819 N BROADWAY WASHINGTON STATE UNIVERSITY 2018-05-11

Stormwater Pollution Prevention Plan 3.1.5 Element#5—Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project include: • Plastic Covering(BMP C123) • Temporary Seeding (BMP C120) The topography of the site is relatively flat and will not trigger high amounts of erosion. Stabilization BMPs such as temporary seeding and/or plastic covering shall be implemented, as necessary,to prevent erosion on exposed soils. Alternate soil stabilization BMPs are included in Appendix C as a quick reference tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit(Appendix D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit(as provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix C after the first sign that existing BMPs are ineffective or failing. The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain exposed and unworked for more than 7 days during the dry season (May 1 to September 30) and 2 days during the wet season(October 1 to April 30). Regardless of the time of year, all soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather forecasts. In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. 3.1.6 Element#6—Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion. The following specific BMPs will be used to protect slopes for this project: • Interceptor Dike and Swale (BMP C200) • Check Dams (BMP C207) The topography of the site is relatively flat. Interceptor ditches and check dams will capture and convey stormwater away from slopes to minimize erosion. 8