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

Everett School District —Bus Facility March 24, 2006 — Storm Drainage Report Page 8 IV. ANALYSIS AND DESIGN OF REQUIRED SEDIMENT CONTROL IiMP'S Erosion control measures for the project are expected to be minimal due to a generally Flat site and the large existing paved and gravel surfaces onsite. Erosion control measures will consist of silt fencing, catch basin inserts, Interceptor ditches, construction entrances and a sediment trap in the form of a vault. The proposed detention/wet vault will be constructed prior to site demolition and utilized as a sediment trap. The potential for sediment-laden water to leave the site is minimal since the most of the site improvements will be constructed in areas that are currently paved. Interceptor ditches will be provided to direct runoff during construction to sediment vault trap for temporary, central collection and to allow for settlement. Clean runoff will be directed or pumped into the wetland via the proposed outfall rock pad. The detention/wet vault will be cleaned as necessary during construction. The storm drainage collection and detention/wet vault will be cleaned prior to approval of the system for regular use. Silt fencing will be located just outside the perimeter of any clearing or grading activities where the topography of the site may allow construction runoff to leave the site. Approximate quantities for the area to be redeveloped as part of this project are 7,150 cubic yards for cut and 6,900 cubic yards for fill. Catch basin inserts shall be utilized and maintained in all proposed and existing catch basin structures on and near the site. Access to the site during construction will be from 80`" Street SW at the western most existing entrance at the north side of the site. A construction entrance will be installed at this entrance.