3313 SMITH AVE 2018-01-01 MF Import

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