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Targeted Drainage Report — Twentieth Ave Substation <br />WO# 100026553 <br />The subgrade will be proof -rolled to a firm non -yielding condition prior to granular fill <br />placement. The void storage is adequate to store the runoff and give it time to slowly <br />percolate into the below native soils. <br />In conclusion, the station yard and gravel perimeter will not function as an impervious <br />surface. <br />The project is subject to Minimum Requirements #1 through #5. <br />2.1 MINIMUM REQUIREMENT #1 —Preparation of Stormwater Site Plans <br />To comply with Minimum Requirement #1, information and analysis of the existing site conditions, a site <br />development layout, and an off -site analysis are provided in the following documents. The plans and reports are <br />prepared in accordance with SMMWW Volume I, Chapter 2. <br />• Site Plan, prepared by Sno. Co. PUD. <br />• SWPP Plan, prepared by Sno. Co. PUD. <br />• Grading and Drainage Plan, prepared by Sno. Co. PUD. <br />• Targeted Drainage Report, prepared by Sno. Co. PUD. <br />• Geotechnical Engineering Report, prepared by Converse Consultants NW <br />2.2 MINIMUM REQUIREMENT #2 —Construction Stormwater Pollution <br />Prevention Plan (SWPPP) <br />To comply with minimum requirement #2 the District has prepared a construction stormwater pollution <br />prevention plan (SWPPP) and addressed the 13 elements as follows: <br />Element #1- Preserve Vegetation/Mark Clearing Limits <br />Vegetation which may be left in place will be, the clearing limits will be identified by using a combination of high <br />visibility fencing and silt fence. <br />Element #2 — Establish Construction Access <br />The site will be accessed in a single location as depicted upon the SWPPP. The access will be stabilized by use of <br />rumble strips. Any tracking that happens will be swept daily or more often if required. <br />Element #3 — Control Flow Rates <br />Not applicable. We do not expect any properties downstream to be affected by the expansion of 20th Avenue <br />substation. <br />Element #4 — Install Sediment Controls <br />Sediment control will be established through the use of silt fence. <br />Element #5 — Stabilize Soils <br />Page 6 <br />