819 N BROADWAY WASHINGTON STATE UNIVERSITY 2018-05-11

ON-SITE STORMWATER MANAGEMENT BMPS The City of Everett's Stormwater Manual requires on-site BMPs to be implemented to the maximum extent feasible, per Minimum Requirement No. 5, On-Site Stormwater Management. After evaluation of the BMPs, it has been determined that dispersion and soil quality BMPs are feasible for this project site. Due to the poor infiltration capacity of the soil, infiltration is not feasible. BMP 12.70: Sheet Flow Dispersion will be implemented on the southeast portion of the site by dispersing runoff from a portion of the pavement into the landscaped area. Also, the soil in the landscaped areas will be amended to comply with BMP 12.20. STORMWATER CONVEYANCE The proposed development includes drainage infrastructure to intercept on-site flows and route them to the proposed detention pond. The conveyance system on the site was sized to safely convey the 25-year, peak flow using the Rational Method. The storm drainage design is shown on the project plans and the capacity calculations are included in Appendix C. 4. Construction Stormwater Pollution Prevention Plan A Construction Stormwater Pollution Prevention Plan (C-SWPPP) is required for this project because the total disturbed area during construction is greater than the 1-acre threshold. A NPDES permit is not required because the project site discharges to the combined sewer; however, the C-SWPPP is independently required by the City of Everett. This report includes a summary of the C-SWPPP (this section) and a copy of the Stormwater Pollution Prevention Plan (see Appendix D). Stormwater Pollution Prevention (SWPP) measures will be provided in accordance with Washington State Department of Ecology (DOE) and City of Everett standards. The project site will have construction fencing set around the perimeter of the site to mark disturbance limits. Temporary construction entrances will be field located to provide access to the sites. Straw wattles or silt fences will be installed on the downhill side of the project sites to prevent sediment leaving the construction area. Catch basin and inlet protection will be installed in all nearby catch basins and inlets. Interceptor ditches with check dams will be placed on the perimeter of the site if needed to convey construction stormwater to a sediment pond. 5. Source Control Plan The Source Control Plan for this project is designed to identify specific activities that may cause negative impacts to stormwater quality and provide mitigation for these impacts. The completed Source Control Worksheet(see Appendix E) identifies the following activity as applicable to this site: • A3.2: Concrete and Asphalt Handling at Construction Sites • A3.6: Landscaping and Vegetation Management Activities • A6.1: Dust Control at Disturbed Land Areas • A7.12: Maintenance of Stormwater Drainage Facilities WSU North Puget Sound at Everett—City of Everett 3