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i <br /> Stormwater Pollution Prevention Plan <br /> equipped with a floatable material separator and gas trap. Please see the stormwater plan and <br /> details on sheets C3 and C4 of the attached improvement plans. <br /> Construction activities will include site preparation, TESC installation,grading for the proposed <br /> building site and parking area, and paving for the proposed parking lot and sidewalks. The <br /> schedule and phasing of BMPs during construction is provided in Section 4.0. <br /> Stormwater runoff volumes were calculated using the Western Washington Hydrology Model <br /> (WWHM). Stormwater discharges match developed discharge durations to pre-developed <br /> durations for the range of pre-developed discharge rates from 50 percent of the two-year peak <br /> flow up to the full 50-year peak flow. <br /> The following summarizes details regarding site areas: <br /> • Total site area: 10.15 acres <br /> • Disturbed area during construction: 0.40 acres <br /> • Disturbed area that is characterized as impervious (i.e., <br /> access roads, staging,parking): 0.25 acres <br /> Basin A <br /> • 2-year stormwater runoff peak flow prior to construction <br /> (existing): 0.070 cfs <br /> • 10-year stormwater runoff peak flow prior to construction <br /> (existing): 0.121 cfs <br /> • 2-year stormwater runoff peak flow after construction: 0.030 cfs <br /> • 10-year stormwater runoff peak flow after construction: 0.056 cfs <br /> Grandview Apartments Clubhouse <br /> SWPPP 4 March,2017 <br />