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Home My WebLink AboutTIR-4036 Technical Information Report (TIR) Renton Senior Housing RJ Development April 2019 SURFACE WATER UTILITY jfarah 07/12/2019 DEVELOPMENT ENGINEERING jchavez 07/16/2019 SCJ Alliance April 2019 Technical Information Report Project Information Project: Renton Senior Housing Prepared for: RJ Development Reviewing Agency Jurisdiction: City of Renton Project Representative Prepared by: SCJ Alliance 8730 Tallon Lane NE, Suite 200 Lacey, WA 98516 360.352.1465 scjalliance.com Contact: Ross Jarvis, PE Project Reference: SCJ #2386.03 Path: N:\Projects\2386 RJ Development\2386.03 Renton Senior Housing\Phase Number\Design\Storm\Technical Information Report.docx SCJ Alliance April 2019 Page i TABLE OF CONTENTS 1. Project Overview ........................................................................................................ 2 1.1 Project Overview ................................................................................................................... 2 1.2 Predeveloped Site Conditions ............................................................................................... 3 1.3 Soils ........................................................................................................................................ 4 2. Conditions and Requirements Summary ..................................................................... 4 3. Offsite Analysis .......................................................................................................... 6 3.1 Downstream Analysis ............................................................................................................ 6 3.2 Upstream Analysis ................................................................................................................. 7 3.3 Resource Review ................................................................................................................... 7 3.4 Field investigation ................................................................................................................. 8 3.5 Drainage System Description and Problem Descriptions ...................................................... 9 4. Flow Control, Low Impact Development (LID) and Water Quality Facility Analysis and Design ................................................................................................................................ 9 4.1 Existing Site Hydrology .......................................................................................................... 9 4.2 Developed Site Hydrology ..................................................................................................... 9 4.3 Performance Standards ....................................................................................................... 10 4.4 On-Site BMPs ....................................................................................................................... 10 4.5 Flow Control System ............................................................................................................ 11 4.6 Water Quality System .......................................................................................................... 12 5. Conveyance System Analysis and Design ................................................................... 13 6. Special Reports and Studies ...................................................................................... 13 7. Other Permits ........................................................................................................... 13 8. CSWPP Analysis and Design ...................................................................................... 13 8.1 ESC Plan Analysis and Design .............................................................................................. 13 8.2 SWPPS Plan Design .............................................................................................................. 15 9. Bond Quantities, Facility Summaries, and Declaration of Covenant ........................... 15 10. Operations and Maintenance Manual ....................................................................... 15 SCJ Alliance April 2019 Page ii LIST OF APPENDICES Appendix A: Determination of Minimum Requirements Worksheets Appendix B: Site Vicinity Maps Appendix C: Basin Map Exhibits Appendix D: Off-Site Analysis Appendix E: Design Calculations and Computations Appendix F: Stormwater Plan Sheets Appendix G: Geotechnical Report Appendix H: Construction SWPPP Appendix I: Worksheets Appendix J: Operations and Maintenance Manual Appendix K: Declaration of Covenant Renton Senior Housing 2 of 15 Technical Information Report 1. PROJECT OVERVIEW The following report was prepared for the proposed Senior Housing Facility and parking lot in Renton. This report was prepared to comply with the minimum technical standards and requirements that are set forth in the 2016 City of Renton Surface Water Design Manual (Manual). 1.1 PROJECT OVERVIEW Project Proponent: RJ Development, LLC Parcel Numbers: 312305-9067, 312305-9094 Total Parcel Area: 4.75 acres Current Zoning: Commercial Required Permits: Utility, building, grading, paving, etc. Site Address: 4500 Talbot Road SE The proposed Renton Senior Housing Facility site is located on two parcels adding up to 4.75 acres. The project is located east of the intersection between Talbot Road South and South 45th Place in Renton, Washington. The site is bordered to the north and south by existing commercial and residential development, to the east by undeveloped land, and to the west by Talbot Road South. A site vicinity map of the proposed project location is enclosed herein as Appendix B. The proposed construction includes the Senior Housing Facility building and pool house as well as the associated parking, utilities, and stormwater improvements, disturbing approximately 3.94 acres. Specifically, the proposed site improvements/construction activities for this project include the following: · Site preparation, grading, and erosion control activities · Construction of Senior Housing Facility and associated parking · Construction/installation of on-site water quality and flow control facilities · Extension of available utilities (i.e., water, sewer, etc.) Table 1 and Table 2 describe the land use of the existing and proposed drainage basins. See the Existing and Proposed Drainage Basin Exhibits in Appendix C. Renton Senior Housing 3 of 15 Technical Information Report Table 1: On-site Land Type Designations Summary Section LAND TYPE DESIGNATIONS AREA (ACRES) % OF TOTAL AREA Total Site Area 4.58 100 Existing Pervious Surface 4.58 100 Existing Impervious Surface 0 0 Drainage Basin Areas 4.58 100 Proposed Pervious Surface 0.92 20.09 Undisturbed Pervious 0.95 20.74 Proposed Pavement Surface 1.28 27.95 Proposed Roof Surface 1.00 21.83 Proposed Sidewalk Surface 0.43 9.39 Table 2: Bypass Basin Land Type Designations Summary Section LAND TYPE DESIGNATIONS AREA (ACRES) % OF TOTAL AREA Total Site Area 0.31 100 Existing Pervious Surface 0.29 93.55 Existing Impervious Surface 0.02 6.45 Drainage Basin Areas 0.31 100 Proposed Pervious Surface 0.19 61.29 Proposed Impervious Surface 0.12 38.71 A TIR worksheet is included in Appendix I. 1.2 PREDEVELOPED SITE CONDITIONS The site is heavily forested. A single-family residence once occupied a small portion of the site area but appears to have been demolished and removed from the property. The existing access road, however, still remains. Topography generally ascends gently to the east. The eastern site area maintains a general gradient of 30 percent while the central and western site area maintains a flatter gradient, on the order of approximately 10 percent. There are no current drainage flow control facilities on the site. For modeling purposes, the existing surface was analyzed to calculate the existing slopes throughout the development, see the table below for more information. Renton Senior Housing 4 of 15 Technical Information Report Table 3: Existing Slope Areas SLOPE (%) AREA (ACRES) 0-5 (Flat) 0.37 5-15 (Moderate) 2.59 15-100 (Steep) 1.79 1.3 SOILS According to the Geotechnical Study completed by Earth Solutions NW LLC (ESNW) in August 2017, the soils on-site contain topsoil in the upper 12 to 18 inches and the native soil below consists of silty sand. A geologic map that is referenced in the study identifies Ground Moraine Deposits across the site and surrounding areas. Groundwater seepage was identified in a few test pits two feet below existing grade when they were dug in November 2006. The test pit located in our detention facility (TP-5) groundwater seepage was encountered at approximately 2 feet below existing grade. It is believed groundwater is likely to be encountered during construction activities. They also determined, in general, the native soil they encountered is not suitable for infiltration. Due to no infiltration in the native soil and high groundwater, the detention vault will have a solid bottom. See Appendix G for the geotechnical report. 2. CONDITIONS AND REQUIREMENTS SUMMARY A Full Drainage Review is required for the project, according to Figure 1.1.2A: Flow Chart for Determining Type of Drainage Review Required. The flow chart is attached in Appendix A. According to the Manual, a project that requires a Full Drainage Review is also required to address all nine core requirements and all six special requirements. Summary of Compliance On-Site The stormwater design complies with all nine core requirements and all six special requirements as follows: Core Requirement #1 – Discharge at the Natural Location – Currently, stormwater runoff from the project parcel sheet flows east to west and into the City’s stormwater system located in Talbot Road. After construction, the majority of the stormwater runoff from the parcel will be collected and conveyed into a detention system. The stormwater runoff will be released into the City’s stormwater system at the predeveloped rates per Core Requirement #3. The frontage improvements and a portion of the west side of the parcel will bypass the stormwater system due to on-site grading. The detention system has been sized for this bypass basin. Additionally, approximately 0.10 acres of landscape area will continue to sheet flow as it does today. All of these areas are shown on the proposed basin areas exhibit in Appendix C. Core Requirement #2 – Offsite Analysis – Per Section 1.2.2 of the Manual, a Level 1 upstream and downstream analysis has been completed and can be found in Section 3 of this Report. No problems were identified in the analysis. The proposed project is required to meet Core Requirement #3 and therefore there are no anticipated adverse affects to the downstream systems. Stormwater runoff rates from the project parcel will match predeveloped conditions, and therefore are anticipated to be less than the rates today. Renton Senior Housing 5 of 15 Technical Information Report Core Requirement #3 – Flow Control – Using Reference 15-A: Flow Control Application Map of the Manual, the proposed project is located within a Flow Control Duration Standard area (Forested Conditions). There are no problems identified in the downstream conveyance and therefore the minimum area-specific flow control performance criteria will be applied to this project using Table 1.2.3.A. Flow control will be provided by a cast in place detention vault. The 2012 Western Washington Hydrology Model (WWHM) was used to size the facility and the flow control release structure. The detention system was sized to detain almost all of the stormwater runoff from the proposed project. It is important to note that the system was designed to overdetain the stormwater runoff on-site to account for the bypass basin that will not be collected in the on-site stormwater system. See Section 4 of this report for more information. Core Requirement #4 – Conveyance System – Per Section 1.2.4.1, the on-site conveyance system will be designed to meet the requirements for new systems. The on-site stormwater conveyance system is designed to have the capacity to convey and contain the 25-year peak flow for the developed conditions of the parcel. In the event that the structures overtop, stormwater runoff will continue to flow throughout the parking areas and to the west into Talbot Road as it does today. Core Requirement #5 – Construction Stormwater Pollution Prevention – A Construction Stormwater Pollution Prevention (CSWPP) Plan has been included in this report as Appendix H which describes the 13 required elements. Further, an erosion control plan has been prepared is part of the engineering plan set in Appendix F. The contractor may need to amend and update these plans as part of development and/or management of the SWPPP. The contractor will be responsible for preparing the full SWPPP which shall comply with all of the required elements and the Washington Department of Ecology requirements for coverage under the NPDES Construction Stormwater General Permit. Core Requirement #6 – Maintenance and Operations – All stormwater facilities on-site will be privately owned and maintained. An Operation and Maintenance Manual has been completed and included herein as Appendix J. The owner is aware they are responsible for operating and maintaining the stormwater system on-site. Core Requirement #7 – Financial Guarantees and Liability – The owner of the property will maintain liability insurance and post with the City of Renton a bond, assignment of funds, or certified check to meet this requirement6. Core Requirement #8 – Water Quality – The proposed project site is considered a multi-family land use and therefore per section 1.2.8.1A of the Manual enhanced treatment is required. Enhanced treatment will be provided for all of the stormwater runoff collected and combined from the pollution generating impervious surfaces, concrete, and landscape areas. The stormwater runoff from the roof area and the courtyards is conveyed separately and does not require treatment, therefore the stormwater runoff from these areas is conveyed directed to the detention system. A Modular Wetland System located on the west side of the parcel is an approved treatment facility and was appropriately sized using WWHM. The bypass basin will not receive any treatment, however, it only contains a small amount of pollution generating impervious surface. See Appendix C for the Treatment Basin Map and Section 4 of this report for more information of the specifications and sizing of the treatment facility. Renton Senior Housing 6 of 15 Technical Information Report Core Requirement #9 – On-site BMPs – BMPs will be used where feasible and to the maximum extent practicable according to the Large Lot BMP Requirements per Section 1.2.9.2.2 and Appendix C of the Manual. Due to the existing steep slopes throughout the project parcel, minimal to no infiltration, and high groundwater levels many of the BMPs are not feasible. See Section 4.4 of this report for further discussion. Special Requirement #1 – Other Adopted Area-Specific Requirements – No additional requirements are known at this time. Special Requirement #2 – Flood Hazard Area Delineation – The proposed project is not located in or adjacent to a flood hazard area. See the FEMA flood map attached in Appendix C. This Special Requirement is not applicable. Special Requirement #3 – Flood Protection Facilities – The proposed project does not rely on an existing flood protection facility. This Special Requirement is not applicable. Special Requirement #4 – Source Control – The proposed project requires a commercial site development permit, therefore water quality source controls applicable to the project will be applied in accordance with the King County Pollution Prevention Manual and Renton Municipal Code, Title IV. Water quality source controls will be installed in accordance with the King County Stormwater Pollution Prevent Manual. BMPs listed below are the minimum required for the site, additional BMPs not listed here may need to be implemented to meet the minimum requirements. · A-8 Storage of Solid and Food Wastes (Including Cooking Grease) · A-10 Treatment, Storage, or Disposal of Dangerous Wastes · A-14 Interior Washing Operations · A-26 Landscaping Activities and Vegetation Management Special Requirement #5 – Oil Control – The project is not considered a high-use site or a redevelopment project of any type; therefore, oil control is not required. Special Requirement #6 – Aquifer Protection Area – The project is not located in an Aquifer Protection Area. See the Groundwater Protection Areas Map in Appendix B. 3. OFFSITE ANALYSIS 3.1 TASK 1: DOWNSTREAM ANALYSIS A Level 1 Analysis was completed for this project. Stormwater from the project site will be collected, detained and released at the predeveloped rates to an existing stormwater system on Talbot Road. The existing system conveys the stormwater runoff down Talbot Road, west on South 43rd Street, through the Valley Medical Center Complex, and then is discharged into Panther Creek. The map below shows the downstream path and the location where it is discharged. Panther Creek is considered the natural discharge location and adverse effects are not anticipated. Storwmater runoff flows are anticipated to stay the same or decrease with the construction of this project and therefore no adverse effects to the downstream system are anticipated at this time. Offsite drainage courses will not be altered with the construction of this project. A small portion of the stormwater runoff from the project site (0.10 acres Renton Senior Housing 7 of 15 Technical Information Report of landscape) will continue to sheet flow down the hill and onto the neighboring parcel as it does today. This drainage pattern will not be altered in flow volumes or direction and therefore no adverse effects are anticipated. Additional site maps with contours can be found in Appendix F. An Offsite Analysis Drainage System Table has also been completed and included herein as Appendix D. Figure 1: Downstream Analysis 3.2 TASK 1: UPSTREAM ANALYSIS There is no foreseen offsite run-on from the adjacent roadway or parcels that will be tributary to the proposed stormwater system. The contours on and adjacent to the parcel were carefully studied to ensure that drainage patterns around the parcel will not be altered in such a way to cause downstream flooding or negative impacts. The east side of the parcel is located at the peak of an uphill slope. The adjacent parcels to the north and south slope away from the parcel and will be altered in such a way that the stormwater runoff from the parcel will no longer flow onto the adjacent areas. Instead the on- site stormwater runoff will be collected and detained on-site and therefore improving the upstream and downstream drainage systems. 3.3 TASK 2: RESOURCE REVIEW Flood Hazard Zone The flood hazard areas within this portion of Renton, Washington, are delineated on the Federal Emergency Mapping Agency (FEMA) National Flood Insurance Program – Flood Insurance Rate Map Renton Senior Housing 8 of 15 Technical Information Report (FIRM) No 53033C0979F, revised May 16, 1995. The project site does not lie in a Flood Zone. See Appendix C for a copy of the FEMA map. Critical Areas According to City of Renton’s GIS site, there are critical areas on the eastern portion of the site. There is high erosion hazard, steep slopes, landslide potential, and regulated slopes. The critical areas located on the project parcels will remain undeveloped. The closest wetland to the site is upstream about 700 feet away. 3.4 TASK 3: FIELD INVESTIGATION Level 1 Inspection: 1. Investigate any problems or reported or observed during the resource review. No problems were identified during the site visit or throughout the resource review on the site or in the downstream conveyance system. 2. Locate all existing/potential constrictions or lack of capacity in the existing drainage system. All existing drainage systems up to the outfall have capacity for the existing stormwater runoff conditions. The proposed project will not increase the runoff flows from the site and therefore all conveyance systems are anticipated to have capacity. One potential constriction identified was the existing depth of the stormwater system located in Talbot Road. In order to allow a minimum 1’ of cover down to the existing catch basin, the invert elevation in the catch basin will be slightly lower than the invert elevation out of the structure. 3. Identify all existing/potential downstream drainage problems as defined in Section 1.2.2.1. There are no known downstream drainage problems or water quality problems requiring special attention at this time. 4. Identify existing/potential overtopping, scouring, bank sloughing, or sedimentation. There are no known existing/potential overtopping, scouring, bank sloughing, or sedimentation at this time. The proposed project will not increase the runoff flows and therefore no potential problems are anticipated. 5. Identify significant destruction of aquatic habitat or organisms (e.g., severe siltation, bank erosion, or incision in a stream). There will be no destruction of aquatic habitat or organisms with the construction of this project. 6. Collect qualitative data on features such as land use, impervious surfaces, topography, and soil types. See Section 1 of this report for all of this qualitative data on the project site. 7. Collect information on pipe sizes, channel characteristics, drainage structures, and relevant critical areas (e.g., wetlands, streams, steep slopes). Survey information was provided for the existing utilities location, sizing and depth. Critical areas in the form of steep slopes are on the project site, these areas will remain undeveloped throughout construction. 8. Verify tributary basins delineated in Task 1. The proposed project site is one tributary basin that discharges stormwater runoff into the City of Renton stormwater system. The City of Renton stormwater system is made up of multiple tributary basins upstream from the project site. Renton Senior Housing 9 of 15 Technical Information Report 9. Contact neighboring property owners or residents in the area about past or existing drainage problems, and describe these in the report (optional). None of the neighboring property owners had concerns of stormwater problems. 10. Note the date and weather conditions at the time of the inspection. January 24th 2019, sprinkling, relatively dry An in-depth field investigation was completed and an Offsite Analysis Drainage System Table has been included herein as Appendix D. 3.5 TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS An Offsite Analysis Drainage System Table is attached in Appendix D, no problems were identified at this time. 4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.1 EXISTING SITE HYDROLOGY Currently, on-site generated stormwater that does not infiltrate directly in the soils sheet flows offsite towards Talbot Road. There are no current drainage flow control facilities on the site. The geotechnical report classified the site soils as type C. See attached Existing Drainage Basin Exhibit in Appendix C. 4.2 DEVELOPED SITE HYDROLOGY The developed site hydrology was modeled using the areas in the table below. Refer to Appendix F for the stormwater plan sheets and the full proposed stormwater design. Table 4: WWHM Modelling Area Breakdown LAND TYPE DESIGNATIONS AREA (ACRES) % OF TOTAL AREA Total On-Site Basin Areas 4.48 91.62 Proposed Roadway/Parking Lot 1.28 26.18 Proposed Roof 1.00 20.45 Proposed Concrete 0.43 8.79 Proposed Landscape 0.82 16.77 Undisturbed Pervious (Forested, Steep) 0.95 19.43 Bypass Basin Areas 0.31 6.35 Proposed Driveway Entrance 0.06 1.23 Renton Senior Housing 10 of 15 Technical Information Report Proposed Concrete 0.06 1.23 Proposed Landscape 0.19 3.89 Off-Site Basin Areas* 0.10 2.03 Proposed Landscape 0.10 2.03 *The Off-Site basin area was not included in modeling calculations for detention and it does not require water quality treatment. 4.3 PERFORMANCE STANDARDS According to Section 1.2.3.1 in the Manual and the City of Renton Flow Control Application Map, attached in Appendix B, the site must meet the Flow Control Duration Standard – Matching Forested requirements. From Table 1.2.3.A the project must apply the Flow Control Duration Standard, which matches the flow duration of predeveloped rates for forested site conditions over the range of flows extending from 50% of the two year up to the full 50-year flow and matches peaks for the two- and ten- year return periods. See Section 4.4 of this section for the design of the flow control system. According to Section 1.2.4.1 of the Manual, this project requires the new pipe systems to be able to convey and contain the 25-year peak flows. See Section 5 for the conveyance system analysis. The project is a commercial site and according to Section 1.2.8.1.A of the Manual, enhanced treatment is required. No additional source control or oil control is required. See part 4.5 of this section for the design of the water quality system. 4.4 ON-SITE BMPS Using Appendix C of the Manual, specific BMPs were determined feasible or infeasible for this project. A geotechnical report was completed in August 2017. It was determined in the report that the site is not suitable for infiltration. Groundwater seepage was also encountered in some areas at a depth of two feet below the existing ground. See below for more in-depth infeasibility discussion. Section C.1.3.2 of the Manual lays out Large Lot BMP Requirements. · Requirement #1: Full Dispersion (Section C2.1) – Per the Infeasibility Criteria in Section C2.1, Full dispersion is not considered feasible where the stormwater discharge would be towards slopes greater than 15%. The parcel does not have adjacent native vegetation sloping away from the impervious surfaces. · Requirement #2: Full Infiltration of Roof Runoff (Section C2.2) – Per the Infeasibility Criteria in Section C2.2, Full infiltration is not considered feasible where geotechnical evaluation deems infiltration not possible. Per the geotechnical report completed in August 2017 (See Appendix G) the site was determined not to be suitable for infiltration. It is also important to note that steep slopes and high groundwater also make infiltration not feasible for this project. · Requirement #3: Full Infiltration (Section C2.2), Limited Infiltration (Section C2.3), Bioretention (Section C2.6), Permeable Pavement (Section C2.7) – Per the Infeasibility Criteria in Sections C2.2, C2.3, C2.6, and C2.7, none of these BMPs are feasible for the same reasons Renton Senior Housing 11 of 15 Technical Information Report listed above. Per the geotechnical report and the steep slopes on-site, infiltration is not feasible for this project. It was stated in the geotechnical report that small portions of soils located throughout the site have the potential for infiltration, however an infiltration test was not completed on these soils. In our experience the inconsistencies of the soils throughout the parcel in conjunction with the groundwater levels make infiltration a dangerous risk to design, therefore infiltration is not feasible. · Requirement #4: Basic Dispersion (Section C2.4) – Per the Infeasiblity Criteria in Section C2.4, basic dispersion is not feasible for the project due to the steep slopes and the geotechnical report (see above). The surrounding areas of the proposed site plan do not contain the required slopes (<15%) and distances of native vegetation (50’ to 100’ depending on the BMP application) to be able to utilize basic dispersion. · Requirement #5: On-Site BMP Application Rates – Per Table C1.3.A, the project site has approximately 55% proposed impervious surface coverage, and therefore requires that 35% of the target impervious surface be mitigated by on-site BMPs. Approximately 0.95 acres of the project site will be considered undisturbed, and will remain forested with native vegetation. Due to the steep slopes (over 15%) of the undisturbed portion of the project site, none of this area can be used for the reduced impervious surface credit (Section C2.9), Native Growth Retention Credit (Section C2.10), and the Tree Retention Credit (Section C2.14). Due to the retaining walls surrounding the project, no stormwater runoff will be allowed to flow onto the native vegetation or the steep slopes, therefore making these credits infeasible. · Requirement #6 – The soil moisture holding capacity of the new pervious surfaces will be protected in accordance with the soil amendment BMP as detailed in Section C2.13. All the areas that are being preserved will be protected from compaction during construction. · Requirement #7 – The proposed roof downspouts will be connected into the stormwater detention vault on-site, therefore not connecting into the local drainage system and not requiring a perforated pipe connection per Section C2.11. 4.5 FLOW CONTROL SYSTEM One (1) on-site detention vault will be constructed as a part of the site improvements for this project. The detention vault will provide flow control for 4.48 acres of the proposed development. The stormwater detention vault will be built using cast-in-place concrete vault sections. The vault will be 7- feet deep in total depth, including 0.5 feet of freeboard and 0.5 feet of dead storage used for sediment collection. The vault will be irregularly shaped with a total storage volume of 51,575 C.F. See the stormwater plans in Appendix F. The vault has been designed to release stormwater off-site at the predeveloped flow rates of 50% of the two-year peak flow up to the 50-year peak flow and matches peaks for the two- and ten-year return periods. A bypass basin containing 0.31 acres was also modelled to account for the stormwater runoff flows from the project area that will not be receiving flow control. The sizing of the detention vault accounts for this bypass basin. WWHM2012 is an approved continuous flow simulation method and was used to model the flow control for the proposed stormwater system. See the figures below taken from the WWHM report included in Appendix E for the pre-developed and developed runoff flows comparison. See the full WWHM report in Appendix E for more information. Renton Senior Housing 12 of 15 Technical Information Report Figure 2: Predeveloped Runoff Flows Figure 3: Developed Runoff Flows Figure 3: Analysis Results The vault will be constructed with a flow control structure, which will include a 1.27-inch diameter orifice at the bottom of the structure, a 2.25-inch diameter orifice 4 feet from the bottom of the structure, a 1.4-inch diameter orifice 5.20 feet from the bottom of the structure, and an 18-inch diameter riser at 6 feet from the bottom of the structure, which allows one foot of freeboard. It is important to note that the vault will have a solid bottom due to the project site not being suitable for infiltration as well as the high groundwater, as noted in the geotechnical report. 4.6 WATER QUALITY SYSTEM A Modular Wetland System will be used to treat all of the runoff that is combined in the on-site conveyance system. This includes all of the pollution-generating impervious surfaces, as well as the concrete walkways and landscaping areas that flow onto the PGIS or in the same conveyance system. This is per the Target Surfaces requirement in Section 1.2.8.1 of the Manual. See Appendix C for the treatment basin areas. The Modular Wetland Systems are equipped with an internal bypass and therefore the off-line flow can be used for treatment requirements. Using WWHM, an off-line flow of 0.1475 cfs needs to be treated. Figure 5: Required On-Site Water Quality Flow Rate Renton Senior Housing 13 of 15 Technical Information Report The MWS-6-8-C will provide the required treatment for this basin. The Modular Wetland is placed upstream of the underground vault. See the stormwater plans in Appendix F. 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN The total runoff for the on-site drainage basin (4.48 acres) is 2.41 cfs during the 100-year storm. The capacity of a 12-inch PVC pipe sloped at 0.5% is 3.27 cfs. Because the roof area does not need to be treated, it will be collected through downspouts and discharged directly into the vault. The capacity of an 8-inch roof drain pipe sloped at 0.5% is 1.11 cfs. The roof area is approximately 1-acre with a developed 100-year peak flow of 0.77 cfs. See Appendix E for design calculations. 6. SPECIAL REPORTS AND STUDIES A geotechnical report was finalized by ESNW on August 3, 2017, and is enclosed herein as Appendix G. A SEPA checklist will be submitted by the Applicant. 7. OTHER PERMITS Utility, grading, and building permits may need to be secured prior to beginning construction activities. Construction Stormwater General Permit (NPDES) from the Department of Ecology (DOE) is also required. 8. CSWPP ANALYSIS AND DESIGN 8.1 ESC PLAN ANALYSIS AND DESIGN The site was designed with the Erosion and Sediment Control Standards in mind. Each measure is described in the Construction Stormwater Pollution Prevention Plan included as Appendix H. 1. Clearing Limits: Prior to site clearing or grading, areas to remain undisturbed during project construction will be delineated on the project’s ESC plan and physically marked on the project site. 2. Cover Measures: Temporary and permanent cover measures shall be provided when necessary to protect disturbed areas. 3. Perimeter Protection: Perimeter protection to filter sediment from sheet flow shall be provided downstream of all disturbed areas prior to upslope grading. 4. Traffic Area Stabilization: Unsurfaced entrances, roads, and parking areas used by construction traffic shall be stabilized to minimize erosion and tracking of sediment offsite. 5. Sediment Retention: Surface water collected from all disturbed areas of the site shall be routed through a sediment pond or trap prior to release from the site, except those areas at the perimeter of Renton Senior Housing 14 of 15 Technical Information Report the site small enough to be treated solely with perimeter protection. Sediment retention facilities shall be installed prior to grading any contributing area. 6. Surface Water Collection: Surface water collection measures (e.g., ditches, berms, etc.) shall be installed to intercept all surface water from disturbed areas, convey it to a sediment pond or trap, and discharge it downstream of any disturbed areas. Areas at the perimeter of the site, which are small enough to be treated solely with perimeter protection, do not require surface water collection. Significant sources of upstream surface water that drain onto disturbed areas shall be intercepted and conveyed to a stabilized discharge point downstream of the disturbed areas. Surface water collection measures shall be installed concurrently with or immediately following rough grading and shall be designed, constructed, and stabilized as needed to minimize erosion. 7. Dewatering Control: The water resulting from construction site dewatering activities must be treated prior to discharge or disposed of as specified. 8. Dust Control: Preventative measures to minimize wind transport of soil shall be implemented when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources. 9. Flow Control: Surface water from disturbed areas must be routed through the project’s onsite flow control facility or other provisions must be made to prevent increases in the existing site conditions two- year and ten-year runoff peaks discharging from the project site during construction (flow control facility, runoff treatment facility, and on-site BMP areas [existing or proposed] shall not be used for this purpose). 10. Control Pollutants: Stormwater pollution prevention (SWPPS) measures are required to prevent, reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or watercourses from construction-related activities such as materials delivery and storage, on-site equipment fueling and maintenance, demolition of existing buildings and disposition of demolition materials and other waste, and concrete handling, washout and disposal. Section D.2.2 of the Manual describes BMPs specific to this purpose; additionally, several of the ESC BMPs described herein are applicable. 11. Protect Existing and Proposed Stormwater Facilities and On-site BMPs: Sedimentation and soil compaction reduce the infiltration capacity of native and engineered soils. Protection measures shall be applied/installed and maintained so as to prevent adverse impacts to existing stormwater facilities and on-site BMPs and areas of proposed stormwater facilities and on-site BMPs for the project. Adverse impacts can prompt the requirement to restore or replace affected stormwater facilities and on-site BMPs. 12. Maintain Protective BMPs: Protection measures shall be maintained to ensure continued performance of their intended function, to prevent adverse impacts to existing BMPs/facilities and areas of proposed BMPs/facilities, and protect other disturbed areas of the project. 13. Manage the Project: Coordination and timing of site development activities relative to ESC concerns and timely inspection, maintenance, and update of protective measures are necessary to effectively manage the project and ensure the success of protective ESC and SWPPS design and implementation. See Appendix D of the Manual for further discussion of Erosion and Sediment Control. Renton Senior Housing 15 of 15 Technical Information Report The steep slopes on site will remain undisturbed. Where retaining walls are constructed, footing drains will be installed to help reduce erosion problems. 8.2 SWPPS PLAN DESIGN A site-specific Construction Stormwater Pollution Prevention Plan is enclosed herein as Appendix H. In general see below for common Spill Prevention measures: · Follow effective pollutant handling and disposal procedures. · Provide cover and containment for materials, fuel, and other pollutants. · Manage the project site to maximize pollutant control and minimize pollutant sources. · Protect from spills and drips of petroleum products and other pollutants. · Avoid overapplication or untimely application of chemicals and fertilizers. · Prevent or treat contamination of stormwater runoff by pH modifying sources. 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT A Bond Quantities Worksheet, facility summaries, and declaration of covenant(s) for privately maintained flow control facilities is enclosed herein as Appendix H. 10. OPERATIONS AND MAINTENANCE MANUAL A site-specific Operations and Maintenance Manual is enclosed herein as Appendix J. APPENDIX A DETERMINATION OF MINIMUM REQUIREMENTS WORKSHEETS RJ Development Ross Jarvis, PE SCJ Alliance (360) 352-1465 Renton Senior Housing 23 N 5 E 31 12/26/17 12/26/17 Black River Drainage Basin Ground Moraine Deposits 5%-30%Yes in parts 5.1.3 Detention Vault Marley Kirkham 425-449-4704 425-449-4704 Modular Wetland & Stormfilter 06/19/2019 APPENDIX B SITE VICINITY MAP PROJECT LOCATION PROJECT LOCATION PROJECT LOCATION APPENDIX C BASIN MAP EXHIBITS TALBOT ROAD S.SCALE IN FEET03060SEC. 31, T23N., R5E., W.M.SITE INFORMATIONBYPASS INFORMATIONJOB No.:DRAWING FILE No.:DATE:HORIZONTAL SCALE:EXHIBIT No:SHEET No:8730 TALLON LANE NE, SUITE 200, LACEY, WA 98516P: 360-352-1465 F: 360-352-1509SCJALLIANCE.COM1"=30'APRIL, 20192386.03EXISTING STORMWATER BASIN.dwgEXISTING STORMWATER BASINRENTON SENIOR HOUSINGEX-011 TALBOT ROAD S.TALBOT ROAD SECCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCSCALE IN FEET03060SEC. 31, T23N., R5E., W.M.SITE INFORMATIONBYPASS BASIN INFORMATIONOFFSITE INFORMATION*JOB No.:DRAWING FILE No.:DATE:HORIZONTAL SCALE:EXHIBIT No:SHEET No:8730 TALLON LANE NE, SUITE 200, LACEY, WA 98516P: 360-352-1465 F: 360-352-1509SCJALLIANCE.COM1"=30'APRIL, 20192386.03PROPOSED STORMWATER BASIN.dwgPROPOSED STORMWATER BASINRENTON SENIOR HOUSINGEX-022 TALBOT ROAD S.TALBOT ROAD SECCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCSCALE IN FEET03060SEC. 31, T23N., R5E., W.M.TREATMENT INFORMATIONJOB No.:DRAWING FILE No.:DATE:HORIZONTAL SCALE:EXHIBIT No:SHEET No:8730 TALLON LANE NE, SUITE 200, LACEY, WA 98516P: 360-352-1465 F: 360-352-1509SCJALLIANCE.COM1"=30'APRIL, 20192386.03TREATMENT STORMWATER BASIN.dwgTREATMENT STORMWATER BASINRENTON SENIOR HOUSINGEX-033 PROJECT LOCATION APPENDIX D OFF-SITE ANALYSIS Black River Drainage Basin03/01/2019Sheet Flow (West side of Parcel)Parcel Area, steep slopes0-50%N/AN/ANot LikelyFlow Control/TreatmentProposed Site Improvements0-5%N/AN/ASystem Failure = follow historic drainage paths tothe eastDownstream City of Renton system is not anticipated to beadversely affected with the construction of this project. Theproposed stormwater design meets all City of Rentonrequirements and will release stormwater runoff at or below theexisting stormwater flows from the parcel. APPENDIX E DESIGN CALCULATIONS AND COMPUTATIONS WWHM2012 PROJECT REPORT DETENTION 2386.03 Renton 4/22/2019 8:53:42 AM Page 2 General Model Information Project Name:2386.03 Renton Site Name: Site Address: City: Report Date:4/22/2019 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 2386.03 Renton 4/22/2019 8:53:42 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.6 C, Forest, Mod 2.4 C, Forest, Steep 1.79 Pervious Total 4.79 Impervious Land Use acre Impervious Total 0 Basin Total 4.79 Element Flows To: Surface Interflow Groundwater 2386.03 Renton 4/22/2019 8:53:42 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Steep 0.95 C, Lawn, Mod 0.82 Pervious Total 1.77 Impervious Land Use acre ROADS FLAT 1.28 ROOF TOPS FLAT 1 SIDEWALKS FLAT 0.43 Impervious Total 2.71 Basin Total 4.48 Element Flows To: Surface Interflow Groundwater Vault Vault 2386.03 Renton 4/22/2019 8:53:42 AM Page 5 Frontage Bypass:Yes GroundWater:No Pervious Land Use acre C, Lawn, Steep 0.19 Pervious Total 0.19 Impervious Land Use acre ROADS MOD 0.06 SIDEWALKS FLAT 0.06 Impervious Total 0.12 Basin Total 0.31 Element Flows To: Surface Interflow Groundwater 2386.03 Renton 4/22/2019 8:53:42 AM Page 7 Mitigated Routing Vault Width:85.95 ft. Length:100 ft. Depth:7 ft. Discharge Structure Riser Height:6 ft. Riser Diameter:18 in. Orifice 1 Diameter:1.27 in.Elevation:0 ft. Orifice 2 Diameter:2.25 in.Elevation:4 ft. Orifice 3 Diameter:1.4 in.Elevation:5.2 ft. Element Flows To: Outlet 1 Outlet 2 Vault Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.197 0.000 0.000 0.000 0.0778 0.197 0.015 0.012 0.000 0.1556 0.197 0.030 0.017 0.000 0.2333 0.197 0.046 0.021 0.000 0.3111 0.197 0.061 0.024 0.000 0.3889 0.197 0.076 0.027 0.000 0.4667 0.197 0.092 0.029 0.000 0.5444 0.197 0.107 0.032 0.000 0.6222 0.197 0.122 0.034 0.000 0.7000 0.197 0.138 0.036 0.000 0.7778 0.197 0.153 0.038 0.000 0.8556 0.197 0.168 0.040 0.000 0.9333 0.197 0.184 0.042 0.000 1.0111 0.197 0.199 0.044 0.000 1.0889 0.197 0.214 0.045 0.000 1.1667 0.197 0.230 0.047 0.000 1.2444 0.197 0.245 0.048 0.000 1.3222 0.197 0.260 0.050 0.000 1.4000 0.197 0.276 0.051 0.000 1.4778 0.197 0.291 0.053 0.000 1.5556 0.197 0.306 0.054 0.000 1.6333 0.197 0.322 0.055 0.000 1.7111 0.197 0.337 0.057 0.000 1.7889 0.197 0.353 0.058 0.000 1.8667 0.197 0.368 0.059 0.000 1.9444 0.197 0.383 0.061 0.000 2.0222 0.197 0.399 0.062 0.000 2.1000 0.197 0.414 0.063 0.000 2.1778 0.197 0.429 0.064 0.000 2.2556 0.197 0.445 0.065 0.000 2.3333 0.197 0.460 0.066 0.000 2.4111 0.197 0.475 0.068 0.000 2.4889 0.197 0.491 0.069 0.000 2.5667 0.197 0.506 0.070 0.000 2.6444 0.197 0.521 0.071 0.000 2.7222 0.197 0.537 0.072 0.000 2.8000 0.197 0.552 0.073 0.000 2.8778 0.197 0.567 0.074 0.000 2386.03 Renton 4/22/2019 8:53:42 AM Page 8 2.9556 0.197 0.583 0.075 0.000 3.0333 0.197 0.598 0.076 0.000 3.1111 0.197 0.613 0.077 0.000 3.1889 0.197 0.629 0.078 0.000 3.2667 0.197 0.644 0.079 0.000 3.3444 0.197 0.659 0.080 0.000 3.4222 0.197 0.675 0.081 0.000 3.5000 0.197 0.690 0.081 0.000 3.5778 0.197 0.705 0.082 0.000 3.6556 0.197 0.721 0.083 0.000 3.7333 0.197 0.736 0.084 0.000 3.8111 0.197 0.752 0.085 0.000 3.8889 0.197 0.767 0.086 0.000 3.9667 0.197 0.782 0.087 0.000 4.0444 0.197 0.798 0.117 0.000 4.1222 0.197 0.813 0.136 0.000 4.2000 0.197 0.828 0.151 0.000 4.2778 0.197 0.844 0.162 0.000 4.3556 0.197 0.859 0.173 0.000 4.4333 0.197 0.874 0.182 0.000 4.5111 0.197 0.890 0.191 0.000 4.5889 0.197 0.905 0.199 0.000 4.6667 0.197 0.920 0.206 0.000 4.7444 0.197 0.936 0.213 0.000 4.8222 0.197 0.951 0.220 0.000 4.9000 0.197 0.966 0.227 0.000 4.9778 0.197 0.982 0.233 0.000 5.0556 0.197 0.997 0.239 0.000 5.1333 0.197 1.012 0.245 0.000 5.2111 0.197 1.028 0.256 0.000 5.2889 0.197 1.043 0.272 0.000 5.3667 0.197 1.058 0.283 0.000 5.4444 0.197 1.074 0.293 0.000 5.5222 0.197 1.089 0.302 0.000 5.6000 0.197 1.105 0.311 0.000 5.6778 0.197 1.120 0.319 0.000 5.7556 0.197 1.135 0.326 0.000 5.8333 0.197 1.151 0.334 0.000 5.9111 0.197 1.166 0.341 0.000 5.9889 0.197 1.181 0.348 0.000 6.0667 0.197 1.197 0.628 0.000 6.1444 0.197 1.212 1.230 0.000 6.2222 0.197 1.227 2.004 0.000 6.3000 0.197 1.243 2.875 0.000 6.3778 0.197 1.258 3.766 0.000 6.4556 0.197 1.273 4.602 0.000 6.5333 0.197 1.289 5.316 0.000 6.6111 0.197 1.304 5.866 0.000 6.6889 0.197 1.319 6.252 0.000 6.7667 0.197 1.335 6.614 0.000 6.8444 0.197 1.350 6.926 0.000 6.9222 0.197 1.365 7.225 0.000 7.0000 0.197 1.381 7.511 0.000 7.0778 0.197 1.396 7.787 0.000 7.1556 0.000 0.000 8.053 0.000 2386.03 Renton 4/22/2019 8:53:42 AM Page 9 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:4.79 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:1.96 Total Impervious Area:2.83 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.168869 5 year 0.27213 10 year 0.337761 25 year 0.415257 50 year 0.468634 100 year 0.518299 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.136616 5 year 0.200989 10 year 0.252255 25 year 0.32787 50 year 0.39274 100 year 0.465516 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.189 0.154 1950 0.217 0.152 1951 0.351 0.331 1952 0.120 0.091 1953 0.094 0.096 1954 0.135 0.101 1955 0.236 0.115 1956 0.184 0.128 1957 0.160 0.136 1958 0.165 0.105 2386.03 Renton 4/22/2019 8:54:11 AM Page 10 1959 0.138 0.094 1960 0.250 0.268 1961 0.136 0.133 1962 0.091 0.082 1963 0.122 0.112 1964 0.161 0.114 1965 0.113 0.116 1966 0.108 0.098 1967 0.252 0.158 1968 0.142 0.137 1969 0.143 0.124 1970 0.122 0.115 1971 0.130 0.137 1972 0.273 0.232 1973 0.128 0.104 1974 0.131 0.122 1975 0.197 0.142 1976 0.137 0.117 1977 0.021 0.100 1978 0.123 0.111 1979 0.069 0.103 1980 0.314 0.239 1981 0.103 0.120 1982 0.232 0.239 1983 0.179 0.117 1984 0.116 0.092 1985 0.066 0.110 1986 0.294 0.155 1987 0.258 0.239 1988 0.106 0.091 1989 0.064 0.088 1990 0.580 0.305 1991 0.320 0.267 1992 0.136 0.107 1993 0.131 0.089 1994 0.044 0.079 1995 0.174 0.117 1996 0.398 0.322 1997 0.331 0.279 1998 0.092 0.125 1999 0.324 0.217 2000 0.134 0.116 2001 0.026 0.112 2002 0.151 0.168 2003 0.212 0.145 2004 0.270 0.322 2005 0.185 0.123 2006 0.198 0.122 2007 0.437 0.477 2008 0.557 0.370 2009 0.260 0.162 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.5796 0.4768 2 0.5573 0.3702 3 0.4368 0.3313 2386.03 Renton 4/22/2019 8:54:11 AM Page 11 4 0.3984 0.3224 5 0.3514 0.3216 6 0.3310 0.3050 7 0.3243 0.2794 8 0.3198 0.2683 9 0.3140 0.2671 10 0.2938 0.2393 11 0.2727 0.2393 12 0.2701 0.2387 13 0.2597 0.2320 14 0.2581 0.2173 15 0.2516 0.1675 16 0.2496 0.1617 17 0.2360 0.1580 18 0.2316 0.1551 19 0.2171 0.1539 20 0.2119 0.1520 21 0.1975 0.1449 22 0.1971 0.1423 23 0.1892 0.1373 24 0.1853 0.1367 25 0.1844 0.1356 26 0.1790 0.1333 27 0.1740 0.1275 28 0.1647 0.1251 29 0.1613 0.1240 30 0.1597 0.1232 31 0.1508 0.1224 32 0.1431 0.1218 33 0.1421 0.1200 34 0.1378 0.1169 35 0.1374 0.1168 36 0.1361 0.1168 37 0.1356 0.1162 38 0.1346 0.1155 39 0.1342 0.1154 40 0.1314 0.1146 41 0.1306 0.1137 42 0.1303 0.1125 43 0.1278 0.1118 44 0.1235 0.1115 45 0.1216 0.1103 46 0.1215 0.1074 47 0.1195 0.1046 48 0.1157 0.1043 49 0.1134 0.1034 50 0.1075 0.1006 51 0.1058 0.0997 52 0.1028 0.0977 53 0.0938 0.0956 54 0.0917 0.0941 55 0.0909 0.0925 56 0.0691 0.0912 57 0.0661 0.0906 58 0.0642 0.0890 59 0.0442 0.0876 60 0.0261 0.0823 61 0.0209 0.0793 2386.03 Renton 4/22/2019 8:54:11 AM Page 13 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0844 14108 13026 92 Pass 0.0883 12799 8861 69 Pass 0.0922 11627 6098 52 Pass 0.0961 10600 4956 46 Pass 0.1000 9854 4455 45 Pass 0.1038 8932 4036 45 Pass 0.1077 8147 3749 46 Pass 0.1116 7488 3489 46 Pass 0.1155 6868 3307 48 Pass 0.1194 6288 3159 50 Pass 0.1232 5807 3009 51 Pass 0.1271 5343 2885 53 Pass 0.1310 4913 2753 56 Pass 0.1349 4635 2691 58 Pass 0.1388 4284 2603 60 Pass 0.1426 3976 2500 62 Pass 0.1465 3683 2408 65 Pass 0.1504 3418 2312 67 Pass 0.1543 3198 2235 69 Pass 0.1582 2982 2167 72 Pass 0.1621 2789 2085 74 Pass 0.1659 2648 2030 76 Pass 0.1698 2473 1965 79 Pass 0.1737 2282 1893 82 Pass 0.1776 2082 1814 87 Pass 0.1815 1921 1720 89 Pass 0.1853 1769 1629 92 Pass 0.1892 1641 1557 94 Pass 0.1931 1502 1489 99 Pass 0.1970 1424 1427 100 Pass 0.2009 1302 1355 104 Pass 0.2047 1190 1278 107 Pass 0.2086 1099 1195 108 Pass 0.2125 1029 1112 108 Pass 0.2164 979 1033 105 Pass 0.2203 927 961 103 Pass 0.2241 881 882 100 Pass 0.2280 830 802 96 Pass 0.2319 796 746 93 Pass 0.2358 746 662 88 Pass 0.2397 702 605 86 Pass 0.2435 659 563 85 Pass 0.2474 619 519 83 Pass 0.2513 574 467 81 Pass 0.2552 535 428 80 Pass 0.2591 492 378 76 Pass 0.2630 460 343 74 Pass 0.2668 425 320 75 Pass 0.2707 393 298 75 Pass 0.2746 355 283 79 Pass 0.2785 319 266 83 Pass 0.2824 289 249 86 Pass 0.2862 261 232 88 Pass 2386.03 Renton 4/22/2019 8:54:11 AM Page 14 0.2901 238 214 89 Pass 0.2940 221 201 90 Pass 0.2979 193 180 93 Pass 0.3018 170 166 97 Pass 0.3056 152 154 101 Pass 0.3095 132 142 107 Pass 0.3134 120 129 107 Pass 0.3173 106 104 98 Pass 0.3212 89 87 97 Pass 0.3250 79 76 96 Pass 0.3289 73 68 93 Pass 0.3328 67 62 92 Pass 0.3367 57 56 98 Pass 0.3406 52 47 90 Pass 0.3444 50 43 86 Pass 0.3483 44 40 90 Pass 0.3522 40 38 95 Pass 0.3561 36 34 94 Pass 0.3600 35 29 82 Pass 0.3639 32 26 81 Pass 0.3677 30 23 76 Pass 0.3716 27 21 77 Pass 0.3755 26 18 69 Pass 0.3794 22 15 68 Pass 0.3833 20 13 65 Pass 0.3871 17 13 76 Pass 0.3910 15 9 60 Pass 0.3949 14 7 50 Pass 0.3988 13 6 46 Pass 0.4027 11 6 54 Pass 0.4065 7 5 71 Pass 0.4104 6 5 83 Pass 0.4143 6 5 83 Pass 0.4182 6 4 66 Pass 0.4221 5 4 80 Pass 0.4259 4 4 100 Pass 0.4298 4 4 100 Pass 0.4337 4 4 100 Pass 0.4376 3 3 100 Pass 0.4415 3 3 100 Pass 0.4453 3 3 100 Pass 0.4492 3 3 100 Pass 0.4531 3 3 100 Pass 0.4570 3 3 100 Pass 0.4609 3 3 100 Pass 0.4648 3 2 66 Pass 0.4686 3 1 33 Pass 2386.03 Renton 4/22/2019 8:54:20 AM Page 18 Appendix Predeveloped Schematic 2386.03 Renton 4/22/2019 8:54:20 AM Page 19 Mitigated Schematic 2386.03 Renton 4/22/2019 8:54:20 AM Page 33 Disclaimer Legal Notice 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. 2005-2019; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com WWHM2012 PROJECT REPORT ON-SITE TREATMENT 2386.03 Renton Treatment 2/27/2019 2:00:22 PM Page 2 General Model Information Project Name:2386.03 Renton Treatment Site Name: Site Address: City: Report Date:2/27/2019 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/07/12 Version:4.2.15 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 2386.03 Renton Treatment 2/27/2019 2:00:22 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 3.19 Pervious Total 3.19 Impervious Land Use acre Impervious Total 0 Basin Total 3.19 Element Flows To: Surface Interflow Groundwater 2386.03 Renton Treatment 2/27/2019 2:00:22 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Steep 0.95 C, Lawn, Flat 0.64 Pervious Total 1.59 Impervious Land Use acre ROADS FLAT 1.28 SIDEWALKS FLAT 0.32 Impervious Total 1.6 Basin Total 3.19 Element Flows To: Surface Interflow Groundwater 2386.03 Renton Treatment 2/27/2019 2:00:22 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:3.19 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:1.59 Total Impervious Area:1.6 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.094983 5 year 0.155638 10 year 0.194638 25 year 0.24103 50 year 0.273164 100 year 0.303179 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.674184 5 year 0.872453 10 year 1.009697 25 year 1.190348 50 year 1.330401 100 year 1.475308 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.109 0.931 1950 0.130 0.869 1951 0.208 0.601 1952 0.065 0.447 1953 0.053 0.483 1954 0.081 0.557 1955 0.129 0.608 1956 0.104 0.601 1957 0.084 0.732 1958 0.093 0.544 2386.03 Renton Treatment 2/27/2019 2:00:52 PM Page 8 1959 0.080 0.517 1960 0.143 0.631 1961 0.079 0.608 1962 0.049 0.485 1963 0.067 0.588 1964 0.095 0.545 1965 0.063 0.741 1966 0.061 0.481 1967 0.146 0.836 1968 0.082 0.903 1969 0.080 0.668 1970 0.064 0.638 1971 0.072 0.746 1972 0.158 0.835 1973 0.070 0.428 1974 0.077 0.694 1975 0.108 0.745 1976 0.077 0.557 1977 0.011 0.520 1978 0.065 0.649 1979 0.039 0.881 1980 0.185 0.947 1981 0.058 0.695 1982 0.120 1.033 1983 0.103 0.755 1984 0.062 0.509 1985 0.037 0.679 1986 0.163 0.625 1987 0.144 0.872 1988 0.057 0.516 1989 0.038 0.645 1990 0.344 1.468 1991 0.182 1.100 1992 0.074 0.509 1993 0.073 0.416 1994 0.024 0.431 1995 0.104 0.609 1996 0.241 0.735 1997 0.186 0.684 1998 0.045 0.614 1999 0.204 1.342 2000 0.072 0.675 2001 0.013 0.675 2002 0.084 0.897 2003 0.125 0.728 2004 0.134 1.269 2005 0.099 0.619 2006 0.112 0.555 2007 0.260 1.290 2008 0.317 1.082 2009 0.148 0.790 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.3439 1.4679 2 0.3169 1.3418 3 0.2600 1.2902 2386.03 Renton Treatment 2/27/2019 2:00:52 PM Page 9 4 0.2409 1.2693 5 0.2075 1.1002 6 0.2038 1.0823 7 0.1859 1.0326 8 0.1855 0.9471 9 0.1824 0.9307 10 0.1628 0.9031 11 0.1575 0.8974 12 0.1477 0.8805 13 0.1458 0.8717 14 0.1437 0.8689 15 0.1432 0.8356 16 0.1339 0.8346 17 0.1298 0.7903 18 0.1291 0.7551 19 0.1253 0.7464 20 0.1203 0.7454 21 0.1118 0.7414 22 0.1093 0.7347 23 0.1077 0.7324 24 0.1042 0.7278 25 0.1040 0.6947 26 0.1029 0.6941 27 0.0994 0.6842 28 0.0954 0.6794 29 0.0932 0.6754 30 0.0839 0.6749 31 0.0839 0.6677 32 0.0821 0.6490 33 0.0808 0.6455 34 0.0799 0.6382 35 0.0799 0.6305 36 0.0787 0.6251 37 0.0774 0.6190 38 0.0770 0.6135 39 0.0745 0.6092 40 0.0727 0.6084 41 0.0724 0.6078 42 0.0724 0.6013 43 0.0698 0.6005 44 0.0673 0.5885 45 0.0651 0.5573 46 0.0651 0.5566 47 0.0641 0.5553 48 0.0634 0.5451 49 0.0620 0.5440 50 0.0609 0.5201 51 0.0582 0.5174 52 0.0567 0.5162 53 0.0526 0.5092 54 0.0490 0.5087 55 0.0455 0.4849 56 0.0394 0.4825 57 0.0375 0.4808 58 0.0368 0.4466 59 0.0244 0.4307 60 0.0130 0.4279 61 0.0113 0.4161 2386.03 Renton Treatment 2/27/2019 2:00:52 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.2484 acre-feet On-line facility target flow:0.2639 cfs. Adjusted for 15 min:0.2639 cfs. Off-line facility target flow:0.1475 cfs. Adjusted for 15 min:0.1475 cfs. 2386.03 Renton Treatment 2/27/2019 2:01:00 PM Page 16 Appendix Predeveloped Schematic 2386.03 Renton Treatment 2/27/2019 2:01:01 PM Page 17 Mitigated Schematic 2386.03 Renton Treatment 2/27/2019 2:01:01 PM Page 28 Disclaimer Legal Notice 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. 2005-2019; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com APPENDIX F STORMWATER PLAN SHEETS APPENDIX G GEOTECHNICAL REPORT EarthSolutionsNWLLC EarthSolutionsNWLLC Geotechnical Engineering Geology Environmental Scientists Construction Monitoring 1805 -136th Place N.E.,Suite 201 Bellevue,WA 98005 (425)449-4704 Fax (425)449-4711 www.earthsolutionsnw.com GEOTECHNICAL ENGINEERING STUDY PROPOSED COMMERCIAL DEVELOPMENT TALBOT ROAD SOUTH AND SOUTH 45th PLACE RENTON,WASHINGTON ES-0895.03 Drwn.CAM Checked CGH Date July 2017 Date 07/20/2017 Proj.No.0895.03 Plate 1 Earth Solutions NWLLC Geotechnical Engineering,Construction Monitoring EarthSolutionsNWLLC EarthSolutionsNWLLC and Environmental Sciences Vicinity Map Talbot Commercial Renton,Washington Reference: King County,Washington Map 686 By The Thomas Guide Rand McNally 32nd Edition NORTH NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. SITE Plate Proj.No. Date Checked By Drwn.ByEarthSolutionsNWLLCGeotechnicalEngineering,ConstructionMonitoringandEnvironmentalSciencesEarthSolutionsNWLLCEarthSolutionsNWLLCtalbotrd.s.160 160 170 170 180 180 190 200 210 220 230 240 240230220210200190 TP-1 TP-2 TP-3 TP-4TP-5 TP-6 TP-1 TP-2 TP-3 TP-4 TP-5 NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. NOTE:The graphics shown on this plate are not intended for design purposes or precise scale measurements,but only to illustrate the approximate test locations relative to the approximate locations of existing and /or proposed site features.The information illustrated is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. LEGEND Approximate Location of ESNW Test Pit,Proj.No. ES-0895,May 2007 Approximate Location of ESNW Test Pit,Proj.No. ES-0690,Nov.2006 Subject Site TP-1 NORTH 0 40 80 160 Scale in Feet1"=80' TP-1 CAM CGH 07/20/2017 0895.03 2TestPitLocationPlanTalbotCommercial Renton,Washington Drwn.CAM Checked CGH Date July 2017 Date 07/20/2017 Proj.No.0895.03 Plate 3 Earth Solutions NWLLC Geotechnical Engineering,Construction MonitoringandEnvironmentalSciences EarthSolutionsNWLLC EarthSolutionsNWLLC RETAINING WALL DRAINAGE DETAIL Talbot Commercial Renton,Washington NOTES: Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 should be 25 to 75 percent. Sheet Drain may be feasible in lieu of Free Draining Backfill,per ESNW recommendations. Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1" Drain Rock. LEGEND: Free Draining Structural Backfill 1 inch Drain Rock 18"Min. Structural Fill Perforated Drain Pipe (Surround In Drain Rock) SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING Drwn.CAM Checked CGH Date July 2017 Date 07/20/2017 Proj.No.0895.03 Plate 4 Earth Solutions NWLLC Geotechnical Engineering,Construction Monitoring and Environmental Sciences EarthSolutionsNWLLC EarthSolutionsNWLLC FOOTING DRAIN DETAIL Talbot Commercial Renton,Washington Slope Perforated Rigid Drain Pipe (Surround with 1"Rock) 18"(Min.) NOTES: Do NOT tie roof downspouts to Footing Drain. Surface Seal to consist of 12"of less permeable,suitable soil.Slope away from building. LEGEND: Surface Seal;native soil or other low permeability material. 1"Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING APPENDIX H CONSTRUCTION SWPPP CITY OF RENTON SURFACE WATER DESIGN MANUAL 2017 City of Renton Surface Water Design Manual 12/12/2016 D-9 D.2 GENERAL CSWPP REQUIREMENTS To satisfy the City of Renton’s requirements for CSWPP, the following steps are required of all construction projects: 1. Design the plan: In accordance with Sections 2.3.1 and 2.3.3 of the SWDM, prepare and submit a technical information report (TIR) and a CSWPP plan (comprised of the ESC plan and the SWPPS plan) for City review. Utilize the standards and details for ESC (Section D.2.1) and SWPPS control (Section D.2.2) of this appendix. Incorporate any City of Renton review comments as necessary to comply with Core Requirement #5, Section 1.2.5 of the SWDM, the Erosion and Sediment Control and Stormwater Pollution Prevention and Spill Control Standards in this appendix. 2. Construct the approved plan: Construct initial ESC, SWPPS and stormwater facility (flow control facility, runoff treatment facility, and on-site BMP) protection measures on site according to the approved CSWPP plan. 3. Maintain the BMPs: Inspect and maintain all CSWPP measures and stormwater facility (flow control facility, runoff treatment facility, and on-site BMP) protection throughout construction in accordance with the inspection and maintenance standards of Section D.2.4.4. Keep current any required documentation and reporting. 4. Manage the project: Make any changes or additions necessary during construction to ensure that CSWPP measures and stormwater facility (flow control facility, runoff treatment facility, and on-site BMP) protection perform in accordance with Core Requirement #5 and Sections D.2.1, D.2.2 and D.2.4. Coordinate construction in consideration of the applied BMP strategies. Ensure pollutant controls, facility processes and reporting requirements are met in accordance with Section D.2.3. The CSWPP supervisor is the primary point of contact for all ESC and SWPPP issues (see Section D.2.3.1). 5. Conclude the plan: Prior to final construction approval, meet all the conditions in Section D.2.4.5 for final stabilization. A National Pollutant Discharge Elimination System (NPDES) General Permit for Construction (pursuant to the Washington State Department of Ecology’s Construction Stormwater General Permit) may also be required for projects that will disturb one or more acres (see SWDM Section 1.2.5.3 for additional information). Proposed projects subject to Simplified Drainage Review as determined in SWDM Section 1.1.2.1 may satisfy City of Renton CSWPP requirements by meeting the Small Site CSWPP requirements specified in Section D.3 and reiterated in Appendix C of the SWDM titled, “Simplified Drainage Requirements.” D.2.1 ESC MEASURES This section details the ESC measures that are required to minimize erosion and sediment transport off a construction site and protect areas of existing and proposed stormwater facilities (flow control facilities, runoff treatment facilities, and on-site BMPs). These ESC measures represent Best Management Practices (BMPs)6 for the control of erosion and entrained sediment as well as other impacts related to construction such as increased runoff due to land disturbing activities. The measures and practices are grouped into nine sections corresponding to each of the nine categories of ESC measures in Core Requirement #5, Section 1.2.5 of the SWDM. The introductory paragraphs at the beginning each section present the basic requirement for that category of measures, the purpose of those measures, installation requirements relative to construction activity, guidelines for the conditions of use, and other information relevant to all measures in the section/category. Compliance with each of the nine categories of the ESC measures, to the 6 Best Management Practices (BMPs) means the best available and reasonable physical, structural, managerial, or behavioral activities, that when singly or in combination, eliminate or reduce the contamination of surface and/or ground waters. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-10 extent applicable and necessary to meet the performance criteria in Section D.2.1, and compliance with the ESC implementation requirements in Section D.2.4, constitutes overall compliance with the City’s ESC Standards. Note: Additional measures shall be required by the City if the existing standards are insufficient to protect adjacent properties, drainage facilities, or water resources. The standards for each individual ESC measure are divided into four sections: 1. Purpose 2. Conditions of Use 3. Design and Installation Specifications 4. Maintenance Requirements. A code and symbol for each measure have also been included for ease of use on ESC plans. Note that the “Conditions of Use” always refers to site conditions. As site conditions change, ESC measures must be changed to remain in compliance with the requirements of this appendix. Whenever compliance with the City’s ESC Standards is required, all of the following categories of ESC measures must be considered for application to the project site as detailed in the following sections: 1. Clearing Limits: Prior to any site clearing or grading, areas to remain undisturbed during project construction shall be delineated on the project’s ESC plan and physically marked on the project site. 2. Cover Measures: Temporary and permanent cover measures shall be provided when necessary to protect disturbed areas. The intent of these measures is to prevent erosion by having as much area as possible covered during any period of precipitation. 3. Perimeter Protection: Perimeter protection to filter sediment from sheet flow shall be provided downstream of all disturbed areas prior to upslope grading. 4. Traffic Area Stabilization: Unsurfaced entrances, roads, and parking areas used by construction traffic shall be stabilized to minimize erosion and tracking of sediment offsite. 5. Sediment Retention: Surface water collected from all disturbed areas of the site shall be routed through a sediment pond or trap prior to release from the site, except those areas at the perimeter of the site small enough to be treated solely with perimeter protection. Sediment retention facilities shall be installed prior to grading any contributing area. 6. Surface Water Collection: Surface water collection measures (e.g., ditches, berms, etc.) shall be installed to intercept all surface water from disturbed areas, convey it to a sediment pond or trap, and discharge it downstream of any disturbed areas. Areas at the perimeter of the site, which are small enough to be treated solely with perimeter protection, do not require surface water collection. Significant sources of upstream surface water that drain onto disturbed areas shall be intercepted and conveyed to a stabilized discharge point downstream of the disturbed areas. Surface water collection measures shall be installed concurrently with or immediately following rough grading and shall be designed, constructed, and stabilized as needed to minimize erosion. 7. Dewatering Control: The water resulting from construction site de-watering activities must be treated prior to discharge or disposed of as specified. 8. Dust Control: Preventative measures to minimize wind transport of soil shall be implemented when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources. 9. Flow Control: Surface water from disturbed areas must be routed through the project’s onsite flow control facility or other provisions must be made to prevent increases in the existing site conditions 2-year and 10-year runoff peaks discharging from the project site during construction (flow control D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-11 facility, runoff treatment facility, and on-site BMP areas [existing or proposed] shall not be used for this purpose). 10. Control Pollutants: Stormwater pollution prevention (SWPPS) measures are required to prevent, reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or watercourses from construction-related activities such as materials delivery and storage, onsite equipment fueling and maintenance, demolition of existing buildings and disposition of demolition materials and other waste, and concrete handling, washout and disposal. Section D.2.2 describes BMPs specific to this purpose; additionally, several of the ESC BMPs described herein are applicable. 11. Protect Existing and Proposed Stormwater Facilities and On-site BMPs: Sedimentation and soil compaction reduce the infiltration capacity of native and engineered soils. Protection measures shall be applied/installed and maintained so as to prevent adverse impacts to existing stormwater facilities and on-site BMPs and areas of proposed stormwater facilities and on-site BMPs for the project. Adverse impacts can prompt the requirement to restore or replace affected stormwater facilities and on-site BMPs. 12. Maintain Protective BMPs: Protection measures shall be maintained to ensure continued performance of their intended function, to prevent adverse impacts to existing BMPs/facilities and areas of proposed BMPs/facilities, and protect other disturbed areas of the project. 13. Manage the Project: Coordination and timing of site development activities relative to ESC concerns, and timely inspection, maintenance and update of protective measures are necessary to effectively manage the project and ensure the success of protective ESC and SWPPS design and implementation. D.2.1.1 CLEARING LIMITS Prior to any site clearing or grading, those areas that are to remain undisturbed during project construction shall be delineated. At a minimum, clearing limits shall be installed at the edges of all critical area buffers and any other areas required to be left uncleared such as portions of the site subject to clearing limits under RMC 4-4-060, areas around significant trees identified to be retained, on-site BMP areas to be protected, and other areas identified to be left undisturbed to protect sensitive features. Purpose: The purpose of clearing limits is to prevent disturbance of those areas of the project site that are not designated for clearing or grading. This is important because limiting site disturbance is the single most effective method for reducing erosion. Clearing limits may also be used to control construction traffic, thus reducing the disturbance of soil and limiting the amount of sediment tracked off site. When to Install: Clearing limits shall be installed prior to the clearing and/or grading of the site. Measures to Use: Marking clearing limits by delineating the site with a continuous length of brightly colored survey tape is sometimes sufficient. The tape may be supported by vegetation or stakes, and it shall be 3 to 6 feet high and highly visible. Critical areas and their buffers require more substantial protection and shall be delineated with plastic or metal safety fences or stake and wire fences. Fencing may be required at the City’s discretion to control construction traffic or at any location where greater protection is warranted. Permanent fencing may also be used if desired by the applicant. Silt fence, in combination with survey flagging, is also an acceptable method of marking critical areas and their buffers. D.2.1.1.1 PLASTIC OR METAL FENCE Code: FE Symbol: Purpose Fencing is intended to (1) restrict clearing to approved limits; (2) prevent disturbance of critical areas, their buffers, and other areas required to be left undisturbed; (3) limit construction traffic to designated construction entrances or roads; and (4) protect areas where marking with survey tape may not provide adequate protection. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-12 Conditions of Use To establish clearing limits, plastic or metal fence may be used: 1. At the boundary of critical areas, their buffers, and other areas required to be left uncleared. 2. As necessary to control vehicle access to and on the site (see Sections D.2.1.4.1 and D.2.1.4.2). Design and Installation Specifications 1. The fence shall be designed and installed according to the manufacturer’s specifications. 2. The fence shall be at least 3 feet high and must be highly visible. 3. The fence shall not be wired or stapled to trees. Maintenance Requirements 1. If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. 2. Disturbance of a critical area, critical area buffer, native growth retention area, or any other area required to be left undisturbed shall be reported to the City for resolution. D.2.1.2 COVER MEASURES Temporary and permanent cover measures shall be provided to protect all disturbed areas, including the faces of cut and fill slopes. Temporary cover shall be installed if an area is to remain unworked for more than seven days during the dry season (May 1 to September 30) or for more than two consecutive working days during the wet season (October 1 to April 30). These time limits may be relaxed if an area poses a low risk of erosion due to soil type, slope gradient, anticipated weather conditions, or other factors. Conversely, the City may reduce these time limits if site conditions warrant greater protection (e.g., adjacent to significant aquatic resources or highly erosive soils) or if significant precipitation (see Section D.2.4.2) is expected. Any area to remain unworked for more than 30 days shall be seeded or sodded, unless the City determines that winter weather makes vegetation establishment infeasible. During the wet season, slopes and stockpiles at 3H:1V or steeper and with more than ten feet of vertical relief shall be covered if they are to remain unworked for more than 12 hours. Also during the wet season, the material necessary to cover all disturbed areas must be stockpiled on site. The intent of these cover requirements is to have as much area as possible covered during any period of precipitation. Purpose: The purpose of covering exposed soils is to prevent erosion, thus reducing reliance on less effective methods that remove sediment after it is entrained in runoff. Cover is the only practical method of reducing turbidity in runoff. Structural measures, such as silt fences and sediment ponds, are only capable of removing coarse particles and in most circumstances have little to no effect on turbidity. When to Install: Any exposed soils that will remain unworked for more than the time limit set above shall be covered by the end of the working day. If the exposed area is to remain unworked for more than 30 days, the area shall be seeded with the temporary seed mix or an equivalent mix that will provide rapid protection (see Section D.2.1.2.6). If the disturbed area is to remain unworked for a year or more or if the area has reached final grade, permanent seed mix or an equivalent mix shall be applied. Measures to Use: Cover methods include the use of surface roughening, mulch, erosion control nets and blankets, plastic covering, seeding, and sodding. Mulch and plastic sheeting are primarily intended to protect disturbed areas for a short period of time, typically days to a few months. Seeding and sodding are measures for areas that are to remain unworked for months. Erosion nets and blankets are to be used in conjunction with seeding steep slopes. The choice of measures is left to the designer; however, there are restrictions on the use of these methods, which are listed in the “Conditions of Use” and the “Design and Installation Specifications” sections for each measure. The methods listed are by no means exhaustive. Variations on the standards presented here are encouraged if other cost-effective products or methods provide substantially equivalent or superior performance. Also, D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-13 the details of installation can, and should, vary with the site conditions. A useful reference on the application of cover measures in the Puget Sound area is Improving the Cost Effectiveness of Highway Construction Site Erosion and Pollution Control, Horner, Guedry, and Kortenhof (1990). D.2.1.2.1 SURFACE ROUGHENING Purpose The purpose of surface roughening is to aid in the establishment of vegetative cover and to reduce runoff velocity, increase infiltration, and provide for sediment trapping through the provision of a rough soil surface. The rough soil surface may be created by operating a tiller or other equipment on the contour to form horizontal depressions or by leaving slopes in a roughened condition by not fine grading. Conditions of Use 1. All slopes steeper than 3H:1V and greater than 5 vertical feet require surface roughening. 2. Areas with grades steeper than 3H:1V should be roughened to a depth of 2 to 4 inches prior to seeding. 3. Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until seeding takes place. 4. Slopes with a stable rock face do not require roughening. 5. Slopes where mowing is planned should not be excessively roughened. Design and Installation Specifications There are different methods for achieving a roughened soil surface on a slope, and the selection of an appropriate method depends upon the type of slope. Roughening methods include stair-step grading, grooving, contour furrows, and tracking. See Figure D.2.1.2.A for information on tracking and contour furrows. Factors to be considered in choosing a method are slope steepness, mowing requirements, and whether the slope is formed by cutting or filling. Sole reliance on roughening for temporary erosion control is of limited effectiveness in intense rainfall events. Stair-step grading may not be practical for sandy, steep, or shallow soils. 1. Disturbed areas that will not require mowing may be stair-step graded, grooved, or left rough after filling 2. Stair Step grading is particularly appropriate in soils containing large amounts of soft rock. Each “step” catches material that sloughs from above, and provides a level site where vegetation can become established. Stairs should be wide enough to work with standard earth moving equipment. Stair steps must be on contour or gullies will form on the slope. 3. Areas that will be mowed (slopes less steep than 3H:1V) may have small furrows left by disking, harrowing, raking, or seed-planting machinery operated on the contour. 4. Graded areas with slopes greater than 3H:1V but less than 2H:1V should be roughened before seeding. This can be accomplished in a variety of ways, including “track walking” or driving a crawler tractor up and down the slope, leaving a pattern of cleat imprints parallel to slope contours. 5. Tracking is done by operating equipment up and down the slope to leave horizontal depressions in the soil. Maintenance Standards Periodically check roughened, seeded, planted, and mulched slopes for rills and gullies, particularly after a significant storm event. Fill these areas slightly above the original grade, then re-seed and mulch as soon as possible. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-14 FIGURE D.2.1.2.A SURFACE ROUGHENING 50'(15 m ) 1 GROOVES WILL CATCH SEED, FERTILIZER, MULCH, RAINFALL AND DECREASE RUNOFF. "TRACKING" WITH MACHINERY UP AND DOWN THE SLOPE PROVIDES GROOVES THAT WILL CATCH SEED, RAINFALL AND REDUCE RUNOFF. CONTOUR FURROWS TRACKING 6" MIN. (150mm) 3 MAX. SURFACE ROUGHENING BY TRACKING AND CONTOUR FURROWS NTS D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-15 D.2.1.2.2 MULCHING Code: MU Symbol: Purpose The purpose of mulching soils is to provide 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 is an enormous variety of mulches that may be used. Only the most common types are discussed in this section. Conditions of Use As a temporary cover measure, mulch should be used: 1. On disturbed areas that require cover measures for less than 30 days 2. As a cover for seed during the wet season and during the hot summer months 3. During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table D.2.1.2.A. Note: Thicknesses may be increased for disturbed areas in or near critical areas or other areas highly susceptible to erosion. Maintenance Standards 1. The thickness of the cover must be maintained. 2. Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related, then the drainage problem shall be assessed and alternate drainage such as interceptor swales may be needed to fix the problem and the eroded area remulched. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-16 TABLE D.2.1.2.A MULCH STANDARDS AND GUIDELINES Mulch Material Quality Standards Application Rates Remarks Straw Air-dried; free from undesirable seed and coarse material 2″–3″ thick; 5 bales per 1,000 sf or 2– 3 tons per acre Cost-effective protection when applied with adequate thickness. Hand-application generally requires greater thickness than blown straw. Straw should be crimped to avoid wind blow. The thickness of straw may be reduced by half when used in conjunction with seeding. Wood Fiber Cellulose No growth inhibiting factors Approx. 25–30 lbs per 1,000 sf or 1,500–2,000 lbs per acre Shall be applied with hydromulcher. Shall not be used without seed and tackifier unless the application rate is at least doubled. Some wood fiber with very long fibers can be effective at lower application rates and without seed or tackifier. Compost No visible water or dust during handling. Must be purchased from supplier with Solid Waste Handling Permit. 2″ thick min.; approx. 100 tons per acre (approx. 1.5 cubic feet per square yard) More effective control can be obtained by increasing thickness to 3″ (2.25 cubic feet per square yard). Excellent mulch for protecting final grades until landscaping because it can be directly seeded or tilled into soil as an amendment. Compost may not be used in Sensitive Lake7 basins unless analysis of the compost shows no phosphorous release. Hydraulic Matrices (Bonded Fiber Matrix [BFM]) This mulch category includes hydraulic slurries composed of wood fiber, paper fiber or a combination of the two held together by a binding system. The BFM shall be a mixture of long wood fibers and various bonding agents. Apply at rates from 3,000 lbs per acre to 4,000 lbs per acre and based on manufacturers recommendations The BFM shall not be applied immediately before, during or immediately after rainfall so that the matrix will have an opportunity to dry for 24 hours after installation. Application rates beyond 2,500 pounds may interfere with germination and are not usually recommended for turf establishment. BFM is generally a matrix where all fiber and binders are in one bag, rather than having to mix components from various manufacturers to create a matrix. BFMs can be installed via helicopter in remote areas. They are approximately $1,000 per acre cheaper to install. Chipped Site Vegetation Average size shall be several inches. 2″ minimum thickness This is a cost-effective way to dispose of debris from clearing and grubbing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above approx. 10% because of its tendency to be transported by runoff. It is not recommended within 200 feet of surface waters. If seeding is expected shortly after mulch, the decomposition of the chipped vegetation may tie up nutrients important to grass establishment. 7 Sensitive lake means a lake that has proved to be particularly prone to eutrophication; the City did not have any lakes that had this designation at the time of SWDM adoption. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-17 D.2.1.2.3 NETS AND BLANKETS Code: NE Symbol: Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. Nets are strands of material woven into an open, but high-tensile strength net (for example, jute matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control nets and blankets should be used: 1. For permanent stabilization of slopes 2H:1V or greater and with more than 10 feet of vertical relief. 2. In conjunction with seed for final stabilization of a slope, not for temporary cover. However, they may be used for temporary applications as long as the product is not damaged by repeated handling. In fact, this method of slope protection is superior to plastic sheeting, which generates high-velocity runoff (see Section D.2.1.2.4). 3. For drainage ditches and swales (highly recommended). The application of appropriate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can capture a great deal of sediment due to their open, porous structure. Synthetic nets and blankets may be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. Design and Installation Specifications 1. See Figure D.2.1.2.B and Figure D.2.1.2.C for typical orientation and installation of nettings and blankets. Note: Installation is critical to the effectiveness of these products. If good ground contact is not achieved, runoff can concentrate under the product, resulting in significant erosion. 2. With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer thoroughly consults the manufacturer’s information and that a site visit takes place in order to ensure that the product specified is appropriate. 3. Jute matting must be used in conjunction with mulch (Section D.2.1.2.2). Excelsior, woven straw blankets, and coir (coconut fiber) blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. Other types of products will have to be evaluated individually. In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. 4. Purely synthetic blankets are allowed but shall only be used for long-term stabilization of waterways. The organic blankets authorized above are better for slope protection and short-term waterway protection because they retain moisture and provide organic matter to the soil, substantially improving the speed and success of re-vegetation. Maintenance Standards 1. Good contact with the ground must be maintained, and there must not be erosion beneath the net or blanket. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-18 2. Any areas of the net or blanket that are damaged or not in close contact with the ground shall be repaired and stapled. 3. If erosion occurs due to poorly controlled drainage, the problem shall be fixed and the eroded area protected. FIGURE D.2.1.2.B WATERWAY INSTALLATION FIGURE D.2.1.2.C SLOPE INSTALLATION •DO NOT STRETCH BLANKETS/MATTINGS TIGHT - ALLOW THE ROLLSTO MOLD TO ANY IRREGULARITIES. •SLOPE SURFACE SHALL BE SMOOTH BEFORE PLACEMENT FOR PROPER SOIL CONTACT. •ANCHOR, STAPLE, AND INSTALL CHECK SLOTS AS PER MANUFACTURER'S RECOMMENDATIONS. •AVOID JOINING MATERIAL IN THE CENTER OF THE DITCH. •LIME, FERTILIZE AND SEED BEFORE INSTALLATION. MIN.4" OVERLAP' MIN.6"OVERLAP SLOPE SURFACE SHALL BE SMOOTH BEFORE PLACEMENT FOR PROPER SOIL CONTACT STAPLING PATTERN AS PERMANUFACTURER'S RECOMMENDATION MIN. 2" OVERLAP LIME, FERTILIZE AND SEED BEFOREINSTALLATION. PLANTING OF SHRUBS, TREES, ETC. SHOULD OCCUR AFTER INSTALLATION DO NOT STRETCH BLANKETS/MATTINGS TIGHT - ALLOW THE ROLLS TO MOLD TO ANY IRREGULARITIES FOR SLOPES LESS THAN 3H:1V, ROLLS MAY BE PLACED IN HORIZONTAL STRIPS BRING MATERIAL DOWN TO A LEVELAREA, TURN THE END UNDER 4" ANDSTAPLE AT 12" INTERVALS ANCHOR IN 6"x6" MIN.TRENCH AND STAPLEAT 12" INTERVALS STAPLE OVERLAPS MAX. 5' SPACING IF THERE IS A BERM AT THE TOP OF SLOPE, ANCHOR UPSLOPE OF THE BERM MIN. 6" OVERLAP D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-19 D.2.1.2.4 PLASTIC COVERING Code: PC Symbol: Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. Conditions of Use 1. Plastic covering may be used on disturbed areas that require cover measures for less than 30 days. 2. Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term applications. 3. Clear plastic sheeting may be used over newly-seeded areas to create a greenhouse effect and encourage grass growth. Clear plastic should not be used for this purpose during the summer months because the resulting high temperatures can kill the grass. 4. Due to rapid runoff caused by plastic sheeting, this method shall not be used upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. Note: There have been many problems with plastic, usually attributable to poor installation and maintenance. However, the material itself can cause problems, even when correctly installed and maintained, because it generates high-velocity runoff and breaks down quickly due to ultraviolet radiation. In addition, if the plastic is not completely removed, it can clog drainage system inlets and outlets. It is highly recommended that alternatives to plastic sheeting be used whenever possible and that its use be limited. Design and Installation Specifications 1. See Figure D.2.1.2.D for details. 2. Plastic sheeting shall have a minimum thickness of 0.06 millimeters. 3. 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. FIGURE D.2.1.2.D PLASTIC COVERING TIRES, SANDBAGS, OREQUIVALENT MAY BE USEDTO WEIGHT PLASTIC SEAMS BETWEEN SHEETS MUST OVERLAP A MINIMUM OF 12" AND BE WEIGHTED OR TAPED TOE IN SHEETINGIN MINIMUM 4"X4"TRENCH PROVIDE ENERGY DISSIPATIONAT TOE WHEN NEEDED 10' MAX. 10' MAX. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-20 Maintenance Standards for Plastic Covering 1. Torn sheets must be replaced and open seams repaired. 2. If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and replaced. 3. When the plastic is no longer needed, it shall be completely removed. D.2.1.2.5 STRAW WATTLES Code: SW Symbol: Purpose Wattles are erosion and sediment control barriers consisting of straw wrapped in biodegradable tubular plastic or similar encasing material. Wattles may reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sediment. Straw wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length. The wattles are placed in shallow trenches and staked along the contour of disturbed or newly constructed slopes. Conditions of Use 1. Install on disturbed areas that require immediate erosion protection. 2. Use on slopes requiring stabilization until permanent vegetation can be established. 3. Can be used along the perimeter of a project, as a check dam in unlined ditches and around temporary stockpiles 4. Wattles can be staked to the ground using willow cuttings for added revegetation. 5. Rilling can occur beneath and between wattles if not properly entrenched, allowing water to pass below and between wattles Design and Installation Specifications 1. It is critical that wattles are installed perpendicular to the flow direction and parallel to the slope contour. 2. Narrow trenches should be dug across the slope, on contour, to a depth of 3 to 5 inches on clay soils and soils with gradual slopes. On loose soils, steep slopes, and during high rainfall events, the trenches should be dug to a depth of 5 to 7 inches, or ½ to 2/3 of the thickness of the wattle. 3. Start construction of trenches and installing wattles from the base of the slope and work uphill. Excavated material should be spread evenly along the uphill slope and compacted using hand tamping or other method. Construct trenches at contour intervals of 3 to 30 feet apart depending on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches should be constructed. 4. Install the wattles snugly into the trenches and abut tightly end to end. Do not overlap the ends. 5. Install stakes at each end of the wattle, and at 4 foot centers along the entire length of the wattle. 6. If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. 7. At a minimum, wooden stakes should be approximately ¾ x ¾ x 24 inches. Willow cuttings or 3/8 inch rebar can also be used for stakes. 8. Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake protruding above the wattle. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-21 Maintenance Standards 1. Inspect wattles prior to forecasted rain, daily during extended rain events, after rain events, weekly during the wet season, and at two week intervals at all other times of the year. 2. Repair or replace split, torn, raveling, or slumping wattles 3. Remove sediment accumulations when exceeding ½ the height between the top of the wattle and the ground surface. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-22 FIGURE D.2.1.2.E STRAW WATTLES 1.STRAW ROLL INSTALLATION REQUIRES THE PLACEMENT AND SECURE STAKING OF THE ROLL IN A TRENCH, 3" x 5" (75-125mm) DEEP, DUG ON CONTOUR. 2.RUNOFF MUST NOT BE ALLOWED TO RUN UNDER OR AROUND ROLL. ROLL SPACING DEPENDS ON SOIL TYPE AND SLOPE STEEPNESS STRAW ROLLS MUST BE PLACED ALONG SLOPE CONTOURS 3'-4' (1.2m) 10'-25' (3-8m) 3"-5"(75-125mm) ADJACENT ROLLSSHALL TIGHTLY ABUT SEDIMENT, ORGANIC MATTER, AND NATIVE SEEDS ARE CAPTURED BEHIND THE ROLLS LIVE STAKE 1" x 1" STAKE 8"-10" DIA. (200-250mm) NOTES: STRAW WATTLESNTS D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-23 D.2.1.2.6 TEMPORARY AND PERMANENT SEEDING Code: SE Symbol: Purpose Seeding is intended to reduce erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use 1. Seeding shall be used throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. 2. Vegetation-lined channels shall be seeded. Channels that will be vegetated should be installed before major earthwork and hydroseeded or covered with a Bonded Fiber Matrix (BFM). 3. Retention/detention ponds shall be seeded as required. 4. At the City’s discretion, seeding without mulch during the dry season is allowed even though it will take more than seven days to develop an effective cover. Mulch is, however, recommended at all times because it protects seeds from heat, moisture loss, and transport due to runoff. 5. Prior to the beginning of the wet season, all disturbed areas shall be reviewed to identify which ones can be seeded in preparation for the winter rains (see Section D.2.4.2). Disturbed areas shall be seeded within one week of the beginning of the wet season. A sketch map of those areas to be seeded and those areas to remain uncovered shall be submitted to the CED inspector. The CED inspector may require seeding of additional areas in order to protect surface waters, adjacent properties, or drainage facilities. 6. At final site stabilization, all disturbed areas not otherwise vegetated or stabilized shall be seeded and mulched (see Section D.2.4.5). Design and Installation Specifications 1. The best time to seed is fall (late September to October) or in spring (mid-March to June). Irrigation is required during the first summer following installation if seeding occurs in spring or summer or during prolonged dry times of year. Areas may also be seeded during the winter months, but it may take additional spring seeding applications to develop a dense groundcover due to cold temperatures. The application and maintenance of mulch is critical for winter seeding. 2. To prevent seed from being washed away, confirm that all required surface water control measures have been installed. 3. The seedbed should not be compacted because soils that are well compacted will not vegetate as quickly or thoroughly. Slopes steeper than 3H:1V shall be surface roughened. Roughening can be accomplished in a variety of ways, but the typical method is track walking, or driving a crawling tractor up and down the slope, leaving cleat imprints parallel to the slope contours. 4. In general, 10-20-20 N-P-K (nitrogen-phosphorus-potassium) fertilizer may be used at a rate of 90 pounds per acre. Slow-release fertilizers are preferred because they are more efficient and have fewer environmental impacts. It is recommended that areas being seeded for final landscaping conduct soil tests to determine the exact type and quantity of fertilizer needed. This will prevent the over- application of fertilizer. Disturbed areas within 200 feet of water bodies and wetlands must use slow- release low-phosphorus fertilizer (typical proportions 3-1-2 N-P-K). 5. The following requirements apply to mulching: a) Mulch is always required for seeding slopes greater than 3H:1V (see Section D.2.1.2.2). b) If seeding during the wet season, mulch is required. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-24 c) The use of mulch may be required during the dry season at the City’s discretion if grass growth is expected to be slow, the soils are highly erodible due to soil type or gradient, there is a water body close to the disturbed area, or significant precipitation (see Section D.2.4.2) is anticipated before the grass will provide effective cover. d) Mulch may be applied on top of the seed or simultaneously by hydroseeding. 6. Hydroseeding is allowed as long as tackifier is included. Hydroseeding with wood fiber mulch is adequate during the dry season. Application of hydroseeded wood fiber mulch should be appropriate for slope angle. Follow manufacturer specifications for application rates. 7. Areas to be permanently landscaped shall use soil amendments. Good quality topsoil shall be tilled into the top six inches to reduce the need for fertilizer and improve the overall soil quality. Most native soils will require the addition of four inches of well-rotted compost to be tilled into the soil to provide a good quality topsoil. Compost used should meet specifications provided in Reference Section 11-C of the SWDM. 8. The seed mixes listed below include recommended mixes for both temporary and permanent seeding. These mixes, with the exception of the wetland mix, shall be applied at a rate of 80 to 100 seeds per square foot. Wet sites should apply 120 to 150 seeds per square foot. Local suppliers should be consulted for information on current Pure Live Seed (PLS) rates and species specific seeds per pound in order to determine seed mix PLS pounds of seed per acre. The appropriate mix depends on a variety of factors, including exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by the City may be used. Table D.2.1.2.B presents the standard mix for those areas where t a temporary or permanent vegetative cover is required. The following mix assumes a desired 150 seeds per square foot and should be applied at approximately 37 pounds of pure live seed per acre. TABLE D.2.1.2.B EROSION CONTROL SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre Spike bentgrass/Agrostis exarata 6 9 0.1 California brome/Bromus carinatus 15 23 9.8 Tufted hairgrass/Deschampsia cespitosa 15 23 0.4 Blue wildrye/Elymus glaucus 18 27 10.7 California oatgrass/Danthonia californica 18 27 5.6 Native red fescue/Festuca rubra var. rubra 18 27 2.4 Meadow barley/Hordeum brachyantherum 10 15 7.7 Table D.2.1.2.C provides just one recommended possibility for landscaping seed. It assumes a desired 100 seeds per square foot and should be applied at 12 pounds of pure live seed per acre. TABLE D.2.1.2.C LANDSCAPING SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre Sideoats grama/Bouteloua curtipendula 20 30 6.8 California oatgrass/Danthonia californica 20 30 6.2 Native red fescue/Festuca rubra var. rubra 30 45 3.9 Prairie junegrass/Koeleria macrantha 30 45 0.8 D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-25 This turf seed mix in Table D.2.1.2.D is for dry situations where there is no need for much water. The advantage is that this mix requires very little maintenance. TABLE D.2.1.2.D LOW-GROWING TURF SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre Hard fescue/Festuca brevipila 25 20 1.5 Sheep fescue/Festuca ovina 30 24 1.5 Native red fescue/Festuca rubra var. rubra 25 20 1.7 Prairie junegrass/Koeleria macrantha 20 16 0.3 Table D.2.1.2.E presents a mix recommended for bioswales and other intermittently wet areas. The mix assumes a desired 150 seeds per square foot and approximately 29 pounds of pure live seed per acre. Sod shall generally not be used for bioswales because the seed mix is inappropriate for this application. Sod may be used for lining ditches to prevent erosion, but it will provide little water quality benefit during the wet season. TABLE D.2.1.2.E BIOSWALE SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre American sloughgrass/Beckmannia syzigachne 15 23 0.9 Tufted hairgrass/Deschampsia cespitosa 20 30 0.5 Blue wildrye/Elymus glaucus 18 27 10.7 Native red fescue/Festuca rubra var. rubra 20 30 2.6 Meadow barley/Hordeum brachyantherum 12 18 9.2 Northwestern mannagrass/Glyceria occidentalis 15 23 4.9 The seed mix shown in Table D.2.1.2.F is a recommended low-growing, non-invasive seed mix appropriate for very wet areas that are not regulated wetlands (if planting in wetland areas, see Section 6.3.1 of the SWDM). Other mixes may be appropriate, depending on the soil type and hydrology of the area. This mixture assumes a target goal of 150 seeds per square foot and should be applied at a rate of 36 pounds per acre. TABLE D.2.1.2.F WET AREA SEED MIX* Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre California brome/Bromus carinatus 15 23 9.8 Columbia brome/Bromus vulgaris 18 27 8.1 Tufted hairgrass/Deschampsia cespitosa 15 23 0.4 California oatgrass/Danthonia californica 15 23 4.7 Native red fescue/Festuca rubra var. rubra 17 26 2.2 Western manna grass/Glyceria occidentalis 10 15 3.3 Meadow barley/Hordeum brachyantherum 10 15 7.7 * Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-26 The meadow seed mix in Table D.2.1.2.G is recommended for areas that will be maintained infrequently or not at all and where colonization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. This seed mix assumes a target goal of 120 seeds per square foot and an application rate of 23 pounds of pure live seed per acre. TABLE D.2.1.2.G MEADOW SEED MIX Common Name/Latin Name % Species Composition Desired Seeds per Square Foot PLS Pounds/Acre Common yarrow/Achillea millefolium 4 5 0.1 Pearly everlasting/Anaphalis margartacae 1 1 0.0 California brome/Bromus carinatus 15 18 7.8 California oatgrass/Danthonia californica 15 18 3.7 Blue wildrye/Elymus glaucus 16 19 7.6 Festuca idahoensis 15 18 1.7 Native red fescue/Festuca rubra var. rubra 18 22 1.9 Sickle keeled lupine/Lupinus albicaulis 1 1 2.2 Fowl bluegrass/Poa palustris 15 18 0.4 Maintenance Standards for Temporary and Permanent Seeding 1. Any seeded areas that fail to establish at least 80 percent cover within one month shall be reseeded. If reseeding is ineffective, an alternate method, such as sodding or nets/blankets, shall be used. If winter weather prevents adequate seed establishment and growth, this time limit may be relaxed at the discretion of the City when critical areas would otherwise be protected. 2. After adequate cover is achieved, any areas that experience erosion shall be re-seeded and protected by mulch. If the erosion problem is drainage related, the problem shall be fixed and the eroded area re- seeded and protected by mulch. 3. Seeded areas shall be supplied with adequate moisture, but not watered to the extent that it causes runoff. D.2.1.2.7 SODDING Code: SO Symbol: Purpose The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize drainage ways where concentrated overland flow will occur. Conditions of Use Sodding may be used in the following areas: 1. Disturbed areas that require short-term or long-term cover 2. Disturbed areas that require immediate vegetative cover 3. All waterways that require vegetative lining (except biofiltration swales—the seed mix used in most sod is not appropriate for biofiltration swales). Waterways may also be seeded rather than sodded, and protected with a net or blanket (see Section D.2.1.2.3). D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-27 Design and Installation Specifications Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense root mat for mechanical strength. The following steps are recommended for sod installation: 1. Shape and smooth the surface to final grade in accordance with the approved grading plan. 2. Amend four inches (minimum) of well-rotted compost into the top eight inches of the soil if the organic content of the soil is less than ten percent. Compost used shall meet compost specifications per SWDM Reference Section 11-C. 3. Fertilize according to the supplier’s recommendations. Disturbed areas within 200 feet of water bodies and wetlands must use non-phosphorus fertilizer. 4. Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface. 5. Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1V. 6. Roll the sodded area and irrigate. 7. When sodding is carried out in alternating strips or other patterns, seed the areas between the sod immediately after sodding. Maintenance Standards If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and protected with a net or blanket. D.2.1.2.8 POLYACRYLAMIDE 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 sediment in two ways. First, PAM increases the soil’s available pore volume, thus increasing infiltration through flocculation 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 1. PAM shall not be directly applied to water or allowed to enter a water body. 2. PAM may be applied to wet soil, but dry soil is preferred due to less sediment loss. 3. PAM will work when applied to saturated soil but is not as effective as applications to dry or damp soil. 4. PAM may be applied only to the following types of bare soil areas that drain to a sediment trap or a sediment pond: • Staging areas • Stockpiles • Pit sites • Balanced cut and fill earthwork • Haul roads prior to placement of crushed rock surfacing • Compacted soil road base SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-28 5. PAM may be applied only during the following phases of construction: • During rough grading operations • After final grade and before paving or final seeding and planting • During a winter shut down of site work. In the case of winter shut down, or where soil will remain unworked for several months, PAM should be used together with mulch. 6. Do not use PAM on a slope that flows directly to a stream or wetland. The stormwater runoff shall pass through a sediment control measure prior to discharging to surface waters. Design and Installation Specifications 1. PAM must be applied using one of two methods of application, “preferred” or “alternative.” The specifications for these methods are described under separate headings below. 2. PAM may be applied in dissolved form with water, or it may be applied in dry, granular or powdered form. The preferred application method is the dissolved form. 3. PAM is to be applied at a maximum rate of ½ pound PAM per 1000 gallons of water per 1 acre of bare soil. Table D.2.1.2.H may be used to determine the PAM and water application rate for disturbed soil areas. Higher concentrations of PAM do not provide any additional effectiveness. 4. Do not add PAM to water discharging from the site. 5. PAM shall be used in conjunction with other ESC measures and not in place of them. When the total drainage area is greater than or equal to 3 acres, PAM treated areas shall drain to a sediment pond per Section D.2.1.5.2. For drainage areas less than 3 acres, PAM treated areas must drain to a sediment trap per Section D.2.1.5.1. Other normally required sediment control measures such as perimeter protection measures (Section D.2.1.3) and surface water collection measures (Section D.2.1.6) shall be applied to PAM treated areas. 6. All areas not being actively worked shall be covered and protected from rainfall. PAM shall not be the only cover BMP used. 7. Keep the granular PAM supply out of the sun. Granular PAM loses its effectiveness in three months after exposure to sunlight and air. 8. Care must be taken to prevent spills of PAM powder onto paved surfaces. PAM, combined with water, is very slippery and can be a safety hazard. During an application of PAM, prevent over-spray from reaching pavement as the pavement will become slippery. If PAM powder gets on skin or clothing, wipe it off with a rough towel rather than washing with water. Washing with water only makes cleanup more difficult, messier, and time consuming. 9. The specific PAM copolymer formulation must be anionic. Cationic PAM shall not be used in any application because of known aquatic toxicity concerns. Only the highest drinking water grade PAM, certified for compliance with ANSI/NSF Standard 60 for drinking water treatment, may be used for soil applications. The Washington State Department of Transportation (WSDOT) lists approved PAM products on their web page. All PAM use shall be reviewed and approved by CED. 10. The PAM anionic charge density may vary from 2 to 30 percent; a value of 18 percent is typical. Studies conducted by the United States Department of Agriculture (USDA)/ARS demonstrated that soil stabilization was optimized by using very high molecular weight (12 to 15 mg/mole), highly anionic (>20% hydrolysis) PAM. 11. PAM must be “water soluble” or “linear” or “non-cross-linked.” Cross-linked or water absorbent PAM, polymerized in highly acidic (pH<2) conditions, are used to maintain soil moisture content. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-29 TABLE D.2.1.2.H PAM AND WATER APPLICATION RATES Disturbed Area (ac) PAM (lbs) Water (gal) 0.50 0.25 500 1.00 0.50 1,000 1.50 0.75 1,500 2.00 1.00 2,000 2.50 1.25 2,500 3.00 1.50 3,000 3.50 1.75 3,500 4.00 2.00 4,000 4.50 2.25 4,500 5.00 2.50 5,000 Preferred Application Method 1. Pre-measure the area where PAM is to be applied and calculate the amount of product and water necessary to provide coverage at the specified application rate (1/2 pound PAM/1,000 gallons/acre). 2. Dissolve pre-measured dry granular PAM with a known quantity of clean water in a bucket several hours or overnight. PAM has infinite solubility in water, but dissolves very slowly. Mechanical mixing will help dissolve PAM. Always add PAM to water – not water to PAM. 3. Pre-fill the water truck about 1/8 full with water. The water does not have to be potable, but it must have relatively low turbidity – in the range of 20 NTU or less. 4. Add PAM/Water mixture to the truck. 5. Completely fill the water truck to specified volume. 6. Spray PAM/Water mixture onto dry soil until the soil surface is uniformly and completely wetted. Alternate Application Method PAM may also be applied as a powder at the rate of 5 pounds per acre. This must be applied on a day that is dry. For areas less than 5 to 10 acres, a hand-held “organ grinder” fertilized spreader set to the smallest setting will work. Tractor mounted spreaders will work for larger areas. Maintenance Standards 1. PAM may be reapplied on actively worked areas after a 48-hour period 2. Reapplication is not required unless PAM treated soil is disturbed or unless turbidity levels show the need for an additional application. If PAM treated soil is left undisturbed, a reapplication may be necessary after two months. More PAM applications may be required for steep slopes, silty and clay soils, (USDA classification Type “C” and “D” soils), long grades, and high precipitation areas. When PAM is applied first to bare soil and then covered with straw, a reapplication may not be necessary for several months. D.2.1.2.9 COMPOST BLANKETS Code: COBL Symbol: Purpose Compost blankets are intended to: SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-30 • Provide immediate temporary protection from erosion by protecting soil from rainfall and slowing flow velocity over the soil surface. • Enhance temporary or permanent plant establishment by conserving moisture, holding seed and topsoil in place, providing nutrients and soil microorganisms, and moderating soil temperatures. • Compost blankets, applied at the proper thickness and tilled into the soil, are also an option for amending soils for permanent landscaping. • Compost generally releases and adds phosphorous to stormwater. Therefore, compost blankets are not recommended for use in watersheds where phosphorous sensitive water resources are located. Unless prior approval is given by the City, they should not be used in Sensitive Lake Watersheds. Conditions of Use 1. Compost blankets may be used unseeded on disturbed areas that require temporary cover measures up to 1 year. Compost applied as temporary cover may be reclaimed and re-used for permanent cover. 2. Compost provides cover for protecting final grades until landscaping can be completed as it can be directly seeded or tilled into soil as an amendment. 3. Compost blankets meet mulch requirements for seed. 4. Seed may be applied to a compost blanket at any time for permanent or temporary stabilization of disturbed areas. Seed may be applied prior to blanket application, on top of blankets, or injected and mixed into the compost as it is applied. 5. Compost blankets may be applied on slopes up to 2H:1V. Design and Installation Specifications 1. Compost shall be applied at a minimum of 2 inches thick, unless otherwise directed by an ESC supervisor or the City. At an application of 2 inches, this will equal approximately 100 tons per acre (compost generally weighs approximately 800 lbs per cubic yard). Thickness shall be increased at the direction of the design engineer for disturbed areas in or near critical areas or other areas highly susceptible to erosion. 2. Compost shall meet criteria in Reference Section 11-C of the SWDM. 3. Compost shall be obtained from a supplier meeting the requirements in Reference Section 11-C. 4. Compost blankets shall be applied over the top of the slope to which it is applied, to prevent water from running under the blanket 5. Compost blankets shall not be used in areas exposed to concentrated flow (e.g., channels, ditches, dikes) Maintenance Standards 1. The specified thickness of the blanket/cover must be maintained. 2. Any areas that show signs of erosion must be re-mulched. If the erosion problem is drainage related, then the drainage problem must first be remedied and then the eroded area re-mulched. D.2.1.3 PERIMETER PROTECTION Perimeter protection to filter sediment from sheetwash shall be located downslope of all disturbed areas and shall be installed prior to upslope grading. Perimeter protection includes the use of vegetated strips as well as, constructed measures, such as silt fences, fiber rolls, sand/gravel barriers, brush or rock filters, triangular silt dikes and other methods. During the wet season, 50 linear feet of silt fence (and the necessary stakes) per acre of disturbed area must be stockpiled on site. Purpose: The purpose of perimeter protection is to reduce the amount of sediment transported beyond the disturbed areas of the construction site. Perimeter protection is primarily a backup means of sediment control. Most, if not all, sediment-laden water is to be treated in a sediment trap or pond. The only D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-31 circumstances in which perimeter control is to be used as a primary means of sediment removal is when the catchment is very small (see below). When to Install: Perimeter protection is to be installed prior to any upslope clearing and grading. Measures to Use: The above measures may be used interchangeably and are not the only perimeter protection measures available. If surface water is collected by an interceptor dike or swale and routed to a sediment pond or trap, there may be no need for the perimeter protection measures specified in this section. Criteria for Use as Primary Treatment: At the boundary of a site, perimeter protection may be used as the sole form of treatment when the flowpath meets the criteria listed below. If these criteria are not met, perimeter protection shall only be used as a backup to a sediment trap or pond. Average Slope Slope Percent Flowpath Length 1.5H:1V or less 67% or less 100 feet 2H:1V or less 50% or less 115 feet 4H:1V or less 25% or less 150 feet 6H:1V or less 16.7% or less 200 feet 10H:1V or less 10% or less 250 feet D.2.1.3.1 SILT FENCE Code: SF Symbol: Purpose Use of a 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 1. Silt fence may be used downslope of all disturbed areas. 2. Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment trap or pond. The only circumstance in which overland flow may be treated solely by a silt fence, rather than by a sediment trap or pond, is when the area draining to the fence is small (see “Criteria for Use as Primary Treatment” in Section D.2.1.3 above). Design and Installation Specifications 1. See Figure D.2.1.3.A and Figure D.2.1.3.B for details. 2. The geotextile used must meet the standards listed below. A copy of the manufacturer’s fabric specifications must be available on site. AOS (ASTM D4751) 30–100 sieve size (0.60–0.15 mm) for slit film 50–100 sieve size (0.30–0.15 mm) for other fabrics Water Permittivity (ASTM D4491) 0.02 sec-1 minimum Grab Tensile Strength (ASTM D4632) (see Specification Note 3) 180 lbs. min. for extra strength fabric 100 lbs. min. for standard strength fabric Grab Tensile Elongation (ASTM D4632) 30% max. (woven) Ultraviolet Resistance (ASTM D4355) 70% min. 3. Standard strength fabric requires wire backing to increase the strength of the fence. Wire backing or closer post spacing may be required for extra strength fabric if field performance warrants a stronger fence. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-32 4. Where the fence is installed, the slope shall be no steeper than 2H:1V. 5. If a typical silt fence (per Figure D.2.1.3.A) is used, the standard 4 x 4 trench may not be reduced as long as the bottom 8 inches of the silt fence is well buried and secured in a trench that stabilizes the fence and does not allow water to bypass or undermine the silt fence. Maintenance Standards 1. Any damage shall be repaired immediately. 2. If concentrated flows are evident uphill of the fence, they must be intercepted and conveyed to a sediment trap or pond. 3. It is important to check the uphill side of the 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 or remove the trapped sediment. 4. Sediment must be removed when the sediment is 6 inches high. 5. If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown, it shall be replaced. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-33 FIGURE D.2.1.3.A SILT FENCE 2"X2" BY 14 Ga. WIRE OR EQUIVALENT, IF STANDARD STRENGTH FABRIC USED NOTE: FILTER FABRIC FENCES SHALL BE INSTALLED ALONG CONTOURS WHENEVER POSSIBLE JOINTS IN FILTER FABRIC SHALL BE SPLICEDAT POSTS. USE STAPLES, WIRE RINGS OREQUIVALENT TO ATTACH FABRIC TO POSTS. FILTER FABRIC BACKFILL TRENCH WITH NATIVE SOIL OR 3/4" TO 1-1/2" WASHED GRAVEL MINIMUM 4"x4" TRENCH 2"x4" WOOD POSTS, STEEL FENCEPOSTS, REBAR, OR EQUIVALENT POST SPACING MAY BEINCREASED TO 8' IFWIRE BACKING IS USED 6' MAX.2' MIN.12" MIN. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-34 FIGURE D.2.1.3.B SILT FENCE INSTALLATION BY SLICING 1.GATHER FABRIC AT POSTS, IF NEEDED. 2.UTILIZE THREE TIES PER POST, ALLWITHIN TOP 8" OF FABRIC. 3.POSITION EACH TIE DIAGONALLY, PUNCTURING HOLES VERTICALLY A MINIMUM OF 1" APART. 4.HANG EACH TIE ON A POST NIPPLE AND TIGHTEN SECURELY. USE CABLE TIES (50 LBS) OF SOFT WIRE. TOP OF FABRIC BELT DIAGONAL ATTACHMENT DOUBLES STRENGTH FLOW STEEL SUPPORT POST1.POST SPACING: 7' MAX. ON OPEN RUNS 4' MAX. ON POOLING AREAS. 2.POST DEPTH: AS MUCH BELOW GROUND AS FABRIC ABOVE GROUND. 3.PONDING HEIGHT MAX. 24" ATTACH FABRIC TO UPSTREAM SIDE OF POST. 4.DRIVE OVER EACH SIDE OF SILT FENCE 2 TO 4 TIMES WITH DEVICE EXERTING 60 P.S.I. OR GREATER. 5.NO MORE THAN 24" OF A 36" FABRIC IS ALLOWED ABOVE GROUND. 6.VIBRATORY PLOW IS NOT ACCEPTABLEBECAUSE OF HORIZONTAL COMPACTION. 100% COMPACTIONEACH SIDE OPERATION ROLL OF SILT FENCE PLOW FABRIC ABOVEGROUND HORIZONTAL CHISEL POINT (76 mm WIDTH)200-300mm SILT FENCE TOP 8" NOTES: ATTACHMENT DETAILS: SILT FENCE INSTALLATION BY SLICING METHOD NTS D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-35 D.2.1.3.2 BRUSH BARRIER Code: BB Symbol: 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 1. Brush barriers may be used downslope of all disturbed areas. 2. Brush barriers 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 a sediment trap or pond. The only circumstance in which overland flow may be treated solely by a barrier, rather than by a sediment trap or pond, is when the area draining to the barrier is small (see “Criteria for Use as Primary Treatment” in Section D.2.1.3). Design and Installation Specifications 1. See Figure D.2.1.3.C for details. 2. The City may require filter fabric (geotextile) anchored over the brush berm to enhance the filtration ability of the barrier. Maintenance Standards 1. There shall be no signs of erosion or concentrated runoff under or around the barrier. If concentrated flows are bypassing the barrier, it must be expanded or augmented by toed-in filter fabric. 2. The dimensions of the barrier must be maintained. FIGURE D.2.1.3.C BRUSH BARRIER IF REQUIRED, DRAPE FILTER FABRICOVER BRUSH AND SECURE IN 4"x4"MIN. TRENCH WITH COMPACTEDBACKFILL MAX. 6" DIAMETER WOODY DEBRIS FOR BARRIER CORE. ALTERNATIVELY TOPSOIL STRIPPINGS MAY BE USED TO FORM THE BARRIER. ANCHOR DOWNHILL EDGE OF FILTER FABRIC WITH STAKES, SANDBAGS, OR EQUIVALENT 2' MIN. HEIGHT 5' MIN. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-36 D.2.1.3.3 VEGETATED STRIP Code: VS Symbol: Purpose Vegetated strips 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 1. Vegetated strips may be used downslope of all disturbed areas. 2. 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 a sediment trap or pond. The only circumstance in which overland flow may be treated solely by a strip, rather than by a sediment trap or pond, is when the area draining to the strip is small (see “Criteria for Use as Primary Treatment” in Section D.2.1.3). Design and Installation Specifications 1. The vegetated strip shall consist of a 25-foot minimum width continuous strip of dense vegetation with a permeable topsoil. Grass-covered, landscaped areas are generally not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips shall consist of undisturbed native growth with a well-developed soil that allows for infiltration of runoff. 2. The slope within the strip shall not exceed 4H:1V. 3. The uphill boundary of the vegetated strip shall be delineated with clearing limits as specified in Section D.2.1.1. Maintenance Standards 1. Any areas damaged by erosion or construction activity shall be seeded immediately and protected by mulch. 2. If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded, sod must be installed using the standards for installation found in Section D.2.1.2.7. If there are indications that concentrated flows are traveling across the buffer, surface water controls must be installed to reduce the flows entering the buffer, or additional perimeter protection must be installed. D.2.1.3.4 TRIANGULAR SILT DIKE (GEOTEXTILE ENCASED CHECK DAM) Code: TSD Symbol: 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. Silt dikes, if attached to impervious surfaces with tack or other adhesive agent may also be used as temporary wheel wash areas, or concrete washout collection areas. Conditions of Use 1. May be used for temporary check dams in ditches. 2. May be used on soil or pavement with adhesive or staples. 3. TSDs have been used to build temporary sediment ponds, diversion ditches, concrete washout facilities, curbing, water bars, level spreaders, and berms. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-37 Design and Installation Specifications 1. TSDs must be made of urethane foam sewn into a woven geosynthetic fabric. 2. 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 3. Install TSDs with ends curved up to prevent water from flowing around the ends 4. Attach the TSDs and their fabric flaps to the ground with wire staples. Wire staples must be No. 11 gauge wire or stronger and shall be 200 mm to 300 mm in length. 5. When multiple units are installed, the sleeve of fabric at the end of the unit shall overlap the abutting unit and be stapled. 6. TSDs must be located and installed as soon as construction will allow. 7. TSDs must be placed perpendicular to the flow of water. 8. When used as check dams, the leading edge must be secured with rocks, sandbags, or a small key slot and staples. 9. When used in grass-lined ditches and swales, the TSD 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 TSD check dams shall be seeded and mulched immediately after dam removal. Maintenance Standards 1. Triangular silt dikes shall be monitored for performance and sediment accumulation during and after each runoff producing rainfall event. Sediment shall be removed when it reaches one half the height of the silt dike. 2. Anticipate submergence and deposition above the triangular silt dike and erosion from high flows around the edges of the dike/dam. Immediately repair any damage or any undercutting of the dike/dam. D.2.1.3.5 COMPOST BERMS Code: COBE Symbol: Purpose Compost berms are an option to meet the requirements of perimeter protection. Compost berms may reduce the transport of sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Compost berms trap sediment by filtering water passing through the berm and allowing water to pond, creating a settling area for solids behind the berm. Organic materials in the compost can also reduce concentrations of metals and petroleum hydrocarbons from construction runoff. Due to the increase in phosphorous seen in the effluent data from compost berms, they should be used with some cautions in areas that drain to phosphorus sensitive water bodies, and should only be used in Sensitive Lake watersheds, such as Lake Sammamish, with the approval from the City or the local jurisdiction. Conditions of Use 1. Compost berms may be used in most areas requiring sediment or erosion control where runoff is in the form of sheet flow or in areas where silt fence is normally considered acceptable. Compost berms may be used in areas where migration of aquatic life such as turtles and salamanders are impeded by the use of silt fence. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-38 2. Compost berms are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed via a drainage system to a sediment pond or trap. 3. For purposes of long-term sediment control objectives, berms may be seeded at the time of installation to create an additional vegetated filtering component. Design and Installation Specifications 1. Compost berms shall be applied using a pneumatic blower device or equivalent, to produce a uniform cross-section and berm density. 2. Compost berms shall be triangular in cross-section. The ratio of base to height dimensions shall be 2:1. 3. The minimum size of a compost berm is a 2-foot base with a 1-foot height. 4. Compost berms shall be sized and spaced as indicated in the table below. SLOPE SLOPE Maximum Slope Length or Berm Spacing (linear feet) Berm Size Required (height x base width) 0% – 2% Flatter than 50:1 250 1 ft x 2 ft 2% – 10% 50:1 – 10:1 125 1 ft x 2 ft 10% – 20% 10:1 – 5:1 100 1 ft x 2 ft 20% – 33% 5:1 – 3:1 75 1 ft x 2 ft 33% – 50% 3:1 – 2:1 50 1.5 ft x 3 ft 5. Compost berms shall not be used on slopes greater than 2H:1V. 6. Compost shall meet criteria in Reference Section 11-C of the SWDM except for the particle size distribution (see Bullet 8). 7. Compost shall be obtained from a supplier meeting the requirements in Reference Section 11-C. 8. Compost particle size distribution shall be as follows: 99% passing a 1 inch sieve, 90% passing a 3/4-inch sieve and a minimum of 70% greater than the 3/8-inch sieve. A total of 98% shall not exceed 3 inches in length. 9. Berms shall be placed on level contours to assist in dissipating flow into sheet flow rather than concentrated flows. Berms shall not be constructed to concentrate runoff or channel water. Sheet flow of water shall be perpendicular to the berm at impact. No concentrated flow shall be directed towards compost berms. 10. Where possible, berms shall be placed 5 feet or more from the toe of slopes to allow space for sediment deposition and collection. 11. In order to prevent water from flowing around the ends of the berms, the ends of the berm shall be constructed pointing upslope so the ends are at a higher elevation than the rest of the berm. 12. A compost blanket extending 10 to 15 feet above the berm is recommended where the surface above the berm is rutted or uneven, to reduce concentrated flow and promote sheet flow into the berm. Maintenance Standards 1. Compost berms shall be regularly inspected to make sure they retain their shape and allow adequate flow-through of stormwater. 2. When construction is completed on site, the berms shall be dispersed for incorporation into the soil or left on top of the site for final seeding to occur. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-39 3. Any damage to berms must be repaired immediately. Damage includes flattening, compacting, rills, eroded areas due to overtopping. 4. If concentrated flows are evident uphill of the berm, the flows must be intercepted and conveyed to a sediment trap or pond. 5. The uphill side of the berm shall be inspected for signs of the berm clogging and acting as a barrier to flows and causing channelization of flows parallel to the berm. If this occurs, replace the berm or remove the trapped sediment. 6. Sediment that collects behind the berm must be removed when the sediment is more than 6 inches deep. D.2.1.3.6 COMPOST SOCKS Code: COSO Symbol: Purpose Compost socks reduce the transport of sediment from a construction site by providing a temporary physical barrier to sediment-laden water and reducing the runoff velocities of overland flow. Compost socks trap sediment by filtering water that passes through the sock and allows water to pond behind the sock, creating a settling area for solids. Organic materials in the compost also may reduce metal and petroleum hydrocarbon concentrations in construction runoff. Compost socks function similarly to compost berms; however, because the compost is contained in a mesh tube, they are appropriate for both concentrated flow and sheet flow. Compost socks may be used to channel concentrated flow on hard surfaces. Conditions of Use 1. Compost socks may be used in areas requiring sediment or erosion control where runoff is in the form of sheet flow or in areas that silt fence is normally considered acceptable. Compost socks may also be used in sensitive environmental areas where migration of aquatic life, including turtles, salamanders and other aquatic life may be impeded by the used of silt fence. 2. Compost socks are not intended to treat substantial amounts of overland flow. However, compost socks may be subjected to some ponding and concentrated flows. If intended primarily as a filtration device, the socks should be sized and placed so that flows do not overtop the socks. 3. For purposes of long term sediment control objectives, compost socks may be seeded at the time of installation to create an additional vegetated filtering component. Design and Installation Specifications 1. Compost socks shall be produced using a pneumatic blower hose or equivalent to fill a mesh tube with compost to create a uniform cross-section and berm density. 2. Socks shall be filled so they are firmly – packed yet flexible. Upon initial filling, the socks shall be filled to have a round cross-section. Once placed on the ground, it is recommended to apply weight to the sock to improve contact with the underlying surface. This may cause the sock to assume an oval shape. 3. Compost socks shall be a minimum of 8 inches in diameter. Larger diameter socks are recommended for areas where ponding is expected behind the sock. 4. Compost socks shall not be used on slopes greater than 2H:1V. 5. Compost shall meet criteria in Reference Section 11-C of the SWDM, except for the particle size distribution (see Bullet 7). 6. Compost shall be obtained from a supplier meeting the requirements in Reference Section 11-C. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-40 7. Compost particle size distribution shall be as follows: 99% passing a 1-inch sieve, 90% passing a 3/4-inch sieve and a minimum of 70% greater than the 3/8-inch sieve. A total of 98% shall not exceed 3 inches in length. 8. In order to prevent water from flowing around the ends of compost socks, the ends must be pointed upslope so the ends of the socks are at a higher elevation than the remainder of the sock. Maintenance Standards 1. Compost socks shall be regularly inspected to make sure the mesh tube remains undamaged, the socks retain their shape, and allow adequate flow through of surface water. If the mesh tube is torn, it shall be repaired using twine, zip-ties, or wire. Large sections of damaged socks must be replaced. Any damage must be repaired immediately upon discovery of damage. 2. When the sock is no longer needed, the socks shall be cut open and the compost dispersed to be incorporated into the soil or left on top of the soil for final seeding to occur. The mesh material must be disposed of properly as solid waste. If spills of oil, antifreeze, hydraulic fluid, or other equipment fluids have occurred that have saturated the sock, the compost must be disposed of properly as a waste. 3. Sediment must be removed when sediment accumulations are within 3 inches of the top of the sock. D.2.1.4 TRAFFIC AREA STABILIZATION Unsurfaced entrances, roads, and parking areas used by construction traffic shall be stabilized to minimize erosion and tracking of sediment off site. Stabilized construction entrances shall be installed as the first step in clearing and grading. At the City’s discretion, road and parking area stabilization is not required during the dry season (unless dust is a concern) or if the site is underlain by coarse-grained soils. Roads and parking areas shall be stabilized immediately after initial grading. Purpose: The purpose of traffic area stabilization is to reduce the amount of sediment transported off site by construction vehicles and to reduce the erosion of areas disturbed by vehicle traffic. Sediment transported off site onto paved streets is a significant problem because it is difficult to effectively remove, and any sediment not removed ends up in the drainage system. Additionally, sediment on public right-of-way can pose a serious traffic hazard. Construction road and parking area stabilization is important because the combination of wet soil and heavy equipment traffic typically forms a slurry of easily erodible mud. Finally, stabilization also is an excellent form of dust control in the summer months. When to Install: The construction entrance is to be installed as the first step in clearing and grading. Construction road stabilization shall occur immediately after initial grading of the construction roads and parking areas. Measures to Use: There are two types of traffic area stabilization: (1) a stabilized construction entrance and (2) construction road/parking area stabilization. Both measures must be used as specified under “Conditions of Use” for each measure. D.2.1.4.1 STABILIZED CONSTRUCTION ENTRANCE Code: CE Symbol: Purpose Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by motor vehicles or runoff by constructing a stabilized pad of quarry spalls at entrances to construction sites. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-41 Conditions of Use Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling on paved roads or other paved areas within 1,000 feet of the site. Access and exits shall be limited to one route if possible, or two for linear projects such as roadway where more than one access/exit is necessary for maneuvering large equipment. For residential construction provide stabilized construction entrances for each residence in addition to the main subdivision entrance. Stabilized surfaces shall be of sufficient length/width to provide vehicle access/parking, based on lot size/configuration. Design and Installation Specifications 1. See Figure D.2.1.4.A for details. 2. 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 following standards: Grab Tensile Strength (ASTM D4632) 200 lbs min. Grab Tensile Elongation (ASTM D4632) 30% max.(woven) Puncture Strength (ASTM D6241) 495 lbs min. AOS (ASTM D4751) 20–45 (U.S. standard sieve size) 3. Do not use crushed concrete, cement, or calcium chloride for construction entrance stabilization because these products raise pH levels in stormwater and concrete discharge to surface waters of the State is prohibited. 4. Hog fuel (wood based mulch) may be substituted for or combined with quarry spalls in areas that will not be used for permanent roads. The effectiveness of hog fuel is highly variable, but it has been used successfully on many sites. It generally requires more maintenance than quarry spalls. Hog fuel is not recommended for entrance stabilization in urban areas. The inspector may at any time require the use of quarry spalls if the hog fuel is not preventing sediment from being tracked onto pavement or if the hog fuel is being carried onto pavement. Hog fuel is prohibited in permanent roadbeds because organics in the subgrade soils cause difficulties with compaction. 5. Fencing (see Section D.2.1.1) shall be installed as necessary to restrict traffic to the construction entrance. 6. Whenever possible, the entrance shall be constructed on a firm, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. Maintenance Standards 1. Quarry spalls (or hog fuel) shall be added if the pad is no longer in accordance with the specifications. 2. If the entrance 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 street sweeping, an increase in the dimensions of the entrance, or the installation of a wheel wash. If washing is used, it shall be done on an area covered with crushed rock, and wash water shall drain to a sediment trap or pond. 3. Any sediment that is tracked onto pavement shall be removed immediately by sweeping. 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 sweeping is ineffective and there is a threat to public safety. If it is necessary to wash the streets, a small sump must be constructed. The sediment would then be washed into the sump where it can be controlled. Wash water must be pumped back onto the site and cannot discharge to systems tributary to surface waters. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-42 4. Any quarry spalls that are loosened from the pad and end up on the roadway shall be removed immediately. 5. If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing (see Section D.2.1.1) shall be installed to control traffic. FIGURE D.2.1.4.A SCHEMATIC REPRESENTATION OF A STABILIZED CONSTRUCTION ENTRANCE D.2.1.4.2 CONSTRUCTION ROAD/PARKING AREA STABILIZATION Code: CRS Symbol: Purpose Stabilizing subdivision roads, parking areas and other onsite vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or runoff. Conditions of Use 1. Roads or parking areas shall be stabilized wherever they are constructed, whether permanent or temporary, for use by construction traffic. 2. Fencing (see Section D.2.1.1) 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 1. 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 •PER KING COUNTY ROAD DESIGN AND CONSTRUCTION STANDARDS (KCRDCS), DRIVEWAYS SHALL BE PAVED TO EDGE OF R-O-W PRIOR TO INSTALLATION OF THE CONSTRUCTION ENTRANCE TO AVOID DAMAGING OF THE ROADWAY. •IT IS RECOMMENDED THAT THE ENTRANCE BE CROWNED SO THAT RUNOFF DRAINS OFF THE PAD. 12" MIN. THICKNESS PROVIDE FULL WIDTH OF INGRESS/EGRESS AREA IF A ROADSIDE DITCH ISPRESENT, INSTALL DRIVEWAY CULVERT PER KCRDCS GEOTEXTILE 4"- 8" QUARRYSPALLS R=25' MIN. 100' M I N . EXISTI N G R O A D 15' MI N. NOTES: D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-43 calcium chloride for soil stabilization. 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, construction roads and parking areas shall be placed on a firm, compacted subgrade. Note: If the area will be used for permanent road or parking installation later in the project, the subgrade will be subject to inspection. 2. Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain transversely. 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 designed in accordance with the standards given in Section D.2.1.6.4 and directed to a sediment pond or trap. 3. 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, 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 vegetated wetlands. If runoff is allowed to sheet flow through adjacent vegetated areas, it is vital to design the roadways and parking areas so that no concentrated runoff is created. 4. In order to control construction traffic, the City may require that signs be erected on site informing construction personnel that vehicles, other than those performing clearing and grading, are restricted to stabilized areas. 5. If construction roads do not adequately reduce trackout to adjacent property or roadways, a wheel wash system will be required. Maintenance Standards Crushed rock, gravel base, hog fuel, etc., shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. D.2.1.4.3 WHEEL WASH Code: WW Symbol: Purpose Wheel wash systems reduce the amount of sediment transported onto paved roadways and into surface water systems by construction vehicles. Conditions of Use When a stabilized construction entrance is not preventing sediment from being tracked onto pavement: • Wheel washing is generally an effective erosion and sediment control method and BMP when installed with careful attention to topography. For example, a wheel wash can be detrimental if installed at the top of a slope abutting a right-of-way where the water from the dripping truck wheels and undercarriage can run unimpeded into the street. • Pressure washing combined with an adequately sized and properly surfaced wash pad with direct drainage discharge to a large 10-foot x 10-foot sump can be very effective. Design and Installation Specifications A suggested detail is shown in Figure D.2.1.4.B. 1. A minimum of 6 inches of asphalt treated base (ATB) over crushed base material or 8 inches over a good subgrade is recommended to pave the wheel wash area. 2. Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-44 3. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. 4. Midpoint spray nozzles are only needed in very muddy conditions. 5. 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 the pond and to help prevent re-suspension of sediment. 6. A drainpipe with a 2- to 3-foot riser should be installed on the low side of the wheel wash pond to allow for easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a closed-loop system. 7. Polyacrylamide (PAM) added to the wheel washwater at a rate of 0.25 to 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 may be used to change the washwater. Maintenance Standards 1. The wheel wash should start out each day with clean, fresh water. 2. The washwater should be changed a minimum of once per day. On large earthwork jobs where more than 10 to 20 trucks per hour are expected, the washwater will need to be changed more often. 3. Wheel wash or tire bath wastewater shall be discharged to a separate onsite treatment system, such as a closed-loop recirculation system or land application, or to the sanitary sewer system with proper approval and/or permits from King County and the City of Renton. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-45 FIGURE D.2.1.4.B WHEEL WASH AND PAVED CONSTRUCTION ENTRANCE 2%SLOPE 15'15'20'15'50' 18' 12' 3' 5' BUILD 8'x8' SUMP TO ACCOMODATE CLEANING BY TRACKHOE.SECTION A-A NTS 8'x8' SUMP, SEE NOTE LOCATE INVERT OF TOP PIPE 1' ABOVE BOTTOM OF WHEEL WASH DRAIN PIPE 1:1 SLOPE WATER LEVEL ELEVATION VIEW NTS PLAN VIEW NTS 6" SLEEVE CURB ASPHALT CURB ON THELOW ROAD SIDE TO DIRECTWATER BACK TO POND 6" ATB CONSTRUCTIONENTRANCE 1-1/2" SCHEDULE 40 FOR SPRAYERS 2% SLOPE MIDPOINT SPRAYNOZZLES, IF NEEDED 3" TRASH PUMP WITH FLOATS ON SUCTION HOSE 2" SCHEDULE 40 6" SLEEVE UNDER ROAD 8'x8' SUMP WITH 5'OF CATCH 6" SEWER PIPE WITH BUTTERFLY VALVES 1:1 SLOPE A A 5:1SLOPE5:1SLOPE 15' ATB APRON TO PROTECTGROUND FROM SPLASHING WATER BALL VALVES NOTE: SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-46 D.2.1.5 SEDIMENT RETENTION Surface water collected from disturbed areas of the site shall be routed through a sediment pond or trap prior to release from the site. An exception is for areas at the perimeter of the site with drainage areas small enough to be treated solely with perimeter protection (see Section D.2.1.3). Also, if the soils and topography are such that no offsite discharge of surface water is anticipated up to and including the developed 2-year runoff event, sediment ponds and traps are not required. A 10-year peak flow using the approved model with 15-minute time steps shall be used for sediment pond/trap sizing if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection (see below). At the City’s discretion, sites may be worked during the dry season without sediment ponds and traps if there is some other form of protection of surface waters, such as a 100-foot forested buffer between the disturbed areas and adjacent surface waters. For small sites, use the criteria defined in Section D.2.1.3, Perimeter Protection to determine minimum flow path length. If the site work has to be extended into the wet season, a back-up plan must be identified in the CSWPP plan and implemented. Protection of catch basins is required for inlets that are likely to be impacted by sediment generated by the project and that do not drain to an onsite sediment pond or trap. Sediment retention facilities shall be installed prior to grading of any contributing area and shall be located so as to avoid interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages. Purpose: The purpose of sediment retention facilities is to remove sediment from runoff generated from disturbed areas. When to Install: The facilities shall be constructed as the first step in the clearing and grading of the site. The surface water conveyances may then be connected to the facilities as site development proceeds. Measures to Use: There are three sediment retention measures in this section. The first two, sediment traps and ponds, serve the same function but for different size catchments. All runoff from disturbed areas must be routed through a trap or pond except for very small areas at the perimeter of the site small enough to be treated solely with perimeter protection (see Section D.2.1.3). The third measure is for catch basin protection. It is only to be used in limited circumstances and is not a primary sediment treatment facility. It is only intended as a backup in the event of failure of other onsite systems. Use of Permanent Drainage Facilities: All projects that are constructing permanent facilities for runoff quantity control are strongly encouraged to use the rough-graded or final-graded permanent facilities for ponds and traps. This includes combined facilities and infiltration facilities. When permanent facilities are used as temporary sedimentation facilities, the surface area requirements of sediment traps (for drainages less than 3 acres) or sediment ponds (more than 3 acres) must be met. If the surface area requirements are larger than the surface area of the permanent facility, then the pond shall be enlarged to comply with the surface area requirement. The permanent pond shall also be divided into two cells as required for sediment ponds. Either a permanent control structure or the temporary control structure described in Section D.2.1.5.2 may be used. If a permanent control structure is used, it may be advisable to partially restrict the lower orifice with gravel to increase residence time while still allowing dewatering of the pond. If infiltration facilities are to be used, the sides and bottom of the facility must only be rough excavated to a minimum of three feet above final grade. Excavation should be done with a backhoe working at “arm’s length” to minimize disturbance and compaction of the infiltration surface. Additionally, any required pretreatment facilities shall be fully constructed prior to any release of sediment-laden water to the facility. Pretreatment and shallow excavation are intended to prevent the clogging of soil with fines. Final grading of the infiltration facility shall occur only when all contributing drainage areas are fully stabilized (see Section D.2.4.5). Selection of the Design Storm: In most circumstances, the developed condition 2-year peak flow using the approved model with 15-minute time steps is sufficient for calculating surface area for ponds and traps and for determining exemptions from the sediment retention and surface water collection requirements (Sections D.2.1.5 and D.2.1.6, respectively). In some circumstances, however, the approved model 10-year 15-minute peak flow should be used. Examples of such circumstances include the following: D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-47 • Sites that are within ¼ mile of salmonid streams, wetlands, and designated sensitive lakes such as Lake Sammamish • Sites where significant clearing and grading is likely to occur during the wet season • Sites with downstream erosion or sedimentation problems. Natural Vegetation: Whenever possible, sediment-laden water shall be discharged into onsite, relatively level, vegetated areas. This is the only way to effectively remove fine particles from runoff. This can be particularly useful after initial treatment in a sediment retention facility. The areas of release must be evaluated on a site-by-site basis in order to determine appropriate locations for and methods of releasing runoff. Vegetated wetlands shall not be used for this purpose. Frequently, it may be possible to pump water from the collection point at the downhill end of the site to an upslope vegetated area. Pumping shall only augment the treatment system, not replace it because of the possibility of pump failure or runoff volume in excess of pump capacity. D.2.1.5.1 SEDIMENT TRAP Code: ST Symbol: Purpose Sediment traps remove sediment from runoff originating from disturbed areas of the site. Sediment traps are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually only result in a small reduction in turbidity. Conditions of Use A sediment trap shall be used where the contributing drainage area is 3 acres or less. Design and Installation Specifications 1. See Figure D.2.1.5.A for details. 2. If permanent runoff control facilities are part of the project, they should be used for sediment retention (see “Use of Permanent Drainage Facilities” in Section D.2.1.5). 3. To determine the trap geometry, first calculate the design surface area (SA) of the trap, measured at the invert of the weir. Use the following equation: SA = FS(Q2/Vs) where Q2 = Design inflow (cfs) from the contributing drainage area based on the developed condition 2-year or 10-year peak discharge using the approved model with 15-minute time steps as computed in the hydrologic analysis. The approved model 10-year 15-minute peak flow shall be used if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection, or if the pond discharge path leaves the site (note provisions must made to prevent increases in the existing site conditions 2-year and 10-year runoff peaks discharging from the project site during construction, see Section D.3.9, Flow Control). If no hydrologic analysis is required, the Rational Method may be used (Section 3.2.1 of the SWDM). Vs = The settling velocity (ft/sec) of the soil particle of interest. The 0.02 mm (medium silt) particle with an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a settling velocity (Vs) of 0.00096 ft/sec. FS = A safety factor of 2 to account for non-ideal settling. Therefore, the equation for computing surface area becomes: SA = 2 x Q2/0.00096 or 2080 square feet per cfs of inflow SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-48 Note: Even if permanent facilities are used, they must still have a surface area that is at least as large as that derived from the above formula. If they do not, the pond must be enlarged. 4. To aid in determining sediment depth, all traps shall have a staff gage with a prominent mark one foot above the bottom of the trap. Maintenance Standards 1. Sediment shall be removed from the trap when it reaches 1 foot in depth. 2. Any damage to the trap embankments or slopes shall be repaired. FIGURE D.2.1.5.A SEDIMENT TRAP NOTE:TRAP MAY BE FORMED BY BERM OR BY PARTIAL OR COMPLETE EXCAVATION 3 H : 1 V M A X . FLAT BOTTOM 1' MIN. 18" MIN. 1' MIN. 1' MIN. DEPTH OVERFLOW SPILLWAY CROSS SECTION TRAP OUTLET NATIVE SOIL OR COMPACTED BACKFILL GEOTEXTILE 6' MIN. MIN.1' DEPTH 2"-4" ROCK MIN. 1' DEPTH 3/4"-1 1/2" WASHED GRAVEL 4' MIN. 3.5'-5' SURFACE AREA DETERMINEDAT TOP OF WEIR DISCHARGE TO STABILIZED CONVEYANCE,OUTLET OR LEVEL SPREADER 3/4"-1 1/2" WASHED GRAVEL GEOTEXTILE 2"-4" ROCK RIPRAP 1' MIN. OVERFLOW D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-49 D.2.1.5.2 SEDIMENT POND Code: SP Symbol: Purpose Sediment ponds remove sediment from runoff originating from disturbed areas of the site. Sediment ponds are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually reduce turbidity only slightly. Conditions of Use A sediment pond shall be used where the contributing drainage area is 3 acres or more. Design and Installation Specifications 1. See Figure D.2.1.5.B, Figure D.2.1.5.C, and Figure D.2.1.5.D for details. 2. If permanent runoff control facilities are part of the project, they should be used for sediment retention (see “Use of Permanent Drainage Facilities” in Section D.2.1.5). Determining Pond Geometry 1. Obtain the discharge from the hydrologic calculations for the 2-year and 10-year peak flows using the approved model with 15-minute time steps (Q2 and Q10). The approved model 10-year 15-minute peak flow shall be used if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection, or if the pond discharge path leaves the site (note provisions must made to prevent increases in the existing site conditions 2-year and 10-year runoff peaks discharging from the project site during construction, see Section D.3.9, Flow Control). If no hydrologic analysis is required, the Rational Method may be used (Section 3.2.1 of the SWDM). 2. Determine the required surface area at the top of the riser pipe with the equation: SA = 2 x Q10/0.00096 or 2080 square feet per cfs of inflow See Section D.2.1.5.1 for more information on the derivation of the surface area calculation. 3. The basic geometry of the pond can now be determined using the following design criteria: • Required surface area SA (from Step 2 above) at top of riser • Minimum 3.5-foot depth from top of riser to bottom of pond • Maximum 3:1 interior side slopes and maximum 2:1 exterior slopes. The interior slopes may be increased to a maximum of 2:1 if fencing is provided at or above the maximum water surface • One foot of freeboard between the top of the riser and the crest of the emergency spillway • Flat bottom • Minimum one foot deep spillway • Length-to-width ratio between 3:1 and 6:1. Sizing of Discharge Mechanisms Principal Spillway: Determine the required diameter for the principal spillway (riser pipe). The diameter shall be the minimum necessary to pass the developed condition 10-year peak flow using the approved model with 15-minute time steps (Q10). Use Figure 5.1.4.H (SWDM Chapter 5) to determine this diameter (h = one foot). Note: A permanent control structure may be used instead of a temporary riser. Emergency Overflow Spillway: Determine the required size and design of the emergency overflow spillway for the developed condition 100-year approved model 15-minute peak flow using the procedure in Section 5.1.1 (“Emergency Overflow Spillway” subsection) of the SWDM. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-50 Dewatering Orifice: Determine the size of the dewatering orifice(s) (minimum 1-inch diameter) using a modified version of the discharge equation for a vertical orifice and a basic equation for the area of a circular orifice. 1. Determine the required area of the orifice with the following equation: hATg hAA sso)10(81.43600x6.0 )2(6 5.0 5.0 −== where Ao = orifice area (square feet) As = pond surface area (square feet) h = head of water above orifice (height of riser in feet) T = dewatering time (24 hours) g = acceleration of gravity (32.2 feet/second2) 2. Convert the required surface area to the required diameter D (inches) of the orifice: ooAADx54.13x24==π 3. The vertical, perforated tubing connected to the dewatering orifice must be at least 2 inches larger in diameter than the orifice to improve flow characteristics. The size and number of perforations in the tubing should be large enough so that the tubing does not restrict flow. The flow rate should be controlled by the orifice. Additional Design Specifications • The pond shall be divided into two roughly equal volume cells by a permeable divider that will reduce turbulence while allowing movement of water between cells. The divider shall be at least one-half the height of the riser and a minimum of one foot below the top of the riser. Wire-backed, 2- to 3-foot high, extra strength filter fabric (see Section D.2.1.3.1) supported by treated 4″ x 4″s may be used as a divider. Alternatively, staked straw bales wrapped with filter fabric (geotextile) may be used. • If the pond is more than 6 feet deep, a different mechanism must be proposed. A riprap embankment is one acceptable method of separation for deeper ponds. Other designs that satisfy the intent of this provision are allowed as long as the divider is permeable, structurally sound, and designed to prevent erosion under or around the barrier. • To aid in determining sediment depth, one-foot intervals shall be prominently marked on the riser. • If an embankment of more than 6 feet is proposed, the pond must comply with the criteria under “Embankments” in Section 5.1.1 of the Surface Water Design Manual. Maintenance Standards 1. Sediment shall be removed from the pond when it reaches 1 foot in depth. 2. Any damage to the pond embankments or slopes shall be repaired. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-51 FIGURE D.2.1.5.B SEDIMENT POND PLAN VIEW FIGURE D.2.1.5.C SEDIMENT POND CROSS SECTION INFLOW NOTE:POND MAY BE FORMED BY BERM OR BY PARTIAL OR COMPLETE EXCAVATION DISCHARGE TO STABILIZED CONVEYANCE, OUTLET OR LEVELSPREADER EMERGENCY OVERFLOW SPILLWAY KEY DIVIDER INTO SLOPE TO PREVENT FLOW AROUND SIDES THE POND LENGTH SHALL BE 3 TO 6 TIMES THE MAXIMUM POND WIDTH SILT FENCE OR EQUIVALENTDIVIDER RISER PIPE POND LENGTH 3H : 1 V M A X . RISER PIPE (PRINCIPALSPILLWAY) OPEN AT TOP WITH TRASH RACK PER FIG. 5.1.1.C DEWATERING DEVICE (SEERISER DETAIL)2H : 1 VMA X .3H:1VMAX.WIRE-BACKED SILTFENCE, STAKED STRAW BALES WRAPPED WITHFILTER FABRIC, OR EQUIVALENT DIVIDER CONCRETE BASE (SEE RISER DETAIL) DISCHARGE TO STABILIZED CONVEYANCE, OUTLET OR LEVEL SPREADER DEWATERING ORIFICE CREST OF EMERGENCY SPILLWAY 1' 6' MIN. BERM WIDTH EMBANKMENT COMPACTED 95% MODIFIED PROCTOR. PERVIOUS MATERIALS SUCH AS GRAVEL OR CLEAN SAND SHALL NOT BE USED. 1' MIN. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-52 FIGURE D.2.1.5.D SEDIMENT POND RISER DETAIL D.2.1.5.3 STORM DRAIN INLET PROTECTION Code: FFP or CBI or CBP Symbol: or or Purpose Storm drain inlets are protected to prevent coarse sediment from entering storm drainage systems. Temporary devices around storm drains assist in improving the quality of water discharged to inlets or catch basins by ponding sediment-laden water. These devices are effective only for relatively small drainage areas. Conditions of Use 1. Protection shall be provided for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless the runoff that enters the catch basin will be conveyed to a sediment pond or trap. 2. Inlet protection may be used anywhere at the applicant’s discretion to protect the drainage system. This will, however, require more maintenance, and it is highly likely that the drainage system will still require some cleaning. 3. The contributing drainage area must not be larger than one acre. Design and Installation Specifications 1. There are many options for protecting storm drain inlets. Two commonly used options are filter fabric protection and catch basin inserts. Filter fabric protection (see Figure D.2.1.5.E) is filter fabric (geotextile) placed over the grate. This method is generally very ineffective and requires intense maintenance efforts. Catch basin inserts (see Figure D.2.1.5.F) are manufactured devices that nest inside a catch basin. This method also requires a high frequency of maintenance to be effective. Both options provide adequate protection, but filter fabric is likely to result in ponding of water above the 3.5' MIN. 18" MIN. 2X RISER DIA. MIN. CORRUGATEDMETAL RISER CONCRETE BASE ALTERNATIVELY, METAL STAKES AND WIRE MAYBE USED TO PREVENTFLOTATION DEWATERING ORIFICE, SCHEDULE 40 STEELSTUB MIN. DIAMETER AS PER CALCULATIONS 6" MIN. PROVIDE ADEQUATESTRAPPING POLYETHYLENE CAP PERFORATED DEWATERING DEVICE,SEE NOTE WATERTIGHT COUPLING TACKWELD NOTE:PERFORATED CORRUGATEDPOLYETHYLENE (CPE) DRAINAGE TUBING, DIAMETERMIN. 2" LARGER THAN DEWATERING ORIFICE. TUBING SHALL COMPLY WITH ASTMF667 AND AASHTO M294. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-53 catch basin, while the insert will not. Thus, filter fabric is only allowed where ponding will not be a traffic concern and where slope erosion will not result if the curb is overtopped by ponded water. Trapping sediment in the catch basins is unlikely to improve the water quality of runoff if it is treated in a pond or trap because the coarse particles that are trapped at the catch basin settle out very quickly in the pond or trap. Catch basin protection normally only improves water quality where there is no treatment facility downstream. In these circumstances, catch basin protection is an important last line of defense. It is not, however, a substitute for preventing erosion. The placement of filter fabric under grates is generally prohibited and the use of filter fabric over grates is strictly limited and discouraged. 2. It is sometimes possible to construct a small sump around the catch basin before final surfacing of the road. This is allowed because it can be a very effective method of sediment control. 3. Block and gravel filters, gravel and wire mesh filter barriers, and bag barriers filled with various filtering media placed around catch basins can be effective when the drainage area is 1 acre or less and flows do not exceed 0.5 cfs. It is necessary to allow for overtopping to prevent flooding. Many manufacturers have various inlet protection filters that are very effective in keeping sediment-laden water from entering the storm drainage system. The following are examples of a few common methods. a) Block and gravel filters (Figure D.2.1.5.G) are a barrier formed around an inlet with standard concrete block and gravel, installed as follows: • Height is 1 to 2 feet above the inlet. • Recess the first row of blocks 2 inches into the ground for stability. • Support subsequent rows by placing a 2x4 through the concrete block opening. • Do not use mortar. • Lay some blocks in the bottom row on their side for dewatering the pooled water. • Place cloth or mesh with ½ inch openings over all block openings. • Place gravel below the top of blocks on slopes of 2:1 or flatter. • An alternate design is a gravel donut. b) Gravel and wire mesh filters consist of a gravel barrier placed over the top of an inlet. This structure generally does not provide overflow. Install as follows: • Cloth or comparable wire mesh with ½ inch openings is placed over inlet. • Coarse aggregate covers the cloth or mesh. • Height/depth of gravel should be 1 foot or more, 18 inches wider than inlet on all sides. c) Curb inlet protection with a wooden weir is a barrier formed around an inlet with a wooden frame and gravel, installed as follows: • Construct a frame and attach wire mesh (½ inch openings) and filter fabric to the frame. • Pile coarse washed aggregate against the wire/fabric. • Place weight on frame anchors. d) Curb and gutter sediment barriers (Figure D.2.1.5.H) consist of sandbags or rock berms (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape, installed as follows: • Bags of either burlap or woven geotextile fabric, filled with a variety of media such as gravel, wood chips, compost or sand stacked tightly allows water to pond and allows sediment to separate from runoff. • Leave a “one bag gap” in the top row of the barrier to provide a spillway for overflow. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-54 • Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 x 3 and at least 2 feet from the inlet. • Construct a horseshoe shaped sedimentation trap on the outside of the berm to sediment trap standards for protecting a culvert inlet. 4. Excavated drop inlet sediment traps are appropriate where relatively heavy flows are expected and overflow capability is needed. If emergency overflow is provided, additional end-of-pipe treatment may be required. Excavated drop inlets consist of an excavated impoundment area around a storm drain. Sediment settles out of the stormwater prior to enter the drain. Install according to the following specifications: a) The impoundment area should have a depth of 1 to 2 feet measured from the crest of the inlet structure. b) Side slopes of the excavated area must be no steeper than 2:1. c) Minimum volume of the excavated area should be 35 cubic yards. d) Install provisions for draining the area to prevent standing water problems. e) Keep the area clear of debris. f) Weep holes may be drilled into the side of the inlet. g) Protect weep holes with wire mesh and washed aggregate. h) Weep holes must be sealed when removing and stabilizing excavated area. i) A temporary dike may be necessary on the down slope side of the structure to prevent bypass flow. Maintenance Standards 1. Any accumulated sediment on or around inlet protection shall be removed immediately. Sediment shall not be removed with water, and all sediment must be disposed of as fill on site or hauled off site. 2. Any sediment in the catch basin insert shall be removed when the sediment has filled one-third of the available storage. The filter media for the insert shall be cleaned or replaced at least monthly. 3. Regular maintenance is critical for all forms of catch basin/inlet protection. Unlike many forms of protection that fail gradually, catch basin protection will fail suddenly and completely if not maintained properly. FIGURE D.2.1.5.E FILTER FABRIC PROTECTION CATCH BASIN NOTE: ONLY TO BE USED WHERE PONDING OF WATER ABOVE THE CATCH BASIN WILL NOT CAUSE TRAFFIC PROBLEMS AND WHERE OVERFLOW WILL NOT RESULT IN EROSION OF SLOPES. GRATESTANDARD STRENGTH FILTER FABRIC D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-55 FIGURE D.2.1.5.F CATCH BASIN INSERT NOTE: THIS DETAIL IS ONLYSCHEMATIC. ANY INSERT IS ALLOWED THAT HAS:•A MIN. 0.5 C.F. OF STORAGE, •THE MEANS TO DEWATER THESTORED SEDIMENT, •AN OVERFLOW, AND•CAN BE EASILY MAINTAINED. OVERFLOW GRATECATCH BASIN POROUS BOTTOM SOLID WALLS FILTER MEDIA FOR DEWATERING SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-56 FIGURE D.2.1.5.G BLOCK AND GRAVEL CURB INLET PROTECTION 1.USE BLOCK AND GRAVEL TYPE SEDIMENT BARRIER WHEN CURB INLET IS LOCATED IN GENTLY SLOPING SEGMENT, WHERE WATER CAN POND AND ALLOW SEDIMENT TO SEPARATE FROM RUNOFF. 2.BARRIER SHALL ALLOW FOR OVERFLOW FROM SEVERE STORM EVENT. 3.INSPECT BARRIERS AND REMOVE SEDIMENT AFTER EACH STORM EVENT. SEDIMENTAND GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEDIATELY. 2x4 WOOD STUD OVERFLOW WATER A A PLAN VIEW NTS SECTION A-A NTS BLOCK AND GRAVEL CURB INLET PROTECTION NTS CATCH BASIN COVER CURB INLET CONCRETE BLOCKS CATCH BASIN COVER CURB INLET CATCH BASIN BACK OF SIDEWALK CURB FACE 3/4" DRAIN GRAVEL (20 mm) WIRE SCREEN OR FILTER FABRIC POND HEIGHT WIRE SCREENOR FILTER FABRIC 2x4 WOOD STUD(100x50 TIMBER STUD) 3/4" DRAIN GRAVEL (20 mm) NOTES: D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-57 FIGURE D.2.1.5.H CURB AND GUTTER BARRIER PROTECTION RUNOFF RUNOFF SPILLWAY 1.PLACE CURB-TYPE SEDIMENT BARRIERS ON GENTLY SLOPING STREET SEGMENTS, WHERE WATER CAN POND AND ALLOW SEDIMENT TO SEPARATE FROM RUNOFF. 2.SANDBAGS OF EITHER BURLAP OR WOVEN GEOTEXTILE FABRIC ARE FILLED WITH GRAVEL, LAYERED AND PACKED TIGHTLY. 3.LEAVE A ONE-SANDBAG GAP IN THE TOP ROW TO PROVIDE A SPILLWAY FOR OVERFLOW. 4.INSPECT BARRIERS AND REMOVE SEDIMENT AFTER EACH STORM EVENT. SEDIMENT AND GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEDIATELY. GRAVEL FILLED SANDBAGS STACKED TIGHTLY DRAIN GRATE GUTTER CURB FACE CURB INLET SANDBAGS TO OVERLAPONTO CURB BACK OF SIDEWALK PLAN VIEW NTS CURB AND GUTTER BARRIER NTS NOTES: SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-58 D.2.1.6 SURFACE WATER COLLECTION All surface water from disturbed areas shall be intercepted, conveyed to a sediment pond or trap, and discharged downslope of any disturbed areas. An exception is for areas at the perimeter of the site with drainage areas small enough to be treated solely with perimeter protection (see Section D.2.1.3). Also, if the soils and topography are such that no offsite discharge of surface water is anticipated up to and including the developed 2-year runoff event, surface water controls are not required. A 10-year approved model 15-minute peak flow shall be used for sizing surface water controls if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection (see the introduction to Section D.2.1.5). At the City’s discretion, sites may be worked during the dry season without surface water controls, if there is some other form of protection of surface waters, such as a 100-foot forested buffer between the disturbed areas and adjacent surface waters. Significant sources of upslope surface water that drain onto disturbed areas shall be intercepted and conveyed to a stabilized discharge point downslope of the disturbed areas. Surface water controls shall be installed concurrently with rough grading. Purpose: The purpose of surface water control is to collect and convey surface water so that erosion is minimized, and runoff from disturbed areas is treated by a sediment pond or trap. Surface water control essentially consists of three elements: 1. Interception of runoff on and above slopes 2. Conveyance of the runoff to a sediment pond or trap (if the runoff was collected from a disturbed area) 3. Release of the runoff downslope of any disturbed areas. When to Install: Surface water controls shall be constructed during the initial grading of an area and must be in place before there is any opportunity for storm runoff to cause erosion. Measures to Install: Interceptor dikes/swales intercept runoff, ditches and pipe slope drains convey the runoff, and riprap or level spreaders help release the runoff in a non-erosive manner. Each measure is to be used under different circumstances so there is very little overlap. However, the two options for releasing water in a non-erosive manner, outlet protection and level spreaders, can be somewhat interchangeable. See Figure D.2.1.6.A for a schematic drawing demonstrating the use of these measures. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-59 FIGURE D.2.1.6.A SKETCH PLAN OF SURFACE WATER CONTROLS D.2.1.6.1 INTERCEPTOR DIKE AND SWALE Code: ID or IS Symbol: or Purpose Interceptor dikes and swales intercept storm runoff from drainage areas on or above disturbed slopes and convey it to a sediment pond or trap. They may also be used to intercept runoff from undisturbed areas and convey the runoff to a point below any exposed soils. Interception of surface water reduces the possibility of slope erosion. Interceptor dikes and swales differ from ditches (see Section D.2.1.6.4) in that they are intended to convey smaller flows along low-gradient drainage ways to larger conveyance systems such as ditches or pipe slope drains. Conditions of Use Interceptor dikes and swales are required in the following situations: 1. At the top of all slopes in excess of 3H:1V and with more than 20 feet of vertical relief. 2. At intervals on any slope that exceeds the dimensions specified in this section for the horizontal spacing of dikes and swales. Design and Installation Specifications 1. See Figure D.2.1.6.B for details of an interceptor dike and Figure D.2.1.6.C for an interceptor swale. 2. Interceptor dikes and swales shall be spaced horizontally as follows: Average Slope Slope Percent Flowpath Length 20H:1V or less 3–5% 300 feet (10 to 20)H:1V 5–10% 200 feet (4 to 10)H:1V 10–25% 100 feet (2 to 4)H:1V 25–50% 50 feet INTERCEPTOR DIKE TOP OF SLOPE TOE OF SLOPE OUTLETPROTECTION DITCH SEDIMENT POND SILT FENCE STREAM PIPE SLOPE DRAIN FLOW ID PD ID OP DI SP SF SF OP SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-60 3. For slopes steeper than 2H:1V with more than 10 feet of vertical relief, benches may be constructed or closer spaced interceptor dikes or swales may be used. Whichever measure is chosen, the spacing and capacity of the measures must be designed by the engineer and the design must include provisions for effectively intercepting the high velocity runoff associated with steep slopes. 4. If the dike or swale intercepts runoff from disturbed areas, it shall discharge to a stable conveyance system that routes the runoff to a sediment pond or trap (see Section D.2.1.5). If the dike or swale intercepts runoff that originates from undisturbed areas, it shall discharge to a stable conveyance system that routes the runoff downslope of any disturbed areas and releases the water at a stabilized outlet. 5. Construction traffic over temporary dikes and swales shall be minimized. Maintenance Standards 1. Damage resulting from runoff or construction activity shall be repaired immediately. 2. If the facilities do not regularly retain storm runoff, the capacity and/or frequency of the dikes/swales shall be increased. FIGURE D.2.1.6.B INTERCEPTOR DIKE FIGURE D.2.1.6.C INTERCEPTOR SWALE DIKE SPACING DEPENDS ON SLOPE GRADIENT 2' MIN.18" MIN. 2 MAX. 12 MAX. 1 DIKE MATERIAL COMPACTED 90% MODIFIED PROCTOR SWALE SPACING DEPENDS ON SLOPE GRADIENT 2' MIN. 1' MIN. LEVEL BOTTOM 2:1 MAX. SLOPE D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-61 D.2.1.6.2 PIPE SLOPE DRAINS Code: PD Symbol: Purpose Pipe slope drains are designed to carry concentrated runoff down steep slopes without causing erosion, or saturation of slide-prone soils. Pipe slope drains may be used to divert water away from or over bare soil to prevent gullies, channel erosion, and saturation of slide prone soils Conditions of Use Pipe slope drains should be used when a temporary or permanent stormwater conveyance is needed to move water down a steep slope to avoid erosion. Pipe slope drains may be: 1. Connected to new catch basins and used temporarily until all permanent piping is installed. 2. Used on any slope with a gradient of 2H:1V or greater and with at least 10 feet of vertical relief. 3. Used to drain water collected from aquifers exposed on cut slopes and convey it to the base of the slope. 4. Used to collect clean runoff from plastic sheet cover and direct away from any exposed soils. 5. Installed in conjunction with silt fence to drain collected water to a controlled area. 6. Used to divert small seasonal streams away from construction. Pipe slope drains have been used successfully on culvert replacement and extension projects. Large flex pipe may be used on larger streams during culvert removal, repair, or replacement. 7. Connected to existing downspouts and roof drains used to divert water away from work areas during building renovation, demolition, and construction projects. 8. Rock-lined ditches or other permanent, non-erosive conveyances used to convey runoff down steep slopes that are not steep slope hazard areas. Design and Installation Specifications 1. See Figure D.2.1.6.D for details. 2. The capacity for temporary drains shall be sufficient to handle the developed 10-year peak flow using the approved model with 15-minute time steps. Up to 30,000 square feet may be drained by each 6-inch minimum diameter pipe without computation of the peak flow. Up to 2 acres may be drained by each 12-inch minimum diameter pipe. Otherwise, the peak flow will need to be computed using the Rational Method described in Section 3.2.1 of the SWDM. 3. The maximum drainage area allowed for any sized pipe is 10 acres. For larger areas, more than one pipe shall be used or a rock-lined channel shall be installed (see SWDM Section 4.4.1, “Open Channels”). 4. The soil around and under the pipe and entrance section shall be thoroughly compacted. 5. The flared inlet section shall be securely connected to the slope drain and be fused or welded, or have flange-bolted mechanical joints to ensure a watertight seal. Ensure that the entrance area is stable and large enough to direct flow into the pipe. 6. Slope drains shall be continuously fused, welded, or flange-bolted mechanical joint pipe systems with proper anchoring to the soil. 7. Where slope drains cross steep slope hazard areas or their associated buffers, the installation shall be on the ground surface, accomplished with minimum alteration. In most circumstances, this requires that slope drains be constructed of corrugated metal, CPE, or equivalent pipe and installed by hand SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-62 (see SWDM Section 4.2.1). Any area disturbed during installation or maintenance must be immediately stabilized. 8. If the pipe slope drain will convey sediment-laden runoff, the runoff must be directed to a sediment retention facility (see Section D.2.1.5). If the runoff is not from a disturbed area or is conveyed from a sediment trap or pond, it must be conveyed to a stabilized discharge point (see Section D.2.1.6.5). 9. Re-establish cover immediately on areas disturbed by the installation. Maintenance Standards 1. The inlet shall not be undercut or bypassed by water. If there are problems, the head wall shall be appropriately reinforced. 2. No erosion shall occur at the outlet point. If erosion occurs, additional protection shall be added. FIGURE D.2.1.6.D PIPE SLOPE DRAIN D.2.1.6.3 SUBSURFACE DRAINS Purpose To intercept, collect, and convey ground water to a satisfactory outlet, using a perforated pipe or conduit below the ground surface. Subsurface drains are also known as “French Drains.” The perforated pipe provides a dewatering mechanism to drain excessively wet soils, provide a stable base for construction, improve stability of structures with shallow foundations, or to reduce hydrostatic pressure and to improve slope stability. Conditions of Use Use when excessive water must be removed from the soil. The soil permeability, depth to water table, and impervious layers are all factors that may govern the use of subsurface drains. Design and Installation Specifications 1. Two types of drains may be used as follows: a) Relief drains are used either to lower the water table in large, relatively flat areas, improve the growth of vegetation, or to remove surface water. They are installed along a slope and drain in the direction of the slope. They may be installed in a grid pattern, a herringbone pattern, or a random pattern. b) Interceptor drains are used to remove excess groundwater from a slope, stabilize steep slopes, and lower the water table below a slope to prevent the soil from becoming saturated. They are INLET AND ALL SECTIONSMUST BE SECURELY FASTENED TOGETHER WITH GASKETEDWATERTIGHT FITTINGS DIKE MATERIAL COMPACTED 90% MODIFIED PROCTOR CPE PIPE (LINED OR UNLINED) OR EQUIVALENT INTERCEPTORDIKE INTERCEPTOR DIKE PROVIDE RIPRAP PAD OREQUIVALENT ENERGY DISSIPATION DISCHARGE TO A STABILIZEDWATERCOURSE, SEDIMENT RETENTION FACILITY OR STABILIZED OUTLET STANDARD FLAREDEND SECTION 12"MIN. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-63 installed perpendicular to a slope and drain to the side of the slope. They usually consist of a single pipe or single pipes instead of a patterned layout. 2. Size of Drains – Size subsurface drains to carry the required capacity without pressurized flow. Minimum diameter for a subsurface drain is 4 inches. 3. Outlet – Ensure that the outlet of a drain empties into a channel or other watercourse above the normal water level. Maintenance Standards 1. Subsurface drains shall be checked periodically to ensure that they are free flowing and not clogged with sediment or roots. 2. The outlet shall be kept clear and free of debris. 3. Surface inlets shall be kept open and free of sediment and other debris. 4. Trees located too close to a subsurface drain often clog the system with roots. If a drain becomes clogged, relocate the drain or remove the trees as a last resort. Drain placement should be planned to minimize this problem. 5. Where drains are crossed by heavy equipment, the line shall be checked to ensure that it is not crushed and have adequate cover protection. D.2.1.6.4 DITCHES Code: DI Symbol: Purpose Ditches convey intercepted runoff from disturbed areas to and from sediment ponds or traps. They also convey runoff intercepted from undisturbed areas around the site to a non-erosive discharge point. Conditions of Use Ditches may be used anywhere that concentrated runoff is to be conveyed on or around the construction site. Temporary pipe systems may also be used to convey runoff. Design and Installation Specifications 1. Channels and ditches shall be sized to accommodate the developed condition 10-year approved model 15-minute peak flow with 0.5 feet of freeboard. If no hydrologic analysis is required for the site, the Rational Method may be used (see Section 3.2.1 of the SWDM). 2. See SWDM Section 4.4.1 for open-channel design requirements. 3. The only exception to the requirements of SWDM Section 4.4.1 is the use of check dams, rather than grass lining, for channels in which the design flow velocity does not exceed 5 fps. See Figure D.2.1.6.E for details on check dam installation. Maintenance Standards 1. Any sediment deposition of more than 0.5 feet shall be removed so that the channel is restored to its design capacity. 2. If the channel capacity is insufficient for the design flow, it must be determined whether the problem is local (e.g., a constriction or bend) or the channel is under-designed. If the problem is local, the channel capacity must be increased through construction of a berm(s) or by excavation. If the problem is under-design, the design engineer shall be notified and the channel redesigned to a more conservative standard to be approved by the City of Renton. 3. The channel shall be examined for signs of scouring and erosion of the bed and banks. If scouring or erosion has occurred, affected areas shall be protected by riprap or an erosion control blanket or net. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-64 FIGURE D.2.1.6.E CHECK DAMS D.2.1.6.5 OUTLET PROTECTION Code: OP Symbol: Purpose Outlet protection prevents scour at conveyance outlets. Conditions of Use Outlet protection is required at the outlets of all ponds, pipes, ditches, or other approved conveyances, and where runoff is conveyed to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch. Design and Installation Specifications For the standard pipe slope drains in Section D.2.1.6.2 and other smaller conveyance systems, the standard rock pad (6 feet by 8 feet) made of 1-foot thick quarry spall is adequate. For all other outlets, the outlet protection shall meet the requirements of the “Outfalls” section of Core Requirement #4 and Section 4.2.2 of the SWDM. Maintenance Standards for Outlet Protection If there is scour at the outlet, the eroded area shall be protected with more conservative measures proposed by the design engineer and approved by the City of Renton. 6" MIN. ROCK MUST COMPLETELY COVER THE BOTTOM AND SIDES OF THE DITCH 24" MIN. 2H:1V SLOPES L 2"- 4" ROCKBA L=THE DISTANCE SUCH THAT POINTS A AND B ARE OF EQUAL ELEVATION CROSS SECTION CHECK DAM SPACING D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-65 D.2.1.6.6 LEVEL SPREADER Code: LS Symbol: Purpose Level spreaders convert concentrated runoff to sheet flow and release it onto areas stabilized by existing vegetation. Conditions of Use Level spreaders may be used where runoff from undisturbed areas or sediment retention facilities is discharged. This practice applies only where the spreader can be constructed on undisturbed soil and the area below the level lip is vegetated and low gradient (see below). Note: Level spreaders are conceptually an ideal way to release stormwater since the vegetation and soil allow for the removal of fines from runoff that cannot be removed by settling or filtration. Unfortunately, the performance record of spreaders in the field is dismal. They are frequently under-designed and, despite the best installations, are rarely perfectly level, which results in the release of stormwater at a particular point. This concentrated runoff can result in catastrophic erosion downslope. Given such design failures, the use of spreaders is not encouraged. However, where slopes are gentle and the water volume is relatively low, spreaders may still be the best method. When proposing their use, the designer shall carefully evaluate the site for possible concerns. Design and Installation Specifications 1. See Figure D.2.1.6.F for detail. Other designs may be used subject to City approval. 2. If runoff velocity as it enters the level spreader is more than 4 fps for the developed condition 10-year approved model 15-minute peak flow, a riprap apron must be provided to dissipate energy before the runoff enters the spreader (Section D.2.1.6.5). 3. The total spreader length shall be at least the square root of the catchment area. The maximum length for an individual spreader is 50 feet, limiting the catchment area that a single spreader may serve to 2500 square feet. Although this is very small, four 50-foot level spreaders next to one another could serve nearly an acre (40,000 square feet). Multiple spreaders shall not be placed uphill or downhill from one another in a configuration that would allow water released from one spreader to enter a downslope spreader. 4. The area below the spreader for a horizontal distance of 100 feet shall not exceed 20 percent and shall be completely vegetated with no areas of instability or erosion. The topography for a horizontal distance of 50 feet below the spreader shall be uniform so that runoff is not funneled into a swale or channel immediately after its release. 5. The level spreader shall be seeded and mulched in accordance with Section D.2.1.2. Maintenance Standards 1. Any damage to the spreader shall be immediately repaired. Ensure flows do not bypass the spreader at the ends of the spreader. 2. The downslope area shall be checked for signs of erosion and to verify that the spreader is not functioning as a point discharge. Any eroded areas shall be immediately stabilized, and the cause determined and eliminated if possible. If the erosion is recurrent and the design, even when properly installed and maintained, is not adequate to prevent erosion, a new method of releasing runoff shall be installed in accordance with the standards of this appendix. Any new design must be approved by the City of Renton. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-66 FIGURE D.2.1.6.F LEVEL SPREADER D.2.1.7 DEWATERING CONTROL Any runoff generated by dewatering shall be treated through construction of a sediment trap (Section D.2.1.5.1) when there is sufficient space or by releasing the water to a well vegetated, gently sloping area. Since pumps are used for dewatering, it may be possible to pump the sediment-laden water well away from the surface water so that vegetation can be more effectively utilized for treatment. Discharge of sediment-laden water from dewatering activities to surface and storm waters is prohibited. If dewatering occurs from areas where the water has come in contact with new concrete, such as tanks, vaults, or foundations, the pH of the water must be monitored and must be neutralized prior to discharge. Clean non-turbid dewatering water, such as well point ground water can be discharged to systems tributary to, or directly to surface waters provided the flows are controlled so no erosion or flooding occurs. Clean water must not be routed through a stormwater sediment pond. Highly turbid or contaminated dewatering water must be handled separately from stormwater. Purpose: To prevent the untreated discharge of sediment-laden water from dewatering of utilities, excavated areas, foundations, etc. When to Install: Dewatering control measures shall be used whenever there is a potential for runoff from dewatering of utilities, excavations, foundations, etc. Measures to install: 1. Foundation, vault, excavation, and trench dewatering water that has similar characteristics to stormwater runoff at the site shall be discharged into a controlled conveyance system prior to discharge to a sediment trap or sediment pond. Foundation and trench dewatering water that has similar characteristics to stormwater runoff at the site must be disposed of through one of the following options depending on site constraints: a) Infiltration, b) Transport offsite in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute surface waters, SPREADER MUST BE LEVEL 18" MIN. REBAR SUPPORTS 8' MIN. SPACING CROSS SECTION DETAIL OF SPREADER DENSELY VEGETATED FOR A MIN. OF 100' AND SLOPELESS THAN 5:1 PRESSURE-TREATED2"X10" 3' MIN. TREATED 2"x10" MAY BE ABUTTED END TO END FOR MAX. SPREADER LENGTH OF 50' 6" MIN. 6" MIN.1" MIN.2H:1V MAX.1' MIN. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-67 c) Discharge to the sanitary sewer discharge with approval from King County and the City of Renton if there is no other option, or d) Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering. 2. Clean, non-turbid dewatering water, such as well-point ground water, may be discharged via stable conveyance to systems tributary to surface waters, provided the dewatering flow does not cause erosion or flooding of receiving waters. 3. Highly turbid or contaminated dewatering water (high pH or other) shall be handled separately from stormwater. See Section D.2.2 , SWPPS Measures. D.2.1.8 DUST CONTROL Preventative measures to minimize the wind transport of soil shall be taken when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources or adjacent properties. Purpose: To prevent wind transport of dust from exposed soil surfaces onto roadways, drainage ways, and surface waters. When to Install: Dust control shall be implemented when exposed soils are dry to the point that wind transport is possible and roadways, drainage ways, or surface waters are likely to be impacted. Dust control measures may consist of chemical, structural, or mechanical methods. Measures to Install: Water is the most common dust control (or palliative) used in the area. When using water for dust control, the exposed soils shall be sprayed until wet, but runoff shall not be generated by spraying. Calcium chloride, Magnesium chloride, Lignin derivatives, Tree Resin Emulsions, and Synthetic Polymer Emulsions may also be used for dust control. Exposed areas shall be re-sprayed as needed. Oil shall not be used for dust control. The following table lists many common dust control measures. Some of the measures are not recommended for use in the City and must have prior approval prior to use from the CED inspector assigned to specific projects. TABLE D.2.1.8.A DUST CONTROL MEASURES Method Considerations Site Preparation Recommended Application Rate Water -Most commonly used practice -Evaporates quickly -Lasts less than 1 day For all liquid agents: -Blade a small surface -Crown or slope surface to avoid ponding -Compact soils if needed -Uniformly pre-wet at 0.03 – 0.3 gal/sq yd -Apply solution under pressure. Overlap solution 6 – 12 inches -Allow treated area to cure 0 – 4 hours -Compact area after curing -Apply second treatment before first treatment becomes ineffective 0.125 gal/sq yd every 20 to 30 minutes Salts Calcium Chloride (CaCl) -Restricts evaporation -Lasts 6–12 months -Can be corrosive -Less effective in low humidity -Can build up in soils and leach by rain Apply 38% solution at 1.21L/m2 (0.27 gal/yd2) or as loose dry granules per manufacturer SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-68 TABLE D.2.1.8.A DUST CONTROL MEASURES Method Considerations Site Preparation Recommended Application Rate Magnesium Chloride (MgCl) -Restricts evaporation -Works at higher temperatures and lower humidity than CaCl -May be more costly than CaCl Apply 26 – 32% solution at 2.3 L/m2 (0.5 gal/yd2) Sodium Chloride (NaCl) -Effective over smaller range of conditions -Less expensive -Can be corrosive -Less effective in low humidity Per Manufacturer Silicates -Generally expensive -Available in small quantities -Require Second application Surfactants -High evaporation rates -Effective for short time periods -Must apply frequently Copolymers -Forms semi-permeable transparent crust -Resists ultraviolet radiation and moisture induced breakdown -Last 1 to 2 years 750 – 940 L/ha (80 – 100 gal/ac) Petroleum Products -Used oil is prohibited as a dust control method -Bind soil particles -May hinder foliage growth -Environmental and aesthetic concerns -Higher cost Use 57 – 63% resins as base. Apply at 750 – 940 L/ha (80–100 gal/ac) Lignin Sulfonate -Paper industry waste product -Acts as dispersing agent -Best in dry climates -Can be slippery -Will decrease Dissolved Oxygen in waterways therefore cannot be used adjacent to surface water systems Loosen surface 25–50 mm (1–2 inches) Need 4–8% fines Vegetable Oils -Coat grains of soils, so limited binding ability -May become brittle -Limited availability Per Manufacturer Spray on Adhesives -Available as organic or synthetic -Effective on dry, hard soils -Forms a crust -Can last 3 to 4 years Per Manufacturer D.2.1.9 FLOW CONTROL Surface water from disturbed areas must be routed through the project’s onsite flow control facility or other provisions must made to prevent increases in the existing site conditions 2-year and 10-year runoff peaks discharging from the project site during construction. Purpose: The purpose of surface water flow control is to mitigate increases in runoff peaks that occur during construction as a result of clearing vegetation, compacting the soil, and adding impervious surface. Such increases can cause or aggravate downstream flooding and erosion. D.2.1 ESC MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-69 When to Install: Surface water flow control shall be installed or otherwise provided prior to any clearing and/or grading of the site, except that required to construct the surface water flow control facilities. Measures to Use: The project’s onsite flow control facility or other equivalent storage facility that meets the peak-matching performance criteria stated above. D.2.1.10 PROTECT EXISTING AND PROPOSED STORMWATER FACILITIES AND ON-SITE BMPS Protection measures shall be applied/installed and maintained so as to prevent adverse impacts to existing stormwater facilities and on-site BMPs and areas of proposed stormwater facilities and on-site BMPs for the project. Adverse impacts can prompt the requirement to restore or replace affected stormwater facilities and on-site BMPs. Purpose: The purpose of protecting existing and proposed stormwater facility and on-site BMP areas is to avoid sedimentation and soil compaction that would adversely affect infiltration, and also avoid contamination by other pollutants. When to Install: Stormwater facility and on-site BMP area protection shall be installed or otherwise provided prior to any clearing and/or grading of the site, except that required to construct stormwater facilities and on-site BMPs. Measures to Use: 1. Protect all stormwater facilities and on-site BMPs and proposed stormwater facility and on-site BMP footprints from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the BMPs/facilities. 2. Stormwater facilities and on-site BMPs shall be restored to their fully functioning condition if they accumulate sediment during construction. Restoring the stormwater facilities and on-site BMPs shall include, at a minimum, removal of sediment and any sediment-laden bioretention soils, and replacing the removed soils with soils meeting the design specification. Replacement with a new fully- functioning stormwater facility and/or on-site BMP may be required if restoration to the fully- functioning condition can’t be accomplished. 3. Prevent compacting Bioretention BMPs/facilities by excluding construction equipment and foot traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment. 4. Control erosion and avoid introducing sediment from surrounding land uses onto permeable pavement BMPs. Do not allow muddy construction equipment on the base material or pavement. Do not allow sediment-laden runoff onto permeable pavements. 5. Permeable pavement BMPs fouled with sediments or no longer passing an initial infiltration text must be cleaned using procedures from Appendix A or the manufacturer’s procedures. 6. Keep all heavy equipment off existing soils under stormwater facilities and on-site BMPs that have been excavated to final grade to retain the infiltration rate of the soils. D.2.1.11 MAINTAIN PROTECTIVE BMPS Protection measures shall be maintained to ensure continued performance of their intended function, to prevent adverse impacts to existing stormwater facilities and on-site BMPs and areas of proposed BMPs/facilities, and protect other disturbed areas of the project. Purpose: The purpose of maintaining protective BMPs is to provide continuous erosion and sediment control protection throughout the life of the project, and avoid sedimentation, soil compaction and contamination by other pollutants that would adversely affect infiltration and surface runoff. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-70 When to Maintain: Protection measures shall be monitored per Section D.2.4.4 at a minimum, and promptly maintained to fully functioning condition as necessary to ensure continued performance of their intended function. Measures to Use: 1. Maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to ensure continued performance of their intended function in accordance with BMP specifications. 2. Remove all temporary erosion and sediment control BMPs prior to final construction approval, or within 30 days after achieving final site stabilization or after the temporary BMPs are no longer needed. 3. Provide protection to all stormwater facilities and on-site BMPs installed for the permanent control of stormwater from sediment and compaction. All stormwater facilities and on-site BMPs that are to remain in place following completion of construction shall be examined and placed in full operating conditions. If sediment enters the stormwater facilities and/or on-site BMPs during construction, it shall be removed and the stormwater facility and on-site BMP shall be returned to the conditions specified in the construction documents or as required for full stormwater facility and on-site BMP replacement. 4. Remove or stabilize trapped sediment on site. Permanently stabilize disturbed soil resulting from removal of erosion and sediment control BMPs or vegetation. D.2.1.12 MANAGE THE PROJECT Coordination and timing of site development activities relative to ESC concerns (Section D.2.4), and timely inspection, maintenance and update of protective measures (Section D.2.3) are necessary to effectively manage the project and ensure the success of protective ESC and SWPPS design and implementation. Projects shall assign a qualified CSWPP Supervisor (Section D.2.3.1) to be the primary contact for ESC and SWPPP issues and reporting, coordination with subcontractors and implementation of the CSWPP plan as a whole. Measures to Use: 1. Phase development projects to the maximum degree practicable and take into account seasonal work limits. 2. Inspection and monitoring – Inspect, maintain, and repair all BMPs as needed to ensure continued performance of their intended function. Conduct site inspections and monitoring in accordance with the Construction Stormwater General Permit and City requirements. 3. Maintaining an updated construction SWPPP – Maintain, update, and implement the SWPPP in accordance with the Construction Stormwater General Permit and City requirements. 4. Projects that disturb one or more acres must have, site inspections conducted by a Certified Erosion and Sediment Control Lead (CESCL) (see Section D.2.3.1). Project sites less than one acre (not part of a larger common plan of development or sale) may have a person without CESCL certification conduct inspections. By the initiation of construction, the SWPPP must identify the CESCL or inspector, who shall be present onsite or on-call at all times. The CESCL or inspector (project sites less than one acre) must have the skills to assess the: • Site conditions and construction activities that could impact the quality of stormwater. • Effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. • The CESCL or inspector must examine stormwater visually for the presence of suspended sediment, turbidity, discoloration, and oil sheen. They must evaluate the effectiveness of BMPs and determine if it is necessary to install, maintain, or repair BMPs to improve the quality of stormwater discharges. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-71 Based on the results of the inspection, construction site operators must correct the problems identified by: • Reviewing the SWPPP for compliance with all construction SWPPP elements and making appropriate revisions within 7 days of the inspection. • Immediately beginning the process of fully implementing and maintaining appropriate source control and/or treatment BMPs as soon as possible, addressing the problems not later than within 10 days of the inspection. If installation of necessary treatment BMPs is not feasible within 10 days, the construction site operator may request an extension within the initial 10-day response period. • Documenting BMP implementation and maintenance in the site log book (applies only to sites that have coverage under the Construction Stormwater General Permit). • 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 day do not require daily inspections. For example, if a stormwater pond discharges continuously over the course of a week, only one inspection is required that week.) The CESCL or inspector may reduce the inspection frequency for temporary stabilized, inactive sites to once every calendar month. D.2.2 SWPPS MEASURES This section details the SWPPS measures that are required to prevent, reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or watercourses from construction-related activities such as materials delivery and storage, onsite equipment fueling and maintenance, demolition of existing buildings and disposition of demolition materials and other waste, and concrete handling, washout and disposal. These SWPPS measures represent Best Management Practices (BMPs)8 for the control of pollutant drips and spills as well as other impacts related to construction such as increased pH in concrete construction and handling activities. Compliance with each of the SWPPS measures, and with any project-specific control measures, to the extent applicable and necessary to meet the performance criteria in Section D.2.2, and compliance with the CSWPP implementation requirements in Section D.2.4, constitutes overall compliance with the City’s CSWPP Standards. Note: Additional measures shall be required by the City if the existing standards are insufficient to protect adjacent properties, drainage facilities, or water resources. The standards for each individual SWPPS measure are divided into four sections: 1. Purpose 2. Conditions of Use 3. Design and Installation Specifications 4. Maintenance Requirements. Note that the “Conditions of Use” always refers to site conditions. As site conditions change, SWPPS measures must be changed to remain in compliance with the requirements of this appendix. Whenever compliance with City SWPPS Standards is required, all of the following SWPPS measures must be considered for application to the project site as detailed in the following sections. The construction pollutant generating concerns addressed by the BMPs that follow include: • Concrete handling, washout and disposal(specifically portland cement concrete) • Sawcutting and surfacing activities • Materials delivery, storage and containment 8 Best Management Practices (BMPs) means the best available and reasonable physical, structural, managerial, or behavioral activities, that when singly or in combination, eliminate or reduce the contamination of surface and/or ground waters. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-72 • Filtration and chemical treatment of construction water to facilitate disposal or discharge to approved locations • Reporting requirements and documentation availability for specific BMP processes Additionally, several of the ESC BMPs described in Section D.2.1 can be applicable to the SWPPS plan, e.g., use of cover, fencing and access protection to protect temporary materials storage locations. The applicant’s material supplier may be a resource (subject to City approval) for BMPs to address specific project applications or proposals. Conditions of approval on adjustments may also specify additional requirements for the SWPPS plan. D.2.2.1 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 discharge to surface waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, concrete process water, and concrete slurry from entering waters of the state. Conditions of Use Any time concrete is used, utilize these management practices. Concrete construction projects include, but are not limited to, curbs, sidewalks, roads, bridges, foundations, floors, stormwater vaults, retaining walls, driveways and runways. Design and Installation Specifications 1. Ensure that washout of concrete trucks, chutes, pumps, and internals is performed at an approved off- site location or in designated concrete washout areas. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. Refer to BMP D.2.2.2 for information on concrete washout areas. 2. 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. 3. Wash off hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels into formed areas only. 4. Wash equipment difficult to move, such as concrete pavers in areas that do not directly drain to natural or constructed stormwater conveyances. 5. Do not allow washdown from areas, such as concrete aggregate driveways, to drain directly to natural or constructed stormwater conveyances. 6. Contain washwater and leftover product in a lined container when no formed areas are available,. Dispose of contained concrete in a manner that does not violate ground water or surface water quality standards. 7. Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface waters. 8. Refer to BMPs D.2.2.7 and D.2.2.8 for pH adjustment requirements. 9. Refer to the Construction Stormwater General Permit for pH monitoring requirements if the project involves one of the following activities: • Significant concrete work (greater than 1,000 cubic yards poured concrete or recycled concrete used over the life of a project). • The use of engineered soils amended with (but not limited to) Portland cement-treated base, cement kiln dust or fly ash. • 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. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-73 D.2.2.2 CONCRETE WASHOUT AREA Purpose Prevent or reduce the discharge of pollutants to stormwater from concrete waste by conducting washout off-site, or performing onsite washout in a designated area to prevent pollutants from entering surface waters or ground water. Conditions of Use Concrete washout area best management practices are implemented on construction projects where: • Concrete is used as a construction material • It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant, etc.). • Concrete trucks, pumpers, or other concrete coated equipment are washed onsite. Note: If less than 10 concrete trucks or pumpers need to be washed out onsite, the washwater may be disposed of in a formed area awaiting concrete or an upland disposal site where it will not contaminate surface or ground water. The upland disposal site shall be at least 50 feet from sensitive areas such as storm drains, open ditches, or water bodies, including wetlands. Design and Installation Specifications Implementation The following steps will help reduce stormwater pollution from concrete wastes: 1. Perform washout of concrete trucks at an approved off-site location or in designated concrete washout areas only. 2. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. 3. Do not allow excess concrete to be dumped onsite, except in designated concrete washout areas. 4. Concrete washout areas may be prefabricated concrete washout containers, or self-installed structures (above-grade or below-grade). 5. 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. 6. 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. 7. Self-installed above-grade structures should only be used if excavation is not practical. Education 1. Discuss the concrete management techniques described in this BMP with the ready-mix concrete supplier before any deliveries are made. 2. Educate employees and subcontractors on the concrete waste management techniques described in this BMP. 3. Arrange for contractor’s superintendent or Certified Erosion and Sediment Control Lead (CESCL) to oversee and enforce concrete waste management procedures. 4. A sign should be installed adjacent to each temporary concrete washout facility to inform concrete equipment operators to utilize the proper facilities. Contracts Incorporate requirements for concrete waste management into concrete supplier and subcontractor agreements. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-74 Location and Placement 1. Locate washout area at least 50 feet from sensitive areas such as storm drains, open ditches, or water bodies, including wetlands. 2. Allow convenient access for concrete trucks, preferably near the area where the concrete is being poured. 3. If trucks need to leave a paved area to access washout, prevent track-out with a pad of rock or quarry spalls (see BMP D.2.1.4.2). These areas should be far enough away from other construction traffic to reduce the likelihood of accidental damage and spills. 4. The number of facilities you install should depend on the expected demand for storage capacity. 5. On large sites with extensive concrete work, washouts should be placed in multiple locations for ease of use by concrete truck drivers. On-Site Temporary Concrete Washout Facility, Transit Truck Washout Procedures: 1. Temporary concrete washout facilities shall be located a minimum of 50 feet from sensitive areas including storm drain inlets, open drainage facilities, and watercourses. (See Figures D.2.2.2.A, D.2.2.2.B, and D.2.2.2.C). 2. Concrete washout facilities shall be constructed and maintained in sufficient quantity and size to contain all liquid and concrete waste generated by washout operations. 3. Washout of concrete trucks shall be performed in designated areas only. 4. Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and discharged into designated washout area or properly disposed of off-site. 5. Once concrete wastes are washed into the designated area and allowed to harden, the concrete should be broken up, removed, and disposed of per applicable solid waste regulations. Dispose of hardened concrete on a regular basis. 6. Temporary Above-Grade Concrete Washout Facility a) Temporary concrete washout facility (type above grade) should be constructed as shown on the details below, with a recommended 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. b) 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. 7. Temporary Below-Grade Concrete Washout Facility a) Temporary concrete washout facilities (type below grade) should be constructed as shown on the details below, with a recommended minimum length and minimum width of 10 ft. The quantity and volume should be sufficient to contain all liquid and concrete waste generated by washout operations. b) Lath and flagging should be commercial type. c) Plastic lining material shall 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. d) Liner seams shall be installed in accordance with manufacturers’ recommendations. e) Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic lining material. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-75 Maintenance Standards Inspection and Maintenance 1. Inspect and verify that concrete washout BMPs are in place prior to the commencement of concrete work. 2. During periods of concrete work, inspect daily to verify continued performance. a) Check overall condition and performance. b) Check remaining capacity (% full). c) If using self-installed washout facilities, verify plastic liners are intact and sidewalls are not damaged. d) If using prefabricated containers, check for leaks. 3. Washout facilities shall be maintained to provide adequate holding capacity with a minimum freeboard of 12 inches. 4. Washout facilities must be cleaned, or new facilities must be constructed and ready for use once the washout is 75% full. 5. If the washout is nearing capacity, vacuum and dispose of the waste material in an approved manner. a) Do not discharge liquid or slurry to waterways, storm drains or directly onto ground. b) Do not use sanitary sewer without local approval. c) Place a secure, non-collapsing, non-water collecting cover over the concrete washout facility prior to predicted wet weather to prevent accumulation and overflow of precipitation. d) Remove and dispose of hardened concrete and return the structure to a functional condition. Concrete may be reused onsite or hauled away for disposal or recycling. 6. When you remove materials from the self-installed concrete washout, build a new structure; 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 Temporary Concrete Washout Facilities 1. When temporary concrete washout facilities are no longer required for the work, the hardened concrete, slurries and liquids shall be removed and properly disposed of. 2. Materials used to construct temporary concrete washout facilities shall be removed from the site of the work and disposed of or recycled. 3. Holes, depressions or other ground disturbance caused by the removal of the temporary concrete washout facilities shall be backfilled, repaired, and stabilized to prevent erosion. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-76 FIGURE D.2.2.2.A CONCRETE WASHOUT AREA (ABOVE GRADE) SECTION B-B NTS SECTION A-ANTS STAPLE DETAILNTS PLAN NTS ABOVE GRADE TEMPORARY CONCRETE WASHOUT FACILITY NTS CONCRETE WASHOUT SIGN DETAIL NTS 10 mil PLASTICLINING PLANNTS TYPE "ABOVE GRADE" WITHWOOD PLANKS TYPE "ABOVE GRADE" WITH STRAW BALES 10 mil PLASTIC LINING 16 GAUGE STEEL WIRE 2" 8" LAG SCREWS ( 12" ) BLACK LETTERS 6" HEIGHT PLYWOOD 4' X 2' PAINTED WHITE WOOD POST 312" x 312" x 8'3' 3' STRAWBALES(TYP.) STAKE (TYP.) WEDGE LOOSE STRAWBETWEEN BALES SAND OR GRAVEL-FILLED BAGS IN CORNERS 10' MIN. RECOMMENDED VARIES WOOD OR METAL STAKES(2 PER BALE) STRAW BALES (2 BALES HIGH, MAX.) ORIGINAL GROUND 10 mil PLASTIC LINING STAPLES (2 PER BALE) SAND OR GRAVEL-FILLED BAGS IN CORNERS NATIVE MATERIAL(OPTIONAL) 10 mil PLASTIC LINING WOOD FRAME SECURELY FASTENED AROUNDENTIRE PERIMETER WITHTWO STAKES TWO-STACKED 2x12 ROUGH WOOD FRAME STAKE (TYP.) 10' MIN. RECOMMENDED VARIES NOTES: 1.ACTUAL LAYOUT DETERMINED INTHE FIELD2.THE CONCRETE WASHOUT SIGNSHALL BE INSTALLED WITHIN 30' OF THE FACILITY 1' MIN. Adapted from CalTrans Fig4-14 SAC 8-14-02 D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-77 FIGURE D.2.2.2.B CONCRETE WASHOUT AREA (BELOW GRADE) FIGURE D.2.2.2.C PREFABRICATED CONCRETE WASHOUT CONTAINER W/RAMP EARTHEN BERM TYPICAL SECTION NTS BELOW GRADE TEMPORARY CONCRETE WASHOUT FACILITY NTS CONCRETE WASHOUT SIGN DETAIL NTS SANDBAG PLAN NTS Adapted from CalTrans Fig4-14 SAC 8-14-02 10 milPLASTIC LINING LAG SCREWS ( 12" ) BLACKLETTERS6" HEIGHT PLYWOOD 4' X 2'PAINTED WHITE WOOD POST 312" x 312" x 8'3' 3' EARTHENBERM 10 mil PLASTIC LINING SANDBAG 10' MIN. RECOMMENDED VARIES BERM 3' LATH AND FLAGGING ON 3 SIDES NOTES: 1.ACTUAL LAYOUT DETERMINED IN THE FIELD 2.THE CONCRETE WASHOUT SIGNSHALL BE INSTALLED WITHIN 30' OFTHE FACILITY SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-78 D.2.2.3 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 surface waters of the State is prohibited. Use this BMP to minimize and eliminate process water and slurry created through sawcutting or surfacing from entering waters of the State. Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Sawcutting and surfacing operations include, but are not limited to, sawing, coring, grinding, roughening, hydro-demolition, bridge and road surfacing Design and Installation Specifications 1. Vacuum slurry and cuttings during cutting and surfacing operations. 2. Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight. 3. Slurry and cuttings shall not drain to any natural or constructed drainage conveyance including stormwater systems. This may require temporarily blocking catch basins. 4. Dispose of collected slurry and cuttings in a manner that does not violate ground water or surface water quality standards. 5. 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 process water in a manner that does not violate ground water or surface water quality standards. 6. Handle and dispose 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 vacuum trucks. D.2.2.4 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 onsite, store materials in a designated area, and install secondary containment. Conditions of Use These procedures are suitable for use at all construction sites with delivery and storage of the following materials: • Petroleum products such as fuel, oil and grease • Soil stabilizers and binders (e.g., Polyacrylamide) • Fertilizers, pesticides and herbicides • Detergents • Asphalt and concrete compounds D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-79 • Hazardous chemicals such as acids, lime, adhesives, paints, solvents and curing compounds • Any other material that may be detrimental if released to the environment Design and Installation Specifications The following steps should be taken to minimize risk: 1. Temporary storage area should be located away from vehicular traffic, near the construction entrance(s), and away from waterways or storm drains. 2. Material Safety Data Sheets (MSDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. 3. Hazardous material storage onsite should be minimized. 4. Hazardous materials should be handled as infrequently as possible. 5. During the wet weather season (October 1 – April 30), consider storing materials in a covered area. 6. Materials should be stored in secondary containments, such as 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 concrete mixing trays. 7. Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, and within secondary containment. 8. 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. Material Storage Areas and Secondary Containment Practices: 1. 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. 2. 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 capacity of the largest container within its boundary, whichever is greater. 3. Secondary containment facilities shall be impervious to the materials stored therein for a minimum contact time of 72 hours. 4. 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. 5. Sufficient separation should be provided between stored containers to allow for spill cleanup and emergency response access. 6. During the wet weather season (October 1 – April 30), each secondary containment facility shall be covered during non-working days, prior to and during rain events. 7. Keep material storage areas clean, organized and equipped with an ample supply of appropriate spill clean-up material (spill kit). 8. The spill kit should include, at a minimum: • 1-Water Resistant Nylon Bag • 3-Oil Absorbent Socks 3″ x 4′ • 2-Oil Absorbent Socks 3″ x 10′ • 12-Oil Absorbent Pads 17″ x 19″ SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-80 • 1-Pair Splash Resistant Goggles • 3-Pair Nitrile Gloves • 10-Disposable Bags with Ties • Instructions D.2.2.5 CONSTRUCTION STORMWATER CHEMICAL TREATMENT Purpose This BMP applies when using stormwater chemicals in batch treatment or flow-through treatment. Turbidity is difficult to control once fine particles are suspended in stormwater runoff from a construction site. Sedimentation ponds are effective at removing larger particulate matter by gravity settling, but are ineffective at removing smaller particulates such as clay and fine silt. Traditional erosion and sediment control BMPs may not be adequate to ensure compliance with the water quality standards for turbidity in receiving water. Chemical treatment can reliably provide exceptional reductions of turbidity and associated pollutants. Chemical treatment may be required to meet turbidity stormwater discharge requirements, especially when construction is to proceed through the wet season. Conditions of Use Formal written approval from Ecology is required for the use of chemical treatment regardless of site size. The City also requires review and approval. When approved, the chemical treatment systems must be included in the SWPPS portion of the project’s CSWPP. Design and Installation Specifications Coagulation and flocculation have been used for over a century to treat water. It is used less frequently for the treatment of wastewater. The use of coagulation and flocculation for treating stormwater is a very recent application. Experience with the treatment of water and wastewater has resulted in a basic understanding of the process, in particular factors that affect performance. This experience can provide insights as to how to most effectively design and operate similar systems in the treatment of stormwater. Fine particles suspended in water give it a milky appearance, measured as turbidity. Their small size, often much less than 1 μm in diameter, give them a very large surface area relative to their volume. These fine particles typically carry a negative surface charge. Largely because of these two factors, small size and negative charge, these particles tend to stay in suspension for extended periods of time. Thus, removal is not practical by gravity settling. These are called stable suspensions. Polymers, as well as inorganic chemicals such as alum, speed the process of clarification. The added chemical destabilizes the suspension and causes the smaller particles to agglomerate. The process consists of three steps: coagulation, flocculation, and settling or clarification. Each step is explained below as well as the factors that affect the efficiency of the process. Coagulation: Coagulation is the first step. It is the process by which negative charges on the fine particles that prevent their agglomeration are disrupted. Chemical addition is one method of destabilizing the suspension, and polymers are one class of chemicals that are generally effective. Chemicals that are used for this purpose are called coagulants. Coagulation is complete when the suspension is destabilized by the neutralization of the negative charges. Coagulants perform best when they are thoroughly and evenly dispersed under relatively intense mixing. This rapid mixing involves adding the coagulant in a manner that promotes rapid dispersion, followed by a short time period for destabilization of the particle suspension. The particles are still very small and are not readily separated by clarification until flocculation occurs. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-81 Flocculation: Flocculation is the process by which fine particles that have been destabilized bind together to form larger particles that settle rapidly. Flocculation begins naturally following coagulation, but is enhanced by gentle mixing of the destabilized suspension. Gentle mixing helps to bring particles in contact with one another such that they bind and continually grow to form “flocs.” As the size of the flocs increases they become heavier and tend to settle more rapidly. Clarification: The final step is the settling of the particles. Particle density, size and shape are important during settling. Dense, compact flocs settle more readily than less dense, fluffy flocs. Because of this, flocculation to form dense, compact flocs is particularly important during water treatment. Water temperature is important during settling. Both the density and viscosity of water are affected by temperature; these in turn affect settling. Cold temperatures increase viscosity and density, thus slowing down the rate at which the particles settle. The conditions under which clarification is achieved can affect performance. Currents can affect settling. Currents can be produced by wind, by differences between the temperature of the incoming water and the water in the clarifier, and by flow conditions near the inlets and outlets. Quiescent water such as that which occurs during batch clarification provides a good environment for effective performance as many of these factors become less important in comparison to typical sedimentation basins. One source of currents that is likely important in batch systems is movement of the water leaving the clarifier unit. Given that flocs are relatively small and light the exit velocity of the water must be as low as possible. Sediment on the bottom of the basin can be resuspended and removed by fairly modest velocities. Coagulants: Polymers are large organic molecules that are made up of subunits linked together in a chain- like structure. Attached to these chain-like structures are other groups that carry positive or negative charges, or have no charge. Polymers that carry groups with positive charges are called cationic, those with negative charges are called anionic, and those with no charge (neutral) are called nonionic. Cationic polymers can be used as coagulants to destabilize negatively charged turbidity particles present in natural waters, wastewater and stormwater. Aluminum sulfate (alum) can also be used as this chemical becomes positively charged when dispersed in water. In practice, the only way to determine whether a polymer is effective for a specific application is to perform preliminary or onsite testing. Polymers are available as powders, concentrated liquids, and emulsions (which appear as milky liquids). The latter are petroleum based, which are not allowed for construction stormwater treatment. Polymer effectiveness can degrade with time and also from other influences. Thus, manufacturers’ recommendations for storage should be followed. Manufacturer’s recommendations usually do not provide assurance of water quality protection or safety to aquatic organisms. Consideration of water quality protection is necessary in the selection and use of all polymers. Criteria for Chemical Treatment Product Use: Chemically treated stormwater discharged from construction sites must be nontoxic to aquatic organisms. The Chemical Technology Assessment Protocol (CTAPE) must be used to evaluate chemicals proposed for stormwater treatment. Only chemicals approved by Ecology under the CTAPE may be used for stormwater treatment. The approved chemicals, their allowable application techniques (batch treatment or flow-through treatment), allowable application rates, and conditions of use can be found at the Department of Ecology Emerging Technologies website: <http://www.ecy.wa.gov/programs/wq/stormwater/newtech/technologies.html>. Treatment System Design Considerations: The design and operation of a chemical treatment system should take into consideration the factors that determine optimum, cost-effective performance. It is important to recognize the following: • Only Ecology approved chemicals may be used and must follow approved dose rate. • The pH of the stormwater must be in the proper range for the polymers to be effective, which is typically 6.5 to 8.5 SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-82 • The coagulant must be mixed rapidly into the water to ensure proper dispersion. • A flocculation step is important to increase the rate of settling, to produce the lowest turbidity, and to keep the dosage rate as low as possible. • Too little energy input into the water during the flocculation phase results in flocs that are too small and/or insufficiently dense. Too much energy can rapidly destroy floc as it is formed. • Care must be taken in the design of the withdrawal system to minimize outflow velocities and to prevent floc discharge. Discharge from a batch treatment system should be directed through a physical filter such as a vegetated swale that would catch any unintended floc discharge. Currently, flow-through systems always discharge through the chemically enhanced sand filtration system. • System discharge rates must take into account downstream conveyance integrity. Polymer Batch Treatment Process Description: A batch chemical treatment system consists of the stormwater collection system (either temporary diversion or the permanent site drainage system), a storage pond, pumps, a chemical feed system, treatment cells, and interconnecting piping. The batch treatment system shall use a minimum of two lined treatment cells in addition to an untreated stormwater storage pond. Multiple treatment cells allow for clarification of treated water while other cells are being filled or emptied. Treatment cells may be ponds or tanks. Ponds with constructed earthen embankments greater than six feet high or which impound more than 10 acre-feet require special engineering analyses. The Ecology Dam Safety Section has specific design criteria for dams in Washington State (see <http://www.ecy.wa.gov/programs/wr/dams/GuidanceDocs.html>). Stormwater is collected at interception point(s) on the site and is diverted by gravity or by pumping to an untreated stormwater storage pond or other untreated stormwater holding area. The stormwater is stored until treatment occurs. It is important that the holding pond be large enough to provide adequate storage. The first step in the treatment sequence is to check the pH of the stormwater in the untreated stormwater storage pond. The pH is adjusted by the application of carbon dioxide or a base until the stormwater in the storage pond is within the desired pH range, 6.5 to 8.5. When used, carbon dioxide is added immediately downstream of the transfer pump. Typically sodium bicarbonate (baking soda) is used as a base, although other bases may be used. When needed, base is added directly to the untreated stormwater storage pond. The stormwater is recirculated with the treatment pump to provide mixing in the storage pond. Initial pH adjustments should be based on daily bench tests. Further pH adjustments can be made at any point in the process. Once the stormwater is within the desired pH range (dependent on polymer being used), the stormwater is pumped from the untreated stormwater storage pond to a treatment cell as polymer is added. The polymer is added upstream of the pump to facilitate rapid mixing. After polymer addition, the water is kept in a lined treatment cell for clarification of the sediment-floc. In a batch mode process, clarification typically takes from 30 minutes to several hours. Prior to discharge samples are withdrawn for analysis of pH, flocculent chemical concentration, and turbidity. If both are acceptable, the treated water is discharged. Several configurations have been developed to withdraw treated water from the treatment cell. The original configuration is a device that withdraws the treated water from just beneath the water surface using a float with adjustable struts that prevent the float from settling on the cell bottom. This reduces the possibility of picking up sediment-floc from the bottom of the pond. The struts are usually set at a minimum clearance of about 12 inches; that is, the float will come within 12 inches of the bottom of the cell. Other systems have used vertical guides or cables which constrain the float, allowing it to drift up and down with the water level. More recent designs have an H-shaped array of pipes, set on the horizontal. This scheme provides for withdrawal from four points rather than one. This configuration reduces the likelihood of sucking settled solids from the bottom. It also reduces the tendency for a vortex to form. Inlet diffusers, a long floating or fixed pipe with many small holes in it, are also an option. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-83 Safety is a primary concern. Design should consider the hazards associated with operations, such as sampling. Facilities should be designed to reduce slip hazards and drowning. Tanks and ponds should have life rings, ladders, or steps extending from the bottom to the top. Polymer Flow-Through Treatment Process Description: At a minimum, a flow-through chemical treatment system consists of the stormwater collection system (either temporary diversion or the permanent site drainage system), an untreated stormwater storage pond, and the chemically enhanced sand filtration system. Stormwater is collected at interception point(s) on the site and is diverted by gravity or by pumping to an untreated stormwater storage pond or other untreated stormwater holding area. The stormwater is stored until treatment occurs. It is important that the holding pond be large enough to provide adequate storage. Stormwater is then pumped from the untreated stormwater storage pond to the chemically enhanced sand filtration system where polymer is added. Adjustments to pH may be necessary before chemical addition. The sand filtration system continually monitors the stormwater for turbidity and pH. If the discharge water is ever out of an acceptable range for turbidity or pH, the water is recycled to the untreated stormwater pond where it can be retreated. For batch treatment and flow-through treatment, the following equipment should be located in a lockable shed: • The chemical injector. • Secondary containment for acid, caustic, buffering compound, and treatment chemical. • Emergency shower and eyewash. • Monitoring equipment which consists of a pH meter and a turbidimeter. System Sizing: Certain sites are required to implement flow control for the developed sites. These sites must also control stormwater release rates during construction. Generally, these are sites that discharge stormwater directly, or indirectly, through a conveyance system, into a fresh water. System sizing is dependent on flow control requirements. Sizing Criteria for Batch Treatment Systems for Flow Control Exempt Water Bodies: The total volume of the untreated stormwater storage pond and treatment ponds or tanks must be large enough to treat stormwater that is produced during multiple day storm events. It is recommended that at a minimum the untreated stormwater storage pond be sized to hold 1.5 times the runoff volume of the 10-year, 24-hour storm event. Bypass should be provided around the chemical treatment system to accommodate extreme storm events. Runoff volume shall be calculated using the methods presented in Chapter 3 of the SWDM. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases, this would be the land cover conditions just prior to final landscaping). Primary settling should be encouraged in the untreated stormwater storage pond. A forebay with access for maintenance may be beneficial. There are two opposing considerations in sizing the treatment cells. A larger cell is able to treat a larger volume of water each time a batch is processed. However, the larger the cell the longer the time required to empty the cell. A larger cell may also be less effective at flocculation and therefore require a longer settling time. The simplest approach to sizing the treatment cell is to multiply the allowable discharge flow rate times the desired drawdown time. A 4-hour drawdown time allows one batch per cell per 8-hour work period, given 1 hour of flocculation followed by two hours of settling. If the discharge is directly to a direct discharge exempt receiving water in Section 1.2.3 (Core Requirement #3) of the SWDM, or to an infiltration system, there is no discharge flow limit. Ponds sized for flow control water bodies must at a minimum meet the sizing criteria for direct discharge exempt receiving waters. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-84 Sizing Criteria for Flow-Through Treatment Systems for Flow Control Exempt Water Bodies: When sizing storage ponds or tanks for flow-through systems for flow control exempt water bodies, the treatment system capacity should be a factor. The untreated stormwater storage pond or tank should be sized to hold 1.5 times the runoff volume of the 10-year, 24-hour storm event minus the treatment system flowrate for an 8-hour period. For a chitosan-enhanced sand filtration system, the treatment system flowrate should be sized using a hydraulic loading rate between 6 to 8 gpm/ft². Other hydraulic loading rates may be more appropriate for other systems. Bypass should be provided around the chemical treatment system to accommodate extreme storms. Runoff volume shall be calculated using the methods presented in Chapter 3 of the SWDM. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases, this would be the land cover conditions just prior to final landscaping). Sizing Criteria for Flow Control Water Bodies: Sites that must implement flow control for the developed site condition must also control stormwater release rates during construction. Construction site stormwater discharges shall not exceed the discharge durations of the pre-developed condition for the range of pre-developed discharge rates from ½ of the 2-year flow through the 10-year flow as predicted by an approved continuous runoff model. The pre- developed condition to be matched shall be the land cover condition immediately prior to the development project. This restriction on release rates can affect the size of the storage pond and treatment cells. The following is how WWHM can be used to determine the release rates from the chemical treatment systems: 1. Determine the pre-developed flow durations to be matched by entering the existing land use area under the “Pre-developed” scenario in WWHM. The default flow range is from ½ of the 2-year flow through the 10-year flow. 2. Enter the post developed land use area in the “Developed Unmitigated” scenario in WWHM. 3. Copy the land use information from the “Developed Unmitigated” to “Developed Mitigated” scenario. 4. While in the “Developed Mitigated” scenario, add a pond element under the basin element containing the post-developed land use areas. This pond element represents information on the available untreated stormwater storage and discharge from the chemical treatment system. In cases where the discharge from the chemical treatment system is controlled by a pump, a stage/storage/discharge (SSD) table representing the pond must be generated outside WWHM and imported into WWHM. WWHM can route the runoff from the post-developed condition through this SSD table (the pond) and determine compliance with the flow duration standard. This would be an iterative design procedure where if the initial SSD table proved to be inadequate, the designer would have to modify the SSD table outside WWHM and re-import in WWHM and route the runoff through it again. The iteration will continue until a pond that complies with the flow duration standard is correctly sized. Notes on SSD table characteristics: • The pump discharge rate would likely be initially set at just below ½ of the 2-year flow from the pre-developed condition. As runoff coming into the untreated stormwater storage pond increases and the available untreated stormwater storage volume gets used up, it would be necessary to increase the pump discharge rate above ½ of the 2-year. The increase(s) above ½ of the 2-year must be such that they provide some relief to the untreated stormwater storage needs but at the same time will not cause violations of the flow duration standard at the higher flows. The final design SSD table will identify the appropriate pumping rates and the corresponding stage and storages. • When building such a flow control system, the design must ensure that any automatic adjustments to the pumping rates will be as a result of changes to the available storage in accordance with the final design SSD table. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-85 5. It should be noted that the above procedures would be used to meet the flow control requirements. The chemical treatment system must be able to meet the runoff treatment requirements. It is likely that the discharge flow rate of ½ of the 2-year or more may exceed the treatment capacity of the system. If that is the case, the untreated stormwater discharge rate(s) (i.e., influent to the treatment system) must be reduced to allow proper treatment. Any reduction in the flows would likely result in the need for a larger untreated stormwater storage volume. If the discharge is to a municipal storm drainage system, the allowable discharge rate may be limited by the capacity of the public system. It may be necessary to clean the municipal storm drainage system prior to the start of the discharge to prevent scouring solids from the drainage system. If the municipal storm drainage system discharges to a water body not on the flow control exempt list, the project site is subject to flow control requirements. Obtain permission from the owner of the collection system before discharging to it. If system design does not allow you to discharge at the slower rates as described above and if the site has a retention or detention pond that will serve the planned development, the discharge from the treatment system may be directed to the permanent retention/detention pond to comply with the flow control requirement. In this case, the untreated stormwater storage pond and treatment system will be sized according to the sizing criteria for flow-through treatment systems for flow control exempt water bodies described earlier except all discharge (water passing through the treatment system and stormwater bypassing the treatment system) will be directed into the permanent retention/detention pond. If site constraints make locating the untreated stormwater storage pond difficult, the permanent retention/detention pond may be divided to serve as the untreated stormwater storage pond and the post- treatment flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The post-treatment flow control pond’s revised dimensions must be entered into the WWHM and the WWHM must be run to confirm compliance with the flow control requirement. Maintenance Standards Monitoring: At a minimum, the following monitoring shall be conducted. Test results shall be recorded on a daily log kept on site. Additional testing may be required by the NPDES permit based on site conditions. Operational Monitoring: • Total volume treated and discharged. • Flow must be continuously monitored and recorded at not greater than 15-minute intervals. • Type and amount of chemical used for pH adjustment. • Amount of polymer used for treatment. • Settling time. Compliance Monitoring: Influent and effluent pH, flocculent chemical concentration, and turbidity must be continuously monitored and recorded at not greater than 15-minute intervals. pH and turbidity of the receiving water. Biomonitoring: Treated stormwater must be non-toxic to aquatic organisms. Treated stormwater must be tested for aquatic toxicity or residual chemicals. Frequency of biomonitoring will be determined by Ecology. Residual chemical tests must be approved by Ecology prior to their use. If testing treated stormwater for aquatic toxicity, you must test for acute (lethal) toxicity. Bioassays shall be conducted by a laboratory accredited by Ecology, unless otherwise approved by Ecology. Acute toxicity tests shall be conducted per the CTAPE protocol. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-86 Discharge Compliance: Prior to discharge, treated stormwater must be sampled and tested for compliance with pH, flocculent chemical concentration, and turbidity limits. These limits may be established by the Construction Stormwater General Permit or a site-specific discharge permit. Sampling and testing for other pollutants may also be necessary at some sites. pH must be within the range of 6.5 to 8.5 standard units and not cause a change in the pH of the receiving water of more than 0.2 standard units. Treated stormwater samples and measurements shall be taken from the discharge pipe or another location representative of the nature of the treated stormwater discharge. Samples used for determining compliance with the water quality standards in the receiving water shall not be taken from the treatment pond prior to decanting. Compliance with the water quality standards is determined in the receiving water. Operator Training: Each contractor who intends to use chemical treatment shall be trained by an experienced contractor. Each site using chemical treatment must have an operator trained and certified by an organization approved by Ecology. Standard BMPs: Surface stabilization BMPs should be implemented on site to prevent significant erosion. All sites shall use a truck wheel wash to prevent tracking of sediment off site. Sediment Removal and Disposal: • Sediment shall be removed from the storage or treatment cells as necessary. Typically, sediment removal is required at least once during a wet season and at the decommissioning of the cells. Sediment remaining in the cells between batches may enhance the settling process and reduce the required chemical dosage. • Sediment that is known to be non-toxic may be incorporated into the site away from drainages. D.2.2.6 CONSTRUCTION STORMWATER FILTRATION Purpose Filtration removes sediment from runoff originating from disturbed areas of the site. Background Information: Filtration with sand media has been used for over a century to treat water and wastewater. The use of sand filtration for treatment of stormwater has developed recently, generally to treat runoff from streets, parking lots, and residential areas. The application of filtration to construction stormwater treatment is currently under development. Conditions of Use Traditional BMPs used to control soil erosion and sediment loss from sites under development may not be adequate to ensure compliance with the water quality standard for turbidity in the receiving water. Filtration may be used in conjunction with gravity settling to remove sediment as small as fine silt (0.5 μm). The reduction in turbidity will be dependent on the particle size distribution of the sediment in the stormwater. In some circumstances, sedimentation and filtration may achieve compliance with the water quality standard for turbidity. The use of construction stormwater filtration does not require approval from Ecology as long as treatment chemicals are not used. Filtration in conjunction with polymer treatment requires testing under the Chemical Technology Assessment Protocol – Ecology (CTAPE) before it can be initiated. Approval from the appropriate regional Ecology office must be obtained at each site where polymers use is proposed prior to use. For more guidance on stormwater chemical treatment see BMP D.2.2.5. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-87 Design and Installation Specifications Two types of filtration systems may be applied to construction stormwater treatment: rapid and slow. Rapid sand filters are the typical system used for water and wastewater treatment. They can achieve relatively high hydraulic flow rates, on the order of 2 to 20 gpm/sf, because they have automatic backwash systems to remove accumulated solids. In contrast, slow sand filters have very low hydraulic rates, on the order of 0.02 gpm/sf, because they do not have backwash systems. Slow sand filtration has generally been used to treat stormwater. Slow sand filtration is mechanically simple in comparison to rapid sand filtration but requires a much larger filter area. Filtration Equipment Sand media filters are available with automatic backwashing features that can filter to 50 μm particle size. Screen or bag filters can filter down to 5 μm. Fiber wound filters can remove particles down to 0.5 μm. Filters should be sequenced from the largest to the smallest pore opening. Sediment removal efficiency will be related to particle size distribution in the stormwater. Treatment Process Description Stormwater is collected at interception point(s) on the site and is diverted to an untreated stormwater sediment pond or tank for removal of large sediment and storage of the stormwater before it is treated by the filtration system. The untreated stormwater is pumped from the trap, pond, or tank through the filtration system in a rapid sand filtration system. Slow sand filtration systems are designed as flow through systems using gravity. Maintenance Standards Rapid sand filters typically have automatic backwash systems that are triggered by a pre-set pressure drop across the filter. If the backwash water volume is not large or substantially more turbid than the untreated stormwater stored in the holding pond or tank, backwash return to the untreated stormwater pond or tank may be appropriate. However, other means of treatment and disposal may be necessary. • Screen, bag, and fiber filters must be cleaned and/or replaced when they become clogged. • Sediment shall be removed from the storage and/or treatment ponds as necessary. Typically, sediment removal is required once or twice during a wet season and at the decommissioning of the ponds. Sizing Criteria for Flow-Through Treatment Systems for Flow Control Exempt Water Bodies: When sizing storage ponds or tanks for flow-through systems for flow control exempt water bodies the treatment system capacity should be a factor. The untreated stormwater storage pond or tank should be sized to hold 1.5 times the runoff volume of the 10-year, 24-hour storm event minus the treatment system flowrate for an 8-hour period. For a chitosan-enhanced sand filtration system, the treatment system flowrate should be sized using a hydraulic loading rate between 6 to 8 gpm/ft². Other hydraulic loading rates may be more appropriate for other systems. Bypass should be provided around the chemical treatment system to accommodate extreme storms. Runoff volume shall be calculated using the methods presented in Chapter 3 of the SWDM (if no chemicals are proposed for use). Worst-case conditions (i.e., producing the most runoff) should be used for analyses (most likely conditions present prior to final landscaping). Sizing Criteria for Flow Control Water Bodies: Sites that must implement flow control for the developed site condition must also control stormwater release rates during construction. Construction site stormwater discharges shall not exceed the discharge durations of the pre-developed condition for the range of pre-developed discharge rates from 1/2 of the 2-year flow through the 10-year flow as predicted by an approved continuous runoff model. The pre- developed condition to be matched shall be the land cover condition immediately prior to the development project. This restriction on release rates can affect the size of the storage pond, the filtration system, and the flow rate through the filter system. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-88 The following is how WWHM can be used to determine the release rates from the filtration systems: 1. Determine the pre-developed flow durations to be matched by entering the land use area under the “Pre-developed” scenario in WWHM. The default flow range is from ½ of the 2-year flow through the 10-year flow. 2. Enter the post developed land use area in the “Developed Unmitigated” scenario in WWHM. 3. Copy the land use information from the “Developed Unmitigated” to “Developed Mitigated” scenario. 4. There are two possible ways to model stormwater filtration systems: a) The stormwater filtration system uses an untreated stormwater storage pond/tank and the discharge from this pond/tank is pumped to one or more filters. In-line filtration chemicals would be added to the flow right after the pond/tank and before the filter(s). Because the discharge is pumped, WWHM can’t generate a stage/storage /discharge (SSD) table for this system. This system is modeled the same way as described Ecology’s BMP C250 (or BMP D.2.2.5 when seeking City approval for non-chemical treatment) and is as follows: While in the “Developed Mitigated” scenario, add a pond element under the basin element containing the post-developed land use areas. This pond element represents information on the available untreated stormwater storage and discharge from the filtration system. In cases where the discharge from the filtration system is controlled by a pump, a stage/storage/discharge (SSD) table representing the pond must be generated outside WWHM and imported into WWHM. WWHM can route the runoff from the post-developed condition through this SSD table (the pond) and determine compliance with the flow duration standard. This would be an iterative design procedure where if the initial SSD table proved to be out of compliance, the designer would have to modify the SSD table outside WWHM and re-import in WWHM and route the runoff through it again. The iteration will continue until a pond that enables compliance with the flow duration standard is designed. Notes on SSD table characteristics: • The pump discharge rate would likely be initially set at just below ½ if the 2-year flow from the pre-developed condition. As runoff coming into the untreated stormwater storage pond increases and the available untreated stormwater storage volume gets used up, it would be necessary to increase the pump discharge rate above ½ of the 2-year. The increase(s) above ½ of the 2-year must be such that they provide some relief to the untreated stormwater storage needs but at the same time they will not cause violations of the flow duration standard at the higher flows. The final design SSD table will identify the appropriate pumping rates and the corresponding stage and storages. • When building such a flow control system, the design must ensure that any automatic adjustments to the pumping rates will be as a result of changes to the available storage in accordance with the final design SSD table. b) The stormwater filtration system uses a storage pond/tank and the discharge from this pond/tank gravity flows to the filter. This is usually a slow sand filter system and it is possible to model it in WWHM as a Filter element or as a combination of Pond and Filter element placed in series. The stage/storage/discharge table(s) may then be generated within WWHM as follows: i. While in the “Developed Mitigated” scenario, add a Filter element under the basin element containing the post-developed land use areas. The length and width of this filter element would have to be the same as the bottom length and width of the upstream untreated stormwater storage pond/tank. ii. In cases where the length and width of the filter is not the same as those for the bottom of the upstream untreated stormwater storage tank/pond, the treatment system may be modeled as a Pond element followed by a Filter element. By having these two elements, WWHM would then generate a SSD table for the storage pond which then gravity flows to the Filter element. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-89 The Filter element downstream of the untreated stormwater storage pond would have a storage component through the media, and an overflow component for when the filtration capacity is exceeded. WWHM can route the runoff from the post-developed condition through the treatment systems in 4b and determine compliance with the flow duration standard. This would be an iterative design procedure where if the initial sizing estimates for the treatment system proved to be inadequate, the designer would have to modify the system and route the runoff through it again. The iteration would continue until compliance with the flow duration standard is achieved. 5. It should be noted that the above procedures would be used to meet the flow control requirements. The filtration system must be able to meet the runoff treatment requirements. It is likely that the discharge flow rate of ½ of the 2-year or more may exceed the treatment capacity of the system. If that is the case, the untreated stormwater discharge rate(s) (i.e., influent to the treatment system) must be reduced to allow proper treatment. Any reduction in the flows would likely result in the need for a larger untreated stormwater storage volume. If system design does not allow you to discharge at the slower rates as described above and if the site has a retention or detention pond that will serve the planned development, the discharge from the treatment system may be directed to the permanent retention/detention pond to comply with the flow control requirements. In this case, the untreated stormwater storage pond and treatment system will be sized according to the sizing criteria for flow-through treatment systems for flow control exempt waterbodies described earlier except all discharges (water passing through the treatment system and stormwater bypassing the treatment system) will be directed into the permanent retention/detention pond. If site constraints make locating the untreated stormwater storage pond difficult, the permanent retention/detention pond may be divided to serve as the untreated stormwater discharge pond and the post-treatment flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The post-treatment flow control pond’s revised dimensions must be entered into the WWHM and the WWHM must be run to confirm compliance with the flow control requirement. D.2.2.7 HIGH PH NEUTRALIZATION USING CO2 Purpose When pH levels in stormwater rise above 8.5 it is necessary to lower the pH levels to the acceptable range of 6.5 to 8.5, this process is called pH neutralization. pH neutralization involves the use of solid or compressed carbon dioxide gas in water requiring neutralization. Neutralized stormwater may be discharged to surface waters under the Construction Stormwater General permit. Neutralized process water such as concrete truck wash-out, hydro-demolition, or saw-cutting slurry must be managed to prevent discharge to surface waters. Any stormwater contaminated during concrete work is considered process wastewater and must not be discharged to surface waters. Reason for pH Neutralization: A pH level range of 6.5 to 8.5 is typical for most natural watercourses, and this neutral pH is required for the survival of aquatic organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may become stressed and may die. Calcium hardness can contribute to high pH values and cause toxicity that is associated with high pH conditions. A high level of calcium hardness in waters of the state is not allowed. The water quality standard for pH in Washington State is in the range of 6.5 to 8.5. Ground water standard for calcium and other dissolved solids in Washington State is less than 500 mg/l. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-90 Conditions of Use Causes of High pH: High pH at construction sites is most commonly caused by the contact of stormwater with poured or recycled concrete, cement, mortars, and other Portland cement or lime containing construction materials. (See BMP D.2.2.1, Concrete Handling for more information on concrete handling procedures). The principal caustic agent in cement is calcium hydroxide (free lime). Advantages of CO2 Sparging: • Rapidly neutralizes high pH water. • Cost effective and safer to handle than acid compounds. • CO2 is self-buffering. It is difficult to overdose and create harmfully low pH levels. • Material is readily available. The Chemical Process: When carbon dioxide (CO2) is added to water (H2O), carbonic acid (H2CO3) is formed which can further dissociate into a proton (H+) and a bicarbonate anion (HCO3-) as shown below: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- The free proton is a weak acid that can lower the pH. Water temperature has an effect on the reaction as well. The colder the water temperature is the slower the reaction occurs and the warmer the water temperature is the quicker the reaction occurs. Most construction applications in Washington State have water temperatures in the 50°F or higher range so the reaction is almost simultaneous. Design and Installation Specifications Treatment Process: High pH water may be treated using continuous treatment, continuous discharge systems. These manufactured systems continuously monitor influent and effluent pH to ensure that pH values are within an acceptable range before being discharged. All systems must have fail safe automatic shut off switches in the event that pH is not within the acceptable discharge range. Only trained operators may operate manufactured systems. System manufacturers often provide trained operators or training on their devices. The following procedure may be used when not using a continuous discharge system: 1. Prior to treatment, the appropriate jurisdiction should be notified in accordance with the regulations set by the jurisdiction. 2. Every effort should be made to isolate the potential high pH water in order to treat it separately from other stormwater onsite. 3. Water should be stored in an acceptable storage facility, detention pond, or containment cell prior to treatment. 4. Transfer water to be treated to the treatment structure. Ensure that treatment structure size is sufficient to hold the amount of water that is to be treated. Do not fill tank completely, allow at least 2 feet of freeboard. 5. The operator samples the water for pH and notes the clarity of the water. As a rule of thumb, less CO2 is necessary for clearer water. This information should be recorded. 6. In the pH adjustment structure, add CO2 until the pH falls in the range of 6.9 to 7.1. Remember that pH water quality standards apply so adjusting pH to within 0.2 pH units of receiving water (background pH) is recommended. It is unlikely that pH can be adjusted to within 0.2 pH units using dry ice. Compressed carbon dioxide gas should be introduced to the water using a carbon dioxide diffuser located near the bottom of the tank, this will allow carbon dioxide to bubble up through the water and diffuse more evenly. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-91 7. Slowly discharge the water making sure water does not get stirred up in the process. Release about 80% of the water from the structure leaving any sludge behind. 8. Discharge treated water through a pond or drainage system. 9. Excess sludge needs to be disposed of properly as concrete waste. If several batches of water are undergoing pH treatment, sludge can be left in treatment structure for the next batch treatment. Dispose of sludge when it fills 50% of tank volume. Sites that must implement flow control for the developed site must also control stormwater release rates during construction. All treated stormwater must go through a flow control facility before being released to surface waters which require flow control. Maintenance Standards Safety and Materials Handling: • All equipment should be handled in accordance with OSHA rules and regulations. • Follow manufacturer guidelines for materials handling. Operator Records: Each operator should provide: • A diagram of the monitoring and treatment equipment. • A description of the pumping rates and capacity the treatment equipment is capable of treating. Each operator should keep a written record of the following: • Client name and phone number. • Date of treatment. • Weather conditions. • Project name and location. • Volume of water treated. • pH of untreated water. • Amount of CO2 needed to adjust water to a pH range of 6.9 to 7.1. • pH of treated water. • Discharge point location and description. A copy of this record should be given to the client/contractor who should retain the record for 3 years. D.2.2.8 PH CONTROL FOR HIGH PH WATER Purpose When pH levels in stormwater rise above 8.5 it is necessary to lower the pH levels to the acceptable range of 6.5 to 8.5, this process is called pH neutralization. Stormwater with pH levels exceeding water quality standards may be treated by infiltration, dispersion in vegetation or compost, pumping to a sanitary sewer, disposal at a permitted concrete batch plant with pH neutralization capabilities, or carbon dioxide sparging. BMP D.2.2.7, High pH Neutralization Using CO2 gives guidelines for carbon dioxide sparging. Reason for pH Neutralization: A pH level range of 6.5 to 8.5 is typical for most natural watercourses, and this pH range is required for the survival of aquatic organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may become stressed and may die. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-92 Conditions of Use Causes of High pH: High pH levels at construction sites are most commonly caused by the contact of stormwater with poured or recycled concrete, cement, mortars, and other Portland cement or lime containing construction materials. (See BMP D.2.2.1, Concrete Handling for more information on concrete handling procedures). The principal caustic agent in cement is calcium hydroxide (free lime). Design and Installation Specifications Disposal Methods: Infiltration • Infiltration is only allowed if soil type allows all water to infiltrate (no surface runoff) without causing or contributing to a violation of surface or ground water quality standards. • Infiltration techniques should be consistent with Chapter 5 of the SWDM Dispersion • Dispersion techniques should be consistent with Appendix C of the SWDM Sanitary Sewer Disposal • Approval from King County and the City of Renton is required prior to disposal via the sanitary sewer. Concrete Batch Plant Disposal • Only permitted facilities may accept high pH water. • Facility should be contacted before treatment to ensure they can accept the high pH water. Stormwater Discharge Any pH treatment options that generate treated water that must be discharged off site are subject to flow control requirements. Sites that must implement flow control for the developed site must also control stormwater release rates during construction. All treated stormwater must go through a flow control facility before being released to surface waters which require flow control. D.2.2.9 USE OF HIGH PH SOIL AMENDMENTS ON CONSTRUCTION SITES The use of soil amendments (including cement treated base [CTB] and cement kiln dust [CKD]) on development sites must be approved by the City. The approval process is described in “Processing Requirements for Use of Soil Amendments on Construction Sites” below. Use of Soil Amendments It is sometimes a construction practice to add soil amendments to the surfaces of some construction areas in order to stabilize the ground for building. This practice includes placing an additive on the ground then mixing with the soil to a specified depth and finally compacting the mix. When mixed with the soil, the moisture in the ground may allow these additives to create a chemical reaction that cures similar to concrete and may absorb excessive moisture to allow soils to be compacted. The end result is a stable site for constructing a road or building pad. Because soil amendments may be rich in lime content and other material, water runoff from these areas can be affected. If not controlled and treated, this could result in a degradation of water quality and natural drainage systems. Because these additives come in a fine powder form, the actual application can create fugitive dust. When mixed with water, some additives can become corrosive. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-93 Definitions The following are definitions of soil amendment products that are allowed for use under these procedures: 1. Cement Kiln Dust (CKD) is a by-product in the manufacturing of cement9. 2. Cement Treated Base (CTB) utilizes Portland Cement Type II as the soil additive. CTB/CKD Soil Amendment BMPs Table D.2.2.9.A on the following pages lists twelve BMP categories of action and specific BMPs for each category to be applied when proposing CTB/CKD soil amendments or using soil amendments onsite. Note: Additional BMPs may be required to prevent adverse impacts to the public and/or the environment. It is the responsibility of the permit holder to remain in compliance with all other applicable local, state, and federal regulations. TABLE D.2.2.9.A CTB/CKD SOIL AMENDMENT BMPS Category of Action Specific Action CTB/CKD Best Management Practices 1. Materials Source Analysis Solubility Testing & Specifications A. If CKD is proposed, a chemical analysis of soluble pollutants of the product to be used will be provided to the Washington State Department of Ecology (Ecology) and the CED review staff in advance of any product is applied. B. CTB/CKD mixing percentage is anticipated to be approximately 3 percent to 5 percent. C. A Geotechnical Engineer will establish the mixing percentage for the onsite soils. D. All treatment procedures shall be directed, monitored, and verified by a Geotechnical Engineer. E. Soil amendments will never occur in excess of the ability of the onsite equipment and resources to meet all BMP requirements specified herein. 2. Site Preparation Runoff Collection System A. Areas that are to be treated as shown on the plan are flagged off to prevent equipment from leaving treated area and going onto untreated areas, and to prevent unauthorized equipment from entering the treated area. B. Assessment of surface runoff collection points are noted. C. Cutoff trenches, collection sumps, and pumps are installed. D. Sealed storage tanks will be properly sized to contain all runoff from treated areas. E. Sealed storage tanks shall be set up and ready for use to treat contact water. F. An approved wheel wash will be constructed at the construction exit, typically a paved ramp sump that utilizes high-pressure washers. G. Copies of Treatment Plan, Approval, and Contingency Plan area are required to be located on site. 9 CKD is collected by air pollution control devices used to clean kiln exhaust during the manufacturing of Portland Cement. EPA has classified CKD a non-hazardous waste product provided management standards are followed for groundwater protection and control of fugitive dust releases. CKD should not to be confused with Fly Ash, which is a by-product of burning coal or wood and incineration of other material. Fly ash can contain major oxides and trace metals, depending upon the fuel source, and is considered too hazardous for use as a soil amendment. Using this product is not authorized or endorsed by Ecology or the City. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-94 TABLE D.2.2.9.A CTB/CKD SOIL AMENDMENT BMPS Category of Action Specific Action CTB/CKD Best Management Practices 3. Lay-down Mixing Equipment A. Exposure of CTB/CKD materials to air to be minimized. Delivery tankers shall be set up to place CTB/CKD directly into spreading trucks or equipment. B. CTB/CKD operations are only allowed during daylight hours. C. Tarps or dust bags will be used over the discharge truck hose at unloading to prevent dust particles for becoming airborne. D. Unloading will occur at the lowest possible pump pressure. E. Unloading and mixing will be avoided on high wind days. PSAPCA Section 9.15 prohibits visible emissions of fugitive dust. F. CTB/CKD to be placed on ground by large wheeled spreaders designed for this purpose capable of measuring application. G. When spreading CTB/CKD it shall be kept 2–3 feet away from untreated areas boundaries to prevent the material from migration and contaminating outside the treatment zone. H. Treatment area will be kept damp/wet at all times CTB/CKD is being spread and mixed. Skirting around applicator/spreader and mixer is required to minimize CTB/CKD dust. I. CTB/CKD is to be roto-tilled into soil immediately after being spread onto soils and shall be done with a skirted tiller. J. Direct auguring machine that measures, spreads, and mixes CTB/CKD in one operation is preferred. K. Compaction will be complete within 2 hours after CTB/CKD application. 4. Site Management Work Progress and Weather Conditions A. Dust suppression by use of water trucks shall be used on areas where work on dry soil is performed and potential airborne contamination may occur. B. The volume of CTB/CKD allowed on site will be limited to the amount that can be used within a normal workday. Every effort will be made to forecast the daily delivery rate to match the daily onsite use rate. C. CTB/CKD will not be added to soils at a rate that exceeds the ability of onsite resources to immediately commence mixing and compacting. D. No work will occur in rain heavier than drizzle, or under drizzle that exceeds 6 hours duration, or under any rainfall which generates runoff from the areas being worked. E. Should the weather change to stop the application, remaining CTB/CKD will be covered and contained to prevent stormwater from entering storage containment, and causing runoff. F. All vehicles and equipment leaving the treatment area/site must be cleaned/washed to prevent CTB/CKD from leaving site. Wash water will be contained and treated as needed. G. CTB/CKD contact water in the wheel wash will be removed from the site via a Vactor truck for transport to an approved off-site treatment or disposal facility in accordance with all federal, state, and local laws and regulations; or, if permitted, to the sanitary sewer system. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-95 TABLE D.2.2.9.A CTB/CKD SOIL AMENDMENT BMPS Category of Action Specific Action CTB/CKD Best Management Practices 5. Surface Water Collection A. Surface runoff from the treated areas is to be collected and stored in onsite sealed treatment tanks. B. A rigid schedule of TESC inspection, maintenance, and drainage controls will be maintained. C. Temporarily plugging and using detention facilities is not allowed as a storage practice. D. Runoff from compacted areas amended with CTB/CKD will be directed to previously sealed tank(s) until pH levels of water are verified to be within acceptable background water limits. No uncontrolled discharge or infiltration from the sealed tank(s) will be allowed. E. Drainage from areas amended with CTB/CKD within the past 72 hours will be prevented from co-mingling with any other project drainage. 6. Discharge Compliance Applicable Regulations A. Any and all discharges from this site will be in compliance with all applicable federal, state, and local laws and regulations pertaining to health and safety, water, air, waste, and wildlife, including the Federal Clean Water Act, Clean Air Act, and Endangered Species Act. Laboratory analysis of water is required prior to discharge to verify compliance. B. No infiltration is allowed to occur if pH readings are above 8.5 standard pH units, or below 6.5 standard pH units. C. A pH meter must be used to determine levels. pH meter is to be calibrated following proper QA/QC procedures. Fresh buffers are to be available to re-calibrate as needed. D. A log of turbidity and pH readings will be kept on site for inspection. E. All treatment of water must be directed, bench tested, monitored and verified by a qualified water quality specialist. F. Treated area water runoff shall not enter the permanent stormwater system. G. Stormwater drainage system within treatment area is to be cleaned out prior to use for regular water runoff conveyance from untreated areas. Water from cleanout is to be tested and treated following the approved treatment criteria. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-96 TABLE D.2.2.9.A CTB/CKD SOIL AMENDMENT BMPS Category of Action Specific Action CTB/CKD Best Management Practices 7. Natural Treatment and Discharge A. The preferred method of disposal of the treatment water will be discharge to the sanitary sewer, provided a permit is obtained to do so. B. If infiltration is proposed, the area of infiltration is to be identified, capacity confirmed, and a contingency discharge plan in place in the event facilities fail to infiltrate. C. For infiltration, pH limits shall be strictly adhered to. D. If a permit to discharge to the sanitary sewer is not obtained, a National Pollutant Discharge Elimination System (NPDES) discharge permit is required from Ecology. The retention volume of the lined pond(s) will also be increased to ensure complete control of the retained volume. Monitoring, bench testing, and controlled discharge rates, with prior approval by Ecology, would be needed prior to discharge to an approved off-site surface drainage system. Sites that currently have NPDES permits will need to amend permit prior to discharge to cover this action. City approval is still required. E. Per RMC 4-6-030, discharges into receiving drainage systems shall not have acid or basic pH levels. F. Sealed storage tanks shall be used to reduce turbidity and pH before discharge. 8. Chemical Treatment A. Carbon dioxide sparging (dry ice pellets) may be used as the chemical treatment agent to reduce the water pH. B. Any means of water treatment to reduce pH will require an NPDES discharge permit from Ecology. Permit would only be granted after bench testing performed by an independent qualified party. C. Active mixing will cease if the residual retention water volume falls below the ability to treat and properly dispose of contact storm water. D. Discharge would only occur after the approval of Ecology, following bench testing and consultation with Ecology. E. All materials for chemical treatment will be on site and property stored, during all phases of CTB/CKD treatment. 9. Water Quality Monitoring A. Turbidity and pH will be monitored on a twice-daily basis, prior to operations and immediately upon ceasing operations, and these measurements will be recorded. Monitoring will also occur immediately after any storm event of ½ inch in 24 hours, or water migration to the retention pond(s), and the measurements recorded. If the pH approaches 8.0, monitoring frequency will increase. B. Turbidity and pH monitoring will occur in all treatment facilities, stormwater detention facilities, infiltration areas (if infiltration is used), and in all surface water areas adjacent to site where stormwater potentially discharges. Additional upstream surface water sites will be established to determine background levels of turbidity and pH. C. All water quality monitoring data will be conducted and evaluated by an independent, qualified party and conducted using professionally supportable test protocols and QA/QC procedures. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-97 TABLE D.2.2.9.A CTB/CKD SOIL AMENDMENT BMPS Category of Action Specific Action CTB/CKD Best Management Practices 10. Reporting Ecology and CED A. All water quality monitoring data will be included in weekly CED TESC reports to CED, and in weekly NPDES reports to Ecology. B. All work, testing, and monitoring associated with the application of CTB/CKD shall be observed by engineer. The engineer shall prepare and submit a report to the assigned CED project inspector indicating BMPs were/were not being met. C. Copies of all reports and logs will be available on site during the soil and surface runoff treatment activities. Other elements to consider: 11. Water Quality – Soils Source Controls A. There may be very small amounts of concrete washout produced onsite as a result of construction of erosion control measures during reclamation. Concrete washout, if any, would be retained in a lined enclosure of at least 6-ml Visqueen or plastic sheeting, with no outlet. The washout retention enclosure would be isolated and separate from any CTB/CKD area runoff. Contents of the lined concrete washout enclosure will be removed from the site via a Vactor truck for disposal in an approved off-site treatment or disposal facility in accordance with all federal, state, and local laws and regulations. Signed trip tickets, as proof of proper disposal, will be provided to Ecology and CED. 12. Water Quality – pH Cover Measures A. Areas amended with CTB/CKD for compaction after CTB/CKD addition will be covered with plastic or Visqueen sheeting, or other impervious material by the end of each working day. B. Temporary cover will be maintained over all compacted areas amended with CTB/CKD until testing confirms that pH levels are stabilized to background measurements. [Note: Curing to avoid pH effects has no relationship to the rate at which material can be compacted in multiple lifts. Compaction will commence immediately after application and mixing, and multiple lifts will occur as quickly as each lift is compacted and ready to accept the next.] C. Should weather conditions prevent mixing, any unmixed CTB/CKD remaining on site will be enclosed in a sealed containment, such as portable silo, or removed from site. Processing Requirements for Use of High pH Soil Amendments on Construction Sites10 Purpose This section establishes procedures for implementing BMPs when using high pH soil amendments on construction sites. See Table D.2.2.9.A for a description of the BMPs. This section outlines an expedited review process and typical approval conditions that will allow contractors and builders to use soil amendments without impacting water quality. Additional BMPs may be required based upon site specific conditions that may warrant more protection. This policy is limited to those amendments, defined below, commonly known to add stability to sloppy soil conditions but which can alter water runoff quality. Authority: RMC 4-6-030(J) prohibits discharges of polluted or contaminated water into surface or storm water drainage systems. The purpose of this statute is to protect surface and ground water by regulating the discharge of potentially contaminated surface water. If soil amendments are proposed with an initial application, an environmental review is required, under SEPA, which assesses impacts, provides public input and mitigated conditions for its use. 10 Excerpted from the King County Stormwater Pollution Prevention Manual (SPPM), BMP Info Sheet #11 SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-98 The City of Renton also requires an engineered design for use of a soil amendment on road surfaces or around drainage systems (see Appendix C). The design may incorporate a thorough assessment of soil composition and laboratory analysis. The SWDM authorizes CED to adopt BMPs for the control and protection of surface water. Currently, for all sites, the BMPs established in this policy are the minimum standards that shall be applied. Procedure An applicant may apply for use of soil amendments allowed under this policy anytime during the permit application review or after the permit has been issued and site construction is underway. After making a submittal to CED, the applicant may receive approval conditions. Conditions may vary from site to site, but typically will include many of the BMPs included in this policy. Applicants should identify any use of soil amendments as early in the process as possible to avoid delays in obtaining approval for use during the construction phase. If a site has known soil and water conditions that might make work during rainy periods difficult, they may want to plan to use soil amendments on their site. Obviously, if this issue is addressed at the permit review phase, implementation in the field can occur without delay. However, because of the potential risks of surface water pollution discharge and required treatment, an environmental assessment will be necessary before conditions for use can be established. Limitations This policy applies to the intended use of soil amendments in areas that will be covered by impervious surfaces. For areas not covered by impervious surfaces, additional reviews, study, and BMPs may be required. In addition, alterations to original approved use plans will require a resubmittal for approval. Approval for the use of the soil amendments can only occur by strictly following the procedures contained herein and not by any other approval obtained from CED. Submittal Requirements To obtain approval for the use of soil amendments allowed under this policy, the applicant shall prepare a submittal package to CED that includes the following: • Letter to CED requesting use of soil amendments at a construction site allowed under this policy. • Document or letter attachment that identifies source of materials and description of mixing and laydown process, plan for disposal of treated contact water, sanitary sewer permits and/or BMPs, and special precautions proposed to prevent the contamination of surface or stormwater drainage systems, other than ‘sealed’ drainage systems. • Site Plan: Show a site plan map which: 1) Shows overall grading plan showing existing and proposed contours. 2) Identifies sensitive areas and permanent or temporary drainage facilities. 3) Identifies areas that soil amendment is planned. 4) Shows depths of application and percent of amendment to be used. 5) Shows location of special wheel wash facility. 6) Shows location of collection and conveyance swales or pipes for contact water. 7) Shows location of sealed storage/treatment tanks or temporary ponds (fully lined). 8) Identifies any discharge point from the site into natural drainage systems. 9) Includes soil log locations that identify seasonal high groundwater areas. • Report and analysis of engineering mix design which includes depths of application and percent of amendment usage. • For proposals that use CKD and CKD additive, provide analysis of source material for soluble contaminants. Include a description of fuel source. D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-99 • Monitoring criteria, including locations for pH and turbidity testing. • Provide contingency plan should use of soil amendment and site and weather conditions result in polluted or contact water entering natural drainage systems. • Provide contact information or water quality specialist assigned to monitor application of soil amendments and BMPs. If the project is under construction, the applicant shall contact the CED inspector assigned to the project to initiate a review for compliance with the BMPs and requirements herein. Otherwise contact the planner or engineer assigned to review the permit or land use application. Review and Approval Once the review has been completed, the applicant shall be notified by letter which stipulates the conditions of approval. Prior to authorizing the use of soil amendments at the site, the applicant shall provide a special restoration financial guarantee cash deposit in the amount as determined by the existing, established processes. Note: It remains the applicant/contractor’s responsibility to comply with any other applicable state or federal regulations such as use of NIOSH respiratory protection, safety goggles, gloves and protective clothing whenever using hazardous materials. Applicable Standards Typically, all proposals using soil amendments shall have these conditions as standard requirements: 1. Prior to any application of CKD/CTB, the general contract shall hold a preconstruction meeting with the assigned CED inspector at least 3 working days in advance. 2. CKD will not be permitted for use in areas adjacent to or in proximity to wetlands and streams areas. CTB may or may not be permitted in these areas. 3. Areas not covered by impervious surfaces: • CKD will not be permitted in areas that will not be covered by impervious surfaces. • If CTB is proposed in these areas, an analysis of whether or not the soil amendment will change the post-development runoff characteristics and the permanent stormwater facilities were sized appropriately shall be submitted for review. Use of CTB in areas not permanently covered by impervious surface may require re-sizing of the permanent stormwater facilities. 4. If CKD is proposed, the contractor shall provide mill certificates verifying the product composition. The contractor/developer must be prepared to follow BMPs during and after soil treatment and be prepared to treat runoff from the treatment area(s) immediately. All stormwater collection systems must be in place and all equipment (pH meters, dry ice, etc.) must be onsite. 5. Collection of stormwater (see BMP #5 in Table D.2.2.9.A): • Stormwater from the application area shall be kept separate from and prevented from comingling with uncontaminated stormwater. • During the application of CKD/CTB, stormwater runoff shall be collected in temporary collection systems and shall not be allowed to enter the permanent facilities. Permanent drainage systems shall be capped to prevent contact stormwater from entering the inlets of the catch basins. Stormwater from the application area shall not be collected in the temporary/permanent detention ponds, even if the underlying soils are ‘impermeable.’ 6. Treatment: If necessary, pH adjustment shall be done in the collection tanks or temporary ponds and not in the permanent detention ponds. 7. Disposal options: The proposal to use CKD/CTB must contain a disposal plan that may include one or a combination of sanitary sewer or approved offsite disposal. Treated contact water may be discharged to the sanitary sewer if authorizations are obtained from the King County and the City of Renton. All discharge conditions (e.g., pH, settleable solids) must be followed. If a sanitary sewer is not available at the site, contact water may be transported offsite to an approved site for disposal and proof of SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-100 proper disposal must be submitted to the City. All authorizations for disposal shall be obtained prior to CKD/CTB application. • Infiltration: Depending on the site conditions, pH-adjusted stormwater may be infiltrated. Prior to infiltration, pH must be between 6.5 and 8.5. • Surface Water: Contact water from the application area shall not be discharged to surface waters, even if treatment has adjusted the pH. 8. Emergency backup plan: An emergency backup plan must be prepared and ready to implement to handle large quantities of stormwater. 9. Monitoring shall be conducted to determine that contact stormwater is not leaving the site. Offsite monitoring shall also be conducted to identify impacts to adjacent water bodies. Bonding may be required to cover mitigation of impacts and restoration. 10. A soils specialist will establish the mixing percentage for onsite soils. Soil amendments will never occur in excess of the ability of the onsite equipment and resources to meet all BMP requirements. 11. For sites one acre or larger, a Construction Stormwater General permit must be obtained from Ecology. Construction Stormwater General permits and ‘Stormwater Pollution Prevention Plans (SWPPPs) must be amended and the use of CKD/CTB must be approved by Ecology prior to application. The contractor/developer shall comply will all federal, state, and local regulations. A health and safety plan may be required for the protection of CED inspectors. Additional BMPs may be applicable depending on mix design, proximity of wetlands or streams (e.g., within 300 feet of class/type I and 100 feet or less for other types) and site conditions. D.2.2.10 MAINTAIN PROTECTIVE BMPS Pollutant protection measures shall be maintained to ensure continued performance of their intended function. Reporting and documentation shall be kept current and made available to CED as indicated. Purpose: The purpose of maintaining protective BMPs is to provide effective pollutant protection when and where required by the plan and the project, and to provide timely and relevant project information. When to Maintain: Protection measures shall be monitored per Section D.2.4.4 at a minimum, continuously during operation, and promptly maintained to fully functioning condition as necessary to ensure continued performance of their intended function. Documentation shall be kept current per specific BMP requirements. Measures to Use: 1. Maintain and repair all pollutant control BMPs as needed to ensure continued performance of their intended function in accordance with BMP specifications. 2. Maintain and repair storage locations for equipment and materials associated with BMP processes. Conduct materials disposal in compliance with City requirements. 3. As required, provide current reporting and performance documentation at an accessible location for the site inspector and other CED staff. 4. Remove all temporary pollutant control BMPs prior to final construction approval, or within 30 days after achieving final site stabilization or after the temporary BMPs are no longer needed. D.2.2.11 MANAGE THE PROJECT SWPPP requirements shall be implemented and managed as part of the overall CSWPP plan. Concrete construction and its impacts are primary among pollutant concerns on site development projects. Fueling operations and materials containment of treatment chemicals and other project materials are also typical D.2.2 SWPPS MEASURES 2017 City of Renton Surface Water Design Manual 12/12/2016 D-101 pollutant concerns. Operations that produce these and other pollutants are often conducted by subcontractors and their laborers, yet may require specific protective measures, documentation and reporting. Protective measures and BMPs need to be made available prior to construction and suitable oversight provided to ensure inspection, monitoring and documentation requirements are met. Projects shall assign a qualified CSWPP Supervisor (Section D.2.3.1) to be the primary contact for SWPPP and ESC issues and reporting, coordination with subcontractors and implementation of the CSWPP plan as a whole. Measures to Use: 1. Phase development projects to the maximum degree practicable and take into account seasonal work limits. 2. Inspection and monitoring – Inspect, maintain, and repair all BMPs as needed to ensure continued performance of their intended function. Conduct site inspections and monitoring in accordance with the Construction Stormwater General Permit and City requirements. Coordinate with subcontractors and laborers to ensure the SWPPP measures are followed. 3. Documentation and reporting – Inspect, maintain, and repair all BMPs as needed to ensure continued performance of their intended function. Document site inspections and monitoring in accordance with the Construction Stormwater General Permit, specific BMP conditions and City requirements. Log sheets provided in Reference Section 8 may be used if appropriate. Follow reporting requirements and provide documentation as requested to CED staff. 4. Maintaining an updated construction SWPPP – Maintain, update, and implement the SWPPP in accordance with the Construction Stormwater General Permit and City requirements. Obtain approval for specific SWPPP measures (e.g., chemical treatments of stormwater) well in advance of need. Coordinate SWPPP plan updates with the site inspector (see Section D.2.4.1). D.2.3 CSWPP PERFORMANCE AND COMPLIANCE PROVISIONS The changing conditions typical of construction sites call for frequent field adjustments of existing ESC and SWPPS measures or additional ESC and SWPPS measures in order to meet required performance. In some cases, strict adherence to specified measures may not be necessary or practicable based on site conditions or project type. In other cases, immediate action may be needed to avoid severe impacts. Therefore, careful attention must be paid to ESC and SWPPS performance and compliance in accordance with the provisions contained in this section. D.2.3.1 CSWPP SUPERVISOR For projects in Targeted, Full, or Large Project Drainage Review, or projects in Directed Drainage Review as determined by CED review staff, the applicant must designate a CSWPP supervisor who shall be responsible for the performance, maintenance, and review of ESC and SWPPS measures and for compliance with all permit conditions relating to CSWPP as described in the CSWPP Standards. The applicant’s selection of a CSWPP supervisor must be approved by the City. (City approval may be rescinded for non-compliance, requiring the applicant to select another CSWPP supervisor and obtain City approval prior to continuing work on the project site.) For projects that disturb one acre or more of land, the CSWPP supervisor must be a Certified Professional in Erosion and Sediment Control (see <www.cpesc.net> for more information) or a Certified Erosion and Sediment Control Lead whose certification is recognized by the City.11 The City may also require a certified ESC professional for sites smaller than one acre of disturbance if CED determines that onsite ESC measures are inadequately installed, located, or maintained. 11 The City’s recognition of certification means that the individual has taken an approved third party training program and has passed the approved test for that training program. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-102 For larger, more sensitive sites, the City may require a certified ESC professional with several years of experience in construction supervision/inspection and a background in geology, soil science, or agronomy. Typically, if a geotechnical consultant is already working on the project, the consultant may also be a certified ESC professional designated as the CSWPP supervisor. The design engineer may also be qualified for this position. This requirement shall only be used for sensitive sites that pose an unusually high risk of impact to surface waters as determined by CED. At a minimum, the project site must meet all of the following conditions in order to require the applicant to designate as the CSWPP supervisor a certified ESC professional with such expertise: • Alderwood soils or other soils of Hydrologic Group C or D • Five acres of disturbance • Large areas (i.e., two or more acres) with slopes in excess of 10 percent. Proximity to streams or wetlands or phosphorus-sensitive lakes, such as Lake Sammamish, shall also be a factor in determining if such expertise in the CSWPP supervisor is warranted. However, proximity alone shall not be a determining factor because even projects that are a considerable distance from surface waters can result in significant impacts if there is a natural or constructed drainage system with direct connections to surface waters. The name, address, and phone number of the CSWPP supervisor shall be supplied to the City prior to the start of construction. A sign shall be posted at all primary entrances to the site identifying the CSWPP supervisor and his/her phone number. The requirement for a CSWPP supervisor does not relieve the applicant of ultimate responsibility for the project and compliance with Renton Municipal Code. D.2.3.2 MONITORING OF DISCHARGES The CSWPP supervisor shall have a turbidity meter onsite and shall use it to monitor surface and storm water discharges from the project site and into onsite wetlands, streams, or lakes whenever runoff occurs from onsite activities and during storm events. The CSWPP supervisor shall keep a log of all turbidity measurements taken onsite and make it available to CED upon request. If the project site is subject to a NPDES general permit for construction issued by the Washington State Department of Ecology (Ecology), then the project must comply with the monitoring requirements of that permit. The CSWPP supervisor shall also use the specific SWPPS BMP procedures for monitoring surface and stormwater discharge for pollutants and acceptable discharge levels. The CSWPP supervisor shall keep logs as required by the procedures of all measurements taken onsite and make them available to CED on request. D.2.3.3 ESC PERFORMANCE ESC measures shall be applied/installed and maintained so as to prevent, to the maximum extent practicable, the transport of sediment from the project site to downstream drainage systems or surface waters or into onsite wetlands, streams, or lakes or onto adjacent properties. This performance is intended to be achieved through proper selection, installation, and operation of the above ESC measures as detailed in the CSWPP Standards (Appendix D) and approved by the City. However, the CSWPP supervisor designated per Section D.2.3.1 or the City may determine at any time during construction that such approved measures are not sufficient and additional action is required based on one of the following criteria: 1. IF a turbidity test of surface and storm water discharges leaving the project site is greater than the benchmark value of 25 nephelometric turbidity units (NTU) set by the Washington State Department of Ecology, but less than 250 NTU, the CSWPP Supervisor shall do all of the following: a) Review the ESC plan for compliance and make appropriate revisions within 7 days of the discharge that exceeded the benchmark of 25 NTU, AND D.2.3 CSWPP PERFORMANCE AND COMPLIANCE PROVISIONS 2017 City of Renton Surface Water Design Manual 12/12/2016 D-103 b) Fully implement and maintain appropriate ESC measures as soon as possible but no later than 10 days after the discharge that exceeded the benchmark, AND c) Document ESC implementation and maintenance in the site log book. 2. IF a turbidity test of surface or storm water entering onsite wetlands, streams, or lakes indicates a turbidity level greater than 5 NTU above background when the background turbidity is 50 NTU or less, or 10% above background when the background turbidity is greater than 50 NTU, then corrective actions and/or additional measures beyond those specified in SWDM Section 1.2.5.1 shall be implemented as deemed necessary by the CED inspector or onsite CSWPP supervisor. 3. IF discharge turbidity is 250 NTU or greater, the CSWPP Supervisor shall do all of the following: a) Notify the City by telephone, AND b) Review the ESC plan for compliance and make appropriate revisions within 7 days of the discharge that exceeded the benchmark of 25 NTU, AND c) Fully implement and maintain appropriate ESC measures as soon as possible but no later than 10 days after the discharge that exceeded the benchmark, AND d) Document ESC implementation and maintenance in the site log book. AND e) Continue to sample discharges until turbidity is 25 NTU or lower, or the turbidity is no more than 10% over background turbidity. 4. IF the City determines that the condition of the construction site poses a hazard to adjacent property or may adversely impact drainage facilities or water resources, THEN additional measures beyond those specified in SWDM Section 1.2.5.1 may be required by the City. D.2.3.4 SWPPS PERFORMANCE SWPPS measures shall be applied/installed and maintained so as to prevent, reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or watercourses or onto adjacent properties. This performance is intended to be achieved through proper selection, installation, and operation of the above SWPPS measures as detailed in the CSWPP Standards (Appendix D) and approved by the City. However, the CSWPP supervisor designated per Section D.2.3.1 or the City may determine at any time during construction that such approved measures are not sufficient and additional action is required based on the criteria described in the specific SWPPS BMP standard and/or conditions of an approved adjustment. D.2.3.5 FLEXIBLE COMPLIANCE Some projects may meet the intent of Core Requirement #5 while varying from specific CSWPP requirements in this appendix. If a project is designed and constructed such that it meets the intent of the core requirement, the City may determine that strict adherence to a specific ESC requirement is unnecessary; an approved adjustment (see Section 1.4) from the SWDM is not required in these circumstances. Certain types of projects are particularly likely to warrant this greater level of flexibility; for instance, projects on relatively flat, well drained soils, projects that are constructed in closed depressions, or projects that only disturb a small percentage of a forested site may meet the intent of this requirement with very few ESC measures. Note, however, that SWPPS requirements may actually be emphasized on well-drained soils, particularly in groundwater protection or well-protection areas, or in close proximity to water bodies. D.2.3.6 ROADS AND UTILITIES COMPLIANCE Road and utility projects often pose difficult erosion control challenges because they frequently cross surface waters and because narrow right-of-way constrains areas available to store and treat sediment- laden water. In most cases, the standards of this appendix may be applied to such linear projects without SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-104 modification. For instance, the ability to use perimeter control rather than a sediment retention facility for small drainage areas (see Section D.2.1.3) will apply to many of these projects. However, there may be some projects that cannot reasonably meet the standards of Core Requirement #5 and this appendix. In these cases, other measures may be proposed that will provide reasonable protection. An adjustment is not required for such projects, unless the City determines that measures proposed by the applicant fail to meet the intent of Core Requirement #5 and this appendix, and that significant adverse impacts to surface water may result. Examples of other measures that may be taken in lieu of the standards of this appendix are: 1. Phasing the project so that the site is worked progressively from end to end, rather than clearing and grubbing the entire length of the project. This results in smaller exposed areas for shorter durations, thus reducing the erosion risk. It is recommended that there be no more than 500 feet of open trench during any phase of construction. 2. Placement of excavated materials from utility trenches on the upslope side of the excavation, to minimize transport of sediment outside of the project area. 3. Mulching and vegetating cut and fill slopes as soon as they are graded. Frequently, this is done at the end of construction when paving or utility installation is complete. Vegetating these areas at the start of the project stabilizes those areas most susceptible to erosion. 4. Protecting all catch basin inlets with catch basin inserts or other inlet protection when these do not drain to ponds or traps. This will not provide the same level of protection as a sediment pond or trap, but can remove most of the sand-sized material entrained in the runoff. 5. Phasing the project so that all clearing and grading in critical area buffers occurs in the dry season. This substantially reduces the chance of erosion and allows for rapid revegetation in the late summer and early fall. 6. Using approved flocculent or other chemical treatment approved by the City to reduce the turbidity of water released from sediment ponds. 7. Hiring a private consultant with expertise in ESC to review and monitor the site. 8. Limiting employee/contractor parking and overnight/weekend parking of construction vehicles to dedicated and controlled areas prepared for drip and spill control. Options in the right-of-way for such areas can be limited. If alternatives are used, it may be appropriate to develop a monitoring program that would monitor compliance with the performance standard of Core Requirement #5 and/or impacts to nearby water resources. Of particular concern are impacts to salmonid spawning gravels. McNeil sampling is a possible method of sampling to determine impacts to spawning gravels (see Section D.2.4.3). D.2.3.7 ALTERNATIVE MEASURES In general, the SWDM only contains those BMPs that are standards of the local industry. There are a variety of other BMPs available that may also be used, even though they are not included in this appendix. Such alternatives may be approved without an adjustment if the alternative will produce a compensating or comparable result with the measures in this appendix. Variations on or modifications of the BMPs in this appendix may also be granted based on the same criteria. An adjustment may be required for products or techniques that are new and untested (see Section 1.4.4 of the SWDM). In addition, the new product or technique must be approved through the state Department of Ecology’s CTAPE program.12 The intent of this requirement is not to discourage new techniques, but to 12 CTAPE stands for Chemical Technology Assessment Protocol – Ecology. For more information, see Ecology’s website at <http://www.ecy.wa.gov/programs/wq/stormwater/newtech/tape_ctape.htm>. D.2.3 CSWPP PERFORMANCE AND COMPLIANCE PROVISIONS 2017 City of Renton Surface Water Design Manual 12/12/2016 D-105 ensure that new techniques are monitored and documented for adequacy and possible inclusion in subsequent versions of the SWDM. D.2.4 CSWPP IMPLEMENTATION REQUIREMENTS This section describes the CSWPP implementation requirements that are required at each construction site. The measures and practices correspond to the implementation requirements in Core Requirement #5. Three of the sections (the CSWPP report (Section D.2.4.1, below), CSWPP maintenance requirements (Section D.2.4.4), and final site stabilization (Section D.2.4.5) are required of every project. The rest of the sections are special requirements that may apply to the project depending on site conditions and project type. The introductory paragraphs at the beginning of most sections present the purpose of the measures and when they should be applied to the site. Compliance with the implementation requirements (as appropriate for the site) ensures compliance with the CSWPP measures. Note, however, that additional measures shall be required by the City if the existing standards are insufficient to protect adjacent properties, drainage facilities, or water resources. D.2.4.1 CSWPP PLAN A CSWPP plan, containing the ESC plan and the SWPPS plan, and showing the location and details of ESC and SWPPS measures, is required for all proposed projects. It shall include a CSWPP report, which includes supporting information for providing ESC and SWPPS measures and meeting CSWPP implementation requirements. A copy of the CSWPP plan with CSWPP report shall be kept at the project site throughout all phases of construction. All of the materials required for the CSWPP report are standard parts of engineering plan submittals for projects requiring drainage review. The simplest approach to preparing this report is to compile the pieces during preparation for submittal and include the report as a separate part of the CSWPP plan submittal package. The CSWPP report shall include the following: 1. A detailed construction sequence, as proposed by the design engineer or erosion control specialist, identifying required ESC measures and implementation requirements; 2. A technical information report (TIR) and ESC and SWPPS plans for CED review in accordance with Sections 2.3.1 and 2.3.3 of the SWDM. Incorporate any City review comments as necessary to comply with Core Requirement #5 of the SWDM (Section 1.2.5) and the Construction Stormwater Pollution Prevention Standards adopted in this appendix; 3. Any calculations or information necessary to size ESC measures and demonstrate compliance with Core Requirement #5; 4. Descriptions and any supporting documentation, operating procedures, precautions, logging and reporting requirements, etc., for the project’s SWPPS BMPs, 5. An inspection and maintenance program in accordance with Section D.2.4.4 that includes the designation of a certified CSWPP supervisor as point of contact; and 6. Anticipated changes or additions necessary during construction to ensure that ESC and SWPPS measures perform in accordance with Core Requirement #5 and Sections D.2.1 and D.2.2. While the CSWPP plan focuses on the initial measures to be applied to the site, any changes or additions necessary during construction to ensure that ESC and SWPPS measures perform in accordance with Core Requirement #5 and Sections D.2.1, D.2.2 and D.2.4 must be identified in the CSWPP report. The City may require large, complex projects to phase construction and submit multiple ESC plans for different stages of construction. Development of new CSWPP plans is not required for changes that are necessary during construction. SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-106 D.2.4.2 WET SEASON REQUIREMENTS Any site with exposed soils during the wet season (October 1 to April 30) shall be subject to the special provisions below. In addition to the ESC cover measures (see Section D.2.1.2), these provisions include covering any newly seeded areas with mulch and identifying and seeding as much disturbed area as possible prior to September 23 in order to provide grass cover for the wet season. A “wet season ESC plan” must be submitted and approved by the City before work proceeds or continues. Wet Season Special Provisions All of the following provisions for wet season construction are detailed in the referenced sections. These requirements are listed here for the convenience of the designer and the reviewer. 1. The allowed time that a disturbed area may remain unworked without cover measures is reduced to two consecutive working days, rather than seven (Section D.2.1.2). 2. Stockpiles and steep cut and fill slopes are to be protected if unworked for more than 12 hours (Section D.2.1.2). 3. Cover materials sufficient to cover all disturbed areas shall be stockpiled on site (Section D.2.1.2). 4. All areas that are to be unworked during the wet season shall be seeded within one week of the beginning of the wet season (Section D.2.1.2.6). 5. Mulch is required to protect all seeded areas (Section D.2.1.2.2). 6. Fifty linear feet of silt fence (and the necessary stakes) per acre of disturbance must be stockpiled on site (Section D.2.1.3.1). 7. Construction road and parking lot stabilization are required for all sites unless the site is underlain by coarse-grained soil (Section D.2.1.4.2). 8. Sediment retention is required unless no offsite discharge is anticipated for the specified design flow (Section D.2.1.5). 9. Surface water controls are required unless no offsite discharge is anticipated for the specified design flow (Section D.2.1.6). 10. Phasing and more conservative BMPs must be evaluated for construction activity near surface waters (Section D.2.4.3). 11. Any runoff generated by dewatering may be required to discharge to the sanitary sewer (with appropriate discharge authorization), portable sand filter systems, or holding tanks (Section D.2.2). D.2.4.3 CRITICAL AREAS RESTRICTIONS Any construction that will result in disturbed areas on or within a stream or associated buffer, a wetland or associated buffer, or within 50 feet of a lake shall be subject to the special provisions below. These provisions include, whenever possible, phasing the project so that construction in these areas is limited to the dry season. The City may require more conservative BMPs, including more stringent cover requirements, in order to protect surface water quality. Any project proposing work within 50 feet of a steep slope hazard area shall evaluate the need for diverting runoff that might flow over the top of the slope. Critical Areas Special Provisions Any project that disturbs areas on or within a stream or associated buffer, wetland or associated buffer, or within 50 feet of a lake has the potential to seriously damage water resources, even if the project is relatively small. While it is difficult to require specific measures for such projects because the CSWPP plan must be very site specific, the following recommendations shall be incorporated into the plan where appropriate: D.2.4 CSWPP IMPLEMENTATION REQUIREMENTS 2017 City of Renton Surface Water Design Manual 12/12/2016 D-107 1. Whenever possible, phase all or part of the project so that it occurs during the dry season. If this is impossible, November through February shall be avoided since this is the most likely period for large, high-intensity storms. 2. All projects shall be completed and stabilized as quickly as possible. Limiting the size and duration of a project is probably the most effective form of erosion control. 3. Where appropriate, sandbags or an equivalent barrier shall be constructed between the project area and the surface water in order to isolate the construction area from high water that might result due to precipitation. 4. Additional perimeter protection shall be considered to reduce the likelihood of sediment entering the surface waters. Such protection might include multiple silt fences, silt fences with a higher AOS, construction of a berm, or a thick layer of organic mulch upslope of a silt fence. 5. If work is to occur within the ordinary high water mark of a stream, most projects must isolate the work area from the stream by diverting the stream or constructing a cofferdam. Certain small projects that propose only a small amount of grading may not require isolation since diversions typically result in disturbance and the release of some sediment to the stream. For such small projects, the potential impacts from construction with and without a diversion must be weighed. 6. If a stream must be crossed, a temporary bridge shall be considered rather than allowing equipment to utilize the streambed for a crossing. For projects in or near a salmonid stream, it may be appropriate to monitor the composition of any spawning gravels within a quarter-mile of the site with a McNeil sampler or similar method approved by the City before, during, and after construction. The purpose of such monitoring would be to determine if the fine content of the gravels increases as a result of construction impacts. Monitoring results could be used to guide erosion control efforts during construction and as a threshold for replacing spawning gravels if the fine content rises significantly. D.2.4.4 MAINTENANCE REQUIREMENTS All ESC and SWPPS measures shall be maintained and reviewed on a regular basis as prescribed in the maintenance requirements for each BMP and in this section. The CSWPP supervisor shall review the site for ESC and SWPPS at least weekly and within 24 hours of significant storms. The CWSPP supervisor shall also review the site for ESC and SWPPS during periods of active construction where maintenance conditions change with construction activity (e.g., site grading operations, or concrete construction and dewatering operations for a detention vault). The City requires a written record of these reviews be kept on site with copies submitted to CED within 48 hours. Documentation If CED requires that a written record be maintained, standard ESC and SWPPS Maintenance Reports forms, included in Section D.4.1, may be used. A copy of all the required maintenance reports shall be kept on site throughout the duration of construction. Detailed maintenance requirements for each ESC measure are provided in Section D.2.1. Maintenance requirements for SWPPS BMPs are specified in Section D.2.2 (as in the case of BMPs related to concrete handling or material containment) or may be specified as part of a treatment or monitoring program, often accompanied with adjustment conditions of approval. Review Timing Weekly reviews shall be carried out every 6 to 8 calendar days. Reviews shall also take place within 24 hours of significant storms. In general, a significant storm is one with more than 0.5 inches of rain in 24 hours or less. Other indications that a storm is “significant” are if the sediment ponds or traps are filled with water, or if gullies form as a result of the runoff. Note: The site is to be in compliance with the regulations of this appendix at all times. The requirement for periodic reviews does not remove the applicant’s responsibility for having the site constantly in SECTION D.2 GENERAL CSWPP REQUIREMENTS 12/12/2016 2017 City of Renton Surface Water Design Manual D-108 compliance with Core Requirement #5 and the requirements of this appendix. The reviews are a mechanism to ensure that all measures are thoroughly checked on a regular basis and that there is documentation of compliance. The requirement for these reviews does not mean that CSWPP is to be ignored in between. D.2.4.5 FINAL STABILIZATION Prior to obtaining final construction approval, the site shall be stabilized, the structural ESC and SWPPS measures (such as silt fences, sediment traps, and concrete waste collection pits) removed, and drainage facilities cleaned. The removal of ESC and SWPPS measures is not required for those projects, such as plats, that will be followed by additional construction under a different permit. In these circumstances, the need for removing or retaining the measures must be evaluated on a site-specific basis. To obtain final construction approval, the following conditions must be met: 1. All disturbed areas of the site shall be vegetated or otherwise permanently stabilized. At a minimum, disturbed areas shall be seeded and mulched (see Section D.2.1.2.6) with a high likelihood that sufficient cover will develop shortly after final approval. Mulch without seeding is not adequate to allow final approval of the permit, except for small areas of mulch used for landscaping. The only exceptions to these requirements are lots within a plat that are to be developed under an approved residential permit immediately following plat approval. In these cases, mulch and/or temporary seeding are adequate for cover. 2. Structural measures such as, but not limited to, silt fences, pipe slope drains, construction entrances, storm drain inlet protection, sediment traps and ponds, concrete washout and collection pits, and pollutant storage shall be removed from the site. Measures that will quickly decompose, such as brush barriers and organic mulches, may be left in place. In the case of silt fences, it may be best to remove fences in conjunction with the seeding, since it may be necessary to bring machinery back in to remove them. This will result in disturbed soils that will again require protection. The CED inspector must approve an applicant’s proposal to remove fencing prior to the establishment of vegetation. In some cases, such as residential building following plat development, it shall be appropriate to leave some or all ESC measures for use during subsequent development. This shall be determined on a site- specific basis. 3. All permanent surface water facilities, including catch basins, manholes, pipes, ditches, channels, flow control facilities, and water quality facilities, shall be cleaned. Existing and newly constructed BMPs/facilities shall be cleaned and/or mitigated as necessary to restore functionality. Any offsite catch basin that required protection during construction (see Section D.2.1.5.3) shall also be cleaned. 4. If only the infrastructure of the site has been developed (e.g., subdivisions and short plats) with building construction to occur under a different permit, then the critical area buffers, Critical Area Tracts, or Critical Area Setback Areas shall be clearly marked as described in Section D.2.1.1 in order to alert future buyers and builders. D.2.4.6 NPDES REQUIREMENTS As part of NPDES implementation, projects that will disturb one or more acres for purposes of constructing or allowing for construction of a development, or projects disturbing less than one acre that are part of a larger common plan of development or sale13 that will ultimately disturb one or more acres, must apply for coverage under Ecology’s Construction Stormwater General Permit. In general, the 13 Common plan of development or sale means a site where multiple separate and distinct construction activities may take place at different times or on different schedules, 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; and 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. D.2.4 CSWPP IMPLEMENTATION REQUIREMENTS 2017 City of Renton Surface Water Design Manual 12/12/2016 D-109 construction stormwater pollution prevention plan required by the SWDM is equivalent to that required by the State. The Ecology stormwater permit application requires the filing of a Notice of Intent (NOI) at least 30 days prior to the start of construction. The only major requirement of the stormwater permit that is not included in the SWDM is a public notice requirement. Note that this public notice for Ecology’s stormwater permit may be published concurrently with other public notices required for permits or SEPA. Contact Ecology at (360) 407-7156 for complete information on permit thresholds, applications, and requirements. D.2.4.7 FOREST PRACTICE PERMIT REQUIREMENTS Projects that will clear more than two acres of forest or 5,000 board feet of timber must apply for a Class IV Special Forest Practice permit from the Washington State Department of Natural Resources (WSDNR). All such clearing is also subject to the State Environmental Policy Act (RCW 43.21C) and will require SEPA review. The City assumes lead agency status for Class IV permits and the application may be consolidated with the associated City development permit or approval. The permit must be initiated with WSDNR, but will then be transferred over to the City to conduct the SEPA review and grant the permit. Contact the WSDNR for complete information on permit thresholds, applications, and requirements. D.2.5 CONSTRUCTION STORMWATER POLLUTION PREVENTION PLANS This section details the specifications and contents for CSWPP plans, containing ESC plans and SWPPS plans. A CSWPP plan includes the plan’s drawings plus a CSWPP report, which provides all supporting information and any additional direction necessary for implementing ESC and SWPPS measures and meeting CSWPP implementation requirements. The CSWPP plan must be submitted to CED as part of a complete engineering plan to facilitate proper drainage review. A copy of the approved CSWPP plan (with CSWPP report) must be kept on the project site (see Section D.2.4.1) at all times during the construction phase. D.2.5.1 ESC PLAN ESC Plan General Specifications The site improvement plan shall be used as the base of the ESC plan. Certain detailed information (e.g., pipe catch basin size, stub-out locations, etc.) that is not relevant may be omitted to make the ESC plan easier to comprehend. At a minimum, the ESC plan shall include all of the information required for the base map of a site improvement plan (see Table 2.3.1A of the SWDM), as well as existing and proposed roads, driveways, parking areas, buildings and drainage facilities (including existing and proposed BMPs/facilities), utility corridors not associated with roadways, relevant critical areas14 and associated buffers, and proposed final topography. A smaller scale may be used to provide better comprehension and understanding. The ESC plan shall generally be designed for proposed topography, not existing topography, since rough grading is usually the first step in site disturbance. The ESC plan shall address all phases of construction (e.g., clearing, grading, installation of utilities, surfacing, and final stabilization). The City may require large, complex projects to phase construction and submit multiple ESC plans for different stages of construction. The ESC plan outlines the minimum requirements for anticipated site conditions. During construction, ESC plans shall be revised as necessary by the CSWPP supervisor or as directed by the City to address changing site conditions, unexpected storm events, or non-compliance with the ESC performance criteria in Section D.2.3.3. If non-compliance with the ESC performance criteria occurs, the plan must be updated 14 Relevant critical areas, for the purposes of drainage review, include aquatic areas, wetlands, flood hazard areas, erosion hazard areas, landslide hazard areas, steep slope hazard areas, and critical aquifer recharge areas. APPENDIX I WORKSHEETS CED Permit #:########UnitReference #PriceUnitQuantity CostBackfill & compaction-embankmentESC-16.50$ CY Check dams, 4" minus rockESC-2SWDM 5.4.6.380.00$ Each Catch Basin ProtectionESC-335.50$ Each16568.00Crushed surfacing 1 1/4" minusESC-4WSDOT 9-03.9(3)95.00$ CY DitchingESC-59.00$ CY Excavation-bulkESC-62.00$ CY Fence, siltESC-7SWDM 5.4.3.11.50$ LF16802,520.00Fence, Temporary (NGPE)ESC-81.50$ LF Geotextile FabricESC-92.50$ SY25006,250.00Hay Bale Silt TrapESC-100.50$ Each HydroseedingESC-11SWDM 5.4.2.40.80$ SY46003,680.00Interceptor Swale / DikeESC-121.00$ LF Jute MeshESC-13SWDM 5.4.2.23.50$ SY Level SpreaderESC-141.75$ LF Mulch, by hand, straw, 3" deepESC-15SWDM 5.4.2.12.50$ SY Mulch, by machine, straw, 2" deepESC-16SWDM 5.4.2.12.00$ SY Piping, temporary, CPP, 6"ESC-1712.00$ LF Piping, temporary, CPP, 8"ESC-1814.00$ LF Piping, temporary, CPP, 12"ESC-1918.00$ LF Plastic covering, 6mm thick, sandbaggedESC-20SWDM 5.4.2.34.00$ SY Rip Rap, machine placed; slopesESC-21WSDOT 9-13.1(2)45.00$ CY Rock Construction Entrance, 50'x15'x1'ESC-22SWDM 5.4.4.11,800.00$ Each Rock Construction Entrance, 100'x15'x1'ESC-23SWDM 5.4.4.13,200.00$ Each13,200.00Sediment pond riser assemblyESC-24SWDM 5.4.5.22,200.00$ Each Sediment trap, 5' high berm ESC-25SWDM 5.4.5.119.00$ LF Sed. trap, 5' high, riprapped spillway berm section ESC-26SWDM 5.4.5.170.00$ LF Seeding, by handESC-27SWDM 5.4.2.41.00$ SY Sodding, 1" deep, level groundESC-28SWDM 5.4.2.58.00$ SY Sodding, 1" deep, sloped groundESC-29SWDM 5.4.2.510.00$ SY TESC SupervisorESC-30110.00$ HR Water truck, dust controlESC-31SWDM 5.4.7140.00$ HR UnitReference #PriceUnitQuantity Cost EROSION/SEDIMENT SUBTOTAL:16,218.00SALES TAX @ 10%1,621.80EROSION/SEDIMENT TOTAL:17,839.80(A)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR EROSION & SEDIMENT CONTROLDescription No.(A)WRITE-IN-ITEMS Page 3 of 14Ref 8-H Bond Quantity WorksheetSECTION II.a EROSION_CONTROLUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostGENERAL ITEMS Backfill & Compaction- embankmentGI-16.00$ CYBackfill & Compaction- trenchGI-29.00$ CYClear/Remove Brush, by hand (SY)GI-31.00$ SYBollards - fixedGI-4240.74$ EachBollards - removableGI-5452.34$ EachClearing/Grubbing/Tree RemovalGI-610,000.00$ AcreExcavation - bulkGI-72.00$ CYExcavation - TrenchGI-85.00$ CYFencing, cedar, 6' highGI-920.00$ LFFencing, chain link, 4'GI-1038.31$ LFFencing, chain link, vinyl coated, 6' highGI-1120.00$ LFFencing, chain link, gate, vinyl coated, 20' GI-121,400.00$ EachFill & compact - common barrowGI-1325.00$ CYFill & compact - gravel baseGI-1427.00$ CYFill & compact - screened topsoilGI-1539.00$ CYGabion, 12" deep, stone filled mesh GI-1665.00$ SYGabion, 18" deep, stone filled mesh GI-1790.00$ SYGabion, 36" deep, stone filled meshGI-18150.00$ SYGrading, fine, by handGI-192.50$ SYGrading, fine, with graderGI-202.00$ SYMonuments, 3' LongGI-21250.00$ EachSensitive Areas SignGI-227.00$ EachSodding, 1" deep, sloped groundGI-238.00$ SYSurveying, line & gradeGI-24850.00$ DaySurveying, lot location/linesGI-251,800.00$ AcreTopsoil Type A (imported)GI-2628.50$ CYTraffic control crew ( 2 flaggers )GI-27120.00$ HRTrail, 4" chipped woodGI-288.00$ SYTrail, 4" crushed cinderGI-299.00$ SYTrail, 4" top courseGI-3012.00$ SYConduit, 2"GI-315.00$ LFWall, retaining, concreteGI-3255.00$ SFWall, rockeryGI-3315.00$ SFSUBTOTAL THIS PAGE:(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)Page 4 of 14Ref 8-H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000syRI-130.00$ SYAC Grinding, 4' wide machine 1000-2000syRI-216.00$ SYAC Grinding, 4' wide machine > 2000syRI-310.00$ SYAC Removal/DisposalRI-435.00$ SYBarricade, Type III ( Permanent )RI-556.00$ LFGuard RailRI-630.00$ LFCurb & Gutter, rolledRI-717.00$ LFCurb & Gutter, verticalRI-812.50$ LFCurb and Gutter, demolition and disposalRI-918.00$ LFCurb, extruded asphaltRI-105.50$ LFCurb, extruded concreteRI-117.00$ LFSawcut, asphalt, 3" depthRI-121.85$ LFSawcut, concrete, per 1" depthRI-133.00$ LFSealant, asphaltRI-142.00$ LFShoulder, gravel, 4" thickRI-1515.00$ SYSidewalk, 4" thickRI-1638.00$ SYSidewalk, 4" thick, demolition and disposalRI-1732.00$ SYSidewalk, 5" thickRI-1841.00$ SYSidewalk, 5" thick, demolition and disposalRI-1940.00$ SYSign, Handicap RI-2085.00$ EachStriping, per stallRI-217.00$ EachStriping, thermoplastic, ( for crosswalk )RI-223.00$ SFStriping, 4" reflectorized lineRI-230.50$ LFAdditional 2.5" Crushed SurfacingRI-243.60$ SYHMA 1/2" Overlay 1.5" RI-2514.00$ SYHMA 1/2" Overlay 2"RI-2618.00$ SYHMA Road, 2", 4" rock, First 2500 SYRI-2728.00$ SYHMA Road, 2", 4" rock, Qty. over 2500SYRI-2821.00$ SYHMA Road, 4", 6" rock, First 2500 SYRI-2945.00$ SYHMA Road, 4", 6" rock, Qty. over 2500 SYRI-3037.00$ SYHMA Road, 4", 4.5" ATBRI-3138.00$ SYGravel Road, 4" rock, First 2500 SYRI-3215.00$ SYGravel Road, 4" rock, Qty. over 2500 SYRI-3310.00$ SYThickened EdgeRI-348.60$ LFSUBTOTAL THIS PAGE:(B)(C)(D)(E)Page 5 of 14Ref 8-H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)PARKING LOT SURFACINGNo.2" AC, 2" top course rock & 4" borrowPL-121.00$ SY2" AC, 1.5" top course & 2.5" base coursePL-228.00$ SY852,380.001764,928.005555155,540.004" select borrowPL-35.00$ SY1.5" top course rock & 2.5" base coursePL-414.00$ SYSUBTOTAL PARKING LOT SURFACING:2,380.004,928.00155,540.00(B)(C)(D)(E)LANDSCAPING & VEGETATIONNo.Street TreesLA-1Median LandscapingLA-2Right-of-Way LandscapingLA-3Wetland LandscapingLA-4SUBTOTAL LANDSCAPING & VEGETATION:(B)(C)(D)(E)TRAFFIC & LIGHTINGNo.SignsTR-1Street Light System ( # of Poles)TR-2Traffic SignalTR-3Traffic Signal ModificationTR-4SUBTOTAL TRAFFIC & LIGHTING:(B)(C)(D)(E)WRITE-IN-ITEMSSUBTOTAL WRITE-IN ITEMS:STREET AND SITE IMPROVEMENTS SUBTOTAL:2,380.004,928.00155,540.00SALES TAX @ 10%238.00492.8015,554.00STREET AND SITE IMPROVEMENTS TOTAL:2,618.005,420.80171,094.00(B)(C)(D)(E)Page 6 of 14Ref 8-H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostDRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/DD-126.00$ SY* (CBs include frame and lid)BeehiveD-290.00$ EachThrough-curb Inlet FrameworkD-3400.00$ EachCB Type ID-41,500.00$ Each11,500.0011,500.001015,000.00CB Type ILD-51,750.00$ EachCB Type II, 48" diameterD-62,300.00$ Each for additional depth over 4' D-7480.00$ FTCB Type II, 54" diameterD-82,500.00$ Each for additional depth over 4'D-9495.00$ FTCB Type II, 60" diameterD-102,800.00$ Each for additional depth over 4'D-11600.00$ FTCB Type II, 72" diameterD-126,000.00$ Each for additional depth over 4'D-13850.00$ FTCB Type II, 96" diameterD-1414,000.00$ Each for additional depth over 4'D-15925.00$ FTTrash Rack, 12"D-16350.00$ EachTrash Rack, 15"D-17410.00$ EachTrash Rack, 18"D-18480.00$ EachTrash Rack, 21"D-19550.00$ EachCleanout, PVC, 4"D-20150.00$ EachCleanout, PVC, 6"D-21170.00$ EachCleanout, PVC, 8"D-22200.00$ EachCulvert, PVC, 4" D-2310.00$ LFCulvert, PVC, 6" D-2413.00$ LFCulvert, PVC, 8" D-2515.00$ LFCulvert, PVC, 12" D-2623.00$ LF15345.0066015,180.00Culvert, PVC, 15" D-2735.00$ LFCulvert, PVC, 18" D-2841.00$ LFCulvert, PVC, 24"D-2956.00$ LFCulvert, PVC, 30" D-3078.00$ LFCulvert, PVC, 36" D-31130.00$ LFCulvert, CMP, 8"D-3219.00$ LFCulvert, CMP, 12"D-3329.00$ LFSUBTOTAL THIS PAGE:1,500.001,845.0030,180.00(B)(C)(D)(E)Quantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESPage 7 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESDRAINAGE (Continued)Culvert, CMP, 15"D-3435.00$ LFCulvert, CMP, 18"D-3541.00$ LFCulvert, CMP, 24"D-3656.00$ LFCulvert, CMP, 30"D-3778.00$ LFCulvert, CMP, 36"D-38130.00$ LFCulvert, CMP, 48"D-39190.00$ LFCulvert, CMP, 60"D-40270.00$ LFCulvert, CMP, 72"D-41350.00$ LFCulvert, Concrete, 8"D-4242.00$ LFCulvert, Concrete, 12"D-4348.00$ LFCulvert, Concrete, 15"D-4478.00$ LFCulvert, Concrete, 18"D-4548.00$ LFCulvert, Concrete, 24"D-4678.00$ LFCulvert, Concrete, 30"D-47125.00$ LFCulvert, Concrete, 36"D-48150.00$ LFCulvert, Concrete, 42"D-49175.00$ LFCulvert, Concrete, 48"D-50205.00$ LFCulvert, CPE Triple Wall, 6" D-5114.00$ LFCulvert, CPE Triple Wall, 8" D-5216.00$ LFCulvert, CPE Triple Wall, 12" D-5324.00$ LFCulvert, CPE Triple Wall, 15" D-5435.00$ LFCulvert, CPE Triple Wall, 18" D-5541.00$ LFCulvert, CPE Triple Wall, 24" D-5656.00$ LFCulvert, CPE Triple Wall, 30" D-5778.00$ LFCulvert, CPE Triple Wall, 36" D-58130.00$ LFCulvert, LCPE, 6"D-5960.00$ LFCulvert, LCPE, 8"D-6072.00$ LFCulvert, LCPE, 12"D-6184.00$ LFCulvert, LCPE, 15"D-6296.00$ LFCulvert, LCPE, 18"D-63108.00$ LFCulvert, LCPE, 24"D-64120.00$ LFCulvert, LCPE, 30"D-65132.00$ LFCulvert, LCPE, 36"D-66144.00$ LFCulvert, LCPE, 48"D-67156.00$ LFCulvert, LCPE, 54"D-68168.00$ LFSUBTOTAL THIS PAGE:(B)(C)(D)(E)Page 8 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESDRAINAGE (Continued)Culvert, LCPE, 60"D-69180.00$ LFCulvert, LCPE, 72"D-70192.00$ LFCulvert, HDPE, 6"D-7142.00$ LFCulvert, HDPE, 8"D-7242.00$ LFCulvert, HDPE, 12"D-7374.00$ LF17012,580.00Culvert, HDPE, 15"D-74106.00$ LFCulvert, HDPE, 18"D-75138.00$ LFCulvert, HDPE, 24"D-76221.00$ LFCulvert, HDPE, 30"D-77276.00$ LFCulvert, HDPE, 36"D-78331.00$ LFCulvert, HDPE, 48"D-79386.00$ LFCulvert, HDPE, 54"D-80441.00$ LFCulvert, HDPE, 60"D-81496.00$ LFCulvert, HDPE, 72"D-82551.00$ LFPipe, Polypropylene, 6"D-8384.00$ LFPipe, Polypropylene, 8"D-8489.00$ LFPipe, Polypropylene, 12"D-8595.00$ LFPipe, Polypropylene, 15"D-86100.00$ LFPipe, Polypropylene, 18"D-87106.00$ LFPipe, Polypropylene, 24"D-88111.00$ LFPipe, Polypropylene, 30"D-89119.00$ LFPipe, Polypropylene, 36"D-90154.00$ LFPipe, Polypropylene, 48"D-91226.00$ LFPipe, Polypropylene, 54"D-92332.00$ LFPipe, Polypropylene, 60"D-93439.00$ LFPipe, Polypropylene, 72"D-94545.00$ LFCulvert, DI, 6"D-9561.00$ LFCulvert, DI, 8"D-9684.00$ LFCulvert, DI, 12"D-97106.00$ LFCulvert, DI, 15"D-98129.00$ LFCulvert, DI, 18"D-99152.00$ LFCulvert, DI, 24"D-100175.00$ LFCulvert, DI, 30"D-101198.00$ LFCulvert, DI, 36"D-102220.00$ LFCulvert, DI, 48"D-103243.00$ LFCulvert, DI, 54"D-104266.00$ LFCulvert, DI, 60"D-105289.00$ LFCulvert, DI, 72"D-106311.00$ LFSUBTOTAL THIS PAGE:12,580.00(B)(C)(D)(E)Page 9 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESSpecialty Drainage ItemsDitching SD-19.50$ CYFlow Dispersal Trench (1,436 base+)SD-328.00$ LF French Drain (3' depth)SD-426.00$ LFGeotextile, laid in trench, polypropyleneSD-53.00$ SYMid-tank Access Riser, 48" dia, 6' deepSD-62,000.00$ Each12,000.00Pond Overflow SpillwaySD-716.00$ SYRestrictor/Oil Separator, 12"SD-81,150.00$ EachRestrictor/Oil Separator, 15"SD-91,350.00$ EachRestrictor/Oil Separator, 18"SD-101,700.00$ EachRiprap, placedSD-1142.00$ CYTank End Reducer (36" diameter)SD-121,200.00$ EachInfiltration pond testingSD-13125.00$ HRPermeable PavementSD-14Permeable Concrete SidewalkSD-15Culvert, Box __ ft x __ ftSD-16SUBTOTAL SPECIALTY DRAINAGE ITEMS:2,000.00(B)(C)(D)(E)STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)Detention PondSF-1Each Detention TankSF-2Each Detention VaultSF-375,000.00$ Each 175,000.00Infiltration PondSF-4Each Infiltration TankSF-5Each Infiltration VaultSF-6Each Infiltration TrenchesSF-7Each Basic Biofiltration SwaleSF-8Each Wet Biofiltration SwaleSF-9Each WetpondSF-10Each WetvaultSF-11Each Sand FilterSF-12Each Sand Filter VaultSF-13Each Linear Sand FilterSF-14Each Proprietary FacilitySF-15Each Bioretention FacilitySF-16Each SUBTOTAL STORMWATER FACILITIES:75,000.00(B)(C)(D)(E)Page 10 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostQuantity Remaining (Bond Reduction) (B)(C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESWRITE-IN-ITEMS (INCLUDE ON-SITE BMPs)WI-1WI-2WI-3WI-4WI-5WI-6WI-7WI-8WI-9WI-10WI-11WI-12WI-13WI-14WI-15SUBTOTAL WRITE-IN ITEMS:DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:1,500.001,845.00119,760.00SALES TAX @ 10%150.00184.5011,976.00DRAINAGE AND STORMWATER FACILITIES TOTAL:1,650.002,029.50131,736.00(B) (C) (D) (E)Page 11 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostConnection to Existing WatermainW-12,000.00$ Each36,000.00Ductile Iron Watermain, CL 52, 4 Inch DiameterW-250.00$ LFDuctile Iron Watermain, CL 52, 6 Inch DiameterW-356.00$ LFDuctile Iron Watermain, CL 52, 8 Inch DiameterW-460.00$ LFDuctile Iron Watermain, CL 52, 10 Inch DiameterW-570.00$ LF1535107,450.00Ductile Iron Watermain, CL 52, 12 Inch DiameterW-680.00$ LFGate Valve, 4 inch DiameterW-7500.00$ EachGate Valve, 6 inch DiameterW-8700.00$ EachGate Valve, 8 Inch DiameterW-9800.00$ EachGate Valve, 10 Inch DiameterW-101,000.00$ Each1111,000.00Gate Valve, 12 Inch DiameterW-111,200.00$ Each22,400.00Fire Hydrant AssemblyW-124,000.00$ Each624,000.00Permanent Blow-Off AssemblyW-131,800.00$ EachAir-Vac Assembly, 2-Inch DiameterW-142,000.00$ EachAir-Vac Assembly, 1-Inch DiameterW-151,500.00$ EachCompound Meter Assembly 3-inch DiameterW-168,000.00$ Each18,000.00Compound Meter Assembly 4-inch DiameterW-179,000.00$ EachCompound Meter Assembly 6-inch DiameterW-1810,000.00$ EachPressure Reducing Valve Station 8-inch to 10-inchW-1920,000.00$ Each120,000.00WATER SUBTOTAL:178,850.00SALES TAX @ 10%17,885.00WATER TOTAL:196,735.00(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR WATERQuantity Remaining (Bond Reduction) (B)(C)Page 1 of 1Ref 8-H Bond Quantity WorksheetSECTION II.d WATERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/1/2019 CED Permit #:########ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostClean OutsSS-11,000.00$ Each33,000.00Grease Interceptor, 500 gallonSS-28,000.00$ EachGrease Interceptor, 1000 gallonSS-310,000.00$ Each110,000.00Grease Interceptor, 1500 gallonSS-415,000.00$ EachSide Sewer Pipe, PVC. 4 Inch DiameterSS-580.00$ LFSide Sewer Pipe, PVC. 6 Inch DiameterSS-695.00$ LF15014,250.00Sewer Pipe, PVC, 8 inch DiameterSS-7105.00$ LF87591,875.00Sewer Pipe, PVC, 12 Inch DiameterSS-8120.00$ LFSewer Pipe, DI, 8 inch DiameterSS-9115.00$ LFSewer Pipe, DI, 12 Inch DiameterSS-10130.00$ LFManhole, 48 Inch DiameterSS-116,000.00$ Each424,000.00Manhole, 54 Inch DiameterSS-136,500.00$ EachManhole, 60 Inch DiameterSS-157,500.00$ EachManhole, 72 Inch DiameterSS-178,500.00$ EachManhole, 96 Inch DiameterSS-1914,000.00$ EachPipe, C-900, 12 Inch DiameterSS-21180.00$ LFOutside DropSS-241,500.00$ LSInside DropSS-251,000.00$ LSSewer Pipe, PVC, ____ Inch DiameterSS-26Lift Station (Entire System)SS-27LSSANITARY SEWER SUBTOTAL:143,125.00SALES TAX @ 10%14,312.50SANITARY SEWER TOTAL:157,437.50(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR SANITARY SEWERQuantity Remaining (Bond Reduction) (B)(C)Page 13 of 14Ref 8-H Bond Quantity WorksheetSECTION II.e SANITARY SEWERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 12/20/2017 Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200Date:Name:Project Name: PE Registration No:CED Plan # (LUA):Firm Name:CED Permit # (U):Firm Address:Site Address:Phone No.Parcel #(s):Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a)Existing Right-of-Way Improvements Subtotal (b)(b)9,522.15$ Future Public Improvements Subtotal(c)282,799.00$ Stormwater & Drainage Facilities (Public & Private) Subtotal(d)(d)311,135.00$ (e)(f)Site RestorationCivil Construction PermitMaintenance Bond120,691.23$ Bond Reduction2Construction Permit Bond Amount 3Minimum Bond Amount is $10,000.001 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering.2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% willcover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering.* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.** Note: All prices include labor, equipment, materials, overhead and profit. 360.352.1465Ross.Jarvis@scjalliance.comWeatherly Inn Renton##-######4500 Talbot Road S312305-9067, 312305-9094FOR APPROVAL########8730 Tallon Lane NE, Suite 200 Lacey WA 98516332,715.63$ P (a) x 100%SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS10/9/2018Ross Jarvis43668SCJ AllianceR((b x 150%) + (d x 100%))S(e) x 150% + (f) x 100%Bond Reduction: Existing Right-of-Way Improvements (Quantity Remaining)2Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2T(P +R - S)Prepared by:Project InformationCONSTRUCTION BOND AMOUNT */**(prior to permit issuance)EST1((b) + (c) + (d)) x 20%-$ MAINTENANCE BOND */**(after final acceptance of construction)7,297.40$ 9,522.15$ 325,418.23$ 7,297.40$ -$ 311,135.00$ -$ Page 1 of 1Ref 8-H Bond Quantity WorksheetSECTION III. BOND WORKSHEETUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/1/2019 APPENDIX J OPERATIONS AND MAINTENANCE MANUAL Renton Senior Housing Maintenance Plan Maintenance Program Cover Sheet Inspection Period: Number of Sheets Attached: Date Inspected: Inspector’s Signature: The following pages contain maintenance needs for most of the components that are part of your drainage system, as well as for some components that you may not have. Let the City know if there are any components that are missing from these pages. Ignore the requirements that do not apply to your system. You should plan to complete a checklist for all system components on the following schedule: (M) Monthly from October (or November) through April (A) Once in late summer (preferably September) (C) Once in mid summer (late July or early August) (S) After any major storm (use 1 inch in 24 hours as a guideline) (B) Biannually (twice per year - refer to individual checklist for timing) (Q) Quarterly Use photocopies of these pages and check off the problems you looked for each time you did an inspection. Add comments on problems found and actions taken. Keep these “checked" sheets in your files, as they will be used to write your annual report. Some items do not need to be looked at every time an inspection is done. The facility - specific maintenance standards contained in this section are intended to be conditions for determining if maintenance actions are required as identified through inspection. They are not intended to be measures of the facility's required condition at all times between inspections. In other words, exceedance of these conditions at any time between inspections and/or maintenance does not automatically constitute a violation of these standards. However, based upon inspection observations, the inspection and maintenance schedules shall be adjusted to minimize the length of time that a facility is in a condition that requires a maintenance action. A TESC certified professional will be designated prior to construction and will conduct inspections as well as identify a maintenance program for any erosion control measures. Renton Senior Housing Maintenance Plan Maintenance covenants shall include the maintenance standards specified by Appendix A in 2017 City of Renton Surface Water Design Manual. Included is a list of maintenance activities and proposed inspection intervals for each element of the private stormwater system, and a guarantee that any maintenance necessary for any element of the stormwater system will be performed to the standards specified by the Manual and within the following schedule: 1. Within one year for wet pool facilities and retention/detention ponds; 2. Within six months for typical maintenance; 3. Within nine months for maintenance requiring re-vegetation; 4. Within two years for maintenance that requires capital construction of less than $25,000. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-6 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged inlet/outlet pipes Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-7 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Access Manhole (cont.) Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-8 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. FROP-T Section Damaged FROP-T T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-9 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED FROP-T Section (cont.) Damaged FROP-T (cont.) Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate. Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing orifice plate Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions to overflow pipe Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip of overflow pipe Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (If applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-10 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and is structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-11 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-12 NO. 6 – CONVEYANCE PIPES AND DITCHES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/root growth in pipe Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Damaged pipes Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive vegetation growth Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Rock lining out of place or missing (If applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-15 NO. 9 – FENCING MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12-18 inches wide permitting access through an opening under a fence. No access under the fence. Wood Posts, Boards and Cross Members Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound. Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound. Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind. Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches. Post plumb to within 1½ inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards. Missing or loose tension wire. Tension wire in place and holding fabric. Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy. Structurally adequate posts or parts with a uniform protective coating. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-16 NO. 10 – GATES/BOLLARDS/ACCESS BARRIERS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Chain Link Fencing Gate Damaged or missing members Missing gate. Gates in place. Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person. Hinges intact and lubed. Gate is working freely. Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Gate is aligned and vertical. Missing stretcher bar, stretcher bands, and ties. Stretcher bar, bands, and ties in place. Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. Bar Gate Damaged or missing cross bar Cross bar does not swing open or closed, is missing or is bent to where it does not prevent vehicle access. Cross bar swings fully open and closed and prevents vehicle access. Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Support post damaged Support post does not hold cross bar up. Cross bar held up preventing vehicle access into facility. Bollards Damaged or missing bollards Bollard broken, missing, does not fit into support hole or hinge broken or missing. No access for motorized vehicles to get into facility. Bollards do not lock Locking assembly or lock missing or cannot be attached to lock bollard in place. No access for motorized vehicles to get into facility. Boulders Dislodged boulders Boulders not located to prevent motorized vehicle access. No access for motorized vehicles to get into facility. Evidence of vehicles circumventing boulders Motorized vehicles going around or between boulders. No access for motorized vehicles to get into facility. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-17 NO. 11 – GROUNDS (LANDSCAPING) MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged tree or shrub identified Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. www.modularwetlands.com Maintenance Guidelines for Modular Wetland System - Linear Maintenance Summary o Remove Trash from Screening Device – average maintenance interval is 6 to 12 months.  (5 minute average service time). o Remove Sediment from Separation Chamber – average maintenance interval is 12 to 24 months.  (10 minute average service time). o Replace Cartridge Filter Media – average maintenance interval 12 to 24 months.  (10-15 minute per cartridge average service time). o Replace Drain Down Filter Media – average maintenance interval is 12 to 24 months.  (5 minute average service time). o Trim Vegetation – average maintenance interval is 6 to 12 months.  (Service time varies). System Diagram Access to screening device, separation chamber and cartridge filter Access to drain down filter Pre-Treatment Chamber Biofiltration Chamber Discharge Chamber Outflow Pipe Inflow Pipe (optional) www.modularwetlands.com Maintenance Procedures Screening Device 1. Remove grate or manhole cover to gain access to the screening device in the Pre- Treatment Chamber. Vault type units do not have screening device. Maintenance can be performed without entry. 2. Remove all pollutants collected by the screening device. Removal can be done manually or with the use of a vacuum truck. The hose of the vacuum truck will not damage the screening device. 3. Screening device can easily be removed from the Pre-Treatment Chamber to gain access to separation chamber and media filters below. Replace grate or manhole cover when completed. Separation Chamber 1. Perform maintenance procedures of screening device listed above before maintaining the separation chamber. 2. With a pressure washer spray down pollutants accumulated on walls and cartridge filters. 3. Vacuum out Separation Chamber and remove all accumulated pollutants. Replace screening device, grate or manhole cover when completed. Cartridge Filters 1. Perform maintenance procedures on screening device and separation chamber before maintaining cartridge filters. 2. Enter separation chamber. 3. Unscrew the two bolts holding the lid on each cartridge filter and remove lid. 4. Remove each of 4 to 8 media cages holding the media in place. 5. Spray down the cartridge filter to remove any accumulated pollutants. 6. Vacuum out old media and accumulated pollutants. 7. Reinstall media cages and fill with new media from manufacturer or outside supplier. Manufacturer will provide specification of media and sources to purchase. 8. Replace the lid and tighten down bolts. Replace screening device, grate or manhole cover when completed. Drain Down Filter 1. Remove hatch or manhole cover over discharge chamber and enter chamber. 2. Unlock and lift drain down filter housing and remove old media block. Replace with new media block. Lower drain down filter housing and lock into place. 3. Exit chamber and replace hatch or manhole cover. www.modularwetlands.com Maintenance Notes 1. Following maintenance and/or inspection, it is recommended the maintenance operator prepare a maintenance/inspection record. The record should include any maintenance activities performed, amount and description of debris collected, and condition of the system and its various filter mechanisms. 2. The owner should keep maintenance/inspection record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspection upon request at any time. 3. Transport all debris, trash, organics and sediments to approved facility for disposal in accordance with local and state requirements. 4. Entry into chambers may require confined space training based on state and local regulations. 5. No fertilizer shall be used in the Biofiltration Chamber. 6. Irrigation should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigation required is dependent on plant species. Some plants may require irrigation. www.modularwetlands.com Maintenance Procedure Illustration Screening Device The screening device is located directly under the manhole or grate over the Pre-Treatment Chamber. It’s mounted directly underneath for easy access and cleaning. Device can be cleaned by hand or with a vacuum truck. Separation Chamber The separation chamber is located directly beneath the screening device. It can be quickly cleaned using a vacuum truck or by hand. A pressure washer is useful to assist in the cleaning process. www.modularwetlands.com Cartridge Filters The cartridge filters are located in the Pre-Treatment chamber connected to the wall adjacent to the biofiltration chamber. The cartridges have removable tops to access the individual media filters. Once the cartridge is open media can be easily removed and replaced by hand or a vacuum truck. Drain Down Filter The drain down filter is located in the Discharge Chamber. The drain filter unlocks from the wall mount and hinges up. Remove filter block and replace with new block. www.modularwetlands.com Trim Vegetation Vegetation should be maintained in the same manner as surrounding vegetation and trimmed as needed. No fertilizer shall be used on the plants. Irrigation per the recommendation of the manufacturer and or landscape architect. Different types of vegetation requires different amounts of irrigation. www.modularwetlands.com Inspection Form Modular Wetland System, Inc. P. 760.433-7640 F. 760-433-3176 E. Info@modularwetlands.com For Office Use Only (city) (Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date / / Time AM / PM Weather Condition Additional Notes Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No Yes Type of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. 2972 San Luis Rey Road, Oceanside, CA 92058 P (760) 433-7640 F (760) 433-3176 Inspection Report Modular Wetlands System Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging the unit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance www.modularwetlands.com Maintenance Report Modular Wetland System, Inc. P. 760.433-7640 F. 760-433-3176 E. Info@modularwetlands.com For Office Use Only (city) (Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date / / Time AM / PM Weather Condition Additional Notes Site Map # Comments: 2972 San Luis Rey Road, Oceanside, CA 92058 P. 760.433.7640 F. 760.433.3176 Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed @ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands System For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ MP / MAemiT// etaD emaN rotcepsnI setoN lanoitiddA noitidnoC rehtaeW Site Map # Comments: 398 Via El Centro, Oceanside, CA 92058 P. 855-566-3938 F. 760.433.3176 Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed @ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands System For Office Use Only (city)(Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ MP / MAemiT// etaD emaN rotcepsnI setoN lanoitiddA noitidnoC rehtaeW Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No YesType of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. 398 Via El Centro, Oceanside, CA 92058 P. 855-566-3938 F. 760.433.3176 Inspection Report Modular Wetlands System Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging theunit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance APPENDIX K DECLARATION OF COVENANT