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2020 0601 Stormwater Report STANDLEY GARAGE REDEVELOPMENT 402 WEST ROAD SE YELM WA 98597 Prepared For: Joe and Constance Standley 10627 11th Ave Ct SE Tacoma, WA 98444 Report Prepared By: J.E. Gibson Engineering and Consulting PO Box 178 Tenino, WA 98589 360.951.1454 Date Prepared Rev. June 1, 2020 December 2019 2 of 7 TABLE OF CONTENTS Stormwater Site Plan Cover Sheet ………………………………………………………………………………………………………………………………………..…1 Table of Contents ………….………………………………………………………………………………………………………………………2 Project Engineer’s Certification …..………………..………………………………………………………………………………………3 Section 1: Project Overview …………………………………………………………………………………………….……………………4 Section 2: Site Conditions ……………………………………………………………………………………………….…………….………5 Existing Site Conditions …………….…..…………………………………………………………………………………………5 Soils Information ………………..……………………………………………………………………………………………………5 Section 3: Off-site Analysis Report …………..……………………………………………………………………………………………5 Section 4: Permanent Stormwater Control Plan …………..……….……………………………………………………..………5 Summary Section ……………………………….………………………………………………………………………………………5 Performance Standards and Goals ……………..……………………………………………………………………………6 Low Impact Development Features ……………….…………………………………………………………………………6 Flow Control System …………………………………………………………………………………………………………………6 Water Quality System …………….…………………………………………………………………………………………………6 Section 5: Permits …………………..….……………………………………………………………..…………………………………………6 Section 6: Construction Stormwater Pollution Prevention Plan ……….……..………………………………………….…7 Appendices Appendix 1: Site Vicinity Map Appendix 2: Design Calculations Appendix 3: Soils Information Appendix 4: Construction Stormwater Pollution Prevention Plan Appendix 5: Operation and Maintenance Manual Appendix 6: TESC and Stormwater Plans PROJECT ENGINEER'S CERTIFICATION The technical material and data contained in these documents were prepared under the supervision and direction of the undersigned, whose seal, as a professional engineer to practice as such, is affixed below. 4'�� C -'j 2 C. 2 0 - o t- -- o� �i'm Gibson, PE Principal 3of7 Date Vol AS — V, 7 W , oc 42010 'PSitST�a�O 4 of 7 SECTION 1: PROJECT OVERVIEW This Stormwater Site Plan was prepared for the proposed commercial development project that will be located at 402 West Road SE, Yelm, WA 98597. The Stormwater Site Plan was prepared to comply with the minimum technical standards and requirements that are set forth in the 2012 Department of Ecology Stormwater Management Manual for Western Washington (SWMMWW) as Amended in December 2014 (The 2014 SWMMWW). The proposed commercial development will be constructed on Thurston County Tax Parcel No. 64303601500. Specifically, the proposed site improvements / construction activities include the following: Site preparation, grading, and erosion control activities Tenant improvements to an existing 2,520 ft2 shop Construction of an impervious surface parking lot Construction of on-site stormwater facilities Reconnection /extension of utilities (water, water, power, cable, etc.) The proposed project improvements will result in more than 5,000 ft2 of new impervious surface area. According to the SWMMWW, Minimum Requirements 1-9 need to be addressed. The following table summarizes how each requirement will be met. MINIMUM REQUIREMENT COMPLIANCE WITH MINIMUM REQUIREMENT #1 - Stormwater Site Plan The contents of this report and the enclosed plans are intended to satisfy this requirement. #2 - Construction SWPPP A Construction SWPPP has been prepared and is enclosed herein as an appendix. #3 - Source Control of Pollution If required, a Source Control Pollution Prevention Plan will be recorded against the property prior to certificate of occupancy. #4 - Drainage Path Preservation Preservation of the site’s previously established natural drainage paths will be maintained to the maximum extent practicable. #5 - Stormwater Management An on-site stormwater retention pond is being proposed; the LID Performance Standard will be met. #6 - Runoff Treatment Basic treatment is required for this project. The on-site stormwater retention pond will be lined with 18-inches of compost amended soils. #7 - Flow Control The on-site stormwater retention pond will infiltrate 100% of on-site generated parking lot runoff. Roof runoff will be routed to drywells. #8 - Wetlands Protection According to Thurston County GIS mapping, the site is not positioned in a mapped wetland. #9 - Operation & Maintenance An Agreement to Maintain Stormwater Facilities will be recorded against the property. Table 1: Compliance with Minimum Technical Requirements 5 of 7 SECTION 2: SITE CONDITIONS Existing Site Conditions The parcel area is approximately 0.50 acres and was previously a meat market. Tenant improvements to the renovate the former meat market into an auto-repair facility are being proposed. The renovation will include the removal of a portion of the building at the front of the structure. The proposed site improvements will disturb approximately 95% of the lot area. The site, generally, slopes in a south-to- north direction. There are no on-site wetlands and/or wetland buffers. According to Thurston County GIS mapping, the site is not positioned in the floodplain. Power will be provided by Puget Sound Energy. City of Yelm water and sewer facilities will be extended into the site. At the time of the project survey, there wasn’t any evidence to suggest that the site was or is being used as a solid waste dump site. Soils Information According to the USDA Natural Resources Conservation Service (NRCS), the on-site soil type is mapped as Spanaway gravelly sandy loam, which is hydrologically classified as a Type A soil. Spanaway gravelly sandy loam is a rapid draining soil type. According to the USDA NRCS, the Ksat infiltration rate ranges from two (2) inches/hour to six (6) inches/hour. Three (3) inches per hour was applied for the design of the on-site stormwater retention pond. The USDA NRCS soil data information is enclosed herein as an appendix. SECTION 3: OFF-SITE ANALYSIS AND REPORT On-site generated stormwater runoff from the proposed commercial development project will be routed to an on-site stormwater retention pond or below-grade infiltration drywells. Off-site discharge is not being proposed. Historic off-site drainage courses will not be altered. Consequently, downstream impacts are not anticipated. SECTION 4: PERMANENT STORMWATER CONTROL PLAN Summary Section An on-site stormwater retention pond will be constructed as a part of the site improvements. Stormwater runoff from the proposed on-site impervious surfaces will be routed to the retention pond. The following tables identifies the different land-type designations and their respective areas: LAND TYPE DESIGNATIONS AREA (ACRES)% OF TOTAL AREA Total Site Area 0.50 100.0% Proposed Impervious Surface Area 0.31 62.0% Proposed Roof Area 0.06 12.0% Proposed Parking Lot Area & Other Hardscapes 0.25 50.0% Proposed Landscaping & Storm Pond Area 0.19 38.0% Table 2: Land Type Designations Summary Table 6 of 7 Performance Standards and Goals Basic Treatment is required for the proposed site improvements. In addition, the on-site stormwater retention pond will need to meet the LID performance standard and Ecology’s flow duration standard. Low Impact Development Features The LID performance standard will be met for this project. Consequently, the construction of bioretention facilities, rain gardens, permeable pavement, etc. are not required for this project. Water Quality System According to Volume I, Section 2.5.6, of the SWMMWW, Basic Treatment is required for this project. Infiltration through the vertical profile of a bioretention soil mix is an acceptable method to satisfy Minimum Requirement No. 6. The retention pond will be lined with eighteen (18) inches of compost amended soils meeting the requirements of BMP T5.13 – Post Construction Soil Quality and Depth. Flow Control System The on-site stormwater retention pond has been designed in accordance with Volume III, Section 3.3, of the SWMMWW. Clear Creek’s 2012 Western Washington Hydrologic Modeling (WWHM) software was used to design the retention pond. 100% of the inflow runoff file from the parking lot and landscaped areas will be infiltrated. Off-site discharge is not proposed. The WWHM report is enclosed herein as an appendix. Below is a screenshot of the output file. Roof runoff will be routed to below-grade drywells. According to Volume III, Section 3.1.1, of the SWMMWW, twenty (20) linear feet of downspout infiltration trench is required per 1,000 square feet of roof area for course sands. The total proposed roof area is 2,520 square feet. Two infiltration trenches are proposed. Each proposed infiltration trench will be twenty-six (26) feet long. SECTION 5: PERMITS Building and Right-of-Way permits will need to be secured from the City of Yelm prior to beginning construction activities. 7 of 7 SECTION 6: CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN A Construction Stormwater Pollution Prevention Plan has been prepared in accordance with Volume II of the SWMMWW and is enclosed herein as an appendix. APPENDIX 1 SITE VICINITY MAP 8730 Tallon Lane NE, Suite 200  Lacey, WA 98516  Office 360.352.1465  Fax 360.352.1509  scjalliance.com N PROJECT LOCATION APPENDIX 2 DESIGN CACLUATIONS WWHM2012 PROJECT REPORT WWHM 6/1/2019 10:03:02 AM Page 2 General Model Information Project Name:WWHM Site Name: Site Address: City: Report Date:6/1/2019 Gage:Lake Lawrence Data Start:1955/10/01 Data End:2008/09/30 Timestep:15 Minute Precip Scale:0.857 Version Date:2017/04/14 Version:4.2.13 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year WWHM 6/1/2019 10:03:02 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Forest, Flat 0.5 Pervious Total 0.5 Impervious Land Use acre Impervious Total 0 Basin Total 0.5 Element Flows To: Surface Interflow Groundwater WWHM 6/1/2019 10:03:02 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 0.19 Pervious Total 0.19 Impervious Land Use acre PARKING FLAT 0.25 Impervious Total 0.25 Basin Total 0.44 Element Flows To: Surface Interflow Groundwater Trapezoidal Pond 1 Trapezoidal Pond 1 WWHM 6/1/2019 10:03:02 AM Page 5 Routing Elements Predeveloped Routing WWHM 6/1/2019 10:03:02 AM Page 6 Mitigated Routing Trapezoidal Pond 1 Bottom Length:23.00 ft. Bottom Width:23.00 ft. Depth:3 ft. Volume at riser head:0.0392 acre-feet. Infiltration On Infiltration rate:3 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):44.034 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):44.034 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 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:2 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 0.012 0.000 0.000 0.000 0.0333 0.012 0.000 0.000 0.037 0.0667 0.012 0.000 0.000 0.038 0.1000 0.012 0.001 0.000 0.038 0.1333 0.013 0.001 0.000 0.039 0.1667 0.013 0.002 0.000 0.040 0.2000 0.013 0.002 0.000 0.040 0.2333 0.013 0.003 0.000 0.041 0.2667 0.013 0.003 0.000 0.042 0.3000 0.014 0.003 0.000 0.042 0.3333 0.014 0.004 0.000 0.043 0.3667 0.014 0.004 0.000 0.044 0.4000 0.014 0.005 0.000 0.044 0.4333 0.015 0.005 0.000 0.045 0.4667 0.015 0.006 0.000 0.046 0.5000 0.015 0.006 0.000 0.046 0.5333 0.015 0.007 0.000 0.047 0.5667 0.016 0.007 0.000 0.048 0.6000 0.016 0.008 0.000 0.049 0.6333 0.016 0.009 0.000 0.049 0.6667 0.016 0.009 0.000 0.050 0.7000 0.017 0.010 0.000 0.051 0.7333 0.017 0.010 0.000 0.052 0.7667 0.017 0.011 0.000 0.052 0.8000 0.017 0.011 0.000 0.053 0.8333 0.018 0.012 0.000 0.054 WWHM 6/1/2019 10:03:02 AM Page 7 0.8667 0.018 0.013 0.000 0.055 0.9000 0.018 0.013 0.000 0.056 0.9333 0.018 0.014 0.000 0.056 0.9667 0.019 0.014 0.000 0.057 1.0000 0.019 0.015 0.000 0.058 1.0333 0.019 0.016 0.000 0.059 1.0667 0.019 0.016 0.000 0.060 1.1000 0.020 0.017 0.000 0.060 1.1333 0.020 0.018 0.000 0.061 1.1667 0.020 0.018 0.000 0.062 1.2000 0.020 0.019 0.000 0.063 1.2333 0.021 0.020 0.000 0.064 1.2667 0.021 0.021 0.000 0.065 1.3000 0.021 0.021 0.000 0.065 1.3333 0.022 0.022 0.000 0.066 1.3667 0.022 0.023 0.000 0.067 1.4000 0.022 0.024 0.000 0.068 1.4333 0.022 0.024 0.000 0.069 1.4667 0.023 0.025 0.000 0.070 1.5000 0.023 0.026 0.000 0.071 1.5333 0.023 0.027 0.000 0.072 1.5667 0.024 0.027 0.000 0.072 1.6000 0.024 0.028 0.000 0.073 1.6333 0.024 0.029 0.000 0.074 1.6667 0.025 0.030 0.000 0.075 1.7000 0.025 0.031 0.000 0.076 1.7333 0.025 0.032 0.000 0.077 1.7667 0.025 0.032 0.000 0.078 1.8000 0.026 0.033 0.000 0.079 1.8333 0.026 0.034 0.000 0.080 1.8667 0.026 0.035 0.000 0.081 1.9000 0.027 0.036 0.000 0.082 1.9333 0.027 0.037 0.000 0.083 1.9667 0.027 0.038 0.000 0.084 2.0000 0.028 0.039 0.000 0.085 2.0333 0.028 0.040 0.064 0.086 2.0667 0.028 0.041 0.182 0.087 2.1000 0.029 0.042 0.333 0.088 2.1333 0.029 0.043 0.509 0.089 2.1667 0.029 0.044 0.703 0.090 2.2000 0.030 0.045 0.907 0.091 2.2333 0.030 0.046 1.115 0.092 2.2667 0.030 0.047 1.318 0.093 2.3000 0.031 0.048 1.509 0.094 2.3333 0.031 0.049 1.683 0.095 2.3667 0.031 0.050 1.834 0.096 2.4000 0.032 0.051 1.960 0.097 2.4333 0.032 0.052 2.060 0.098 2.4667 0.032 0.053 2.138 0.099 2.5000 0.033 0.054 2.227 0.100 2.5333 0.033 0.055 2.300 0.101 2.5667 0.033 0.056 2.371 0.102 2.6000 0.034 0.057 2.439 0.103 2.6333 0.034 0.059 2.506 0.104 2.6667 0.034 0.060 2.571 0.105 2.7000 0.035 0.061 2.635 0.106 2.7333 0.035 0.062 2.697 0.107 2.7667 0.036 0.063 2.757 0.108 WWHM 6/1/2019 10:03:02 AM Page 8 2.8000 0.036 0.064 2.817 0.110 2.8333 0.036 0.066 2.875 0.111 2.8667 0.037 0.067 2.932 0.112 2.9000 0.037 0.068 2.988 0.113 2.9333 0.037 0.069 3.042 0.114 2.9667 0.038 0.071 3.096 0.115 3.0000 0.038 0.072 3.149 0.116 3.0333 0.039 0.073 3.201 0.117 WWHM 6/1/2019 10:03:02 AM Page 9 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.5 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.19 Total Impervious Area:0.25 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.000758 5 year 0.002105 10 year 0.00388 25 year 0.007924 50 year 0.013011 100 year 0.020811 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 Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1956 0.002 0.000 1957 0.001 0.000 1958 0.000 0.000 1959 0.000 0.000 1960 0.000 0.000 1961 0.002 0.000 1962 0.000 0.000 1963 0.000 0.000 1964 0.000 0.000 1965 0.000 0.000 WWHM 6/1/2019 10:03:24 AM Page 10 1966 0.000 0.000 1967 0.001 0.000 1968 0.000 0.000 1969 0.000 0.000 1970 0.000 0.000 1971 0.003 0.000 1972 0.005 0.000 1973 0.000 0.000 1974 0.001 0.000 1975 0.000 0.000 1976 0.001 0.000 1977 0.000 0.000 1978 0.001 0.000 1979 0.000 0.000 1980 0.000 0.000 1981 0.001 0.000 1982 0.001 0.000 1983 0.000 0.000 1984 0.000 0.000 1985 0.000 0.000 1986 0.001 0.000 1987 0.001 0.000 1988 0.000 0.000 1989 0.000 0.000 1990 0.003 0.000 1991 0.004 0.000 1992 0.000 0.000 1993 0.000 0.000 1994 0.000 0.000 1995 0.002 0.000 1996 0.006 0.000 1997 0.004 0.000 1998 0.001 0.000 1999 0.000 0.000 2000 0.000 0.000 2001 0.000 0.000 2002 0.003 0.000 2003 0.000 0.000 2004 0.025 0.000 2005 0.004 0.000 2006 0.018 0.000 2007 0.008 0.000 2008 0.000 0.000 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0253 0.0000 2 0.0182 0.0000 3 0.0078 0.0000 4 0.0060 0.0000 5 0.0053 0.0000 6 0.0043 0.0000 7 0.0041 0.0000 8 0.0040 0.0000 9 0.0033 0.0000 10 0.0029 0.0000 11 0.0026 0.0000 WWHM 6/1/2019 10:03:24 AM Page 11 12 0.0025 0.0000 13 0.0025 0.0000 14 0.0018 0.0000 15 0.0014 0.0000 16 0.0010 0.0000 17 0.0010 0.0000 18 0.0009 0.0000 19 0.0009 0.0000 20 0.0009 0.0000 21 0.0007 0.0000 22 0.0006 0.0000 23 0.0006 0.0000 24 0.0005 0.0000 25 0.0004 0.0000 26 0.0004 0.0000 27 0.0004 0.0000 28 0.0004 0.0000 29 0.0004 0.0000 30 0.0004 0.0000 31 0.0004 0.0000 32 0.0004 0.0000 33 0.0004 0.0000 34 0.0004 0.0000 35 0.0004 0.0000 36 0.0004 0.0000 37 0.0004 0.0000 38 0.0004 0.0000 39 0.0004 0.0000 40 0.0004 0.0000 41 0.0004 0.0000 42 0.0004 0.0000 43 0.0004 0.0000 44 0.0004 0.0000 45 0.0004 0.0000 46 0.0004 0.0000 47 0.0004 0.0000 48 0.0004 0.0000 49 0.0004 0.0000 50 0.0004 0.0000 51 0.0004 0.0000 52 0.0004 0.0000 53 0.0004 0.0000 WWHM 6/1/2019 10:03:24 AM Page 12 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0004 689 0 0 Pass 0.0005 148 0 0 Pass 0.0006 120 0 0 Pass 0.0008 98 0 0 Pass 0.0009 80 0 0 Pass 0.0010 61 0 0 Pass 0.0011 51 0 0 Pass 0.0013 48 0 0 Pass 0.0014 44 0 0 Pass 0.0015 38 0 0 Pass 0.0017 37 0 0 Pass 0.0018 33 0 0 Pass 0.0019 32 0 0 Pass 0.0020 30 0 0 Pass 0.0022 29 0 0 Pass 0.0023 27 0 0 Pass 0.0024 26 0 0 Pass 0.0025 22 0 0 Pass 0.0027 19 0 0 Pass 0.0028 18 0 0 Pass 0.0029 16 0 0 Pass 0.0031 16 0 0 Pass 0.0032 14 0 0 Pass 0.0033 13 0 0 Pass 0.0034 11 0 0 Pass 0.0036 9 0 0 Pass 0.0037 9 0 0 Pass 0.0038 9 0 0 Pass 0.0040 9 0 0 Pass 0.0041 8 0 0 Pass 0.0042 6 0 0 Pass 0.0043 5 0 0 Pass 0.0045 5 0 0 Pass 0.0046 5 0 0 Pass 0.0047 5 0 0 Pass 0.0048 5 0 0 Pass 0.0050 5 0 0 Pass 0.0051 5 0 0 Pass 0.0052 5 0 0 Pass 0.0054 4 0 0 Pass 0.0055 4 0 0 Pass 0.0056 4 0 0 Pass 0.0057 4 0 0 Pass 0.0059 4 0 0 Pass 0.0060 4 0 0 Pass 0.0061 3 0 0 Pass 0.0062 3 0 0 Pass 0.0064 3 0 0 Pass 0.0065 3 0 0 Pass 0.0066 3 0 0 Pass 0.0068 3 0 0 Pass 0.0069 3 0 0 Pass 0.0070 3 0 0 Pass WWHM 6/1/2019 10:03:24 AM Page 13 0.0071 3 0 0 Pass 0.0073 3 0 0 Pass 0.0074 3 0 0 Pass 0.0075 3 0 0 Pass 0.0077 3 0 0 Pass 0.0078 3 0 0 Pass 0.0079 2 0 0 Pass 0.0080 2 0 0 Pass 0.0082 2 0 0 Pass 0.0083 2 0 0 Pass 0.0084 2 0 0 Pass 0.0085 2 0 0 Pass 0.0087 2 0 0 Pass 0.0088 2 0 0 Pass 0.0089 2 0 0 Pass 0.0091 2 0 0 Pass 0.0092 2 0 0 Pass 0.0093 2 0 0 Pass 0.0094 2 0 0 Pass 0.0096 2 0 0 Pass 0.0097 2 0 0 Pass 0.0098 2 0 0 Pass 0.0099 2 0 0 Pass 0.0101 2 0 0 Pass 0.0102 2 0 0 Pass 0.0103 2 0 0 Pass 0.0105 2 0 0 Pass 0.0106 2 0 0 Pass 0.0107 2 0 0 Pass 0.0108 2 0 0 Pass 0.0110 2 0 0 Pass 0.0111 2 0 0 Pass 0.0112 2 0 0 Pass 0.0114 2 0 0 Pass 0.0115 2 0 0 Pass 0.0116 2 0 0 Pass 0.0117 2 0 0 Pass 0.0119 2 0 0 Pass 0.0120 2 0 0 Pass 0.0121 2 0 0 Pass 0.0122 2 0 0 Pass 0.0124 2 0 0 Pass 0.0125 2 0 0 Pass 0.0126 2 0 0 Pass 0.0128 2 0 0 Pass 0.0129 2 0 0 Pass 0.0130 2 0 0 Pass WWHM 6/1/2019 10:03:24 AM Page 14 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. WWHM 6/1/2019 10:03:24 AM Page 15 LID Report WWHM 6/1/2019 10:03:30 AM Page 16 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. WWHM 6/1/2019 10:03:30 AM Page 17 Appendix Predeveloped Schematic WWHM 6/1/2019 10:03:30 AM Page 18 Mitigated Schematic WWHM 6/1/2019 10:03:30 AM Page 19 Predeveloped UCI File WWHM 6/1/2019 10:03:30 AM Page 20 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 WWHM.wdm MESSU 25 MitWWHM.MES 27 MitWWHM.L61 28 MitWWHM.L62 30 POCWWHM1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 7 IMPLND 11 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 *** 7 A/B, 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 *** 7 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 ********* WWHM 6/1/2019 10:03:30 AM Page 21 7 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 *** 7 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 7 0 5 0.8 400 0.05 0.3 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 7 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 7 0.1 0.5 0.25 0 0.7 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 7 0 0 0 0 3 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 11 PARKING/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 11 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 11 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 11 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 11 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** WWHM 6/1/2019 10:03:30 AM Page 22 # - # ***PETMAX PETMIN 11 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 11 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 7 0.19 RCHRES 1 2 PERLND 7 0.19 RCHRES 1 3 IMPLND 11 0.25 RCHRES 1 5 ******Routing****** PERLND 7 0.19 COPY 1 12 IMPLND 11 0.25 COPY 1 15 PERLND 7 0.19 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-007 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 *** <------><--------><--------><--------><--------><--------><--------> *** WWHM 6/1/2019 10:03:30 AM Page 23 1 1 0.01 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 0.012144 0.000000 0.000000 0.000000 0.033333 0.012356 0.000408 0.000000 0.037378 0.066667 0.012570 0.000824 0.000000 0.038025 0.100000 0.012786 0.001246 0.000000 0.038678 0.133333 0.013004 0.001676 0.000000 0.039336 0.166667 0.013223 0.002113 0.000000 0.040000 0.200000 0.013444 0.002558 0.000000 0.040669 0.233333 0.013668 0.003010 0.000000 0.041344 0.266667 0.013893 0.003469 0.000000 0.042025 0.300000 0.014119 0.003936 0.000000 0.042711 0.333333 0.014348 0.004410 0.000000 0.043403 0.366667 0.014579 0.004892 0.000000 0.044100 0.400000 0.014811 0.005382 0.000000 0.044803 0.433333 0.015045 0.005880 0.000000 0.045511 0.466667 0.015281 0.006385 0.000000 0.046225 0.500000 0.015519 0.006899 0.000000 0.046944 0.533333 0.015758 0.007420 0.000000 0.047669 0.566667 0.016000 0.007949 0.000000 0.048400 0.600000 0.016243 0.008487 0.000000 0.049136 0.633333 0.016489 0.009032 0.000000 0.049878 0.666667 0.016736 0.009586 0.000000 0.050625 0.700000 0.016984 0.010148 0.000000 0.051378 0.733333 0.017235 0.010718 0.000000 0.052136 0.766667 0.017488 0.011297 0.000000 0.052900 0.800000 0.017742 0.011884 0.000000 0.053669 0.833333 0.017998 0.012480 0.000000 0.054444 0.866667 0.018256 0.013084 0.000000 0.055225 0.900000 0.018516 0.013697 0.000000 0.056011 0.933333 0.018778 0.014318 0.000000 0.056803 0.966667 0.019041 0.014949 0.000000 0.057600 1.000000 0.019307 0.015588 0.000000 0.058403 1.033333 0.019574 0.016236 0.000000 0.059211 1.066667 0.019843 0.016893 0.000000 0.060025 1.100000 0.020114 0.017559 0.000000 0.060844 1.133333 0.020387 0.018234 0.000000 0.061669 1.166667 0.020661 0.018918 0.000000 0.062500 1.200000 0.020938 0.019611 0.000000 0.063336 1.233333 0.021216 0.020314 0.000000 0.064178 1.266667 0.021496 0.021026 0.000000 0.065025 1.300000 0.021778 0.021747 0.000000 0.065878 1.333333 0.022062 0.022478 0.000000 0.066736 1.366667 0.022347 0.023218 0.000000 0.067600 1.400000 0.022635 0.023967 0.000000 0.068469 1.433333 0.022924 0.024727 0.000000 0.069344 1.466667 0.023215 0.025496 0.000000 0.070225 1.500000 0.023508 0.026274 0.000000 0.071111 1.533333 0.023803 0.027063 0.000000 0.072003 1.566667 0.024099 0.027861 0.000000 0.072900 1.600000 0.024398 0.028669 0.000000 0.073803 1.633333 0.024698 0.029488 0.000000 0.074711 1.666667 0.025000 0.030316 0.000000 0.075625 1.700000 0.025304 0.031154 0.000000 0.076544 WWHM 6/1/2019 10:03:30 AM Page 24 1.733333 0.025610 0.032003 0.000000 0.077469 1.766667 0.025917 0.032862 0.000000 0.078400 1.800000 0.026227 0.033731 0.000000 0.079336 1.833333 0.026538 0.034610 0.000000 0.080278 1.866667 0.026851 0.035500 0.000000 0.081225 1.900000 0.027166 0.036400 0.000000 0.082178 1.933333 0.027483 0.037311 0.000000 0.083136 1.966667 0.027802 0.038233 0.000000 0.084100 2.000000 0.028122 0.039165 0.000000 0.085069 2.033333 0.028444 0.040107 0.064540 0.086044 2.066667 0.028769 0.041061 0.182234 0.087025 2.100000 0.029095 0.042025 0.333520 0.088011 2.133333 0.029422 0.043001 0.509662 0.089003 2.166667 0.029752 0.043987 0.703432 0.090000 2.200000 0.030084 0.044984 0.907676 0.091003 2.233333 0.030417 0.045993 1.115035 0.092011 2.266667 0.030752 0.047012 1.318080 0.093025 2.300000 0.031089 0.048043 1.509672 0.094044 2.333333 0.031428 0.049085 1.683468 0.095069 2.366667 0.031769 0.050138 1.834531 0.096100 2.400000 0.032111 0.051203 1.960035 0.097136 2.433333 0.032455 0.052279 2.060036 0.098178 2.466667 0.032802 0.053366 2.138326 0.099225 2.500000 0.033150 0.054465 2.227125 0.100278 2.533333 0.033500 0.055576 2.300165 0.101336 2.566667 0.033851 0.056699 2.370955 0.102400 2.600000 0.034205 0.057833 2.439693 0.103469 2.633333 0.034560 0.058979 2.506546 0.104544 2.666667 0.034917 0.060137 2.571662 0.105625 2.700000 0.035276 0.061307 2.635170 0.106711 2.733333 0.035637 0.062489 2.697182 0.107803 2.766667 0.036000 0.063683 2.757800 0.108900 2.800000 0.036365 0.064889 2.817115 0.110003 2.833333 0.036731 0.066107 2.875206 0.111111 2.866667 0.037099 0.067338 2.932146 0.112225 2.900000 0.037469 0.068581 2.988001 0.113344 2.933333 0.037841 0.069836 3.042832 0.114469 2.966667 0.038215 0.071103 3.096691 0.115600 3.000000 0.038590 0.072383 3.149630 0.116736 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 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 END MASS-LINK 2 WWHM 6/1/2019 10:03:30 AM Page 25 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 WWHM 6/1/2019 10:03:30 AM Page 26 Predeveloped HSPF Message File WWHM 6/1/2019 10:03:30 AM Page 27 Mitigated HSPF Message File WWHM 6/1/2019 10:03:30 AM Page 28 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2019; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com APPENDIX 3 SOILS INFORMATION Thurston County Area, Washington 110—Spanaway gravelly sandy loam, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 2ndb6 Elevation: 330 to 1,310 feet Mean annual precipitation: 35 to 65 inches Mean annual air temperature: 50 degrees F Frost-free period: 150 to 200 days Farmland classification: Prime farmland if irrigated Map Unit Composition Spanaway and similar soils: 100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Spanaway Setting Landform: Outwash plains, terraces Parent material: Volcanic ash over gravelly outwash Typical profile H1 - 0 to 15 inches: gravelly sandy loam H2 - 15 to 20 inches: very gravelly loam H3 - 20 to 60 inches: extremely gravelly sand Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat excessively drained Capacity of the most limiting layer to transmit water (Ksat): High (1.98 to 5.95 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Low (about 3.8 inches) Interpretive groups Land capability classification (irrigated): 3s Land capability classification (nonirrigated): 3s Hydrologic Soil Group: A Forage suitability group: Droughty Soils (G002XS401WA) Hydric soil rating: No Data Source Information Soil Survey Area: Thurston County Area, Washington Survey Area Data: Version 12, Sep 10, 2018 Map Unit Description: Spanaway gravelly sandy loam, 0 to 3 percent slopes---Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/15/2019 Page 1 of 1 Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/15/2019 Page 1 of 351987405198750519876051987705198780519879051988005198810519882051987505198760519877051987805198790519880051988105198820530380530390530400530410530420530430 530380 530390 530400 530410 530420 530430 46° 56' 32'' N 122° 36' 3'' W46° 56' 32'' N122° 36' 0'' W46° 56' 29'' N 122° 36' 3'' W46° 56' 29'' N 122° 36' 0'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 15 30 60 90 Feet 0 5 10 20 30 Meters Map Scale: 1:398 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Thurston County Area, Washington Survey Area Data: Version 12, Sep 10, 2018 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Mar 29, 2016—Oct 10, 2016 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/15/2019 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 110 Spanaway gravelly sandy loam, 0 to 3 percent slopes 0.6 100.0% Totals for Area of Interest 0.6 100.0% Soil Map—Thurston County Area, Washington Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/15/2019 Page 3 of 3 APPENDIX 4 CONSTRUCTION SWPPP STANDLEY GARAGE REDEVELOPMENT 402 WEST ROAD SE CONSTRUCTION SWPPP PREPARED BY J.E. GIBSON CONSULTING JUNE 2019 2 of 10 TABLE OF CONTENTS Construction Stormwater Pollution Prevention Plan Cover Sheet …………………………………………………………………………………………………………………………………………..1 Table of Contents ……………………………………………………………………………………………………………………………………2 Construction Stormwater Pollution Prevention Elements ……………………………………………………………………..3 Objective of the Stormwater Pollution Prevention Plan …………………………………………………………………..3 Summary of the Elements ……………………………………………………………………………………………………………….3 Element #1 – Mark Clearing Limits ………………………………………………………………………………………………3-4 Element #2 – Establish Construction Access …………………………………………………………………………………….4 Element #3 – Control Flow Rates …………………………………………………………………………………………………….4 Element #4 – Install Sediment Controls …………………………………………………………………………………………..4 Element #5 – Stabilize Soils …………………………………………………………………………………………………………….5 Element #6 – Protect Slopes ……………………………………………………………………………………………………………5 Element #7 – Protect Drain Inlets …………………………………………………………………………………………………….5 Element #8 – Stabilize Channels and Outlets ……..……………………………………………………………………………6 Element #9 – Control Pollutants ………………………………………………………………………………………………………6 Element #10 – Control Dewatering ………………………………………………………………………………………………….6 Element #11 – Maintain BMPs ………..………………………………………………………………………………………………7 Element #12 – Manage the Project …….………………………………………………………………………………………….7-8 Element #13 – Protection of Low Impact Development BMPs …………………………………………………………8 Project Description ……………………………………………………………………………………………………………………………….9 Location ………………………………………………………………………………………………………………………………………….9 Project Overview …………………………………………………………………………………………………………………………….9 Existing Site Conditions ………………………………………………………………………………………………………………………...9 Existing Drainage System ………………………………………………………………………………………………………………..9 Existing Topography and Vegetation ………………………………………………………………………………………………9 Adjacent Areas ………………………………………………………………………………………………………………………………………9 Critical Areas …………………………………………………………………………………………………………………………………………9 Soils ………………………………………………………………………………………………………………………………………………………9 Erosion Problem Areas …….………….….……………………………………………………………………………………………………10 Construction Phasing …………..………………………………………………………………………………………………………………10 Construction Schedule …………………..……………………………………………………………………………………………………10 Engineering Calculations ………………….………………………………………………………………………………………………….10 Site Plan ………………………………………………………………………………………………………………………………………………10 References ………………………………………………………………………………………………………………………………………….10 3 of 10 CONSTRUCTION STORMWATER POLLUTION PREVENTION ELEMENTS Objective of Stormwater Pollution Prevention Plan The purpose of a Construction Stormwater Pollution Prevention Plan (SWPPP) is to describe the potential for pollution problems during the duration of a construction project. The SWPPP also explains and illustrates the measures that may need to be taken on the construction site to control said problems. The SWPPP is a guideline for the Contractor to follow during the construction process to prevent erosion and migration of sediments. Erosion control measures are not limited to those that are identified in this SWPPP or on the temporary erosion and sediment control plans. Construction Best Management Practices (BMPs) shall be installed as necessary to meet the Department of Ecology’s guidelines for construction stormwater pollution prevention and the requirements that are set forth in the National Pollutant Discharge Elimination System (NPDES) Permit. This SWPPP was prepared in accordance to the established guidelines and BMPs that are set forth in Volume 2 of the 2014 Department of Ecology Stormwater Management Manual for Western Washington (SWMMWW). The SWMMWW describes the thirteen (13) elements of construction stormwater pollution prevention. The thirteen (13) elements include the following: Element 1 – Mark Clearing Limits Element 2 – Establish Construction Access Element 3 – Control Flow Rates Element 4 – Install Sediment Controls Element 5 – Stabilize Soils Element 6 – Protect Slopes Element 7 – Protect Drain Inlets Element 8 – Stabilize Channels and Outlets Element 9 – Control Pollutants Element 10 – Control Dewatering Element 11 – Maintain BMPs Element 12 – Manage the Project Element 13 – Protection of Low Impact Development BMPs Summary of Elements The BMPs listed in this report, or their equivalent, are required. Any revisions by the Contractor to the BMPs listed in the SWPPP shall be approved by the Engineer in writing. Thus, if the Contractor does not require a BMP or needs to modify a BMP, the Contractor shall document the reason(s) and present the documentation to the Engineer for approval. Element 1 - Mark Clearing Limits Prior to beginning land disturbing activities, which include site clearing and grading, the Contractor shall mark the clearing limits (including trees) that are to be preserved within the construction zone. High- visibility fences shall be installed/erected as shown on the temporary erosion and sediment control plan and in accordance with the landscaping plan. The following BMPs are applicable for this project. If the 4 of 10 following BMPs are not shown on the construction plan set, the Engineer reserves the right to direct the Contractor to install, construct, and/or implement said BMPs. BMP C101: Preserving Natural Vegetation BMP C103: High-Visibility Plastic or Metal Fence with Backup Support BMP C104: Stake and Wire Fence Element 2 - Establish Construction Access A stabilized construction entrance shall be constructed to minimize the tracking of sediment onto any public road. The stabilized construction entrance shall be constructed per the TESC plans and details and in accordance with the requirements of BMP C105. BMP C105: Stabilized Construction Entrance Element 3 - Control Flow Rates Properties and waterways downstream from the development site shall be protected from erosion due to increases in the volume, velocity, and/or peak flow rates of stormwater runoff from the project site. The following BMPs are applicable for this project. If the following BMPs are not shown on the construction plan set, the Engineer reserves the right to direct the Contractor to install, construct, and/or implement said BMPs. BMP C240: Sediment Trap BMP C241: Temporary Sediment Pond Element 4 - Install Sediment Controls Prior to leaving a construction site or prior to discharging into an infiltration facility, stormwater runoff must pass through a sediment pond or some other appropriate BMP for removal of sediments. Silt fencing and straw bale barriers shall be constructed as shown on the temporary and erosion sediment control plans. The following BMPs are applicable for this project. If the following BMPs are not shown on the construction plan set, the Engineer reserves the right to direct the Contractor to install, construct, and/or implement said BMPs. BMP C230: Straw Bale Barrier BMP C231: Brush Barrier BMP C232: Gravel Filter Berm BMP C233: Silt Fence BMP C234: Vegetated Filter Strip BMP C235: Straw Wattles BMP C240: Sediment Trap BMP C241: Temporary Sediment Pond BMP C251: Construction Stormwater Filtration 5 of 10 Element 5 - Stabilize Soils All exposed and unworked soils shall be stabilized by application of effective BMPs, which protect the soil from the erosive forces of raindrop impact, flowing water, and from wind erosion. From October 01 through April 30 of each calendar year, no soils shall remain exposed and unworked form more than two (2) days. From May 01 to September 30 of each calendar year, no soils shall remain exposed and unworked for more than seven (7) days. This condition applies to all on-site soils, whether at final grade or not. In areas where the on-site soils will remain unworked for more than the aforementioned time duration limits or have reached final grade, seeding and mulching shall be installed in accordance with BMP C120 and C121. Sod shall be installed in accordance with BMP C124 for disturbed areas that require immediate vegetative cover. Dust control shall be used as needed to prevent wind transport of dust from disturbed soil surfaces and in accordance with BMP C140. If the following BMPs are not shown on the construction plan set, the Engineer reserves the right to direct the Contractor to install, construct, and/or implement said BMPs. BMP C120: Temporary and Permanent Seeding BMP C121: Mulching BMP C123: Plastic Covering BMP C124: Sodding BMP C125: Topsoiling BMP C140: Dust Control Element 6 - Protecting Slopes Slopes shall be constructed in such a manner that will minimize erosion. This shall include, but is not limited to: placing excavated material on the uphill side of trenches, collecting drainage at the top of slopes, etc. If the following BMPs are not shown on the construction plan set, the Engineer reserves the right to direct the Contractor to install, construct, and/or implement said BMPs. BMP C200: Interceptor Dike and Swale BMP C205: Subsurface Drains BMP C206: Level Spreader BMP C207: Check Dams Element 7 - Protect Drain Inlets All storm drain catch basins/inlets that are in use during construction, as well as all existing structures within the project limits, shall be protected so that stormwater runoff shall not enter any conveyance system without first being filtered or treated to remove sediment from sediment laden runoff. Install storm drain inlet protection devices as shown on the erosion and sediment control plans and in accordance with BMP C220. BMP C220: Storm Drain Inlet Protection 6 of 10 Element 8 - Stabilize Channels and Outlets All temporary on-site conveyance channels shall be constructed and stabilized to prevent erosion. Stabilization that is adequate to prevent erosion of outlets and drainage channels shall be provided. If the following BMPs are not shown on the construction plan set, the Engineer reserves the right to direct the Contractor to install, construct, and/or implement said BMPs. BMP C202: Channel Lining BMP C209: Outlet Protection Element 9 - Control Pollutants All pollutants, including waste materials and demolition of debris, that are generated or brought on-site during construction activities shall be handled and disposed of in a manner that does not cause contamination of stormwater. Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drawdown, solvent and degreasing cleaning operations, fuel tank drawdown and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Emergency repairs may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle. Application of agricultural chemicals, including fertilizers and pesticides, shall be conducted in a manner and at application rates that will not result in loss of chemical(s) to stormwater runoff. Manufacturers’ recommendations shall be followed for application rates and procedures. The following Source Control BMPs will be prepared/implemented by the Contractor for this project. A Spill Prevention Plan Maintenance of storm drainage facilities Street sweeping at an interval that’s prescribed by the Engineer and/or the City of Centralia Element 10 - Control Dewatering All foundation, vault, and trench dewatering activities shall be routed to a sediment pond for basic filtering/treatment. Clean, non-turbid dewatered water, as determined by the Certified Professional in Erosion and Sediment Control, can be discharged to systems tributary to state surface waters, provided the dewatering flow does not cause erosion or flooding to receiving waters. Highly turbid or otherwise contaminated dewatered water that’s from construction equipment operation, clamshell digging, concrete tremie pour, or work inside a cofferdam, shall be handled separately from stormwater at the site. Some disposal options, depending on site constraints, may include: Transport off-site in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute State waters On-site treatment using chemical treatment or other suitable treatment technologies Sanitary sewer discharge with local sewer district’s approval if there is no other option 7 of 10 Element 11 - Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. All maintenance and repairs shall be completed in accordance with the practices, procedures, and materials for each respective BMP. Sediment Control BMPs shall be inspected weekly or after a runoff-producing storm event during the dry season and daily during the wet season. All temporary erosion and Sediment Control BMPs shall be removed within thirty (30) days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on-site. Disturbed soil areas resulting from removal of BMPs or vegetation shall be permanently stabilized. Element 12 - Manage the Project Phasing of Construction - the project shall be phased where feasible in order to prevent, to the maximum extent practicable, the transport of sediment from the site during construction. Revegetation of exposed areas and maintenance of said vegetation shall be an integral part of the clearing activities for each phase. Seasonal Work Limitations - from October 01 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt-laden runoff will be prevented from leaving the construction site. The following activities are exempt for the seasonal clearing and grading limitations: 1. Routine maintenance and necessary repair of erosion and sediment control BMPs. 2. Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to the soil. 3. Activities where there is 100% infiltration of surface runoff within the site in approved and installed erosion and sediment control facilities. Inspection and Monitoring - all BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. The Certified Professional in Erosion and Sediment Control for this project is ______________________________. ______________________________ shall be on-site or on-call at all times during construction. The role of the Certified Professional in Erosion and Sediment Control is to identify problems or failures of erosion control measures in the field and to promptly initiate corrective measures. The Certified Professional in Erosion and Sediment Control shall be compensated by the Contractor. Sampling and analysis of discharged stormwater from the construction site may be necessary to ensure compliance with the standards. 8 of 10 Whenever inspection and/or monitoring reveals that the BMPs identified in the Construction SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, the Construction SWPPP shall be modified, as appropriate, in a timely manner. Maintenance of the Construction SWPPP - the Construction SWPPP shall be retained on-site or within reasonable access to the site. The Construction SWPPP shall be modified whenever there is a significant change in the design, construction, operation, and/or maintenance of any BMP. Element 13 – Protect Low Impact Development BMPs Protect all biofiltration swale and detention pond BMPs from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the biofiltration swale and/or detention pond. Restore BMPs to their fully functioning condition if they accumulate sediment during construction. Restoring the BMP must include removal of sediment and any sediment-laden swale and/or pond soils, and replacing the removed soils with soils meeting the design specification. Prevent compacting the biofiltration soil and detention pond BMPs by excluding construction equipment and foot traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment. Keep all heavy equipment off existing soils under LID facilities that have been excavated to final grade to retain the infiltration rate of the soils. BMP C102: Buffer Zone BMP C103: High Visibility Fence BMP C200: Interceptor Dike and Swale BMP C201: Grass-Lined Channels BMP C207: Check Dams BMP C208: Triangular Silt Dike BMP C231: Brush Barrier BMP C233: Silt Fence BMP C234: Vegetated Strip 9 of 10 PROJECT DESCRIPTION Location The proposed commercial development project will be located at 402 West Road SE, Yelm, WA 98597. Project Overview The proposed site improvements / construction activities include the following: Site preparation, grading, and erosion control activities Tenant improvements to an existing 2,520 ft2 shop Construction of an impervious surface parking lot Construction of on-site stormwater facilities Reconnection /extension of utilities (water, water, power, cable, etc.) EXISTING SITE CONDITIONS Existing Drainage System There are existing catch basins and stormwater conveyance piping on-site that will be removed and/or abandoned as a part of the project improvements. There are no existing water quality and/or flow control facilities. Existing Topography & Vegetation The site slopes in a south-to-north direction. The site was previously developed and operated as a meat market. The site has prairie grass and a handful of mature on-site trees. ADJACENT AREAS The project site surrounded by other commercial and residential properties. CRITICAL AREAS According to best available information, there are no on-site critical areas. SOILS According to the USDA Natural Resources Conservation Service (NRCS), the on-site soil type is mapped as Spanaway gravelly sandy loam, which is hydrologically classified as a Type A soil. Spanaway gravelly sandy loam is a rapid draining soil type 10 of 10 EROSION PROBLEM AREAS Potential on-site erosion control problems are not anticipated for this project. CONSTRUCTION PHASING This project will be completed in one (1) phase. CONSTRUCTION SCHEDULE Anticipated construction activities and sequences are shown in the following table. CONSTRUCTION ACTIVITY ANTICIPATED DATE OF COMPLETION Contractor Notice to Proceed Summer 2019 Install Erosion Control Facilities Summer 2019 Begin Site Rough Grading Summer 2019 Begin Installing Site Utilities Summer 2019 Stabilize Site Fall 2019 Project Substantial Completion Fall 2019 Table 1: Anticipated Construction Schedule ENGINEERING CALCULATIONS Refer to this project’s Stormwater Site Plan for stormwater design calculations. SITE PLAN See the project’s storm and temporary erosion control plans REFERENCES Volume II of the 2014 Department of Ecology Stormwater Management Manual for Western Washington. APPENDIX 5 OPERATION AND MAINTENANCE MANUAL STANDLEY GARAGE REDEVELOPMENT 402 WEST ROAD SE MAINTENANCE PROGRAM PREPARED BY J.E. GIBSON CONSULTING JUNE 2019 TABLE OF CONTENTS Stormwater Facility Maintenance Program Cover Sheet …………………………………………..………………………………………………………………………………………………1 Table of Contents ………………….………………………………………………………………………………………………………………2 Estimate of Annual Maintenance Costs ……………….………………………………………………….……………………………3 Maintenance Plan Schedule …………………..………..……………………………………………………………………………………4 Location of Operations and Maintenance Manual ………………..……………..………………………………………………5 Written Description of Facilities …………………….………………………………………………………………………………………6 Required Recordkeeping and Reports ……………….……………………………………………………………………………………7 Maintenance Activity Log ………………………………………………………………………………………………………………………8 Site Plan …………………………………………..……………………………………………………………………………………………………9 Maintenance Program …………………………………………………………………………………..……………………………………10 ESTIMATE OF ANNUAL MAINTENANCE COSTS ITEM #DESCRIPTION QTY.UNIT COST / UNIT ANNUAL COST Stormwater Piping1. pipe jetting 40 LF $0.50 $20.00 Infiltration Pond2. Maintenance 1 LS $250.00 $250.00 Subtotal $270.00 Contingency @ 10%$30.00 Total $300.001 1 2019 Net Present Value MAINTENANCE PLAN SCHEDULE On-site drainage facilities, which include stormwater piping and catch basins, will require routine maintenance. The following pages contain maintenance needs for most of the components that are a part of this project’s drainage system, as well as for some components that the project may not have. The checklist should be completed for all system components in accordance with the following schedule: M. Monthly from October through April A. Annually, once in late summer (preferably September) S. Storm-based, after any major storm event (use 1-inch in 24-hours as a guideline) Using copies of these pages, check off the problems investigated each time an inspection was performed. Add comments on problems found and actions taken. Some items do not need to be looked at every time an inspection is done. Use the suggested frequency as a guideline for the inspection. The following governing jurisdictions may be called for technical assistance. CONTACT PHONE NUMBER City of Yelm Public Works (360) 458-8410 Department of Ecology Stormwater Division (360) 407-6438 LOCATION OF OPERATIONS AND MAINTENANCE MANUAL This manual will be kept on-site at 402 West Road SE, Yelm, WA 98597. The manual shall be made available to City of Yelm personnel upon request. WRITTEN DESCRIPTION OF FACILITIES The construction of water quality and flow control facilities were required for this project. The on-site stormwater facilities were designed from the technical guidance that is provided in the 2012 Department of Ecology Stormwater Management Manual for Western Washington as amended in December 2014. The on-site stormwater facilities were designed to reduce pollutant loads and concentrations in stormwater runoff as well as to mitigate, to the maximum extent practicable, the impacts of increased stormwater runoff volumes and flow rates to receiving waters. The project was graded in such a manner so as to maintain, to the maximum extent practicable, the existing landform. The on-site water quality facilities were designed to treat the minimum water quality flow rate and treatment volume from pollution generating impervious surface runoff. This project’s stormwater facilities include stormwater conveyance piping and catch basins. Refer to the Site Plan on page 9 for more information. REQUIRED RECORDKEEPING AND REPORTS If required, the Owner shall submit an annual report to the authority having jurisdiction by August 31st of each calendar year which will include, at a minimum, the following: Name, address, and telephone number of the person(s) responsible for plan implementation and the person(s) completing the report. Time period covered by the report. A chronological summary of activities conducted to implement the program(s) required by the Operations & Maintenance Plan. This information shall be logged in the logbook with any additional comments/narrative. For any activities that are completed by paid parties, include a copy of the invoice for services. An outline of planned activities for the next year. MAINTENANCE ACTIVITY LOG Maintenance ActivityMaintenance Activity LogStandley GarageDate SITE PLAN MAINTENANCE PROGRAM Inspection Period __________________________________________ Number of Sheets Attached __________________________________________ Date Inspected __________________________________________ Name of Inspector __________________________________________ Inspector’s Signature __________________________________________ APPENDIX 6 TESC AND STORMWATER PLANS