1304 80TH ST SW EVERETT SCHOOL DISTRICT 2018-01-02 MF Import

Everett School District— Bus Facility March 24, 2006 — Storm Drainage Report Page 4 Major site improvements for the Everett School District Bus Facility include construction of a large asphalt parking lot for buses and a stormwater system to collect, control, and treat runoff. Other major site improvements include a bus fueling/washing station located just south of the renovated bus driver building and necessary utilities to serve the building and bus fueling/washing station. The existing parking area just north of the renovated bus driver building will remain without any major alteration. The most significant stormwater related benefit of this project is the proposed stormwater flow control and water treatment for the entire developed site. Currently, the majority of runoff from existing roof, pavement, and gravel areas is collected and conveyed into the existing wetland at the northeast corner of the site without the benefit of stormwater treatment or flow dissipation at the outfall. The project area analyyred for flow cont of (further described in Section V. under Runoff Control Analysis) Includes approximately 5 acres. The project area consists of all land that will be cleared, disturbed or changes in land cover type under proposed conditions. The following table gives the proposed condition land use covers and respective Curve Numbers for the project area for Type'C' soils. Table 2. Developed Aiea 5 readsheet ( Site Drainage Area to Detention On Site Off Site Bypass Facility Type Area Acres Area Acres Area Acres Acres Impervious - Building Roofs, Asphalt and Concrete Pavement CN = 98 4.665 1 0 0.027 4.64 Pervious - Landscaping CN = 86 0.562 0.144 0.335 0.31 Sub-Total Drainage Area 5.227 0.144 0.362 5.01