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Part 3 Stormwater Management Plan <br />Conceptual Drainage Plan <br />Stormwater drainage for the Phase 1 Division 12 impervious areas will be collected in <br />catch basins and conveyed via storm drainage pipes to the existing storm sewer <br />infrastucture. Integral to this stormwater management concept is the update to the <br />Master Drainage Plan for Phase 1. <br />The Phase 1 Division 12 project area soils are generally classified as Qgm — Bullfrog <br />Moraine (glacial moraine deposits), till, group C. <br />Infiltration and Detention Facilities <br />No major infiltration or detention facilities are proposed on site. The proposed project <br />will be conveyed to existing offsite stormwater control facilities. <br />Water Quality Treatment <br />Water quality treatment will be provided for runoff from impervious road and roof <br />surfaces requiring stormwater treatment. Treatment can be provided in one of several <br />Department of Ecology recommended treatment facility types. The water quality <br />treatment option proposed for the Suncadia site will be a stormfilter system. All water <br />quality facilities will be sized to treat the water quality storm. The water quality storm is <br />that storm for which all storms equal or smaller in size account for 90 percent of the <br />average annual runoff. For Phase 1, the water quality design storm is 1.68 inches in 24 - <br />hours. The water quality facility is described below. <br />Stormwater Management StormFilter System <br />Stormwater Management's StormFilter System is a Best Management Practice <br />(BMP) designed to meet most federal, state, and local requirements for treating <br />stormwater runoff in compliance with the Clean Water Act. The StormFilter, a <br />passive, flow-through, stormwater filtration system, improves the quality of <br />stormwater runoff from the urban environment before it enters receiving <br />waterways by removing non -point source pollutants, including sediment (TSS), oil <br />and grease, soluble metals, nutrients, organics, and trash and debris. <br />September 2016 Phase 1 Division 12 Engineering <br />Summary <br />Encompass Engineering & Surveying <br />