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t <br /> Stormwater Technical Memo <br /> � Project: 20090010 SN�ift Bus Rapid Transit <br /> Northern Terminal at Everett Station <br /> Perteet <br /> TO: GcorRc F3axtcr, Evcrett Transit <br /> CC: Filc <br /> FROM: Erik F.mcrson, PF. <br /> DA'I'E: May 13,2009 <br /> RF.: Documcntation of Storm���atcr Standards Compliancc <br /> The Swift Bus Rapid Transit (BRT) North End Station will be constructed in a portion of <br /> the Everett Station comptex south of the existing bus platform and west of the newly <br /> constr�cted Sound Transit train platform. The purpose of this memorandum is to <br /> document the project's approach to storm water quality treatment and flow control <br /> requirements. No storm water mitigation facilities are proposed for the project due to the <br /> following: <br /> 1. The project lies within the North Everett combined sewer zone. Water quality <br /> treatment is therefore not required due to the treatment received in the City's <br /> sewer treatment plant. Detention is only required in this zone for pipe capacity <br /> issues. <br /> 2. The site currently drains to a detention faciiily installed during the construction of <br /> Everelt Stalion to mitigate capacity issues due to that projecL Since the BRT <br /> project lies within the limit of the original collection area (or this detention system <br /> lhe proposed developmenYs flow impacls have already been accounted for by <br /> the original project. <br /> 3. The sile is currently nearly 100% impervious.The project will not increase, and <br /> will likely show a minor reduction i�, lhe total impervious area on the site. Under <br /> City of Everett drainage code lhe project would not be required to provide <br /> improvements for treatment or detention because there is no increase in <br /> impervious area and c��respcndingly no increase in site runoff. <br /> 4. Sound Transit is compleling lhe conslruction of a parking lot and pedestrian <br /> overpass project within the bounds of the Everett Transit compiex. As part of this <br /> plan the BRT site was anticipated to be turned into a parking lot. Permits were <br /> issued for these improvements prior to the BRT project beginning. Since no <br /> additional storm waler improvements were required for the Sound Transit design <br /> it is assumed that the BRT project will not require them either. <br /> During preliminary design of the project the City of Everett indicated that this <br /> assessment appeared to be correct. At the time the City's main concern was the <br /> S��•ili 13R'I'North'fcmiinal:u l:��crctt Sta�ion Pagc 1 <br /> 1)ucumeiu:uion oCS�onuwater StanJ:vJs('mnplianee Slornn��ater Tcchnical Memo <br />