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STORMWATER SITE PLAN May 10,2017 <br /> OAKES AVENUE APARTMENTS PAGE 8 <br /> 1 <br /> SOILS DESCRIPTION <br /> A geotechnical report prepared for the site by GeoTest, Inc. dated December 09, 2016 and <br /> describes the soil as Vashon Till. A total of five test pits were explored to generally discover a <br /> thin layer of loose organic duff over Vashon Till. No seepage was observed in any of the test <br /> pits but seepage due to perched flow may be expected during wet weather construction. The <br /> geotech report and NRSC soil data are attached in the appendix. <br /> UPSTREAM ANALYSIS <br /> There is no upstream flow onto the site under existing conditions. Proposed conditions will <br /> grade a drive aisle and access to the north and receive approximately 430 sf of PGS from that <br /> drive aisle extension. <br /> The site essentially sheet flows east and contains walls along the north and south property <br /> lines. The west edge of the property is bound by Oakes Avenue with curb and gutter, no on-site <br /> flow is expected. <br /> DOWNSTREAM ANALYSIS <br /> The existing site sheetflows westerly towards the alley. Storm runoff is captured and conveyed <br /> into the combined sewer system. This site is considered new development and produces less <br /> than 5,000 sf of total new plus replaced hardscape which drains to the existing combination <br /> it sewer system. <br /> .This site is not expected to create or exacerbate.downstream conditions. <br /> P:\Work(Share le)'Proiectst20I6i16-208 Rainier Building Co\Cls\[)OCS\Drain,2017 05 10 16-20S Oakes Drain Rpt.doc <br />