3900 BROADWAY BASE FILE 2016-01-01 MF Import

� stopped. These fill soils are not suitable for shallow foundations and will require removal and replacement with sWctural fill for Floor slabs and paving. A detailed report of the geotechnical investigations is included in Appendix C. 1.3 �eveioped Conditions Summary The proposed development area of the site is approximately 5.11 acres, of which 53 percent is impervious surface. A new administration facility, along with pedestrian walks and plazas, vehicular parking, a�d associated utilides, will be constructed at this site. Stormwater runoff from the site will be conveyed in a series of catch basins and storm pipe to the two stormwater detention pipe systems, where it will outlet to an existing sanitary sewer mainline downstream of the projeR site. 2.O OFFSITE ANALYSIS 2.1 Downstream Analysis The project area has one drainage discharge location. Refer [o the Existing Conditions Map in Appendix A, Exhibit A-2. Stormwater runoff from the site sheet Flows to the northern edge of the site, where it is captured in a surface swale and routed to the sanit�+ry sewer mainline within the Memorial Stadium parking lot. See Exhibit A-2 in Appendix A for existing conditions. � 2.2 Mitigatian of Existing or Potential aroblems As described by City of Everett Public Works Department staff, the existing combined sewer system experiences capacity issues downstream of the project site. The City recently changed its stormwater management requirements to address these issues. The changes are outlined in the in[erim policy dated August 17, ZO11 which supersedes Public Works Policy #1-11 for stormwater control in Combined Sewer Areas. Stomiwater detention calculations included in Appendix B demonstrate that the proposed project meets the new management requirements and does �ot increase the potential for problems downstream. 2.3 Upstream Ar,alysis At the project site, stormwater runoff from upstream properties is collected and controlled before entering the project sife, and therefore is expected to be minimal. See the Developed Conditions Map in Appendix A for more information. 3.O ANALYSIS AND DESIGN OF REQUIRED EROSION AND SEDIME�iT CONTROL BEST MANAGEMENT PRACTICES (BMPS� All new development that includes land alteration activities of 1 acre or more requires specific erosion and sediment control. As the site is not located near a sediment/erosion sensitive feature, there are no special seasonal limitations for this project. 3.1 Construction Stormwater Pollution Prevention Plan (SWPPP) Elements 1 through 12 1. Mark Clearing Limiks—All areas to remain undisturbed during the construction of the project will be delineated prior to any site clearing or grading. Stormwater Site Ptan Report OQ00 Everett Schaol Distrrt ■ Community P.esource Cen[er 2 2083B7.10