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Thomson Residence March 5, 2021 <br />Stormwater Site Plan Report Section III, Page 1 <br />Section III — Off -Site Analysis <br />Section III Summary <br />Task 1— Define and map the study area <br />Task 2 — Review all available information on the study area <br />Task 3 — Field inspect the study area <br />Task 4 — Describe the drainage system, and its existing and predicted problems <br />Task 1— Define and map the study area <br />An initial qualitative analysis shall document potential off -site impacts of stormwater discharges for each <br />upstream drainage system entering a site, and each downstream drainage system leaving a site according <br />to Section 1-2.6.2 of the 2014 SWMMWW. The downstream analysis shall extend from the project site to <br />the receiving water, or up to one -quarter mile, whichever is less. In this case, runoff from the project site <br />will be conveyed downstream in a combined sewer main from Thomson Ave to Crescent Ave, so one - <br />quarter mile will be the extend of the downstream analysis. <br />Task 2 — Review all available information on the study area <br />Runoff from the project will be conveyed to a detention tank with a flow control structure and an overflow <br />into the existing sewer main on Thomson Ave. From here, the combined sewer flows north on Thomson <br />Ave and then east on Crescent Ave through conveyance pipes and manholes. It reaches the quarter -mile <br />mark at the intersection of Grand Ave and 42"d St NE. Figure II-1 below was gathered from the Everett City <br />GIS Map and shows the project site and the quarter -mile mark. <br />C 250 4th Avenue South, Suite 200 <br />Edmonds, WA 98020 <br />ENGINEERING ph.425.778.8500 1 f.425,778.5536 <br />www.cgengineering.com <br />