 BMPs Description of Action(s) Required for Implementation Schedule Milestone and Completion Date(s) Person Responsible for Action Source Control BMPs 1. 2. 3 4. 5. 6. 7. 8. Water Quality Facilities 1. 2. 3. 4. Flow Control Facilities 1. 2. 3. 4. On-Site BMPs 1. 2. 3. 4. REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual Ref 8-E-6 Pollution Prevention Team Completed by: ______________________ Title: ______________________________ Date: ______________________________ Responsible Official: Title: Team Leader: Office Phone: Cell Phone: Responsibilities: (1) Title: Office Phone: Cell Phone: Responsibilities: (2) Title: Office Phone: Cell Phone: Responsibilities: REFERENCE 8-E: CSWPP WORKSHEET FORMS 2022 City of Renton Surface Water Design Manual 6/22/2022 8-E-7 Employee Training Completed by: Title: Date: Describe the annual training of employees on the SWPPP, addressing spill response, good housekeeping, and material management practices. Training Topics 1.) LINE WORKERS Brief Description of Training Program/Materials (e.g., film, newsletter course) Schedule for Training (list dates) Attendees Spill Prevention and Response Good Housekeeping Material Management Practices 2.) P2 TEAM: SWPPP Implementation Monitoring Procedures REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEETS 6/22/2022 2022 City of Renton Surface Water Design Manual Ref 8-E-8 List of Significant Spills and Leaks Completed by: Title: Date: List all spills and leaks of toxic or hazardous pollutants that were significant but are not limited to, release of oil or hazardous substances in excess of reportable quantities. Although not required, we suggest you list spills and leaks of non-hazardous materials. Date (month/ day/ year) Location (as indicated on site map) Description Response Procedure Preventive Measure Taken Type of Material Quantity Source, If Known Reason for Spill/Leak Amount of Material Recovered Material no longer exposed to stormwater (Yes/No) REFERENCE 8-E: CSWPP WORKSHEET FORMS 2022 City of Renton Surface Water Design Manual 6/22/2022 8-E-9 Potential Pollutant Source Identification Completed by: Title: Date: List all potential stormwater pollutants from materials handled, treated, or stored onsite. Potential Stormwater Pollutant Stormwater Pollutant Source Likelihood of pollutant being present in your stormwater discharge. If yes, explain REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEETS 6/22/2022 2022 City of Renton Surface Water Design Manual Ref 8-E-10 Material Inventory Completed by: Title: Date: List materials handled, treated, stored, or disposed of at the project site that may potentially be exposed to precipitation or runoff. Material Purpose/Location Quantity (Units) Likelihood of contact with stormwater If Yes, describe reason: Past Spill or Leak Used Produced Stored (indicate per wk. or yr.) Yes No 26 | P a g e Appendix E – Construction Stormwater General Permit (CSWGP) 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 Disturbance 1 Weekly Site Inspections Weekly Sampling w/ Turbidity Meter Weekly Sampling w/ Transparency Tube Weekly pH Sampling 2 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 method 3 Required Yes Sites that disturb 5 acres or more Required Required Not Required 4 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