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23194-R-SSP-2024-08-21 Preliminary Stormwater Site Plan PREPARED BY Convergent Energy & Power Alex White, P.E. PREPARED FOR CLIENT ADDRESS Convergent Energy & Power 7 Times Square Tower, Suite 3504 New York, NY 10036 SITE ADDRESS JURISDICTION DATE PROJECT NO. 16220 Railway Road S.E. Yelm, Washington Yelm, WA 08/21/2024 23194 A L E X W HITE P R O F ESSION A L E N G I N E ERR EGIS T E R E D S TATE O F W A SHI N G T O N 21036777 08/21/2024 St o r m w a t e r S i t e P l a n Ba r g h a us e n C o n s u l t i n g E n g i n e e r s , I n c . Co n v e r g e n t E n e r g y & P o w e r Ye l m , W a s h i n g t o n Ou r J o b N o . 23 1 9 4 23194.001-SSP.doc TABLE OF CONTENTS 1.0 PROJECT OVERVIEW Figure 1.1 – Vicinity Map Figure 1.2 – Flow Chart for Determining Minimum Requirements 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Analysis of the Minimum Requirements 3.0 EXISTING CONDITIONS SUMMARY Figure 3.1 – Soil Survey Map Figure 3.2 – Sensitive Areas Map Figure 3.3 – Assessor's Map Figure 3.4 – FEMA Map Figure 3.5 – Critical Aquifer Recharge Map 4.0 OFF-SITE ANALYSIS REPORT 5.0 PERMANENT STORMWATER CONTROL PLAN 5.1 Existing Site Hydrology Figure 5.1.1 – Predeveloped Basin Map 5.2 Developed Site Hydrology Figure 5.2.1 – Developed Basin Map 5.3 Performance Standards and Goals Figure 5.3.1 – Flow Chart for Determining LID MR#5 Requirements 5.4 Low Impact Development Features 5.5 Flow Control System Figure 5.5.1 – Sizing Calculations 5.6 Water Quality System 5.7 Conveyance System Analysis and Design 6.0 CONSTURCTION STORMWATER POLLUTION PREVENTION PLAN Figure 6.1 – Construction Stormwater Pollution Prevention Plan 7.0 SPECIAL REPORTS AND STUDIES Figure 7.1 – Geotechnical Memo for Infiltration Rates dated August 8, 2024 8.0 OTHER PERMITS 23194.001-SSP.doc 9.0 OPERATIONS AND MAINTENANCE MANUAL 10.0 DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND TREATMENT FACILITIES 11.0 DECLARATION OF COVENANT FOR PRIVEATELY MAINTAINED ON-SITE STORMWATER MANAGEMENT BMPS 12.0 BOND QUANTITIES WORKSHEET 23194.001-SSP.doc 1.0 PROJECT OVERVIEW The project is located within a portion of Section 19, Township 17 North, Range 2 East, Willamette Meridian, City of Yelm, Thurston County, Washington. Specifically, the site is located at 16220 Railway Road SE, Yelm, Washington 98597 and currently exists as primarily undeveloped land with a canopy structure. There are also several residential structures located on the southeast portion of the site that shall remain and are outside of the limits of disturbance. The site is located within the Moderate Density Residential zone. See Figure 1.1 for the Vicinity Map. The proposed development includes a battery storage area, photovoltaic modules, and a gravel access road. Existing site slopes range from 0 to 15%, generally in the northwest direction. The project is classified as a new development and proposes more than 5,000 square feet of new hard surfaces; therefore, this project shall comply with Minimum Requirements 1 through 9 of the Department of Ecology’s 2019 Stormwater Management Manual for Western Washington (SWMMWW) and provide information and data to support the project’s design intent for stormwater runoff from the on-site improvements. See Figure 1.2 for the Minimum Requirements Flow Chart. In addition, the proposed new and replaced hard surfaces will be surfaced with gravel which will see infrequent use and classified as non-pollution generating. The area beneath the solar panels will be impervious and therefore, the solar panels are classified as an impervious surface . Please see the remainder of this report for a discussion on how this project intends to comply with all the minimum requirements of the 2019 SWMMWW. Horizontal: Scale: Vertical: For: Title: V I C I N I T Y M A P Job Number N.T.S.N/A 23194 DATE: 8/08/24 Convergent Energy Yelm, Washington P:\23000s\23194\exhibit\graphics\23194 vmap.cdr RE FER ENC E: MapQuest (2024) SITE Figure I-3.1: Flow Chart for Determining Requirements for New Development 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 89 23194.001-SSP.doc 2.0 CONDITIONS AND REQUIREMENTS SUMMARY This section contains the following information: 2.1 Analysis of the Minimum Requirements 23194.001-SSP.doc 2.1 Analysis of the Minimum Requirements MINIMUM REQUIREMENTS HOW PROJECT HAS ADDRESSED REQUIREMENT No. 1: Preparation of Stormwater Site Plans This Minimum Requirement has been fulfilled by the preparation and completion of this Stormwater Site Plan. No. 2: Construction Stormwater Pollution Prevention (SWPP) A completed Preliminary Construction Stormwater Pollution Prevention Plan (SWPPP) will be submitted together with this report. No. 3: Source Control of Pollution All known, available, and reasonable Source Control BMPs will be applied to this project in accordance with those applicable to the proposed redevelopment No. 4: Preservation of Natural Drainage Systems and Outfalls This project intends to collect runoff to fully infiltrate the stormwater. The proposed infiltration measures shall be designed so that stormwater runoff will not cause any adverse impact to the downstream receiving waters and properties. No. 5: On-site Stormwater Management This project triggers Core Requirements No 1 through 9, and is located outside the UGA on a parcel that is larger than 5 acres. This project will meet the LID Performance Standard through Flow Control BMPs per the 2019 SWMMWW. All soil in the lawn and landscaped areas for the site will be amended to meet the Post-Construction Soil Quality and Depth requirement. No. 6: Runoff Treatment The proposed gravel road is expected to see infrequent use and will be classified as a non-pollution generating surface. Therefore, this project proposes less than 5,000 square feet of pollution generating hard surfaces and does not require water quality treatment. No. 7: Flow Control This project proposes to infiltrate the majority of on-site runoff thus the effective impervious surfaces are less than 10,000 square feet. The stormwater runoff experienced by the proposed photovoltaic modules will be sheet flowed off the module and into the proposed landscaping; therefore, the area covered by the proposed photovoltaic modules will be classified as a pervious surface. WWHM calculations of the infiltration facility sizing have been provided in this report. No. 8: Wetlands Protection There is an observed wetland to the southwest of the site; however, all work associated with this site will be located outside the wetland buffer. In addition, this project will propose infiltration of all stormwater runoff to the maximum extent feasible; therefore, negative impacts on the wetland is not anticipated. No. 9: Operation and Maintenance An Operation and Maintenance Manual will be provided in Section 9.0 of this Stormwater Site Plan during Final Engineering Review. 23194.001-SSP.doc 3.0 EXISTING CONDITIONS SUMMARY The existing site is primarily undeveloped with trees and shrubs and a canopy structure. There are several residential structures located on the southeast portion of the site; however, this project proposes those structures to remain outside the limits of disturbance. The overall site topography contains slopes of approximately 0% to 15%, generally sloping in the northwest direction. The project is located in FEMA Zone AE and Zone X . Per section 18.19.040.D.1 of the City municipal code, developments within Zone AE are subjected to “No Rise Standard,” therefore, this project ensures that no “net fill” takes place within Zone AE. The on-site soil consists of Spanaway gravelly sandy loam. See Figure 3.1 and Figure 3.4. An existing wetland is observed to the southwest of the site; however, all work associated with this site will be located outside the wetland buffer. In addition, this project will propose infiltration of all stormwater runoff to the maximum extent feasible; therefore, negative impacts on the wetland is not anticipated. See Figure 3.2 for the sensitive areas map. The site is located in a Category 1 Critical Aquifer Recharge area . However, all on-site runoff to be infiltrated will be from non-pollution generating surfaces; therefore, this development does not anticipate any activity that will adversely affect the recharging of the aquifer. Horizontal: Scale: Vertical: For: Title: S O I L S U RV E Y M A P Job Number N.T.S.N/A 23194 DATE: 8/08/24 Convergent Energy Yelm, Washington P:\23000s\23194\exhibit\graphics\23194 soil.cdr RE FER ENCE: US DA, Natural Resources Conservation Service L E GE N D: SITE 110 = Spanaway gravelly sandy loam, 0-3% slopes A HSG 111 = Spanaway gravelly sandy loam, 3-15% slopes A Horizontal: Scale: Vertical: For: Title: S E N S I T I V E A R E A S M A P Job Number N.T.S.N/A 23194 DATE: 8/08/24 Convergent Energy Yelm, Washington P:\23000s\23194\exhibit\graphics\23194 sens.cdr RE FER ENC E: www.thurstoncountywa.gov SITE Horizontal: Scale: Vertical: For: Title: A S S E S S O R M A P Job Number N.T.S.N/A 23194 DATE: 8/08/24 Convergent Energy Yelm, Washington P:\23000s\23194\exhibit\graphics\23194 amap.cdr RE FER ENC E: www.thurstoncountywa.gov SITE Horizontal: Scale: Vertical: For: Title: F E M A M A P Job Number N.T.S.N/A 23194 DATE: 8/08/24 Convergent Energy Yelm, Washington P:\23000s\23194\exhibit\graphics\23194 fema.cdr RE FER ENC E: Federal Emergency Management Agency (Portion of Map 53067C0353F, Oct. 2023) SITE LE G E N D Legend Scale 1: Critical Aquifer Recharge Map 9,843 The information included on this map has been compiled by Thurston County staff from a variety of sources and is subject to change without notice. Additional elements may be present in reality that are not represented on the map. Ortho-photos and other data may not align. The boundaries depicted by these datasets are approximate. This document is not intended for use as a survey product. ALL DATA IS EXPRESSLY PROVIDED ‘AS IS’ AND ‘WITH ALL FAULTS’. Thurston County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. In no event shall Thurston County be liable for direct, indirect, incidental, consequential, special, or tort damages of any kind, including, but not limited to, lost revenues or lost profits, real or anticipated, resulting from the use, misuse or reliance of the information contained on this map. If any portion of this map or disclaimer is missing or altered, Thurston County removes itself from all responsibility from the map and the data contained within. The burden for determining fitness for use lies entirely with the user and the user is solely responsible for understanding the accuracy limitation of the information contained in this map. Authorized for 3rd Party reproduction for personal use only. 8/19/2024Published: Map Created Using GeoData Public Website Note: Feet 0 900450Critical Aquifer Recharge Areas 1 2 3 Parcel Boundaries Roads - Major <all other values> I 5 ACCESS; US 101 ACCESS; US 101 SB OFF RAMP I 5; US 101 Roads Railroads County Border Olympia Municipal Airport Water Bodies (River - Large Scale) ©2024 Thurston County 23194.001-SSP.doc 4.0 OFF-SITE ANALYSIS REPORT Stormwater runoff on-site will be conveyed via sheet flow and proposed v-ditches across the site and intercepted by an infiltration trench located along the northwest of the property to be fully infiltrated. At the time of this report preparation, there did not appear to be any identified drainage problems with the project vicinity. The project intends to infiltrate on-site runoff to the maximum extent feasible, and therefore, is not anticipated to negatively impact downstream conveyance systems or properties. 23194.001-SSP.doc 5.0 PERMANENT STORMWATER CONTROL PLAN This section contains the following information: 5.1 Existing Site Hydrology 5.2 Developed Site Hydrology 5.3 Performance Standards and Goals 5.4 Low Impact Development Features 5.5 Flow Control System 5.6 Water Quality System 5.7 Conveyance System Analysis and Design 23194.001-SSP.doc 5.1 Existing Site Hydrology The existing site topography exhibits slopes of approximately 0% to 15%, generally sloping in the west direction and with the highest elevations located on the east side of the property. Stormwater runoff appears to either infiltrate or disperse into the existing vegetation. Please see Figure 5.1.1. for the existing basin map. Predeveloped Basins The Predeveloped Basin tributary to the Drainage Facility can be broken down as follows: For a detailed explanation of the procedures used for the sizing of the proposed drainage facility, please reference Section 5.4 of this report. Impervious Pervious Total Area 0.28 Ac 9.29 Ac 9.58 Ac Fo r : Ti t l e : 1 23 1 9 4 CO N V E R G E N T E N E R G Y A N D P O W E R 7 T I M E S S Q U A R E T O W E R , S U I T E 3 5 0 4 NE W Y O R K , N Y 1 0 0 3 6 CO N V E R G E N T P O W E R & E N E R G Y 16 2 2 0 R A I L W A Y R D . S E YE L M , W A 9 8 5 9 7 A L E X W HITE P R OF ESSIONA L E N G I N EERREGISTERED S TAT E O F W ASHIN G T O N 21036777 SCALE: 1"=30' 1 PR E D E V E L O P E D B A S I N M A P 23194.001-SSP.doc 5.2 Developed Site Hydrology The site will maintain the same general topographic grading characteristics and will be primarily comprised of landscaping and gravel surfaces. The onsite runoff is proposed to flow via sheet flow and v-ditch into the proposed infiltration trench to be fully infiltrated. Please see Figure 5.2.1 for the proposed basin map. Developed Basins The Developed Basin tributary to the Drainage Facility can be broken down as follows: A detailed report on the procedures used for the sizing of the proposed infiltration facility is provided in Section 5.4 of this report. Impervious Pervious Total Area 0.66 Ac 4.46 Ac 5.12 Ac Fo r : Ti t l e : 1 23 1 9 4 CO N V E R G E N T E N E R G Y A N D P O W E R 7 T I M E S S Q U A R E T O W E R , S U I T E 3 5 0 4 NE W Y O R K , N Y 1 0 0 3 6 CO N V E R G E N T P O W E R & E N E R G Y 16 2 2 0 R A I L W A Y R D . S E YE L M , W A 9 8 5 9 7 A L E X W HITE P R OF ESSIONA L E N G I N EERREGISTERED S TAT E O F W ASHIN G T O N 21036777 SCALE: 1"=30' 1 DE V E L O P E D B A S I N M A P 23194.001-SSP.doc 5.3 Performance Standards and Goals The project has been designed to comply with the Standard Flow Control Requirements outlined in the 2019 SWMMWW. The flow control facility shall be designed to match durations from 50 percent of the 2-year flow to the full 50-year flows of the pre-developed condition. Figure I-3.3: Flow Chart for Determining MR #5 Requirements 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 118 23194.001-SSP.doc 5.4 Low Impact Development Features The project has chosen to meet the Low Impact Development Performance Standards for all on-site impervious surfaces and to apply BMP T5.13: Post Construction Soil Quality and Depth for all landscaped areas. The WWHM2012 calculations demonstrate compliance with the Low Impact Development Performance Standards by fully infiltrating on-site runoff. 23194.001-SSP.doc 5.5 Flow Control System This project proposes greater than 10,000 square feet of new and replaced impervious surfaces and must provide flow control such that “stormwater discharges shall match developed discharge durations to pre-developed durations for the range of pre-developed discharge rates from 50 percent of the 2-year peak flow up to the 50-year peak flow.” This project proposes to infiltrate on-site runoff within a proposed infiltration trench along the northwest portion of the site. As previously mentioned, the stormwater runoff from the solar panels will sheet flow onto the proposed landscaping; therefore, the area covered by the proposed photovoltaic modules will be classified as a pervious surface. This infiltration facility was sized and modeled in WWHM2012 to fully infiltrate on-site runoff captured and comply with the LID Performance Standard. By infiltrating runoff from the proposed impervious areas, the total effective impervious area is reduced below 10,000 square feet. See Figure 5.5.1 for infiltration facility calculations. WWHM2012 PROJECT REPORT 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 2 General Model Information WWHM2012 Project Name:23194-Infiltration Ditch Site Name:Convergent Power and Energy Site Address:16220 Railway Rd SE City:Yelm Report Date:8/21/2024 Gage:Lake Lawrence Data Start:1955/10/01 Data End:2008/09/30 Timestep:15 Minute Precip Scale:0.857 Version Date:2023/01/27 Version:4.2.19 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 5.12 Pervious Total 5.12 Impervious Land Use acre Impervious Total 0 Basin Total 5.12 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 4.46 Pervious Total 4.46 Impervious Land Use acre ROADS FLAT 0.66 Impervious Total 0.66 Basin Total 5.12 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 5 Routing Elements Predeveloped Routing 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 6 Mitigated Routing Trapezoidal Pond 1 Bottom Length:728.00 ft. Bottom Width:3.50 ft. Depth:1 ft. Volume at riser head:0.0419 acre-feet. Infiltration On Infiltration rate:24 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):565.306 Total Volume Through Riser (ac-ft.):0.001 Total Volume Through Facility (ac-ft.):565.307 Percent Infiltrated:100 Total Precip Applied to Facility:10.993 Total Evap From Facility:2.071 Side slope 1:3 To 1 Side slope 2:3 To 1 Side slope 3:3 To 1 Side slope 4:3 To 1 Discharge Structure Riser Height:0.5 ft. Riser Diameter:12 in. Element Flows To: Outlet 1 Outlet 2 Pond Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.058 0.000 0.000 0.000 0.0111 0.059 0.000 0.000 1.442 0.0222 0.060 0.001 0.000 1.469 0.0333 0.061 0.002 0.000 1.496 0.0444 0.063 0.002 0.000 1.524 0.0556 0.064 0.003 0.000 1.551 0.0667 0.065 0.004 0.000 1.578 0.0778 0.066 0.004 0.000 1.605 0.0889 0.067 0.005 0.000 1.632 0.1000 0.068 0.006 0.000 1.659 0.1111 0.069 0.007 0.000 1.686 0.1222 0.070 0.007 0.000 1.713 0.1333 0.071 0.008 0.000 1.741 0.1444 0.073 0.009 0.000 1.768 0.1556 0.074 0.010 0.000 1.795 0.1667 0.075 0.011 0.000 1.822 0.1778 0.076 0.012 0.000 1.849 0.1889 0.077 0.012 0.000 1.876 0.2000 0.078 0.013 0.000 1.904 0.2111 0.079 0.014 0.000 1.931 0.2222 0.080 0.015 0.000 1.958 0.2333 0.082 0.016 0.000 1.985 0.2444 0.083 0.017 0.000 2.012 0.2556 0.084 0.018 0.000 2.040 0.2667 0.085 0.019 0.000 2.067 0.2778 0.086 0.020 0.000 2.094 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 7 0.2889 0.087 0.021 0.000 2.121 0.3000 0.088 0.022 0.000 2.148 0.3111 0.089 0.023 0.000 2.176 0.3222 0.091 0.024 0.000 2.203 0.3333 0.092 0.025 0.000 2.230 0.3444 0.093 0.026 0.000 2.257 0.3556 0.094 0.027 0.000 2.285 0.3667 0.095 0.028 0.000 2.312 0.3778 0.096 0.029 0.000 2.339 0.3889 0.097 0.030 0.000 2.366 0.4000 0.098 0.031 0.000 2.394 0.4111 0.100 0.032 0.000 2.421 0.4222 0.101 0.033 0.000 2.448 0.4333 0.102 0.034 0.000 2.475 0.4444 0.103 0.036 0.000 2.503 0.4556 0.104 0.037 0.000 2.530 0.4667 0.105 0.038 0.000 2.557 0.4778 0.106 0.039 0.000 2.585 0.4889 0.108 0.040 0.000 2.612 0.5000 0.109 0.041 0.000 2.639 0.5111 0.110 0.043 0.012 2.667 0.5222 0.111 0.044 0.035 2.694 0.5333 0.112 0.045 0.064 2.721 0.5444 0.113 0.046 0.099 2.749 0.5556 0.114 0.048 0.138 2.776 0.5667 0.115 0.049 0.182 2.803 0.5778 0.117 0.050 0.229 2.831 0.5889 0.118 0.052 0.280 2.858 0.6000 0.119 0.053 0.333 2.885 0.6111 0.120 0.054 0.389 2.913 0.6222 0.121 0.056 0.448 2.940 0.6333 0.122 0.057 0.509 2.967 0.6444 0.123 0.058 0.572 2.995 0.6556 0.124 0.060 0.637 3.022 0.6667 0.126 0.061 0.703 3.050 0.6778 0.127 0.062 0.770 3.077 0.6889 0.128 0.064 0.838 3.104 0.7000 0.129 0.065 0.907 3.132 0.7111 0.130 0.067 0.976 3.159 0.7222 0.131 0.068 1.046 3.187 0.7333 0.132 0.070 1.115 3.214 0.7444 0.134 0.071 1.183 3.241 0.7556 0.135 0.073 1.251 3.269 0.7667 0.136 0.074 1.318 3.296 0.7778 0.137 0.076 1.383 3.324 0.7889 0.138 0.077 1.447 3.351 0.8000 0.139 0.079 1.509 3.379 0.8111 0.140 0.080 1.569 3.406 0.8222 0.141 0.082 1.627 3.433 0.8333 0.143 0.083 1.683 3.461 0.8444 0.144 0.085 1.736 3.488 0.8556 0.145 0.087 1.786 3.516 0.8667 0.146 0.088 1.834 3.543 0.8778 0.147 0.090 1.879 3.571 0.8889 0.148 0.092 1.921 3.598 0.9000 0.149 0.093 1.960 3.626 0.9111 0.151 0.095 1.996 3.653 0.9222 0.152 0.097 2.029 3.681 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 8 0.9333 0.153 0.098 2.060 3.708 0.9444 0.154 0.100 2.088 3.736 0.9556 0.155 0.102 2.114 3.763 0.9667 0.156 0.103 2.138 3.791 0.9778 0.157 0.105 2.160 3.818 0.9889 0.158 0.107 2.182 3.846 1.0000 0.160 0.109 2.203 3.873 1.0111 0.161 0.110 2.251 3.901 23194-Infiltration Ditch 8/21/2024 11:34:51 AM Page 9 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:5.12 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:4.46 Total Impervious Area:0.66 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.224054 5 year 0.4018 10 year 0.555889 25 year 0.797628 50 year 1.015548 100 year 1.269096 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 Annual Peaks 23194-Infiltration Ditch 8/21/2024 11:36:40 AM Page 10 Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.240 0.000 1957 0.616 0.000 1958 0.155 0.000 1959 0.174 0.000 1960 0.318 0.000 1961 0.201 0.000 1962 0.074 0.000 1963 0.302 0.000 1964 0.209 0.000 1965 0.198 0.000 1966 0.111 0.000 1967 0.224 0.000 1968 0.166 0.000 1969 0.102 0.000 1970 0.189 0.000 1971 0.242 0.000 1972 0.350 0.000 1973 0.201 0.000 1974 0.711 0.000 1975 0.159 0.000 1976 0.250 0.000 1977 0.060 0.000 1978 0.214 0.000 1979 0.181 0.000 1980 0.201 0.000 1981 0.298 0.000 1982 0.180 0.000 1983 0.291 0.000 1984 0.219 0.000 1985 0.093 0.000 1986 0.380 0.000 1987 0.274 0.000 1988 0.139 0.000 1989 0.157 0.000 1990 1.069 0.000 1991 0.498 0.000 1992 0.155 0.000 1993 0.093 0.000 1994 0.160 0.000 1995 0.284 0.000 1996 0.372 0.000 1997 0.264 0.000 1998 0.347 0.000 1999 0.154 0.000 2000 0.163 0.000 2001 0.056 0.000 2002 0.292 0.000 2003 0.135 0.000 2004 0.980 0.000 2005 1.434 0.023 2006 0.412 0.000 2007 0.299 0.000 2008 0.626 0.000 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 23194-Infiltration Ditch 8/21/2024 11:36:40 AM Page 11 Rank Predeveloped Mitigated 1 1.4338 0.0227 2 1.0685 0.0000 3 0.9804 0.0000 4 0.7108 0.0000 5 0.6260 0.0000 6 0.6162 0.0000 7 0.4976 0.0000 8 0.4119 0.0000 9 0.3803 0.0000 10 0.3722 0.0000 11 0.3500 0.0000 12 0.3475 0.0000 13 0.3181 0.0000 14 0.3022 0.0000 15 0.2993 0.0000 16 0.2977 0.0000 17 0.2922 0.0000 18 0.2906 0.0000 19 0.2839 0.0000 20 0.2740 0.0000 21 0.2639 0.0000 22 0.2500 0.0000 23 0.2424 0.0000 24 0.2395 0.0000 25 0.2239 0.0000 26 0.2186 0.0000 27 0.2144 0.0000 28 0.2087 0.0000 29 0.2012 0.0000 30 0.2008 0.0000 31 0.2005 0.0000 32 0.1976 0.0000 33 0.1887 0.0000 34 0.1808 0.0000 35 0.1796 0.0000 36 0.1737 0.0000 37 0.1663 0.0000 38 0.1633 0.0000 39 0.1601 0.0000 40 0.1589 0.0000 41 0.1565 0.0000 42 0.1553 0.0000 43 0.1552 0.0000 44 0.1543 0.0000 45 0.1395 0.0000 46 0.1353 0.0000 47 0.1112 0.0000 48 0.1016 0.0000 49 0.0928 0.0000 50 0.0928 0.0000 51 0.0738 0.0000 52 0.0603 0.0000 53 0.0562 0.0000 23194-Infiltration Ditch 8/21/2024 11:36:40 AM Page 12 LID Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0179 233423 2 0 Pass 0.0189 224502 2 0 Pass 0.0198 215954 2 0 Pass 0.0208 207776 2 0 Pass 0.0217 200157 2 0 Pass 0.0227 193094 2 0 Pass 0.0236 186218 0 0 Pass 0.0246 179416 0 0 Pass 0.0255 172874 0 0 Pass 0.0265 166723 0 0 Pass 0.0274 160887 0 0 Pass 0.0284 154996 0 0 Pass 0.0293 149513 0 0 Pass 0.0303 144328 0 0 Pass 0.0312 139366 0 0 Pass 0.0322 134571 0 0 Pass 0.0331 130037 0 0 Pass 0.0341 125725 0 0 Pass 0.0350 121636 0 0 Pass 0.0360 117808 0 0 Pass 0.0369 114165 0 0 Pass 0.0379 110690 0 0 Pass 0.0388 107326 0 0 Pass 0.0398 104074 0 0 Pass 0.0407 100840 0 0 Pass 0.0417 97792 0 0 Pass 0.0426 94930 0 0 Pass 0.0436 92124 0 0 Pass 0.0445 89411 0 0 Pass 0.0455 86753 0 0 Pass 0.0464 84151 0 0 Pass 0.0474 81679 0 0 Pass 0.0483 79282 0 0 Pass 0.0493 76959 0 0 Pass 0.0502 74729 0 0 Pass 0.0512 72592 0 0 Pass 0.0521 70603 0 0 Pass 0.0531 68577 0 0 Pass 0.0540 66700 0 0 Pass 0.0550 64879 0 0 Pass 0.0559 63095 0 0 Pass 0.0569 61366 0 0 Pass 0.0578 59712 0 0 Pass 0.0588 58114 0 0 Pass 0.0597 56553 0 0 Pass 0.0607 55066 0 0 Pass 0.0616 53617 0 0 Pass 0.0626 52204 0 0 Pass 0.0635 50922 0 0 Pass 0.0645 49695 0 0 Pass 0.0655 48487 0 0 Pass 0.0664 47335 0 0 Pass 0.0674 46220 0 0 Pass 23194-Infiltration Ditch 8/21/2024 11:36:40 AM Page 13 0.0683 45105 0 0 Pass 0.0693 44008 0 0 Pass 0.0702 42968 0 0 Pass 0.0712 42001 0 0 Pass 0.0721 41035 0 0 Pass 0.0731 40050 0 0 Pass 0.0740 39121 0 0 Pass 0.0750 38154 0 0 Pass 0.0759 37225 0 0 Pass 0.0769 36314 0 0 Pass 0.0778 35478 0 0 Pass 0.0788 34642 0 0 Pass 0.0797 33861 0 0 Pass 0.0807 33062 0 0 Pass 0.0816 32300 0 0 Pass 0.0826 31594 0 0 Pass 0.0835 30888 0 0 Pass 0.0845 30200 0 0 Pass 0.0854 29531 0 0 Pass 0.0864 28862 0 0 Pass 0.0873 28211 0 0 Pass 0.0883 27561 0 0 Pass 0.0892 26929 0 0 Pass 0.0902 26334 0 0 Pass 0.0911 25758 0 0 Pass 0.0921 25219 0 0 Pass 0.0930 24643 0 0 Pass 0.0940 24086 0 0 Pass 0.0949 23528 0 0 Pass 0.0959 23008 0 0 Pass 0.0968 22487 0 0 Pass 0.0978 22004 0 0 Pass 0.0987 21540 0 0 Pass 0.0997 21112 0 0 Pass 0.1006 20648 0 0 Pass 0.1016 20294 0 0 Pass 0.1025 19886 0 0 Pass 0.1035 19495 0 0 Pass 0.1044 19086 0 0 Pass 0.1054 18733 0 0 Pass 0.1063 18352 0 0 Pass 0.1073 18010 0 0 Pass 0.1082 17628 0 0 Pass 0.1092 17300 0 0 Pass 0.1101 16942 0 0 Pass 0.1111 16644 0 0 Pass 0.1120 16275 0 0 Pass 23194-Infiltration Ditch 8/21/2024 11:36:54 AM Page 14 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.1120 16275 0 0 Pass 0.1212 13457 0 0 Pass 0.1303 11078 0 0 Pass 0.1394 9188 0 0 Pass 0.1485 7726 0 0 Pass 0.1577 6564 0 0 Pass 0.1668 5507 0 0 Pass 0.1759 4628 0 0 Pass 0.1850 3866 0 0 Pass 0.1942 3282 0 0 Pass 0.2033 2780 0 0 Pass 0.2124 2386 0 0 Pass 0.2215 2059 0 0 Pass 0.2307 1775 0 0 Pass 0.2398 1517 0 0 Pass 0.2489 1293 0 0 Pass 0.2581 1106 0 0 Pass 0.2672 936 0 0 Pass 0.2763 798 0 0 Pass 0.2854 658 0 0 Pass 0.2946 566 0 0 Pass 0.3037 487 0 0 Pass 0.3128 422 0 0 Pass 0.3219 369 0 0 Pass 0.3311 308 0 0 Pass 0.3402 275 0 0 Pass 0.3493 247 0 0 Pass 0.3584 215 0 0 Pass 0.3676 194 0 0 Pass 0.3767 172 0 0 Pass 0.3858 162 0 0 Pass 0.3949 154 0 0 Pass 0.4041 144 0 0 Pass 0.4132 130 0 0 Pass 0.4223 124 0 0 Pass 0.4315 117 0 0 Pass 0.4406 109 0 0 Pass 0.4497 100 0 0 Pass 0.4588 92 0 0 Pass 0.4680 82 0 0 Pass 0.4771 74 0 0 Pass 0.4862 70 0 0 Pass 0.4953 62 0 0 Pass 0.5045 56 0 0 Pass 0.5136 51 0 0 Pass 0.5227 47 0 0 Pass 0.5318 44 0 0 Pass 0.5410 39 0 0 Pass 0.5501 36 0 0 Pass 0.5592 30 0 0 Pass 0.5684 26 0 0 Pass 0.5775 19 0 0 Pass 0.5866 13 0 0 Pass 23194-Infiltration Ditch 8/21/2024 11:36:54 AM Page 15 0.5957 11 0 0 Pass 0.6049 6 0 0 Pass 0.6140 6 0 0 Pass 0.6231 5 0 0 Pass 0.6322 4 0 0 Pass 0.6414 4 0 0 Pass 0.6505 4 0 0 Pass 0.6596 4 0 0 Pass 0.6687 4 0 0 Pass 0.6779 4 0 0 Pass 0.6870 4 0 0 Pass 0.6961 4 0 0 Pass 0.7052 4 0 0 Pass 0.7144 3 0 0 Pass 0.7235 3 0 0 Pass 0.7326 3 0 0 Pass 0.7418 3 0 0 Pass 0.7509 3 0 0 Pass 0.7600 3 0 0 Pass 0.7691 3 0 0 Pass 0.7783 3 0 0 Pass 0.7874 3 0 0 Pass 0.7965 3 0 0 Pass 0.8056 3 0 0 Pass 0.8148 3 0 0 Pass 0.8239 3 0 0 Pass 0.8330 3 0 0 Pass 0.8421 3 0 0 Pass 0.8513 3 0 0 Pass 0.8604 3 0 0 Pass 0.8695 3 0 0 Pass 0.8787 3 0 0 Pass 0.8878 3 0 0 Pass 0.8969 3 0 0 Pass 0.9060 3 0 0 Pass 0.9152 3 0 0 Pass 0.9243 3 0 0 Pass 0.9334 3 0 0 Pass 0.9425 3 0 0 Pass 0.9517 3 0 0 Pass 0.9608 3 0 0 Pass 0.9699 3 0 0 Pass 0.9790 3 0 0 Pass 0.9882 2 0 0 Pass 0.9973 2 0 0 Pass 1.0064 2 0 0 Pass 1.0155 2 0 0 Pass 23194-Infiltration Ditch 8/21/2024 11:36:54 AM Page 16 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. 23194-Infiltration Ditch 8/21/2024 11:36:54 AM Page 17 LID Report 23194-Infiltration Ditch 8/21/2024 11:37:15 AM Page 18 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 23194-Infiltration Ditch 8/21/2024 11:37:15 AM Page 19 Appendix Predeveloped Schematic 23194-Infiltration Ditch 8/21/2024 11:37:17 AM Page 20 Mitigated Schematic 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 21 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1955 10 01 END 2008 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 23194-Infiltration Ditch.wdm MESSU 25 Pre23194-Infiltration Ditch.MES 27 Pre23194-Infiltration Ditch.L61 28 Pre23194-Infiltration Ditch.L62 30 POC23194-Infiltration Ditch1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 10 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 10 C, Forest, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 10 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 10 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 22 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 10 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 10 0 4.5 0.08 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 10 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 10 0.2 0.5 0.35 6 0.5 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 10 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 23 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 10 5.12 COPY 501 12 PERLND 10 5.12 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 0.857 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 0.857 IMPLND 1 999 EXTNL PREC 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 24 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 25 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1955 10 01 END 2008 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 23194-Infiltration Ditch.wdm MESSU 25 Mit23194-Infiltration Ditch.MES 27 Mit23194-Infiltration Ditch.L61 28 Mit23194-Infiltration Ditch.L62 30 POC23194-Infiltration Ditch1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 16 IMPLND 1 RCHRES 1 COPY 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Trapezoidal Pond 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 26 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 4 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 27 # - # ***PETMAX PETMIN 1 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 16 4.46 RCHRES 1 2 PERLND 16 4.46 RCHRES 1 3 IMPLND 1 0.66 RCHRES 1 5 ******Routing****** PERLND 16 4.46 COPY 1 12 IMPLND 1 0.66 COPY 1 15 PERLND 16 4.46 COPY 1 13 RCHRES 1 1 COPY 501 17 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Trapezoidal Pond-005 2 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 28 1 1 0.14 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 91 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.058494 0.000000 0.000000 0.000000 0.011111 0.059614 0.000656 0.000000 1.442651 0.022222 0.060733 0.001325 0.000000 1.469751 0.033333 0.061854 0.002006 0.000000 1.496856 0.044444 0.062974 0.002699 0.000000 1.523965 0.055556 0.064094 0.003405 0.000000 1.551080 0.066667 0.065215 0.004124 0.000000 1.578200 0.077778 0.066336 0.004854 0.000000 1.605325 0.088889 0.067457 0.005598 0.000000 1.632454 0.100000 0.068578 0.006353 0.000000 1.659589 0.111111 0.069700 0.007122 0.000000 1.686728 0.122222 0.070821 0.007902 0.000000 1.713873 0.133333 0.071943 0.008695 0.000000 1.741022 0.144444 0.073065 0.009501 0.000000 1.768177 0.155556 0.074187 0.010319 0.000000 1.795336 0.166667 0.075310 0.011150 0.000000 1.822500 0.177778 0.076433 0.011993 0.000000 1.849669 0.188889 0.077556 0.012848 0.000000 1.876843 0.200000 0.078679 0.013716 0.000000 1.904022 0.211111 0.079802 0.014597 0.000000 1.931206 0.222222 0.080925 0.015490 0.000000 1.958395 0.233333 0.082049 0.016395 0.000000 1.985589 0.244444 0.083173 0.017313 0.000000 2.012788 0.255556 0.084297 0.018243 0.000000 2.039991 0.266667 0.085421 0.019186 0.000000 2.067200 0.277778 0.086546 0.020142 0.000000 2.094414 0.288889 0.087671 0.021109 0.000000 2.121632 0.300000 0.088796 0.022090 0.000000 2.148856 0.311111 0.089921 0.023083 0.000000 2.176084 0.322222 0.091046 0.024088 0.000000 2.203317 0.333333 0.092172 0.025106 0.000000 2.230556 0.344444 0.093297 0.026136 0.000000 2.257799 0.355556 0.094423 0.027179 0.000000 2.285047 0.366667 0.095550 0.028235 0.000000 2.312300 0.377778 0.096676 0.029302 0.000000 2.339558 0.388889 0.097803 0.030383 0.000000 2.366821 0.400000 0.098929 0.031476 0.000000 2.394089 0.411111 0.100056 0.032581 0.000000 2.421362 0.422222 0.101183 0.033699 0.000000 2.448640 0.433333 0.102311 0.034830 0.000000 2.475922 0.444444 0.103438 0.035973 0.000000 2.503210 0.455556 0.104566 0.037128 0.000000 2.530502 0.466667 0.105694 0.038297 0.000000 2.557800 0.477778 0.106822 0.039477 0.000000 2.585102 0.488889 0.107951 0.040670 0.000000 2.612410 0.500000 0.109079 0.041876 0.000000 2.639722 0.511111 0.110208 0.043094 0.012432 2.667040 0.522222 0.111337 0.044325 0.035147 2.694362 0.533333 0.112466 0.045569 0.064540 2.721689 0.544444 0.113596 0.046824 0.099321 2.749021 0.555556 0.114726 0.048093 0.138729 2.776358 0.566667 0.115855 0.049374 0.182234 2.803700 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 29 0.577778 0.116985 0.050668 0.229424 2.831047 0.588889 0.118116 0.051974 0.279955 2.858399 0.600000 0.119246 0.053292 0.333520 2.885756 0.611111 0.120377 0.054624 0.389839 2.913117 0.622222 0.121508 0.055967 0.448641 2.940484 0.633333 0.122639 0.057324 0.509662 2.967856 0.644444 0.123770 0.058693 0.572643 2.995232 0.655556 0.124901 0.060074 0.637321 3.022614 0.666667 0.126033 0.061468 0.703432 3.050000 0.677778 0.127165 0.062875 0.770709 3.077391 0.688889 0.128297 0.064294 0.838881 3.104788 0.700000 0.129429 0.065726 0.907676 3.132189 0.711111 0.130562 0.067170 0.976818 3.159595 0.722222 0.131694 0.068627 1.046030 3.187006 0.733333 0.132827 0.070097 1.115035 3.214422 0.744444 0.133960 0.071579 1.183559 3.241843 0.755556 0.135094 0.073074 1.251329 3.269269 0.766667 0.136227 0.074581 1.318080 3.296700 0.777778 0.137361 0.076101 1.383552 3.324136 0.788889 0.138495 0.077634 1.447495 3.351577 0.800000 0.139629 0.079179 1.509672 3.379022 0.811111 0.140763 0.080736 1.569860 3.406473 0.822222 0.141898 0.082307 1.627854 3.433928 0.833333 0.143033 0.083890 1.683468 3.461389 0.844444 0.144168 0.085485 1.736538 3.488854 0.855556 0.145303 0.087093 1.786929 3.516325 0.866667 0.146438 0.088714 1.834531 3.543800 0.877778 0.147574 0.090348 1.879270 3.571280 0.888889 0.148709 0.091994 1.921105 3.598765 0.900000 0.149845 0.093652 1.960035 3.626256 0.911111 0.150981 0.095324 1.996100 3.653751 0.922222 0.152118 0.097007 2.029388 3.681251 0.933333 0.153254 0.098704 2.060036 3.708756 0.944444 0.154391 0.100413 2.088233 3.736265 0.955556 0.155528 0.102135 2.114227 3.763780 0.966667 0.156665 0.103869 2.138326 3.791300 0.977778 0.157803 0.105616 2.160903 3.818825 0.988889 0.158940 0.107376 2.182401 3.846354 1.000000 0.160078 0.109148 2.203335 3.873889 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 0.857 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 0.857 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP WDM 2 PREC ENGL 0.857 RCHRES 1 EXTNL PREC WDM 1 EVAP ENGL 0.76 RCHRES 1 EXTNL POTEV END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL RCHRES 1 HYDR O 1 1 1 WDM 1001 FLOW ENGL REPL RCHRES 1 HYDR O 2 1 1 WDM 1002 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1003 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 30 END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 17 RCHRES OFLOW OVOL 1 COPY INPUT MEAN END MASS-LINK 17 END MASS-LINK END RUN 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 31 Predeveloped HSPF Message File 23194-Infiltration Ditch 8/21/2024 11:37:18 AM Page 32 Mitigated HSPF Message File 23194-Infiltration Ditch 8/21/2024 11:37:18 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. 2005-2024; 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 23194.001-SSP.doc 5.6 Water Quality System The proposed gravel road is expected to see infrequent use and will be classified as a non - pollution generating surface; therefore, this project proposes less than 5,000 square feet of pollution generating hard surfaces and does not require water quality treatment. 23194.001-SSP.doc 5.7 Conveyance System Analysis and Design The majority of the runoff will sheet flow across the site. The only conveyance element proposed is a ditch along the southern property line to capture any incidental runoff that does not sheet flow to the west. Conveyance calculations may be provided at the request of the City upon subsequent submittal. 23194.001-SSP.doc 6.0 CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN The Construction Stormwater Pollution Prevention Plan has been included as Figure 6.1 in this report. Construction Stormwater General Permit Stormwater Pollution Prevention Plan (SWPPP) for Convergent Energy & Power Prepared for: The Washington State Department of Ecology Southwest Regional Office 300 Desmond Drive S.E. Lacey, WA 98503-1274 Phone: (360) 407-6300 Permittee / Owner Developer Operator / Contractor Convergent Energy & Power Convergent Energy & Power TBD 16220 Railway Road S.E. Yelm, WA 98597 Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD TBD TBD SWPPP Prepared By Name Organization Contact Phone Number Alex White, P.E. Barghausen Consulting Engineers, Inc. (425) 251-6222 SWPPP Preparation Date August 21, 2024 Project Construction Dates Activity / Phase Start Date End Date TBD TBD TBD P a g e | 1 Table of Contents 1 Project Information .............................................................................................................. 4 1.1 Existing Conditions ...................................................................................................... 4 1.2 Proposed Construction Activities .................................................................................. 4 2 Construction Stormwater Best Management Practices (BMPs) ........................................... 6 2.1 The 13 Elements .......................................................................................................... 7 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits ........................................ 7 2.1.2 Element 2: Establish Construction Access ............................................................ 8 2.1.3 Element 3: Control Flow Rates ............................................................................. 9 2.1.4 Element 4: Install Sediment Controls ...................................................................10 2.1.5 Element 5: Stabilize Soils ....................................................................................11 2.1.6 Element 6: Protect Slopes....................................................................................12 2.1.7 Element 7: Protect Drain Inlets ............................................................................13 2.1.8 Element 8: Stabilize Channels and Outlets ..........................................................14 2.1.9 Element 9: Control Pollutants ...............................................................................15 2.1.10 Element 10: Control Dewatering ..........................................................................17 2.1.11 Element 11: Maintain BMPs .................................................................................18 2.1.12 Element 12: Manage the Project ..........................................................................19 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs .................................20 3 Pollution Prevention Team .................................................................................................21 4 Monitoring and Sampling Requirements ............................................................................22 4.1 Site Inspection ............................................................................................................22 4.2 Stormwater Quality Sampling ......................................................................................22 4.2.1 Turbidity Sampling ...............................................................................................22 4.2.2 pH Sampling ........................................................................................................24 5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies .........................25 5.1 303(d) Listed Waterbodies ..........................................................................................25 6 Reporting and Record Keeping ..........................................................................................26 6.1 Record Keeping ..........................................................................................................26 6.1.1 Site Log Book ......................................................................................................26 6.1.2 Records Retention ...............................................................................................26 6.1.3 Updating the SWPPP ...........................................................................................26 6.2 Reporting ....................................................................................................................27 6.2.1 Discharge Monitoring Reports ..............................................................................27 6.2.2 Discharge Monitoring Reports (DMRs).................................................................27 6.2.3 Notification of Noncompliance ..............................................................................27 P a g e | 2 List of Tables Table 1 – pH-Modifying Sources ............................................................................................16 Table 2 – Management ............................................................................................................19 Table 3 – Team Information ....................................................................................................21 Table 4 – Turbidity Sampling Method ....................................................................................22 Table 5 – pH Sampling Method ..............................................................................................24 List of Appendices Appendix/Glossary A. Site Map B. BMP Detail C. Site Inspection Form D. Engineering Calculations P a g e | 3 List of Acronyms and Abbreviations Acronym / Abbreviation Explanation 303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies BFO Bellingham Field Office of the Department of Ecology BMP(s) Best Management Practice(s) CESCL Certified Erosion and Sediment Control Lead CO2 Carbon Dioxide CRO Central Regional Office of the Department of Ecology CSWGP Construction Stormwater General Permit CWA Clean Water Act DMR Discharge Monitoring Report DO Dissolved Oxygen Ecology Washington State Department of Ecology EPA United States Environmental Protection Agency ERO Eastern Regional Office of the Department of Ecology ERTS Environmental Report Tracking System ESC Erosion and Sediment Control GULD General Use Level Designation NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Units NWRO Northwest Regional Office of the Department of Ecology pH Power of Hydrogen RCW Revised Code of Washington SPCC Spill Prevention, Control, and Countermeasure su Standard Units SWMMEW Stormwater Management Manual for Eastern Washington SWMMWW Stormwater Management Manual for Western Washington SWPPP Stormwater Pollution Prevention Plan TESC Temporary Erosion and Sediment Control SWRO Southwest Regional Office of the Department of Ecology TMDL Total Maximum Daily Load VFO Vancouver Field Office of the Department of Ecology WAC Washington Administrative Code WSDOT Washington Department of Transportation WWHM Western Washington Hydrology Model P a g e | 4 1 Project Information Project/Site Name: Convergent Energy and Power Street/Location: 16220 Railway Road SE City: Yelm State: WA Zip code: 98597 Subdivision: NA Receiving waterbody: Groundwater 1.1 Existing Conditions Total acreage (including support activities such as off-site equipment staging yards, material storage areas, borrow areas). Total acreage: 9.58 AC Disturbed acreage: 4.00 AC Existing structures: The existing site is primarily undeveloped with various residential structures that will remain undisturbed. Landscape Topography: The existing topography of the site exhibits slopes ranging from 0 to 15%, generally sloping towards the east. Drainage patterns: The existing drainage patterns on-site either infiltrate or disperse into the vegetation. Existing Vegetation: Native vegetation is present throughout the project site. Critical Areas (wetlands, streams, high erosion risk, steep or difficult to stabilize slopes): An existing wetland is observed southeast of the project site. The site also appears to be within the Category 1 critical aquifer recharge area. List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: N/A Currently no known pollutants contaminants exist on-site. 1.2 Proposed Construction Activities Description of site development (example: subdivision): This project proposes the construction of photovoltaic modules, battery storage area, and hardscaping. Description of construction activities (example: site preparation, demolition, excavation): Construction activities will include clearing of existing vegetation and earth work such as excavation and site grading. Description of site drainage including flow from and onto adjacent properties. Must be consistent with Site Map in Appendix A: P a g e | 5 The grading aims to contain all run-off within the project boundary and convey the runoff to the proposed infiltration facility. Description of final stabilization (example: extent of revegetation, paving, landscaping): Final site stabilization will include the installation of landscape and hardscapes, such as gravel surfacing. Contaminated Site Information: Proposed activities regarding contaminated soils or groundwater (example: on-site treatment system, authorized sanitary sewer discharge): N/A P a g e | 6 2 Construction Stormwater Best Management Practices (BMPs) The SWPPP is a living document reflecting current conditions and changes throughout the life of the project. These changes may be informal (i.e., hand-written notes and deletions). Update the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design. P a g e | 7 2.1 The 13 Elements 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits List and describe BMPs: In order to protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked and enclosed within a construction fence prior to any land disturbing activities. This fence will encompass all areas subject to construction, as well as delineate all areas where no construction is to take place. A silt fence will also be placed in certain areas as shown on the accompanying Site Plan, in order to protect the soil and vegetation outside the construction area. Refer to Appendix B: Construction BMPs for detailed drawings of the proposed BMPs. The proposed BMPs relevant to vegetation preservation/clearing limits are: • BMP C103: High Visibility Plastic or Metal Fence • BMP C233: Silt Fence Installation Schedules: BMPs listed above (Silt Fence and High Visibility Plastic or Metal Fence) will be installed prior to any land disturbing activity. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 8 2.1.2 Element 2: Establish Construction Access List and describe BMPs: In order to protect the adjacent existing asphalt pavement from dirt and debris, the project will construct a Construction Entrance. See Appendix A: Site Plan for the proposed location of the construction entrance. • BMP C105: Construction Access Installation Schedules: Construction Entrance shall be installed prior to the commencement of construction activities. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 9 2.1.3 Element 3: Control Flow Rates Will you construct stormwater retention and/or detention facilities? Yes No Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? Yes No List and describe BMPs: A sediment trap will be installed for purposes of controlling flow rates during construction. See Appendix A for the location of the sediment trap, Appendix B for detailed drawings of the proposed BMPs, and Appendix D for engineering calculations for the sediment trap. The proposed BMP relevant to flow control is: • BMP C240: Sediment Trap Installation Schedules: The BMP listed above (Sediment Trap) will be installed prior to any land disturbing activity. Inspection and Maintenance plan: Inspect sediment trap after each rainfall event. Responsible Staff: TBD P a g e | 10 2.1.4 Element 4: Install Sediment Controls List and describe BMPs: On-site sediment contamination shall be controlled by the implementation of silt fences and/or straw wattles. Silt fences will be placed in the necessary areas where soil from the areas marked for excavation may interfere and contaminate with soils located either off site or adjacent. Moreover, wattles are suggested in disturbed area that require immediate erosion protection and on exposed soils during the period of short construction interruptions or over winter months. See Appendix A for the location of silt fences on site and Appendix B for detailed drawings of the proposed BMPs. The proposed BMP that will be installed for sediment control is: • BMP C233: Silt Fence • BMP C235: Wattles Installation Schedules: Sediment Controls will be installed prior to any land disturbance activity. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 11 2.1.5 Element 5: Stabilize Soils West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Anticipated project dates: Start date: TBD End date: TBD Will you construct during the wet season? TBD List and describe BMPs: Soils exposed and unworked for the time period specified above shall be stabilized with the application of effective BMPs to prevent erosion throughout the duration of the project. Soil stockpiles shall be stabilized or covered using plastic sheeting and where possible, located away from storm inlets, waterways, and drainage channels. The practice of Dust Control is also recommended to prevent wind transport of dust onto roadways and drainage ways. Refer to Appendix B for detailed drawings of the BMPs used. The proposed BMPs specific to Soil Stabilization are: • BMP C123: Plastic Covering • BMP C140: Dust Control Installation Schedules: BMPs shall be implemented as soon as land disturbing activity begins and installed where applicable for the duration of the project. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 12 2.1.6 Element 6: Protect Slopes Will steep slopes be present at the site during construction? Yes No List and describe BMPs: All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion. Temporary and permanent seeding shall be used at all exposed areas pursuant to the prior mentioned schedule (seasonal restrictions). Soil stockpiles shall be stabilized or covered using plastic sheeting and where possible, located away from storm inlets, waterways, and drainage channels. The proposed BMPs specific to Slope Protection are: • BMP C120: Temporary and Permanent Seeding • BMP C123: Plastic Covering Installation Schedules: BMPs shall be implemented as soon as land disturbing activity begins and installed where applicable for the duration of the project. Implementation of one or more of alternative BMPs may be necessary after the first sign that existing BMPs are ineffective or failing. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 13 2.1.7 Element 7: Protect Drain Inlets List and describe BMPs: All storm drain inlets, both existing and those installed during construction must be protected to prevent unfiltered or untreated water from entering the drainage conveyance system; however, the first priority is to keep all access roads clean of sediment and keep untreated water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment-laden runoff on or near the project site. This includes inlets and culverts located offsite. Inlet protection devices shall be cleaned and replaced or removed when sediment has filled a third of the available storage (unless a different standard is specified by the product manufacturer). The following inlet protection measures will be proposed for this project: • BMP C220: Storm Drain Inlet Protection Installation Schedules: Storm Drain Inlet Protection will be provided at the start of the project and will be maintained for the duration of the project. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 14 2.1.8 Element 8: Stabilize Channels and Outlets Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches, will be installed at the outlets of all conveyance systems. List and describe BMPs: The project site is located west of the Cascade Mountain Crest. As such, where there are any temporary on-site conveyance channels, they shall be designed, constructed, and stabilized to prevent erosion from the expected peak 10-minute velocity of flow from a Type 1A, 10-year, 24-hour recurrence interval storm for the developed condition. An on-site sediment trap is proposed for this project along with a temporary conveyance channel; therefore, an Outlet Control BMP is proposed. The following inlet protection measures will be proposed for this project: • BMP C209: Outlet Protection Installation Schedules: Outlet Protection will be provided at the start of the project and will be maintained for the duration of the project. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 15 2.1.9 Element 9: Control Pollutants List and describe BMPs: All pollutants, including waste materials and demolition debris, which occur on site will be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. The following practices will be implemented: • All vehicles, equipment, and petroleum product storage/dispensing areas will be inspected regularly to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills. • In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if raining, over the vehicle. • Any chemicals stored in the construction areas will conform to the appropriate source control BMPs listed in Volume IV of the Ecology stormwater manual. All chemicals shall have cover, containment, and protection provided on site, pursuant to BMP C153 for Material Delivery, Storage and Containment. Proposed BMPs applicable to Pollutant Control: • BMP C140: Dust Control • BMP C151: Concrete Handling • BMP C 152: Sawcutting and Surface Pollution Prevention • BMP C 153: Material Delivery, Storage, and Containment • BMP C154: Concrete Washout Area Installation Schedules: BMPs shall be installed as necessary to control pollutants for the duration of construction. Inspection and Maintenance plan: TBD Responsible Staff: TBD Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? Yes No Will wheel wash or tire bath system BMPs be used during construction? Yes No Will pH-modifying sources be present on-site? Yes No P a g e | 16 Table 1 – pH-Modifying Sources None Bulk cement Cement kiln dust Fly ash Other cementitious materials New concrete washing or curing waters Waste streams generated from concrete grinding and sawing Exposed aggregate processes Dewatering concrete vaults Concrete pumping and mixer washout waters Recycled concrete Recycled concrete stockpiles Other (i.e., calcium lignosulfate) [please describe: ] Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas with appropriate BMPs installed. Will uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters? Yes No P a g e | 17 2.1.10 Element 10: Control Dewatering List and describe BMPs: • Discharge clean, non-turbid de-watering water, such as well-point groundwater, to systems tributary to, or directly into surface waters of the state, provided that the de- watering flow does not cause erosion or flooding of receiving waters or interfere with the operation of the system. Do not route clean dewatering water through stormwater sediment ponds. Note that "surface waters of the state" may exist on a construction site as well as off site; for example, a creek running through a site. • Highly turbid or contaminated dewatering water shall be handled separately from stormwater. • Clean, non-turbid dewatering water, such as well-point ground water, can be discharged to systems tributary to, or directly into surface waters of the state, provided the dewatering flow does not cause erosion or flooding of receiving waters. Clean dewatering water should not be routed through stormwater sediment ponds. • Other dewatering disposal options may include: o Transport off site in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters. o Infiltration. o Ecology-approved on-site chemical treatment or other suitable treatment technologies. o Sanitary sewer discharge with local sewer district approval, if there is no other option. o Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering. Depending on the time of year, dewatering activities may occur during the installation of on-site stormwater conveyance systems and/or excavation activities. Installation Schedules: Dewatering controls will be installed prior to any significant excavation activities. Inspection and Maintenance plan: TBD Responsible Staff: TBD P a g e | 18 2.1.11 Element 11: Maintain BMPs All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP specification (see Volume II of the SWMMWW or Chapter 7 of the SWMMEW). Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to once every calendar month. All temporary ESC BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal of either BMPs or vegetation shall be permanently stabilized. Additionally, protection must be provided for all BMPs installed for the permanent control of stormwater from sediment and compaction. BMPs that are to remain in place following completion of construction shall be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed, and the facility shall be returned to conditions specified in the construction documents. P a g e | 19 2.1.12 Element 12: Manage the Project The project will be managed based on the following principles: • Projects will be phased to the maximum extent practicable and seasonal work limitations will be taken into account. • Inspection and monitoring: o Inspection, maintenance, and repair of all BMPs will occur as needed to ensure performance of their intended function. o Site inspections and monitoring will be conducted in accordance with Special Condition S4 of the CSWGP. Sampling locations are indicated on the Site Map. Sampling station(s) are located in accordance with applicable requirements of the CSWGP. • Maintain an updated SWPPP. o The SWPPP will be updated, maintained, and implemented in accordance with Special Conditions S3, S4, and S9 of the CSWGP. As site work progresses the SWPPP will be modified routinely to reflect changing site conditions. The SWPPP will be reviewed monthly to ensure the content is current. Table 2 – Management Design the project to fit the existing topography, soils, and drainage patterns Emphasize erosion control rather than sediment control Minimize the extent and duration of the area exposed Keep runoff velocities low Retain sediment on-site Thoroughly monitor site and maintain all ESC measures Schedule major earthwork during the dry season Other (please describe) P a g e | 20 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs The project proposes to protect the locations of proposed stormwater infiltration facilities from sediment laden runoff, and compaction during construction. High visibility fencing will be used to clearly mark the locations of these facilities and ensure that compaction of the subsurface soils does not take place. P a g e | 21 3 Pollution Prevention Team Table 3 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) TBD TBD Resident Engineer Alex White, P.E. (425) 251-6222 Emergency Ecology Contact Staff on Duty (425) 649-7130 Emergency Permittee/ Owner Contact TBD TBD Non-Emergency Owner Contact TBD TBD Monitoring Personnel TBD TBD Ecology Regional Office Southwest Regional Office (360) 407-6300 P a g e | 22 4 Monitoring and Sampling Requirements Monitoring includes visual inspection, sampling for water quality parameters of concern, and documentation of the inspection and sampling findings in a site log book. A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements • Site inspections • Stormwater sampling data Create your own Site Inspection Form or use the Construction Stormwater Site Inspection Form found on Ecology’s website: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html File a blank form under Appendix D. The site log book must be maintained on-site within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See CSWGP Special Condition S8 and Section 5 of this template. 4.1 Site Inspection Site inspections will be conducted at least once every calendar week and within 24 hours following any discharge from the site. For sites that are temporarily stabilized and inactive, the required frequency is reduced to once per calendar month. The discharge point(s) are indicated on the Site Map (see Appendix A) and in accordance with the applicable requirements of the CSWGP. 4.2 Stormwater Quality Sampling 4.2.1 Turbidity Sampling Requirements include calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: Check the analysis method you will use: Table 4 – Turbidity Sampling Method Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size) The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency less than 33 centimeters. P a g e | 23 If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater than 6 cm, the following steps will be conducted: 1. Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site log book. If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will be conducted: 1. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) within 24 hours. • Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima): (509) 575-2490 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/CRO_nerts_online.html • Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/ERO_nerts_online.html • Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/NWRO_nerts_online.html • Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/SWRO_nerts_online.html 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period 3. Document BMP implementation and maintenance in the site log book. 4. Continue to sample discharges daily until one of the following is true: • Turbidity is 25 NTU (or lower). • Transparency is 33 cm (or greater). • Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater • The discharge stops or is eliminated. P a g e | 24 4.2.2 pH Sampling pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards poured concrete over the life of the project). The use of recycled concrete or engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD] or fly ash) also requires pH monitoring. For significant concrete work, pH sampling will start the first day concrete is poured and continue until it is cured, typically three (3) weeks after the last pour. For engineered soils and recycled concrete, pH sampling begins when engineered soils or recycled concrete are first exposed to precipitation and continues until the area is fully stabilized. If the measured pH is 8.5 or greater, the following measures will be taken: 1. Prevent high pH water from entering storm sewer systems or surface water. 2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate technology such as carbon dioxide (CO2) sparging (liquid or dry ice). 3. Written approval will be obtained from Ecology prior to the use of chemical treatment other than CO2 sparging or dry ice. Method for sampling pH: Check the analysis method you will use: Table 5 – pH Sampling Method pH meter pH test kit Wide range pH indicator paper P a g e | 25 5 Discharges to 303(d) or Total Maximum Daily Load (TMD L) Waterbodies 5.1 303(d) Listed Waterbodies Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? Yes No P a g e | 26 6 Reporting and Record Keeping 6.1 Record Keeping This section does not need to be filled out. It is a list of reminders for the permittee. 6.1.1 Site Log Book A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements • Site inspections • Sample logs 6.1.2 Records Retention Records will be retained during the life of the project and for a minimum of three (3) years following the termination of permit coverage in accordance with Special Condition S5.C of the CSWGP. Permit documentation to be retained on-site: • CSWGP • Permit Coverage Letter • SWPPP • Site Log Book Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP. 6.1.3 Updating the SWPPP The SWPPP will be modified if: • Found ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. • There is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine additional or modified BMPs are necessary for compliance. An updated timeline for BMP implementation will be prepared. P a g e | 27 6.2 Reporting 6.2.1 Discharge Monitoring Reports 6.2.2 Discharge Monitoring Reports (DMRs) will be submitted to Ecology monthly. If there was no discharge during a given monitoring period the DMR will be submitted as required, reporting “No Discharge”. The DMR due date is fifteen (15) days following the end of each calendar month. 6.2.3 Notification of Noncompliance DMRs will be reported online through Ecology’s WQWebDMR System. If any of the terms and conditions of the permit is not met, and the resulting noncompliance may cause a threat to human health or the environment, the following actions will be taken: 1. Ecology will be notified within 24-hours of the failure to comply by calling the applicable Regional office ERTS phone number (Regional office numbers listed below). 2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or correct the noncompliance. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3. A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days, unless requested earlier by Ecology. Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6 cm or less, the Ecology Regional office will be notified by phone within 24 hours of analysis as required by Special Condition S5.A of the CSWGP. • Central Region at (509) 575-2490 for Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, or Yakima County • Eastern Region at (509) 329-3400 for Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, or Whitman County • Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit, Snohomish, or Whatcom County • Southwest Region at (360) 407-6300 for Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, or Wahkiakum Include the following information: 1. Your name and / Phone number 2. Permit number 3. City / County of project 4. Sample results 5. Date / Time of call 6. Date / Time of sample P a g e | 28 7. Project name In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH water. P a g e | 29 Appendix/Glossary A. Site Map B. BMP Detail C. Site Inspection Form D. Engineering Calculations Fo r : Ti t l e : 4 23 1 9 4 CO N V E R G E N T E N E R G Y A N D P O W E R 7 T I M E S S Q U A R E T O W E R , S U I T E 3 5 0 4 NE W Y O R K , N Y 1 0 0 3 6 CO N V E R G E N T P O W E R & E N E R G Y 16 2 2 0 R A I L W A Y R D . S E YE L M , W A 9 8 5 9 7 A L E X W HITE P R OF ESSIONA L E N G I N EERREGISTERED S TAT E O F W ASHIN G T O N 21036777 SCALE: 1"=40' C2 . 0 PR E L I M . D E M O A N D T E S C P L A N burying and smothering vegetation.  l Vegetative buffer zones for streams, lakes or other waterways shall be established by the  local permitting authority or other state or federal permits or approvals. Maintenance Standards Inspect the area frequently to make sure flagging remains in place and the area remains undis- turbed. Replace all damaged flagging immediately. Remove all materials located in the buffer area  that may impede the ability of the vegetation to act as a filter. BMP C103: High-Visibility Fence Purpose High-visibility fencing is intended to:  l Restrict clearing to approved limits.  l Prevent disturbance of sensitive areas, their buffers, and other areas required to be left undis- turbed.  l Limit construction traffic to designated construction entrances, exits, or internal roads.  l Protect areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits plastic, fabric, or metal fence may be used:  l At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared.  l As necessary to control vehicle access to and on the site. Design and Installation Specifications High-visibility plastic fence shall be composed of a high-density polyethylene material and shall be at  least four feet in height. Posts for the fencing shall be steel or wood and placed every 6 feet on center  (maximum) or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches  with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope shall be used as  a top stringer to prevent sagging between posts. The fence color shall be high-visibility orange. The  fence tensile strength shall be 360 lbs/ft using the ASTM D4595 testing method. If appropriate install fabric silt fence in accordance with BMP C233:  Silt Fence to act as high-visibility  fence. Silt fence shall be at least 3 feet high and must be highly visible to meet the requirements of  this BMP. Metal fences shall be designed and installed according to the manufacturer's specifications. Metal fences shall be at least 3 feet high and must be highly visible. Fences shall not be wired or stapled to trees. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 274 Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and  visibility restored. BMP C105: Stabilized Construction Access Purpose Stabilized construction accesses are established to reduce the amount of sediment transported onto  paved roads outside the project site by vehicles or equipment. This is done by constructing a sta- bilized pad of quarry spalls at entrances and exits for project sites. Conditions of Use Construction accesses shall be stabilized wherever traffic will be entering or leaving a construction  site if paved roads or other paved areas are within 1,000 feet of the site. For residential subdivision construction sites, provide a stabilized construction access for each res- idence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient  length/width to provide vehicle access/parking, based on lot size and configuration. On large commercial, highway, and road projects, the designer should include enough extra mater- ials in the contract to allow for additional stabilized accesses not shown in the initial Construction  SWPPP. It is difficult to determine exactly where access to these projects will take place; additional  materials will enable the contractor to install them where needed. Design and Installation Specifications See Figure II-3.1: Stabilized Construction Access for details. Note: the 100’ minimum length of the  access shall be reduced to the maximum practicable size when the size or configuration of the site  does not allow  the full length (100’). Construct stabilized construction accesses with a 12-inch thick pad of 4-inch to 8-inch quarry spalls,  a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed con- crete, cement, or calcium chloride for construction access stabilization because these products raise  pH levels in stormwater and concrete discharge to waters of the State is prohibited. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up  into the rock pad. The geotextile shall meet the standards listed in Table II-3.2: Stabilized Con- struction Access Geotextile Standards. Geotextile Property Required Value Grab Tensile  Strength (ASTM D4751)200  psi min. Table II-3.2: Stabilized Construction Access Geotextile Standards 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 275 Geotextile Property Required Value Grab Tensile  Elongation (ASTM D4632)30%  max. Mullen Burst  Strength (ASTM D3786-80a)400  psi min. AOS (ASTM D4751)20-45  (U.S. standard sieve size) Table II-3.2: Stabilized Construction Access Geotextile Standards (continued)  l Consider early installation of the first lift of asphalt in areas that will be paved; this can be used  as a stabilized access. Also consider the installation of excess concrete as a stabilized access.  During large concrete pours, excess concrete is often available for this purpose.  l Fencing (see BMP C103:  High-Visibility Fence) shall be installed as necessary to restrict  traffic to the construction access.  l Whenever possible, the access shall be constructed on a firm, compacted subgrade. This can  substantially increase the effectiveness of the pad and reduce the need for maintenance.  l Construction accesses should avoid crossing existing sidewalks and back of walk drains if at  all possible. If a construction access must cross a sidewalk or back of walk drain, the full length  of the sidewalk and back of walk drain must be covered and protected from sediment leaving  the site. Alternative Material Specification WSDOT has raised safety concerns about the Quarry Spall rock specified above. WSDOT observes  that the 4-inch to 8-inch rock sizes can become trapped between Dually truck tires, and then  released off-site at highway speeds. WSDOT has chosen to use a modified specification for the rock  while continuously verifying that the Stabilized Construction Access remains effective. To remain  effective, the BMP must prevent sediment from migrating off site. To date, there has been no per- formance testing to verify operation of this new  specification. Jurisdictions may use the alternative  specification, but must perform increased off-site inspection if they use, or allow others to use, it. Stabilized Construction Accesses may use material that meets the requirements of WSDOT's Stand- ard Specifications for Road, Bridge, and Municipal Construction Section 9-03.9(1) (WSDOT, 2016)  for ballast except for the following special requirements. The grading and quality requirements are listed in Table II-3.3: Stabilized Construction Access  Alternative Material Requirements. Sieve Size Percent Passing 2½″99-100 Table II-3.3: Stabilized Construction Access Alternative Material Requirements 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 276 Sieve Size Percent Passing 2″65-100 ¾″40-80 No. 4 5 max. No. 100 0-2 % Fracture 75 min. Table II-3.3: Stabilized Construction Access Alternative Material Requirements (continued)  l All percentages are by weight.  l The sand equivalent value and dust ratio requirements do not apply.  l The fracture requirement shall be at least one fractured face and will apply the combined  aggregate retained on the No. 4 sieve in accordance with FOP for AASHTO T 335. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the specifications.  l If the access is not preventing sediment from being tracked onto pavement, then alternative  measures to keep the streets free of sediment shall be used. This may include replace- ment/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of  the access, or the installation of BMP C106: Wheel Wash.  l Any sediment that is tracked onto pavement shall be removed by shoveling or street sweep- ing. The sediment collected by sweeping shall be removed or stabilized on site. The pavement  shall not be cleaned by washing down the street, except when high efficiency sweeping is inef- fective and there is a threat to public safety. If it is necessary to wash the streets, the con- struction of a small sump to contain the wash water shall be considered. The sediment would  then be washed into the sump where it can be controlled.  l Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high effi- ciency mechanical sweeper because this creates dust and throws soils into storm systems or  conveyance ditches.  l Any quarry spalls that are loosened from the pad, which end up on the roadway shall be  removed immediately.  l If vehicles are entering or exiting the site at points other than the construction access(es),  BMP C103:  High-Visibility Fence shall be installed to control traffic. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 277  l Upon project completion and site stabilization, all construction accesses intended as per- manent access for maintenance shall be permanently stabilized. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 278 Figure II-3.1: Stabilized Construction Access 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 279 Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C106: Wheel Wash Purpose Wheel washes reduce the amount of sediment transported onto paved roads by washing dirt from  the wheels of motor vehicles prior to the motor vehicles leaving the construction site. Conditions of Use  l Use a wheel wash when BMP C105:  Stabilized Construction Access is not preventing sed- iment from being tracked off site.  l Wheel washing is generally an effective BMP when installed with careful attention to topo- graphy. For example, a wheel wash can be detrimental if installed at the top of a slope abut- ting a right-of-way where the water from the dripping truck can run unimpeded into the street.  l Pressure washing combined with an adequately sized and surfaced pad with direct drainage  to a large 10-foot x 10-foot sump can be very effective.  l Wheel wash wastewater is not stormwater. It is commonly called process water, and must be  discharged to a separate on-site treatment system that prevents discharge to waters of the  State, or to the sanitary sewer with local sewer district approval.  l Wheel washes may use closed-loop recirculation systems to conserve water use.  l Wheel wash wastewater shall not include wastewater from concrete washout areas.  l When practical, the wheel wash should be placed in sequence with BMP C105:  Stabilized  Construction Access. Locate the wheel wash such that vehicles exiting the wheel wash will  enter directly onto BMP C105:  Stabilized Construction Access. In order to achieve this, BMP  C105:  Stabilized Construction Access may need to be extended beyond the standard install- ation to meet the exit of the wheel wash. Design and Installation Specifications Suggested details are shown in Figure II-3.2: Wheel Wash. The Local Permitting Authority may  allow  other designs. A minimum of 6 inches of asphalt treated base (ATB) over crushed base mater- ial or 8 inches over a good subgrade is recommended to pave the wheel wash. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 280 Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will  work well to test clearance. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck  tongues with water. Midpoint spray nozzles are only needed in extremely muddy conditions. Wheel wash systems should be designed with a small grade change, 6- to 12-inches for a 10-foot- wide pond, to allow sediment to flow  to the low side of pond to help prevent re-suspension of sed- iment. A drainpipe with a 2- to 3-foot riser should be installed on the low  side of the pond to allow for  easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a  closed-loop system. Polyacrylamide (PAM) added to the wheel wash water at a rate of 0.25 - 0.5  pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is  already being used for dust or erosion control and is being applied by a water truck, the same truck  can be used to change the wash water. Maintenance Standards The wheel wash should start out each day with fresh water. The wheel wash water should be changed a minimum of once per day. On large earthwork jobs  where more than 10-20 trucks per hour are expected, the wheel wash water will need to be changed  more often. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 281 Figure II-3.2: Wheel Wash 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 282 BMP C107: Construction Road / Parking Area Stabilization Purpose Stabilizing roads, parking areas, and other on-site vehicle transportation routes immediately after  grading reduces erosion caused by construction traffic or stormwater runoff. Conditions of Use Roads and parking areas shall be stabilized wherever they are constructed, whether permanent or  temporary, for use by construction traffic. BMP C103:  High-Visibility Fence shall be installed, if necessary, to limit the access of vehicles to only  those roads and parking areas that are stabilized. Design and Installation Specifications  l On areas that will receive asphalt as part of the project, install the first lift as soon as possible.  l A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course  shall be applied immediately after grading or utility installation. A 4-inch course of asphalt  treated base (ATB) may also be used, or the road/parking area may be paved. It may also be  possible to use cement or calcium chloride for soil stabilization. If cement or cement kiln dust is  used for roadbase stabilization, pH  monitoring and BMP C252:  Treating and Disposing of  High pH Water is necessary to evaluate and minimize the effects on stormwater. If the area  will not be used for permanent roads, parking areas, or structures, a 6-inch depth of hog fuel  may also be used, but this is likely to require more maintenance. Whenever possible, con- struction roads and parking areas shall be placed on a firm, compacted subgrade.  l Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to  drain. Drainage ditches shall be provided on each side of the roadway in the case of a  crowned section, or on one side in the case of a super-elevated section. Drainage ditches  shall be directed to a sediment control BMP.  l Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet- flows into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not  adequate. If this area has at least 50 feet of vegetation that water can flow  through, then it is  generally preferable to use the vegetation to treat runoff, rather than a sediment pond or trap.  The 50 feet shall not include wetlands or their buffers. If runoff is allowed to sheetflow through  adjacent vegetated areas, it is vital to design the roadways and parking areas so that no con- centrated runoff is created.  l Storm drain inlets shall be protected to prevent sediment-laden water entering the drainage  system (see BMP C220:  Inlet Protection). Maintenance Standards Inspect stabilized areas regularly, especially after large storm events. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 283 Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and  to stabilize any areas that have eroded. Following construction, these areas shall be restored to pre-construction condition or better to pre- vent future erosion. Perform street cleaning at the end of each day or more often if necessary. BMP C120: Temporary and Permanent Seeding Purpose Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative cover is one of  the most effective methods of reducing erosion. Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will  remain unworked for more than 30 days. The optimum seeding windows for western Washington are April 1 through June 30 and September  1 through October 1. Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. Between October 1 and March 30 seeding requires a cover of mulch or an erosion control blanket  until 75 percent grass cover is established. Review all disturbed areas in late August to early September and complete all seeding by the end of  September. Otherwise, vegetation will not establish itself enough to provide more than average pro- tection. Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and  transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding.  See BMP C121: Mulching for specifications. Seed and mulch all disturbed areas not otherwise vegetated at final site stabilization. Final sta- bilization means the completion of all soil disturbing activities at the site and the establishment of a  permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement,  riprap, gabions, or geotextiles) which will prevent erosion. See BMP T5.13: Post-Construction Soil  Quality and Depth. Design and Installation Specifications General  l Install channels intended for vegetation before starting major earthwork and hydroseed with a  Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control  blankets over the top of hydroseed. Before allowing water to flow in vegetated channels,  establish 75 percent vegetation cover. If vegetated channels cannot be established by seed  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 284 before water flow; install sod in the channel bottom — over top of hydromulch and erosion con- trol blankets.  l Confirm the installation of all required surface water control measures to prevent seed from  washing away.  l Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 per- cent tackifier. See BMP C121: Mulching for specifications.  l Areas that will have seeding only and not landscaping may need compost or meal-based  mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on  the disturbed soil surface before application. See BMP T5.13: Post-Construction Soil Quality  and Depth.  l When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up  in contact with the soil surface. This reduces the ability to establish a good stand of grass  quickly. To overcome this, consider increasing seed quantities by up to 50 percent.  l Enhance vegetation establishment by dividing the hydromulch operation into two phases:  o Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in  the first lift.  o Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by:  o Installing the mulch, seed, fertilizer, and tackifier in one lift.  o Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per  acre.  o Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance  vegetative establishment. The increased cost may be offset by the reduced need for:  o Irrigation.  o Reapplication of mulch.  o Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and Bon- ded Fiber Matrix/ Mechanically Bonded Fiber Matrix (BFM/MBFMs) (3,000 pounds per acre  minimum).  l Seed may be installed by hand if:  o Temporary and covered by straw, mulch, or topsoil.  o Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or  erosion blankets.  l The seed mixes listed in Table II-3.4: Temporary and Permanent Seed Mixes include  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 285 recommended mixes for both temporary and permanent seeding.  l Apply these mixes, with the exception of the wet area seed mix, at a rate of 120 pounds per  acre. This rate can be reduced if soil amendments or slow-release fertilizers are used. Apply  the wet area seed mix at a rate of 60 pounds per acre.  l Consult the local suppliers or the local conservation district for their recommendations. The  appropriate mix depends on a variety of factors, including location, exposure, soil type, slope,  and expected foot traffic. Alternative seed mixes approved by the local authority may be used,  depending on the soil type and hydrology of the area. Common Name Latin Name % Weight % Purity % Germination Temporary Erosion Control Seed Mix A standard mix for areas requiring a temporary vegetative cover. Chewings or   annual blue grass Festuca rubra var. commutata or Poa anna 40 98 90 Perennial rye  Lolium perenne 50 98 90 Redtop or colonial  bentgrass  Agrostis alba or  Agrostis tenuis 5 92 85 White dutch clover Trifolium repens 5 98 90 Landscaping Seed Mix A recommended mix for landscaping seed. Perennial rye blend Lolium perenne 70 98 90 Chewings and red  fescue blend Festuca rubra var. commutata or Fes- tuca rubra 30 98 90 Low-Growing Turf Seed Mix A turf seed mix for dry situations where there is no need for watering. This mix requires very little main- tenance. Dwarf tall fescue  (several  varieties) Festuca arundin- acea var. 45 98 90 Dwarf perennial  rye (Barclay) Lolium perenne var. barclay 30 98 90 Red fescue Festuca rubra 20 98 90 Colonial bentgrass Agrostis tenuis 5 98 90 Bioswale Seed Mix A seed mix for bioswales and other intermittently wet areas. Tall or meadow fes-Festuca arundin-75-80 98 90 Table II-3.4: Temporary and Permanent Seed Mixes 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 286 Common Name Latin Name % Weight % Purity % Germination cue acea or   Festuca elatior Seaside/Creeping  bentgrass Agrostis palustris 10-15 92 85 Redtop bentgrass Agrostis alba or  Agrostis gigantea 5-10 90 80 Wet Area Seed Mix A low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wet- lands. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable. Tall or meadow fes- cue Festuca arundin- acea or Festuca elatior 60-70 98 90 Seaside/Creeping  bentgrass Agrostis palustris 10-15 98 85 Meadow foxtail Alepocurus praten- sis 10-15 90 80 Alsike clover Trifolium hybridum 1-6 98 90 Redtop bentgrass Agrostis alba 1-6 92 85 Meadow Seed Mix A recommended meadow seed mix for infrequently maintained areas or non-maintained areas where col- onization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seed- ing should take place in September or very early October in order to obtain adequate establishment prior to  the winter months. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending  the soil can reduce the need for clover. Redtop or Oregon  bentgrass Agrostis alba or  Agrostis ore- gonensis 20 92 85 Red fescue Festuca rubra 70 98 90 White dutch clover Trifolium repens 10 98 90 Table II-3.4: Temporary and Permanent Seed Mixes (continued) Roughening and Rototilling  l The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk  slopes before seeding if engineering purposes require compaction. Backblading or smoothing  of slopes greater than 4H:1V is not allowed if they are to be seeded.  l Restoration-based landscape practices require deeper incorporation than that provided by a  simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to  improve long-term permeability, infiltration, and water inflow qualities. At a minimum,  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 287 permanent areas shall use soil amendments to achieve organic matter and permeability per- formance defined in engineered soil/landscape systems. For systems that are deeper than 8  inches complete the rototilling process in multiple lifts, or prepare the engineered soil system  per specifications and place to achieve the specified depth. Fertilizers  l Conducting soil tests to determine the exact type and quantity of fertilizer is recommended.  This will prevent the over-application of fertilizer.  l Organic matter is the most appropriate form of fertilizer because it provides nutrients (includ- ing nitrogen, phosphorus, and potassium) in the least water-soluble form.  l In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer at a rate of 90  pounds per acre. Always use slow-release fertilizers because they are more efficient and  have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agit- ate, more than 20 minutes before use. Too much agitation destroys the slow-release coating.  l There are numerous products available that take the place of chemical fertilizers. These  include several with seaweed extracts that are beneficial to soil microbes and organisms. If  100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be  necessary. Cottonseed meal provides a good source of long-term, slow-release, available  nitrogen. Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix  l On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix  (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre  with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during  application. Numerous products are available commercially. Most products require 24-36  hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally,  products come in 40-50 pound bags and include all necessary ingredients except for seed and  fertilizer.  l Install products per manufacturer's instructions.  l BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation  establishment. Advantages over blankets include:  o BFM and MBFMs do not require surface preparation.  o Helicopters can assist in installing BFM and MBFMs in remote areas.  o On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses  for safety.  o Installing BFM and MBFMs can save at least $1,000 per acre compared to blankets. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 288 BMP C123: Plastic Covering Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. Conditions of Use Plastic covering may be used on disturbed areas that require cover measures for less than 30 days,  except as stated below.  l Plastic is particularly useful for protecting cut and fill slopes and stockpiles. However, the rel- atively rapid breakdown of most polyethylene sheeting makes it unsuitable for applications  greater than six months.  l Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that  might be adversely impacted by concentrated runoff. Such areas include steep and/or  unstable slopes.  l Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on- site measures to counteract the increases. Creating a trough with wattles or other material  can convey clean water away from these areas.  l To prevent undercutting, trench and backfill rolled plastic covering products.  l Although the plastic material is inexpensive to purchase, the cost of installation, maintenance,  removal, and disposal add to the total costs of this BMP.  l Whenever plastic is used to protect slopes, install water collection measures at the base of the  slope. These measures include plastic-covered berms, channels, and pipes used to convey  clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a  plastic covered slope with dirty runoff from a project.  l Other uses for plastic include:  o Temporary ditch liner.  o Pond liner in temporary sediment pond.  o Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel  being stored.  o Emergency slope protection during heavy rains.  o Temporary drainpipe (“elephant trunk”) used to direct water. Design and Installation Specifications  l Plastic slope cover must be installed as follows:  1. Run plastic up and down the slope, not across the slope.  2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 298  3. Provide a minimum of 8-inch overlap at the seams.  4. On long or wide slopes, or slopes subject to wind, tape all seams.  5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope  and backfill with soil to keep water from flowing underneath.  6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them  together with twine to hold them in place.  7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This  prevents high velocity runoff from contacting bare soil, which causes extreme erosion.  8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be  staked in place.  l Plastic sheeting shall have a minimum thickness of 0.06 millimeters.  l If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall  be installed at the toe of the slope in order to reduce the velocity of runoff. Maintenance Standards  l Torn sheets must be replaced and open seams repaired.  l Completely remove and replace the plastic if it begins to deteriorate due to ultraviolet radi- ation.  l Completely remove plastic when no longer needed.  l Dispose of old tires used to weight down plastic sheeting appropriately. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C124: Sodding Purpose The purpose of sodding is to establish turf for immediate erosion protection and to stabilize drainage  paths where concentrated overland flow will occur. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 299 Conditions of Use Sodding may be used in the following areas:  l Disturbed areas that require short-term or long-term cover.  l Disturbed areas that require immediate vegetative cover.  l All waterways that require vegetative lining. Waterways may also be seeded rather than sod- ded, and protected with a net or blanket. Design and Installation Specifications Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense  root mat for mechanical strength. The following steps are recommended for sod installation:  1. Shape and smooth the surface to final grade in accordance with the approved grading plan.  Consider any areas (such as swales) that  need to be overexcavated below design elevation to  allow  room for placing soil amendment and sod.  2. Amend 4 inches (minimum) of compost into the top 8 inches of the soil if the organic content of  the soil is less than ten percent or the permeability is less than 0.6 inches per hour. See  https://ecology.wa.gov/Waste-Toxics/Reducing-recycling-waste/Organic-mater- ials/Managing-organics-compost for further information.  3. Fertilize according to the sod supplier's recommendations.  4. Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface.  5. Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction  of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a  close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1V. Staple  the upstream edge of each sod strip.  6. Roll the sodded area and irrigate.  7. When sodding is carried out in alternating strips or other patterns, seed the areas between the  sod immediately after sodding. Maintenance Standards If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a  healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation,  instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix,  and protected with a net or blanket. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 300 BMP C140: Dust Control Purpose Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage  ways, and surface waters. Conditions of Use Use dust control in areas (including roadways) subject to surface and air movement of dust where  on-site or off-site impacts to roadways, drainage ways, or surface waters are likely. Design and Installation Specifications  l Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching,  or paving is impractical, apply gravel or landscaping rock.  l Limit dust generation by clearing only those areas where immediate activity will take place,  leaving the remaining area(s) in the original condition. Maintain the original ground cover as  long as practical.  l Construct natural or artificial windbreaks or windscreens. These may be designed as enclos- ures for small dust sources.  l Sprinkle the site with water until the surface is wet. Repeat as needed. To prevent carryout of  mud onto the street, refer to BMP C105:  Stabilized Construction Access and BMP C106:  Wheel Wash.  l Irrigation water can be used for dust control. Irrigation systems should be installed as a first  step on sites where dust control is a concern.  l Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and  cautions regarding handling and application. Used oil is prohibited from use as a dust sup- pressant. Local governments may approve other dust palliatives such as calcium chloride or  PAM.  l PAM (BMP C126:  Polyacrylamide (PAM) for Soil Erosion Protection) added to water at a rate  of 0.5 pounds per 1,000 gallons of water per acre and applied from a water truck is more effect- ive than water alone. This is due to increased infiltration of water into the soil and reduced  evaporation. In addition, small soil particles are bonded together and are not as easily trans- ported by wind. Adding PAM may reduce the quantity of water needed for dust control. Note  that the application rate specified here applies to this BMP, and is not the same application  rate that is specified in BMP C126:  Polyacrylamide (PAM) for Soil Erosion Protection, but the  downstream protections still apply. Refer to BMP C126:  Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use.  PAM shall not be directly applied to water or allowed to enter a water body.  l Contact your local Air Pollution Control Authority for guidance and training on other dust con- trol measures. Compliance with the local Air Pollution Control Authority constitutes  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 313 compliance with this BMP.  l Use vacuum street sweepers.  l Remove mud and other dirt promptly so it does not dry and then turn into dust.  l Techniques that can be used for unpaved roads and lots include:  o Lower speed limits. High vehicle speed increases the amount of dust stirred up from  unpaved roads and lots.  o Upgrade the road surface strength by improving particle size, shape, and mineral types  that make up the surface and base materials.  o Add surface gravel to reduce the source of dust emission. Limit the amount of fine  particles (those smaller than .075 mm) to 10 to 20 percent.  o Use geotextile fabrics to increase the strength of new  roads or roads undergoing recon- struction.  o Encourage the use of alternate, paved routes, if available.  o Apply chemical dust suppressants using the admix method, blending the product with  the top few inches of surface material. Suppressants may also be applied as surface  treatments.  o Limit dust-causing work on windy days.  o Pave unpaved permanent roads and other trafficked areas. Maintenance Standards Respray area as necessary to keep dust to a minimum. BMP C150: Materials on Hand Purpose Keep quantities of erosion prevention and sediment control materials on the project site at all times  to be used for regular maintenance and emergency situations such as unexpected heavy rains. Hav- ing these materials on-site reduces the time needed to replace existing or implement new  BMPs  when inspections indicate that existing BMPs are not meeting the Construction SWPPP require- ments. In addition, contractors can save money by buying some materials in bulk and storing them at  their office or yard. Conditions of Use  l Construction projects of any size or type can benefit from having materials on hand. A small  commercial development project could have a roll of plastic and some gravel available for  immediate protection of bare soil and temporary berm construction. A large earthwork project,  such as highway construction, might have several tons of straw, several rolls of plastic, flexible  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 314 pipe, sandbags, geotextile fabric and steel “T” posts.  l Materials should be stockpiled and readily available before any site clearing, grubbing, or  earthwork begins. A large contractor or project proponent could keep a stockpile of materials  that are available for use on several projects.  l If storage space at the project site is at a premium, the contractor could maintain the materials  at their office or yard. The office or yard must be less than an hour from the project site. Design and Installation Specifications Depending on project type, size, complexity, and length, materials and quantities will vary. A good  minimum list of items that will cover numerous situations includes:  l Clear Plastic, 6 mil  l Drainpipe, 6 or 8 inch diameter  l Sandbags, filled  l Straw Bales for mulching  l Quarry Spalls  l Washed Gravel  l Geotextile Fabric  l Catch Basin Inserts  l Steel "T" Posts  l Silt fence material  l Straw Wattles Maintenance Standards  l All materials with the exception of the quarry spalls, steel “T” posts, and gravel should be kept  covered and out of both sun and rain.  l Re-stock materials as needed. BMP C151: Concrete Handling Purpose Concrete work can generate process water and slurry that contain fine particles and high pH, both of  which can violate water quality standards in the receiving water. Concrete spillage or concrete dis- charge to waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, con- crete process water, and concrete slurry from entering waters of the State. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 315 Conditions of Use Any time concrete is used, utilize these management practices. Concrete construction project com- ponents include, but are not limited to:  l Curbs  l Sidewalks  l Roads  l Bridges  l Foundations  l Floors  l Runways Disposal options for concrete, in order of preference are:  1. Off-site disposal  2. Concrete wash-out areas (see BMP C154: Concrete Washout Area)  3. De minimus washout to formed areas awaiting concrete Design and Installation Specifications  l Wash concrete truck drums at an approved off-site location or in designated concrete  washout areas only. Do not wash out  concrete trucks onto the ground (including formed areas  awaiting concrete), or into storm drains, open ditches, streets, or streams. Refer to BMP  C154: Concrete Washout Area for information on concrete washout areas.  o Return unused concrete remaining in the truck and pump to the originating batch plant  for recycling. Do not dump excess concrete on site, except in designated concrete  washout areas as allowed in BMP C154: Concrete Washout Area.  l Wash small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats,  trowels, and wheelbarrows) into designated concrete washout areas or into formed areas  awaiting concrete pour.  l At no time shall concrete be washed off into the footprint of an area where an infiltration fea- ture will be installed.  l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas.  l Do not allow washwater from areas, such as concrete aggregate driveways, to drain directly  (without detention or treatment) to natural or constructed stormwater conveyances.  l Contain washwater and leftover product in a lined container when no  designated concrete  washout areas (or formed areas, allowed as described above) are available. Dispose of con- tained concrete and concrete washwater (process water) properly. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 316  l Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface  waters.  l Refer to BMP C252:  Treating and Disposing of High pH Water for pH adjustment require- ments.  l Refer to the Construction Stormwater General Permit (CSWGP) for pH monitoring require- ments if the project involves one of the following activities:  o Significant concrete work (as defined in the CSWGP).  o The use of soils amended with (but not limited to) Portland cement-treated base,  cement kiln dust or fly ash.  o Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for  high pH. Maintenance Standards Check containers for holes in the liner daily during concrete pours and repair the same day. BMP C152: Sawcutting and Surfacing Pollution Prevention Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles  and high pH (concrete cutting), both of which can violate the water quality standards in the receiving  water. Concrete spillage or concrete discharge to waters of the State is prohibited. Use this BMP to  minimize and eliminate process water and slurry created through sawcutting or surfacing from enter- ing waters of the State. Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Saw- cutting and surfacing operations include, but are not limited to:  l Sawing  l Coring  l Grinding  l Roughening  l Hydro-demolition  l Bridge and road surfacing 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 317 Design and Installation Specifications  l Vacuum slurry and cuttings during cutting and surfacing operations.  l Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight.  l Slurry and cuttings shall not drain to any natural or constructed drainage conveyance includ- ing stormwater systems. This may require temporarily blocking catch basins.  l Dispose of collected slurry and cuttings in a manner that does not violate ground water or sur- face water quality standards.  l Do not allow process water generated during hydro-demolition, surface roughening or similar  operations to drain to any natural or constructed drainage conveyance including stormwater  systems. Dispose of process water in a manner that does not violate ground water or surface  water quality standards.  l Handle and dispose of cleaning waste material and demolition debris in a manner that does  not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an  appropriate disposal site. Maintenance Standards Continually monitor operations to determine whether slurry, cuttings, or process water could enter  waters of the state. If inspections show  that a violation of water quality standards could occur, stop  operations and immediately implement preventive measures such as berms, barriers, secondary  containment, and/or vacuum trucks. BMP C153: Material Delivery, Storage, and Containment Purpose Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses  from material delivery and storage. Minimize the storage of hazardous materials on-site, store mater- ials in a designated area, and install secondary containment. Conditions of Use Use at construction sites with delivery and storage of the following materials:  l Petroleum products such as fuel, oil and grease  l Soil stabilizers and binders (e.g., Polyacrylamide)  l Fertilizers, pesticides and herbicides  l Detergents  l Asphalt and concrete compounds 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 318  l Hazardous chemicals such as acids, lime, adhesives, paints, solvents, and curing compounds  l Any other material that may be detrimental if released to the environment Design and Installation Specifications  l The temporary storage area should be located away from vehicular traffic, near the con- struction entrance(s), and away from waterways or storm drains.  l Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be  kept in their original labeled containers.  l Hazardous material storage on-site should be minimized.  l Hazardous materials should be handled as infrequently as possible.  l During the wet weather season (Oct 1 – April 30), consider storing materials in a covered  area.  l Materials should be stored in secondary containments, such as an earthen dike, horse trough,  or even a children’s wading pool for non-reactive materials such as detergents, oil, grease,  and paints. Small amounts of material may be secondarily contained in “bus boy” trays or con- crete mixing trays.  l Do not store chemicals, drums, or bagged materials directly on the ground. Place these items  on a pallet and, when possible, within secondary containment.  l If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater  on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of  drums, preventing water from collecting.  l Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be  stored in approved containers and drums and shall not be overfilled. Containers and drums  shall be stored in temporary secondary containment facilities.  l Temporary secondary containment facilities shall provide for a spill containment volume able  to contain 10% of the total enclosed container volume of all containers, or 110% of the capa- city of the largest container within its boundary, whichever is greater.  l Secondary containment facilities shall be impervious to the materials stored therein for a min- imum contact time of 72 hours.  l Sufficient separation should be provided between stored containers to allow for spill cleanup  and emergency response access.  l During the wet weather season (Oct 1 – April 30), each secondary containment facility shall  be covered during non-working days, prior to and during rain events.  l Keep material storage areas clean, organized and equipped with an ample supply of appro- priate spill clean-up material (spill kit).  l The spill kit should include, at a minimum: 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 319  o 1-Water Resistant Nylon Bag  o 3-Oil Absorbent Socks 3”x 4’  o 2-Oil Absorbent Socks 3”x 10’  o 12-Oil Absorbent Pads 17”x19”  o 1-Pair Splash Resistant Goggles  o 3-Pair Nitrile Gloves  o 10-Disposable Bags with Ties  o Instructions Maintenance Standards  l Secondary containment facilities shall be maintained free of accumulated rainwater and spills.  In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed  into drums. These liquids shall be handled as hazardous waste unless testing determines  them to be non-hazardous.  l Re-stock spill kit materials as needed. BMP C154: Concrete Washout Area Purpose Prevent or reduce the discharge of pollutants from concrete waste to stormwater by conducting  washout off-site, or performing on-site washout in a designated area. Conditions of Use Concrete washout areas are implemented on construction projects where:  l Concrete is used as a construction material  l It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant,  etc.).  l Concrete truck drums are washed on-site. Note that auxiliary concrete truck components (e.g. chutes and hoses) and small concrete  handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheel- barrows) may be washed into formed areas awaiting concrete pour. At no time shall concrete be washed off into the footprint of an area where an infiltration feature will  be installed. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 320 Design and Installation Specifications Implementation  l Perform washout of concrete truck drums at an approved off-site location or in designated con- crete washout areas only.  l Do not wash out concrete onto non-formed areas, or into storm drains, open ditches, streets,  or streams.  l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas.  l Do not allow excess concrete to be dumped on-site, except in designated concrete washout  areas as allowed above.  l Concrete washout areas may be prefabricated concrete washout containers, or self-installed  structures (above-grade or below-grade).  l Prefabricated containers are most resistant to damage and protect against spills and leaks.  Companies may offer delivery service and provide regular maintenance and disposal of solid  and liquid waste.  l If self-installed concrete washout areas are used, below-grade structures are preferred over  above-grade structures because they are less prone to spills and leaks.  l Self-installed above-grade structures should only be used if excavation is not practical.  l Concrete washout areas shall be constructed and maintained in sufficient quantity and size to  contain all liquid and concrete waste generated by washout operations. Education  l Discuss the concrete management techniques described in this BMP with the ready-mix con- crete supplier before any deliveries are made.  l Educate employees and subcontractors on the concrete waste management techniques  described in this BMP.  l Arrange for the contractor’s superintendent or Certified Erosion and Sediment Control Lead  (CESCL) to oversee and enforce concrete waste management procedures.  l A sign should be installed adjacent to each concrete washout area to inform concrete equip- ment operators to utilize the proper facilities. Contracts Incorporate requirements for concrete waste management into concrete supplier and subcontractor  agreements. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 321 Location and Placement  l Locate concrete washout areas at least 50 feet from sensitive areas such as storm drains,  open ditches, water bodies, or wetlands.  l Allow convenient access to the concrete washout area for concrete trucks, preferably near the  area where the concrete is being poured.  l If trucks need to leave a paved area to access the concrete washout area, prevent track-out  with a pad of rock or quarry spalls (see BMP C105:  Stabilized Construction Access). These  areas should be far enough away from other construction traffic to reduce the likelihood of acci- dental damage and spills.  l The number of concrete washout areas you install should depend on the expected demand  for storage capacity.  l On large sites with extensive concrete work, concrete washout areas should be placed in mul- tiple locations for ease of use by concrete truck drivers. Concrete Truck Washout Procedures  l Washout of concrete truck drums shall be performed in designated concrete washout areas  only.  l Concrete washout from concrete pumper bins can be washed into concrete pumper trucks  and discharged into designated concrete washout areas or properly disposed of off-site. Concrete Washout Area Installation  l Concrete washout areas should be constructed as shown in the figures below, with a recom- mended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to  contain all liquid and concrete waste generated by washout operations.  l Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free  of holes, tears, or other defects that compromise the impermeability of the material.  l Lath and flagging should be commercial type.  l Liner seams shall be installed in accordance with manufacturers’ recommendations.  l Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the  plastic lining material. Maintenance Standards Inspection and Maintenance  l Inspect and verify that concrete washout areas are in place prior to the commencement of con- crete work.  l Once concrete wastes are washed into the designated washout area and allowed to harden,  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 322 the concrete should be broken up, removed, and disposed of per applicable solid waste reg- ulations. Dispose of hardened concrete on a regular basis.  l During periods of concrete work, inspect the concrete washout areas daily to verify continued  performance.  o Check overall condition and performance.  o Check remaining capacity (% full).  o If using self-installed concrete washout areas, verify plastic liners are intact and side- walls are not damaged.  o If using prefabricated containers, check for leaks.  l Maintain the concrete washout areas to provide adequate holding capacity with a minimum  freeboard of 12 inches.  l Concrete washout areas must be cleaned, or new concrete washout areas must be con- structed and ready for use once the concrete washout area is 75% full.  l If the concrete washout area is nearing capacity, vacuum and dispose of the waste material in  an approved manner.  l Do not discharge liquid or slurry to waterways, storm drains or directly onto ground.  l Do not discharge to the sanitary sewer without local approval.  l Place a secure, non-collapsing, non-water collecting cover over the concrete washout  area prior to predicted wet weather to prevent accumulation and overflow of pre- cipitation.  l Remove and dispose of hardened concrete and return the structure to a functional con- dition. Concrete may be reused on-site or hauled away for disposal or recycling.  l When you remove materials from a self-installed concrete washout area, build a new struc- ture; or, if the previous structure is still intact, inspect for signs of weakening or damage, and  make any necessary repairs. Re-line the structure with new  plastic after each cleaning. Removal of Concrete Washout Areas  l When concrete washout areas are no longer required for the work, the hardened concrete,  slurries and liquids shall be removed and properly disposed of.  l Materials used to construct concrete washout areas shall be removed from the site of the work  and disposed of or recycled.  l Holes, depressions or other ground disturbance caused by the removal of the concrete  washout areas shall be backfilled, repaired, and stabilized to prevent erosion. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 323 Figure II-3.7: Concrete Washout Area with Wood Planks 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 324 Figure II-3.8: Concrete Washout Area with Straw Bales 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 325 Figure II-3.9: Prefabricated Concrete Washout Container w/Ramp 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 326 BMP C160: Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of  erosion and sediment control (ESC), and water quality protection. The designated person shall be  responsible for ensuring compliance with all local, state, and federal erosion and sediment control  and water quality requirements. Construction sites one acre or larger that discharge to waters of the  State must designate a Certified Erosion and Sediment Control Lead (CESCL) as the responsible  representative. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge stormwater to sur- face waters of the state. Sites less than one acre may have a person without CESCL certification  conduct inspections. The CESCL shall:  l Have a current certificate proving attendance in an erosion and sediment control training  course that meets the minimum ESC training and certification requirements established by  Ecology. Ecology has provided the minimum requirements for CESCL course training, as well as a list  of ESC training and certification providers at:  https://ecology.wa.gov/Regulations-Permits/Permits-certifications/Certified-erosion-sed- iment-control  OR  l Be a Certified Professional in Erosion and Sediment Control (CPESC). For additional inform- ation go to:  http://www.envirocertintl.org/cpesc/ Specifications  l CESCL certification shall remain valid for three years.  l The CESCL shall have authority to act on behalf of the contractor or project proponent and  shall be available, or on-call, 24 hours per day throughout the period of construction.  l The Construction SWPPP shall include the name, telephone number, fax number, and  address of the designated CESCL. See II-2 Construction Stormwater Pollution Prevention  Plans (Construction SWPPPs).  l A CESCL may provide inspection and compliance services for multiple construction projects  in the same geographic region, but must be on site whenever earthwork activities are  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 327 occurring that could generate release of turbid water.  l Duties and responsibilities of the CESCL shall include, but are not limited to the following:  o Maintaining a permit file on site at all times which includes the Construction SWPPP  and any associated permits and plans.  o Directing BMP installation, inspection, maintenance, modification, and removal.  o Updating all project drawings and the Construction SWPPP with changes made.  o Completing any sampling requirements including reporting results using electronic Dis- charge Monitoring Reports (WebDMR).  o Facilitate, participate in, and take corrective actions resulting from inspections per- formed by outside agencies or the owner.  o Keeping daily logs, and inspection reports. Inspection reports should include:  n Inspection date/time.  n Weather information; general conditions during inspection and approximate  amount of precipitation since the last inspection.  n Visual monitoring results, including a description of discharged stormwater. The  presence of suspended sediment, turbid water, discoloration, and oil sheen shall  be noted, as applicable.  n Any water quality monitoring performed during inspection.  n General comments and notes, including a brief description of any BMP repairs,  maintenance or installations made as a result of the inspection.  n A summary or list of all BMPs implemented, including observations of all  erosion/sediment control structures or practices. The following shall be noted:  1. Locations of BMPs inspected.  2. Locations of BMPs that need maintenance.  3. Locations of BMPs that failed to operate as designed or intended.  4. Locations of where additional or different BMPs are required. BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by  wind, rain, runoff, and vehicle tracking. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 328 Conditions of Use The construction sequence schedule is an orderly listing of all major land-disturbing activities  together with the necessary erosion and sedimentation control measures planned for the project.  This type of schedule guides the contractor on work to be done before other work is started so that  serious erosion and sedimentation problems can be avoided. Following a specified work schedule that coordinates the timing of land-disturbing activities and the  installation of control measures is perhaps the most cost-effective way of controlling erosion during  construction. The removal of ground cover leaves a site vulnerable to erosion. Construction sequen- cing that limits land clearing, provides timely installation of erosion and sedimentation controls, and  restores protective cover quickly can significantly reduce the erosion potential of a site. Design Considerations  l Minimize construction during rainy periods.  l Schedule projects to disturb only small portions of the site at any one time. Complete grading  as soon as possible. Immediately stabilize the disturbed portion before grading the next por- tion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses. II-3.3 Construction Runoff BMPs BMP C200: Interceptor Dike and Swale Purpose Provide a dike of compacted soil or a swale at the top or base of a disturbed slope or along the peri- meter of a disturbed construction area to convey stormwater. Use the dike and/or swale to intercept  the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can  prevent storm runoff from entering the work area or sediment-laden runoff from leaving the con- struction site. Conditions of Use Use an interceptor dike or swale where runoff from an exposed site or disturbed slope must be con- veyed to an erosion control BMP which can safely convey the stormwater.  l Locate upslope of a construction site to prevent runoff from entering the disturbed area.  l When placed horizontally across a disturbed slope, it reduces the amount and velocity of run- off flowing down the slope.  l Locate downslope to collect runoff from a disturbed area and direct it to a sediment  BMP (e.g.  BMP C240:  Sediment Trap or BMP C241:  Sediment Pond (Temporary)). 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 329 Design and Installation Specifications  l Dike and/or swale and channel must be stabilized with temporary or permanent vegetation or  other channel protection during construction.  l Steep grades require channel protection and check dams.  l Review construction for areas where overtopping may occur.  l Can be used at the top of new  fill before vegetation is established.  l May be used as a permanent diversion channel to carry the runoff.  l Contributing area for an individual dike or swale should be one acre or less.  l Design the dike and/or swale to contain flows calculated by one of the following methods:  o Single Event Hydrograph Method: The peak volumetric flow rate calculated using a 10- minute time step from a Type 1A, 10-year, 24-hour frequency storm for the worst-case  land cover condition. OR  o Continuous Simulation Method: The 10-year peak flow rate, as determined by an  approved continuous runoff model with a 15-minute time step for the worst-case land  cover condition. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analysis  (in most cases, this would be the land cover conditions just prior to final landscaping). Interceptor Dikes Interceptor dikes shall meet the following criteria:  l Top Width: 2 feet minimum.  l Height:  1.5 feet minimum on berm.  l Side Slope: 2H:1V or flatter.  l Grade: Depends on topography, however, dike system minimum is 0.5%, and maximum is  1%.  l Compaction: Minimum of 90 percent ASTM D698 standard proctor.  l Stabilization: Depends on velocity and reach. Inspect regularly to ensure stability.  l Ground Slopes <5%: Seed and mulch applied within 5 days of dike construction (see BMP  C121: Mulching).  l Ground Slopes 5 - 40%: Dependent on runoff velocities and dike materials. Stabilization  should be done immediately using either sod or riprap, or other measures to avoid erosion.  l The upslope side of the dike shall provide positive drainage to the dike outlet. No erosion shall  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 330 occur at the outlet. Provide energy dissipation measures as necessary. Sediment-laden runoff  must be released through a sediment trapping facility.  l Minimize construction traffic over temporary dikes. Use temporary cross culverts for channel  crossing.  l See Table II-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope for recom- mended horizontal spacing between dikes. Average Slope Slope Percent Flowpath Length 20H:1V or less 3-5%300  feet (10 to 20)H:1V 5-10%200  feet (4 to 10)H:1V 10-25%100  feet (2 to 4)H:1V 25-50%50  feet Table II-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope Interceptor Swales Interceptor swales shall meet the following criteria:  l Bottom Width: 2 feet minimum; the cross-section bottom shall be level.  l Depth: 1-foot minimum.  l Side Slope: 2H:1V or flatter.  l Grade: Maximum 5 percent, with positive drainage to a suitable outlet (such as BMP C241:   Sediment Pond (Temporary)).  l Stabilization: Seed as per BMP C120: Temporary and Permanent Seeding, or BMP C202:   Riprap Channel Lining, 12 inches thick riprap pressed into the bank and extending at least 8  inches vertical from the bottom. Maintenance Standards  l Inspect diversion dikes and interceptor swales once a week and after every rainfall. Imme- diately remove sediment from the flow area.  l Damage caused by construction traffic or other activity must be repaired before the end of  each working day.  l Check outlets and make timely repairs as needed to avoid gully formation. When the area  below the temporary diversion dike is permanently stabilized, remove the dike and fill and sta- bilize the channel to blend with the natural surface. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 331 BMP C207: Check Dams Purpose Construction of check dams across a swale or ditch reduces the velocity of concentrated flow and dis- sipates energy at the check dam. Conditions of Use Use check dams where temporary or permanent channels are not yet vegetated, channel lining is  infeasible, and/or velocity checks are required.  l Check dams may not be placed in streams unless approved by the State Department of Fish  and Wildlife.   l Check dams may not be placed in wetlands without approval from a permitting agency.  l Do not place check dams below the expected backwater from any salmonid bearing water  between October 1 and May 31 to ensure that there is no loss of high flow refuge habitat for  overwintering juvenile salmonids and emergent salmonid fry. Design and Installation Specifications  l Construct rock check dams from appropriately sized rock. The rock used must be large  enough to stay in place given the expected design flow  through the channel. The rock must be  placed by hand or by mechanical means (do not dump the rock to form the dam) to achieve  complete coverage of the ditch or swale and to ensure that the center of the dam is lower than  the edges.  l Check dams may also be constructed of either rock or pea-gravel filled bags. Numerous new  products are also available for this purpose. They tend to be re-usable, quick and easy to  install, effective, and cost efficient.  l Place check dams perpendicular to the flow of water.  l The check dam should form a triangle when viewed from the side. This prevents undercutting  as water flows over the face of the check dam rather than falling directly onto the ditch bottom.  l Before installing check dams, impound and bypass upstream water flow away from the work  area. Options for bypassing include pumps, siphons, or temporary channels.  l Check dams combined with sumps work more effectively at slowing flow  and retaining sed- iment than a check dam alone. A deep sump should be provided immediately upstream of the  check dam.  l In some cases, if carefully located and designed, check dams can remain as permanent install- ations with very minor regrading. They may be left as either spillways, in which case accu- mulated sediment would be graded and seeded, or as check dams to prevent further  sediment from leaving the site.  l The maximum spacing between check dams shall be such that the downstream toe of the  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 351 upstream dam is at the same elevation as the top of the downstream dam.  l Keep the maximum height at 2 feet at the center of the check dam.  l Keep the center of the check dam at least 12 inches lower than the outer edges at natural  ground elevation.  l Keep the side slopes of the check dam at 2H:1V or flatter.  l Key the stone into the ditch banks and extend it beyond the abutments a minimum of 18  inches to avoid washouts from overflow around the dam.  l Use filter fabric foundation under a rock or sand bag check dam. If a blanket ditch liner is used,  filter fabric is not necessary. A piece of organic or synthetic blanket cut to fit will also work for  this purpose.  l In the case of grass-lined ditches and swales, all check dams and accumulated sediment shall  be removed when the grass has matured sufficiently to protect the ditch or swale - unless the  slope of the swale is greater than 4 percent. The area beneath the check dams shall be  seeded and mulched immediately after dam removal.  l Ensure that channel appurtenances, such as culvert entrances below check dams, are not  subject to damage or blockage from displaced stones.   l See Figure II-3.16: Rock Check Dam. Maintenance Standards Check dams shall be monitored for performance and sediment accumulation during and after each  rainfall that produces runoff. Sediment shall be removed when it reaches one half the sump depth.  l Anticipate submergence and deposition above the check dam and erosion from high flows  around the edges of the dam.  l If significant erosion occurs between dams, install a protective riprap liner in that portion of the  channel. See BMP C202:  Riprap Channel Lining. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 352 Figure II-3.16: Rock Check Dam 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 353 BMP C208: Triangular Silt Dike (TSD) Purpose Triangular silt dikes (TSDs) may be used as check dams, for perimeter protection, for temporary soil  stockpile protection, for drop inlet protection, or as a temporary interceptor dike. Conditions of Use  l TSDs may be used on soil or pavement with adhesive or staples.  l TSDs have been used to build temporary:  o BMP C241:  Sediment Pond (Temporary);  o BMP C200: Interceptor Dike and Swale;  o BMP C154: Concrete Washout Area;  o BMP C203: Water Bars;  o BMP C206:  Level Spreader;   o BMP C220:  Inlet Protection;  o BMP C207:  Check Dams  o curbing; and  o berms. Design and Installation Specifications  l TSDs are made of urethane foam sewn into a woven geosynthetic fabric.  l TSDs are triangular, 10 inches to 14 inches high in the center, with a 20-inch to 28-inch base.  A 2 foot apron extends beyond both sides of the triangle along its standard section of 7 feet. A  sleeve at one end allows attachment of additional sections as needed.  l Install with ends curved up to prevent water from flowing around the ends.  l The fabric flaps and check dam units are attached to the ground with wire staples. Wire  staples should be No. 11 gauge wire and should be 200 mm to 300 mm in length.  l When multiple units are installed, the sleeve of fabric at the end of the unit shall overlap the  abutting unit and be stapled.  l When used as check dams:  o TSDs should be located and installed as soon as construction will allow.  o TSDs should be placed perpendicular to the flow of water.  o The leading edge of the TSD must be secured with rocks, sandbags, or a small key slot  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 354 and staples.  o In the case of grass-lined ditches and swales, check dams and accumulated sediment  shall be removed when the grass has matured sufficiently to protect the ditch or swale  unless the slope of the swale is greater than 4 percent. The area beneath the check  dams shall be seeded and mulched immediately after dam removal. Maintenance Standards  l Inspect TSDs for performance and sediment accumulation during and after each rainfall that  produces runoff. Remove sediment when it reaches one half the height of the TSD.  l Anticipate submergence and deposition above the TSD  and erosion from high flows around  the edges of the TSD. Immediately repair any damage or any undercutting of the TSD. BMP C209: Outlet Protection Purpose Outlet protection prevents scour at conveyance outlets and minimizes the potential for downstream  erosion by reducing the velocity of concentrated stormwater flows. Conditions of Use Use outlet protection at the outlets of all ponds, pipes, ditches, or other conveyances  that discharge  to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch. Design and Installation Specifications  l The receiving channel at the outlet of a pipe shall be protected from erosion by lining a min- imum of 6 feet downstream and extending up the channel sides a minimum of 1–foot above  the maximum tailwater elevation, or 1-foot above the crown, whichever is higher. For pipes lar- ger than 18 inches in diameter, the outlet protection lining of the channel shall be four times  the diameter of the outlet pipe.  l Standard wingwalls, tapered outlets, and paved channels should also be considered when  appropriate for permanent culvert outlet protection (WSDOT, 2015).  l BMP C122:  Nets and Blankets or BMP C202:  Riprap Channel Lining provide suitable options  for lining materials.  l With low flows, BMP C201: Grass-Lined Channels can be an effective alternative for lining  material.  l The following guidelines shall be used for outlet protection with riprap:  o If the discharge velocity at the outlet is less than 5 fps, use 2-inch to 8-inch riprap. Min- imum thickness is 1-foot.  o For 5 to 10 fps discharge velocity at the outlet, use 24-inch to 48-inch riprap. Minimum  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 355 thickness is 2 feet.  o For outlets at the base of steep slope pipes (pipe slope greater than 10 percent), use an  engineered energy dissipator.  o Filter fabric or erosion control blankets should always be used under riprap to prevent  scour and channel erosion. See BMP C122:  Nets and Blankets.  l Bank stabilization, bioengineering, and habitat features may be required for disturbed areas.  This work may require a Hydraulic Project Approval (HPA) from the Washington State Depart- ment of Fish and Wildlife. See I-2.11 Hydraulic Project Approvals. Maintenance Standards  l Inspect and repair as needed.  l Add rock as needed to maintain the intended function.  l Clean energy dissipator if sediment builds up. BMP C220: Inlet Protection Purpose Inlet protection prevents coarse sediment from entering drainage systems prior to permanent sta- bilization of the disturbed area. Conditions of Use Use inlet protection at inlets that are operational before permanent stabilization of the disturbed  areas that contribute runoff to the inlet. Provide protection for all storm drain inlets downslope and  within 500 feet of a disturbed or construction area, unless  those inlets are preceded by a sediment  trapping BMP. Also consider inlet protection for lawn and yard drains on new home construction. These small and  numerous drains coupled with lack of gutters can add significant amounts of sediment into the roof  drain system. If possible, delay installing lawn and yard drains until just before landscaping, or cap  these drains to prevent sediment from entering the system until completion of landscaping. Provide  18-inches of sod around each finished lawn and yard drain. Table II-3.10: Storm Drain Inlet Protection lists several options for inlet protection. All of the methods  for inlet protection tend to plug and require a high frequency of maintenance. Limit contributing drain- age areas for an individual inlet to one acre or less. If possible, provide emergency overflows with  additional end-of-pipe treatment where stormwater ponding would cause a hazard. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 356 Type of Inlet Pro- tection Emergency Overflow Applicable for Paved/ Earthen Sur- faces Conditions of Use Drop Inlet Protection Excavated  drop  inlet protection Yes, temporary  flooding may   occur Earthen Applicable for heavy flows. Easy   to maintain. Large area requirement:   30'x30'/acre Block  and gravel  drop inlet pro- tection Yes Paved or Earthen Applicable for heavy  concentrated flows.  Will not pond. Gravel and wire  drop inlet pro- tection No Paved or Earthen Applicable for  heavy concentrated flows.  Will pond. Can withstand traffic. Catch  basin filters Yes Paved or Earthen Frequent maintenance  required. Curb Inlet Protection Curb  inlet pro- tection with  wooden weir Small capacity  overflow Paved Used for sturdy, more compact  install- ation. Block and gravel  curb inlet pro- tection Yes Paved Sturdy, but  limited filtration. Culvert Inlet Protection Culvert  inlet sed- iment trap N/A N/A 18 month expected life. Table II-3.10: Storm Drain Inlet Protection Design and Installation Specifications Excavated Drop Inlet Protection Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet.  Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe- cifications for excavated drop inlet protection include:  l Provide a depth of 1-2 ft as measured from the crest of the inlet structure.  l Slope sides of excavation should be no steeper than 2H:1V.  l Minimum volume of excavation is 35 cubic yards.  l Shape the excavation to fit the site, with the longest dimension oriented toward the longest  inflow area.  l Install provisions for draining to prevent standing water.  l Clear the area of all debris. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 357  l Grade the approach to the inlet uniformly.  l Drill weep holes into the side of the inlet.  l Protect weep holes with screen wire and washed aggregate.  l Seal weep holes when removing structure and stabilizing area.  l Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass  flow. Block and Gravel Filter A block and gravel filter is a barrier formed around the inlet with standard concrete blocks and gravel.  See Figure II-3.17: Block and Gravel Filter. Design and installation specifications for block gravel fil- ters include:  l Provide a height of 1 to 2 feet above the inlet.  l Recess the first row of blocks 2-inches into the ground for stability.  l Support subsequent courses by placing a pressure treated wood 2x4 through the block open- ing.  l Do not use mortar.  l Lay some blocks in the bottom row on their side to allow  for dewatering the pool.  l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings.  l Place gravel to just below the top of blocks on slopes of 2H:1V or flatter.  l An alternative design is a gravel berm surrounding the inlet, as follows:  o Provide a slope of 3H:1V on the upstream side of the berm.  o Provide a slope of 2H:1V on the downstream side of the berm.  o Provide a 1-foot wide level stone area between the gravel berm and the inlet.  o Use stones 3 inches in diameter or larger on the upstream slope of the berm.  o Use gravel ½- to ¾-inch at a minimum thickness of 1-foot on the downstream slope of  the berm. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 358 Figure II-3.17: Block and Gravel Filter   2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 359 Gravel and Wire Mesh Filter Gravel and wire mesh filters are gravel barriers placed over the top of the inlet. This method does not  provide an overflow. Design and installation specifications for gravel and wire mesh filters include:  l Use a hardware cloth or comparable wire mesh with ½-inch openings.  o Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot bey- ond each side of the inlet structure.  o Overlap the strips if more than one strip of mesh is necessary.  l Place coarse aggregate over the wire mesh.  o Provide at least a 12-inch depth of aggregate over the entire inlet opening and extend at  least 18-inches on all sides. Catch Basin Filters Catch  basin filters are designed by manufacturers for construction sites. The limited sediment stor- age capacity increases the amount of inspection and maintenance required, which may be daily for  heavy sediment loads. To reduce maintenance requirements, combine a catch  basin filter with  another type of inlet protection. This type of inlet protection provides flow  bypass without overflow  and therefore may be a better method for inlets located along active rights-of-way. Design and install- ation specifications for catch basin filters include:  l Provides 5 cubic feet of storage.  l Requires dewatering provisions.  l Provides a high-flow bypass that will not clog under normal use at a construction site.  l Insert the catch  basin filter in the catch  basin just below the grating. Curb Inlet Protection with Wooden Weir Curb inlet protection with wooden weir is an option that consists of a barrier formed around a curb  inlet with a wooden frame and gravel. Design and installation specifications for curb inlet protection  with wooden weirs include:  l Use wire mesh with ½-inch openings.  l Use extra strength filter cloth.  l Construct a frame.  l Attach the wire and filter fabric to the frame.  l Pile coarse washed aggregate against the wire and fabric.  l Place weight on the frame anchors. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 360 Block and Gravel Curb Inlet Protection Block and gravel curb inlet protection is a barrier formed around a curb inlet with concrete blocks and  gravel. See Figure II-3.18: Block and Gravel Curb Inlet Protection. Design and installation spe- cifications for block and gravel curb inlet protection include:  l Use wire mesh with ½-inch openings.  l Place two concrete blocks on their sides abutting the curb at either side of the inlet opening.  These are spacer blocks.  l Place a 2x4 stud through the outer holes of each spacer block to align the front blocks.  l Place blocks on their sides across the front of the inlet and abutting the spacer blocks.  l Place wire mesh over the outside vertical face.  l Pile coarse aggregate against the wire to the top of the barrier. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 361 Figure II-3.18: Block and Gravel Curb Inlet Protection   2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 362 Curb and Gutter Sediment Barrier Curb and gutter sediment barrier is a sandbag or rock berm (riprap and aggregate) 3 feet high and 3  feet wide in a horseshoe shape. See Figure II-3.19: Curb and Gutter Barrier. Design and installation  specifications for curb and gutter sediment barrier include:  l Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high  and 3 feet wide, at least 2 feet from the inlet.  l Construct a horseshoe shaped sedimentation trap on the upstream side of the berm. Size the  trap to sediment trap standards for protecting a culvert inlet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 363 Figure II-3.19: Curb and Gutter Barrier 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 364 BMP C233: Silt Fence Purpose Silt fence reduces the transport of coarse sediment from a construction site by providing a temporary  physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use Silt fence may be used downslope of all disturbed areas.  l Silt fence shall prevent sediment carried by runoff from going beneath, through, or over the  top of the silt fence, but shall allow the water to pass through the fence.  l Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial  amounts of overland flow. Convey any concentrated flows through the drainage system to a  sediment trapping BMP.  l Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide  an adequate method of silt control for anything deeper than sheet or overland flow. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 370 Figure II-3.22: Silt Fence 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 371 Design and Installation Specifications  l Use in combination with other construction stormwater BMPs.  l Maximum slope steepness (perpendicular to the silt fence line) 1H:1V.  l Maximum sheet or overland flow path length to the silt fence of 100 feet.  l Do not allow flows greater than 0.5 cfs.  l Use geotextile fabric that meets the following standards. All geotextile properties listed below  are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or  exceed the values shown in Table II-3.11: Geotextile Fabric Standards for Silt Fence): Geotextile Property Minimum Average Roll Value Polymeric  Mesh AOS  (ASTM D4751) 0.60 mm maximum for slit film  woven (#30 sieve).  0.30 mm  maximum for all other geotextile types (#50 sieve).  0.15 mm minimum for all fabric  types (#100 sieve). Water  Permittivity  (ASTM D4491) 0.02 sec-1 minimum Grab  Tensile Strength  (ASTM D4632) 180 lbs. Minimum for extra  strength fabric.  100 lbs  minimum for standard strength fabric. Grab Tensile Strength  (ASTM D4632) 30% maximum Ultraviolet  Resistance  (ASTM D4355) 70%  minimum Table II-3.11: Geotextile Fabric Standards for Silt Fence  l Support standard strength geotextiles with wire mesh, chicken wire, 2-inch x 2-inch wire,  safety fence, or jute mesh to increase the strength of the geotextile. Silt fence materials are  available that have synthetic mesh backing attached.  l Silt fence material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum  of six months of expected usable construction life at a temperature range of 0°F to 120°F.  l One-hundred percent biodegradable silt fence is available that is strong, long lasting, and can  be left in place after the project is completed, if permitted by the local jurisdiction.  l Refer to Figure II-3.22: Silt Fence for standard silt fence details. Include the following Stand- ard Notes for silt fence on construction plans and specifications:  1. The Contractor shall install and maintain temporary silt fences at the locations shown in  the Plans.  2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those  activities. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 372  3. The silt fence shall have a 2-feet min. and a 2½-feet max. height above the original  ground surface.  4. The geotextile fabric shall be sewn together at the point of manufacture to form fabric  lengths as required. Locate all sewn seams at support posts. Alternatively, two sections  of silt fence can be overlapped, provided  that the overlap is long enough and that the  adjacent silt fence sections are close enough together to prevent silt laden water from  escaping through the fence at the overlap.  5. Attach the geotextile fabric on the up-slope side of the posts and secure with staples,  wire, or in accordance with the manufacturer's recommendations. Attach the geotextile  fabric to the posts in a manner that reduces the potential for tearing.  6. Support the geotextile fabric with wire or plastic mesh, dependent on the properties of  the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely  to the up-slope side of the posts with the geotextile fabric up-slope of the mesh.  7. Mesh support, if used, shall consist of steel wire with a maximum mesh spacing of 2- inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh  shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh  must be as resistant to the same level of ultraviolet radiation as the geotextile fabric it  supports.  8. Bury the bottom of the geotextile fabric 4-inches min. below the ground surface. Backfill  and tamp soil in place over the buried portion of the geotextile fabric, so that no flow can  pass beneath the silt fence and scouring cannot occur. When wire or polymeric back-up  support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches  min.  9. Drive or place the silt fence posts into the ground 18-inches min. A 12–inch min. depth  is allowed if topsoil or other soft subgrade soil is not present and 18-inches cannot be  reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of  3H:1V or steeper and the slope is perpendicular to the fence. If required post depths  cannot be obtained, the posts shall be adequately secured by bracing or guying to pre- vent overturning of the fence due to sediment loading.  10. Use wood, steel or equivalent posts. The spacing of the support posts shall be a max- imum of 6-feet. Posts shall consist of either:  l Wood with minimum dimensions of 2 inches by 2 inches by 3 feet. Wood shall be  free of defects such as knots, splits, or gouges.  l No. 6 steel rebar or larger.  l ASTM A 120 steel pipe with a minimum diameter of 1-inch.  l U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft.  l Other steel posts having equivalent strength and bending resistance to the post  sizes listed above.  11. Locate silt fences on contour as much as possible, except at the ends of the fence,  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 373 where the fence shall be turned uphill such that the silt fence captures the runoff water  and prevents water from flowing around the end of the fence.  12. If the fence must cross contours, with the exception of the ends of the fence, place  check dams perpendicular to the back of the fence to minimize concentrated flow and  erosion. The slope of the fence line where contours must be crossed shall not be  steeper than 3H:1V.  l Check dams shall be approximately 1-foot deep at the back of the fence. Check  dams shall be continued perpendicular to the fence at the same elevation until  the top of the check dam intercepts the ground surface behind the fence.  l Check dams shall consist of crushed surfacing base course, gravel backfill for  walls, or shoulder ballast. Check dams shall be located every 10 feet along the  fence where the fence must cross contours.  l Refer to Figure II-3.23: Silt Fence Installation by Slicing Method for slicing method details. The  following are specifications for silt fence installation using the slicing method:  1. The base of both end posts must be at least 2- to 4-inches above the top of the geo- textile fabric on the middle posts for ditch checks to drain properly. Use a hand level or  string level, if necessary, to mark base points before installation.  2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard  applications.  3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as  possible to the geotextile fabric, enabling posts to support the geotextile fabric from  upstream water pressure.  4. Install posts with the nipples facing away from the geotextile fabric.  5. Attach the geotextile fabric to each post with three ties, all spaced within the top 8- inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each  puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post  nipple when tightening to prevent sagging.  6. Wrap approximately 6-inches of the geotextile fabric around the end posts and secure  with 3 ties.  7. No more than 24-inches of a 36-inch geotextile fabric is allowed above ground level.  8. Compact the soil immediately next to the geotextile fabric with the front wheel of the  tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the  upstream side first and then each side twice for a total of four trips. Check and correct  the silt fence installation for any deviation before compaction. Use a flat-bladed shovel  to tuck the fabric deeper into the ground if necessary. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 374 Figure II-3.23: Silt Fence Installation by Slicing Method 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 375 Maintenance Standards  l Repair any damage immediately.  l Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment trap- ping BMP.  l Check the uphill side of the silt fence for signs of the fence clogging and acting as a barrier to  flow  and then causing channelization of flows parallel to the fence. If this occurs, replace the  fence and remove the trapped sediment.  l Remove sediment deposits when the deposit reaches approximately one-third the height of  the silt fence, or install a second silt fence.  l Replace geotextile fabric that has deteriorated due to ultraviolet breakdown. BMP C234: Vegetated Strip Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a  physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use  l Vegetated strips may be used downslope of all disturbed areas.  l Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat  substantial amounts of overland flow. Any concentrated flows must be conveyed through the  drainage system to BMP C241:  Sediment Pond (Temporary) or other sediment trapping  BMP. The only circumstance in which overland flow  can be treated solely by a vegetated strip,  rather than by a sediment trapping BMP, is when the following criteria are met (see Table II- 3.12: Contributing Drainage Area for Vegetated Strips): Average Contributing Area Slope Average Contributing Area Per- cent Slope Max Contributing area Flowpath Length 1.5H : 1V or flatter 67% or flatter 100 feet 2H : 1V or  flatter 50% or flatter 115 feet 4H : 1V or  flatter 25% or flatter 150  feet 6H : 1V or  flatter 16.7% or flatter 200  feet 10H  : 1V or  flatter 10% or flatter 250  feet Table II-3.12: Contributing Drainage Area for Vegetated Strips 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 376 Design and Installation Specifications  l The vegetated strip shall consist of a continuous strip of dense vegetation with topsoil for a min- imum of a 25-foot length along the flowpath. Grass-covered, landscaped areas are generally  not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips  shall consist of undisturbed native growth with a well-developed soil that allows for infiltration  of runoff.  l The slope within the vegetated strip shall not exceed 4H:1V.  l The uphill boundary of the vegetated strip shall be delineated with clearing limits. Maintenance Standards  l Any areas damaged by erosion or construction activity shall be seeded immediately and pro- tected by mulch.  l If more than 5 feet of the original vegetated strip width has had vegetation removed or is being  eroded, sod must be installed.  l If there are indications that concentrated flows are traveling across the vegetated strip, storm- water runoff controls must be installed to reduce the flows entering the vegetated strip, or addi- tional perimeter protection must be installed. BMP C235: Wattles Purpose Wattles are temporary erosion and sediment control barriers consisting of straw, compost, or other  material that is wrapped in netting made of natural plant fiber or similar encasing material. They  reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sed- iment. Conditions of Use  l Wattles shall consist of cylinders of plant material such as weed-free straw, coir, wood chips,  excelsior, or wood fiber or shavings encased within netting made of natural plant fibers  unaltered by synthetic materials.  l Use wattles:  o In disturbed areas that require immediate erosion protection.  o On exposed soils during the period of short construction delays, or over winter months.  o On slopes requiring stabilization until permanent vegetation can be established.  l The material used dictates the effectiveness period of the wattle. Generally, wattles are effect- ive for one to two seasons. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 377  l Prevent rilling beneath wattles by entrenching and overlapping wattles to prevent water from  passing between them. Design Criteria  l See Figure II-3.24: Wattles for typical construction details.  l Wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length.   l Install wattles perpendicular to the flow  direction and parallel to the slope contour.  l Place wattles in shallow trenches, staked along the contour of disturbed or newly constructed  slopes. Dig narrow trenches across the slope (on contour) to a depth of 3- to 5-inches on clay  soils and soils with gradual slopes. On loose soils, steep slopes, and areas with high rainfall,  the trenches should be dug to a depth of 5- to 7- inches, or 1/2 to 2/3 of the thickness of the  wattle.  l Start building trenches and installing wattles from the base of the slope and work up. Spread  excavated material evenly along the uphill slope and compact it using hand tamping or other  methods.  l Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil  type, and rainfall. The steeper the slope the closer together the trenches.  l Install the wattles snugly into the trenches and overlap the ends of adjacent wattles 12 inches  behind one another.  l Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle.  l If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle  and into the soil.  l Wooden stakes should be approximately 0.75 x 0.75 x 24 inches min. Willow  cuttings or 3/8- inch rebar can also be used for stakes.  l Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake pro- truding above the wattle. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 378 Figure II-3.24: Wattles 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 379 Maintenance Standards  l Wattles may require maintenance to ensure they are in contact with soil and thoroughly  entrenched, especially after significant rainfall on steep sandy soils.  l Inspect the slope after significant storms and repair any areas where wattles are not tightly  abutted or water has scoured beneath the wattles. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not  pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions  may choose not to accept these products, or may require additional testing prior to consideration for  local use. Products that Ecology has approved as functionally equivalent are available for review on  Ecology’s website at:  https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C236: Vegetative Filtration Purpose Vegetative filtration as a BMP is used in conjunction with detention storage in the form of portable  tanks or BMP C241:  Sediment Pond (Temporary), BMP C206:  Level Spreader, and a pumping sys- tem with surface intake. Vegetative filtration improves turbidity levels of stormwater discharges by fil- tering runoff through existing vegetation where undisturbed forest floor duff layer or established lawn  with thatch layer are present.  Vegetative filtration can also be used to infiltrate dewatering waste  from foundations, vaults, and trenches as long as runoff does not occur. Conditions of Use  l For every five acres of disturbed soil use one acre of grass field, farm pasture, or wooded  area. Reduce or increase this area depending on project size, ground water table height, and  other site conditions.  l Wetlands shall not be used for vegetative filtration.  l Do not use this BMP in areas with a high ground water table, or in areas that will have a high  seasonal ground water table during the use of this BMP.  l This BMP may be less effective on soils that prevent the infiltration of the water, such as hard  till.  l Using other effective source control measures throughout a construction site will prevent the  generation of additional highly turbid water and may reduce the time period or area need for  this BMP.  l Stop distributing water into the vegetated filtration area if standing water or erosion results. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 380  l On large projects that phase the clearing of the site, areas retained with native vegetation may  be used as a temporary vegetative filtration area. Design Criteria  l Find land adjacent to the project site that has a vegetated field, preferably a farm field, or  wooded area.  l If the site does not contain enough vegetated field area consider obtaining permission from  adjacent landowners (especially for farm fields).  l Install a pump and downstream distribution manifold depending on the project size. Generally,  the main distribution line should reach 100 to 200-feet long (large projects, or projects on tight  soil, will require systems that reach several thousand feet long with numerous branch lines off  of the main distribution line).  l The manifold should have several valves, allowing for control over the distribution area in the  field.  l Install several branches of 4-inch diameter schedule 20 polyvinyl chloride (PVC), swaged-fit  common septic tight-lined sewer line, or 6-inch diameter fire hose, which can convey the tur- bid water out to various sections of the field. See Figure II-3.25: Manifold and Branches in a  Wooded, Vegetated Spray Field.  l Determine the branch length based on the field area geography and number of branches. Typ- ically, branches stretch from 200-feet to several thousand feet. Lay the branches on contour  with the slope.  l On uneven ground, sprinklers perform well. Space sprinkler heads so that spray patterns do  not overlap.  l On relatively even surfaces, a level spreader using 4-inch perforated pipe may be used as an  alternative option to the sprinkler head setup. Install drain pipe at the highest point on the field  and at various lower elevations to ensure full coverage of the filtration area. Place the pipe   with the holes up to allow for gentle weeping evenly out all holes.  Leveling the pipe by staking  and using sandbags may be required.  l To prevent over saturating of the vegetative filtration area, rotate the use of branches or spray  heads. Repeat as needed based on monitoring the spray field. Average Slope Average Area % Slope Estimated Flowpath Length (ft) 1.5H:1V 67%250 2H:1V 50%200 4H:1V 25%150 6H:1V 16.7%115 10H:1V 10%100 Table II-3.13: Flowpath Guidelines for Vegetative Filtration 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 381 Figure II-3.25: Manifold and Branches in a Wooded, Vegetated Spray Field 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 382 Maintenance Standards  l Monitor the spray field on a daily basis to ensure that over saturation of any portion of the field  doesn’t occur at any time. The presence of standing puddles of water or creation of con- centrated flows visually signify that over saturation of the field has occurred.  l Monitor the vegetated spray field all the way down to the nearest surface water, or farthest  spray area, to ensure that the water has not caused overland or concentrated flows, and has  not created erosion around the spray nozzle(s).  l Do not exceed water quality standards for turbidity.  l Ecology recommends that a separate inspection log be developed, maintained and kept with  the existing site logbook to aid the operator conducting inspections. This separate “Field Filtra- tion Logbook” can also aid in demonstrating compliance with permit conditions.  l Inspect the spray nozzles daily, at a minimum, for leaks and plugging from sediment particles.  l If erosion, concentrated flows, or over saturation of the field occurs, rotate the use of branches  or spray heads or move the branches to a new field location.  l Check all branches and the manifold for unintended leaks. BMP C240: Sediment Trap Purpose A sediment trap is a small temporary ponding area with a gravel outlet used to collect and store sed- iment from sites during construction. Sediment traps, along with other perimeter controls, shall be  installed before any land disturbance takes place in the drainage area. Conditions of Use  l Sediment traps are intended for use on sites where the tributary drainage area is less than 3  acres, with no unusual drainage features, and a projected build-out time of six months or less.  The sediment trap is a temporary measure (with a design life of approximately 6 months) and  shall be maintained until the tributary area is permanently protected against erosion by veget- ation and/or structures.  l Sediment traps are only effective in removing sediment down to about the medium silt size  fraction. Runoff with sediment of finer grades (fine silt and clay) will pass through untreated,  emphasizing the need to control erosion to the maximum extent first.  l Projects that are constructing permanent Flow  Control BMPs, or Runoff Treatment BMPs  that use ponding for treatment, may use the rough-graded or final-graded permanent BMP  footprint for the temporary sediment trap. When permanent BMP footprints are used as tem- porary sediment traps, the surface area requirement of the sediment trap must be met. If the  surface area requirement of the sediment trap is larger than the surface area of the per- manent BMP, then the sediment trap shall be enlarged beyond the permanent BMP footprint  to comply with the surface area requirement. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 383  l A floating pond skimmer may be used for the sediment trap outlet if approved by the Local Per- mitting Authority.  l Sediment traps may not be feasible on utility projects due to the limited work space or the  short-term nature of the work. Portable tanks may be used in place of sediment traps for utility  projects. Design and Installation Specifications  l See Figure II-3.26: Cross Section of Sediment Trap and Figure II-3.27: Sediment Trap Outlet  for details.  l To determine the sediment 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 =   o Option 1 - Single Event Hydrograph Method: Q2 = Peak volumetric flow rate calculated using a 10-minute time step from a Type 1A,  2-year, 24-hour frequency storm for the developed condition. The 10-year peak volu- metric flow rate shall be used if the project size, expected timing and duration of con- struction, or downstream conditions warrant a higher level of protection.   o Option 2 - For construction sites that are less than 1 acre, the Rational Method may be  used to determine Q2. Vs = The settling velocity 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 set- tling velocity (Vs) of 0.00096 ft/sec. FS = A safety factor of 2 to account for non-ideal settling. Therefore, the equation for computing sediment trap surface area becomes: SA  = 2 x Q2/0.00096  or 2080 square feet per cfs of inflow  l Sediment trap depth shall be 3.5 feet minimum from the bottom of the trap to the top of the  overflow weir.  l To aid in determining sediment depth, all sediment traps shall have a staff gauge with a prom- inent mark 1-foot above the bottom of the trap. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 384  l Design the discharge from the sediment trap by using the guidance for discharge from tem- porary sediment ponds in BMP C241:  Sediment Pond (Temporary). Maintenance Standards  l Sediment shall be removed from the trap when it reaches 1-foot in depth.  l Any damage to the trap embankments or slopes shall be repaired. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 385 Figure II-3.26: Cross Section of Sediment Trap 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 386 Figure II-3.27: Sediment Trap Outlet 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 387 Construction Stormwater Site Inspection Form Page 1 Project Name Permit # Inspection Date Time Name of Certified Erosion Sediment Control Lead (CESCL) or qualified inspector if less than one acre Print Name: Approximate rainfall amount since the last inspection (in inches): Approximate rainfall amount in the last 24 hours (in inches): Current Weather Clear Cloudy Mist Rain Wind Fog A. Type of inspection: Weekly Post Storm Event Other B. Phase of Active Construction (check all that apply): Pre Construction/installation of erosion/sediment controls Clearing/Demo/Grading Infrastructure/storm/roads Concrete pours Vertical Construction/buildings Utilities Offsite improvements Site temporary stabilized Final stabilization C. Questions: 1. Were all areas of construction and discharge points inspected? Yes No 2. Did you observe the presence of suspended sediment, turbidity, discoloration, or oil sheen Yes No 3. Was a water quality sample taken during inspection? (refer to permit conditions S4 & S5) Yes No 4. Was there a turbid discharge 250 NTU or greater, or Transparency 6 cm or less?* Yes No 5. If yes to #4 was it reported to Ecology? Yes No 6. Is pH sampling required? pH range required is 6.5 to 8.5. Yes No If answering yes to a discharge, describe the event. Include when, where, and why it happened; what action was taken, and when. *If answering yes to # 4 record NTU/Transparency with continual sampling daily until turbidity is 25 NTU or less/ transparency is 33 cm or greater. Sampling Results: Date: Parameter Method (circle one) Result Other/Note NTU cm pH Turbidity tube, meter, laboratory pH Paper, kit, meter Construction Stormwater Site Inspection Form Page 2 D. Check the observed status of all items. Provide “Action Required “details and dates. Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 1 Clearing Limits Before beginning land disturbing activities are all clearing limits, natural resource areas (streams, wetlands, buffers, trees) protected with barriers or similar BMPs? (high visibility recommended) 2 Construction Access Construction access is stabilized with quarry spalls or equivalent BMP to prevent sediment from being tracked onto roads? Sediment tracked onto the road way was cleaned thoroughly at the end of the day or more frequent as necessary. 3 Control Flow Rates Are flow control measures installed to control stormwater volumes and velocity during construction and do they protect downstream properties and waterways from erosion? If permanent infiltration ponds are used for flow control during construction, are they protected from siltation? 4 Sediment Controls All perimeter sediment controls (e.g. silt fence, wattles, compost socks, berms, etc.) installed, and maintained in accordance with the Stormwater Pollution Prevention Plan (SWPPP). Sediment control BMPs (sediment ponds, traps, filters etc.) have been constructed and functional as the first step of grading. Stormwater runoff from disturbed areas is directed to sediment removal BMP. 5 Stabilize Soils Have exposed un-worked soils been stabilized with effective BMP to prevent erosion and sediment deposition? Construction Stormwater Site Inspection Form Page 3 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 5 Stabilize Soils Cont. Are stockpiles stabilized from erosion, protected with sediment trapping measures and located away from drain inlet, waterways, and drainage channels? Have soils been stabilized at the end of the shift, before a holiday or weekend if needed based on the weather forecast? 6 Protect Slopes Has stormwater and ground water been diverted away from slopes and disturbed areas with interceptor dikes, pipes and or swales? Is off-site storm water managed separately from stormwater generated on the site? Is excavated material placed on uphill side of trenches consistent with safety and space considerations? Have check dams been placed at regular intervals within constructed channels that are cut down a slope? 7 Drain Inlets Storm drain inlets made operable during construction are protected. Are existing storm drains within the influence of the project protected? 8 Stabilize Channel and Outlets Have all on-site conveyance channels been designed, constructed and stabilized to prevent erosion from expected peak flows? Is stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes and downstream conveyance systems? 9 Control Pollutants Are waste materials and demolition debris handled and disposed of to prevent contamination of stormwater? Has cover been provided for all chemicals, liquid products, petroleum products, and other material? Has secondary containment been provided capable of containing 110% of the volume? Were contaminated surfaces cleaned immediately after a spill incident? Were BMPs used to prevent contamination of stormwater by a pH modifying sources? Construction Stormwater Site Inspection Form Page 4 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 9 Cont. Wheel wash wastewater is handled and disposed of properly. 10 Control Dewatering Concrete washout in designated areas. No washout or excess concrete on the ground. Dewatering has been done to an approved source and in compliance with the SWPPP. Were there any clean non turbid dewatering discharges? 11 Maintain BMP Are all temporary and permanent erosion and sediment control BMPs maintained to perform as intended? 12 Manage the Project Has the project been phased to the maximum degree practicable? Has regular inspection, monitoring and maintenance been performed as required by the permit? Has the SWPPP been updated, implemented and records maintained? 13 Protect LID Is all Bioretention and Rain Garden Facilities protected from sedimentation with appropriate BMPs? Is the Bioretention and Rain Garden protected against over compaction of construction equipment and foot traffic to retain its infiltration capabilities? Permeable pavements are clean and free of sediment and sediment laden- water runoff. Muddy construction equipment has not been on the base material or pavement. Have soiled permeable pavements been cleaned of sediments and pass infiltration test as required by stormwater manual methodology? Heavy equipment has been kept off existing soils under LID facilities to retain infiltration rate. E. Check all areas that have been inspected. All in place BMPs All disturbed soils All concrete wash out area All material storage areas All discharge locations All equipment storage areas All construction entrances/exits Construction Stormwater Site Inspection Form Page 5 F. Elements checked “Action Required” (section D) describe corrective action to be taken. List the element number; be specific on location and work needed. Document, initial, and date when the corrective action has been completed and inspected. Element # Description and Location Action Required Completion Date Initials Attach additional page if needed Sign the following certification: “I certify that this report is true, accurate, and complete, to the best of my knowledge and belief” Inspected by: (print) (Signature) Date: Title/Qualification of Inspector: SEDIMENT POND SIZING CALCULATIONS Project Name: Date:08/15/24 Street Location: Our Job No.:23194 Municipality: Engineer: FS =2 Q2 =2.4812 cfs WWHM VS =0.00096 ft/s SA = 5169.17 ft2 Convergent Energy and Power 16220 Railway Road SE City of Yelm Aspen Lee Minimum Area of Sediment Trap = 5,170 ft2 Page 1 of 1 23194-Sediment Trap Sizing Page 1 of 1 23194-Sediment Trap Sizing 23194.001-SSP.doc 7.0 SPECIAL REPORTS AND STUDIES This section contains the following information: Figure 7.1 – Geotechnical Memo for Infiltration Rates dated August 8, 2024 3 Convergent Energy and Power 7 Times Square I Suite 3504 I New York, NY 10036 M: 360.941.4134 convergentep.com From: Scott Riegel <scottr@esnw.com> Sent: Thursday, August 8, 2024 7:17 AM To: Brandon Summers <bsummers@convergentep.com> Cc: John Neer <johnn@esnw.com> Subject: Re: PSE Site Work ES-9923/9924 Hi Brandon, We completed fieldwork on both Rochester and Yelm sites and are proceeding with lab testing and report preparation. Below is a quick summary of conditions encountered at each site. ES-9923 Rochester, WA Soil conditions were explored at 8 locations. Soils consisted of topsoil about 6 - 10 inches thick that transitioned to recessional outwash sand and gravel layers. Maximum depth was controlled largely by caving of the cohesionless soils to a depth of 10 feet below existing grade and no groundwater was observed. Soils are suitable for conventional foundations. Infiltration testing was completed within the undisturbed outwash soils and we measured rates of 134.7 iph (constant) and 129 iph (falling) at the first location and at the second location, we measured rates of 58.7 iph (constant) and 50.5 iph (falling). These are unfactored rates and a preliminary design infiltration rate of 20 in/hr may be used for screening purposes. ES-9924 Yelm, WA Soil conditions were explored at 8 locations. Soils consisted of topsoil about 6 - 10 inches thick that transitioned to recessional outwash sand and gravel layers. Maximum depth was controlled largely by caving of the cohesionless soils to a depth of eight feet below existing grade and no groundwater was observed. Soils are suitable for conventional foundations. Infiltration testing was completed within the undisturbed outwash soils and measured rates of 194.3 iph (constant) and 257.2 iph (falling) at the first location and we measured rates of 71.6 iph (constant) and 60.9 iph (falling) at the second location. These are unfactored rates and a preliminary design infiltration rate of 24 in/hr may be used for screening purposes. Hope this helps and let us know if you need additional information from the design team while we work on the reports. Thank you, Scott Riegel, L.G., L.E.G. Associate Principal Geologist Earth Solutions NW, LLC Puget Sound/Western WA: 15365 NE 90th St, Ste 100 • Redmond, WA 98052 • P (425) 449-4704 Tri-Cities/Eastern WA: 3130 Varney Ln, Ste 105 • Pasco, WA 99301 • P (509) 905-0275 scottr@esnw.com • C (206) 793-9044 This e-mail is intended for the use of the individual to whom it is addressed and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If the receiver of this e-mail is not the intended recipient or the employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. 23194.001-SSP.doc 8.0 OTHER PERMITS Other permits for this development will be provided in this section during Final Engineering Review. 23194.001-SSP.doc 9.0 OPERATIONS AND MAINTENANCE MANUAL An Operations and Maintenance Manual will be provided in this section during Final Engineering Review. 23194.001-SSP.doc 10.0 DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED FLOW CONTROL AND TREATMENT FACILITIES A declaration of covenant for privately maintained flow control will be provided in this section during Final Engineering Review. 23194.001-SSP.doc 11.0 DECLARATION OF COVENANT FOR PRIVATELY MAINTAINED ON-SITE STORMWATER MANAGEMENT BMPS A declaration of covenant for privately maintained on-site stormwater management BMPs will be provided in this section during Final Engineering Review. 23194.001-SSP.doc 12.0 BOND QUANTITIES WORKSHEET A completed Bond Quantities Worksheet will be provided in this section during Final Engineering Review.