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MAGNUSSON <br /> KLEMENCIC <br /> ASSOCIATES ■ <br /> boring depths explored, and are expected to consist of medium dense to very dense silty sand with <br /> varying amounts of gravel, hard silt, and clay. <br /> Perched groundwater was noted at depths of roughly 13 and 19 feet below existing grade for two <br /> exploratory borings. The regional groundwater table was not encountered. <br /> One key conclusion of the 2012 geotechnical report was that the anticipated subgrade of glacially <br /> consolidated soil is typically not suitable for infiltration,with an infiltration rate of less than 0.25 <br /> inches/hour; therefore a design infiltration rate of up to 0.20 inches/hour was recommended. As a <br /> result, infiltrating stormwater facilities have been considered infeasible for the North Site project. In <br /> addition, most existing landscape areas have underdrains, likely in reaction to observed ponding or <br /> muddy areas on the existing site,further emphasizing this absence of infiltration. <br /> GROUND COVER <br /> The existing site is covered by a variety of materials. Existing impervious areas include the CUP building, <br /> asphalt pavement, a small amount of concrete pavement, and concrete sidewalks. Various landscape <br /> areas make up the existing pervious areas and range from turf lawn and ground covers around the <br /> parking areas to well established shrubs and trees within the landscape buffer surrounding the site. <br /> Existing pervious and impervious surfaces are discussed in Section VIII, Permanent Stormwater Control <br /> Plan. <br /> CRITICAL AREAS <br /> There are no critical areas within or adjacent to the North Site project as defined by Chapter 37, Critical <br /> Areas, of the Everett Municipal Code. <br /> ADJACENT AREAS <br /> The existing buildings, parking facilities, and utility infrastructure, both on and adjacent to the project <br /> site, are shown on the site survey drawings in Appendix A. <br /> III. SITE DEVELOPMENT PLAN WITH ON-SITE <br /> STORMWATER MANAGEMENT <br /> PROJECT THRESHOLDS <br /> Threshold Discharge <br /> The project site discharges to a single drainage location and a single threshold discharge area. <br /> Impervious Surface <br /> The existing and proposed impervious areas for the North Site and clinic facility are summarized in <br /> Table 1. <br /> Storm Drainage Report <br /> 3 <br /> Providence Regional Medical Center Everett North Site, Everett, Washington <br />