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Stormwater Pollution Prevention Plan <br /> I <br /> In some cases, sediment discharge in concentrated runoff can be controlled using permanent <br /> I <br /> stormwater BMPs (e.g., infiltration swales, ponds, trenches). Sediment loads can limit the <br /> effectiveness of some permanent stormwater BMPs, such as those used for infiltration or <br /> biofiltration; however, those BMPs designed to remove solids by settling (wet ponds or sediment <br /> I ponds) can be used during the construction phase. When permanent stormwater BMPs will be <br /> used to control sediment discharge during construction, the structure will be protected from <br /> excessive sedimentation with adequate erosion and sediment control BMPs. Any accumulated <br /> I sediment shall be removed after construction is complete and the remainder of the site has <br /> been stabilized. <br /> I The following BMPs will be implemented as end-of-pipe sediment controls as required to meet <br /> permitted turbidity limits in the site discharge(s). Prior to the implementation of these <br /> technologies, sediment sources and erosion control and soil stabilization BMP efforts will be <br /> Imaximized to reduce the need for end-of-pipe sedimentation controls. <br /> I . Temporary Sediment Trap (BMP C240) <br /> I ■ Construction Stormwater Filtration (BMP C251) <br /> ■ Construction Stormwater Chemical Treatment(BMP C 250) (implemented <br /> Ionly with prior written approval from Ecology). <br /> 3.1.5 Element #5 — Stabilize Soils <br /> IExposed and unworked soils shall be stabilized with the application of effective BMPs to prevent <br /> erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be <br /> Iused on this project include: <br /> Temporary and Permanent Seeding (BMP C120) <br /> II <br /> • Mulching (BMP C121) <br /> II Dust Control (BMP C 140) <br /> Seedingshall occur on all areas to remain unworked pursuant to below. Dust shall be <br /> I controlled if construction occurs during the summer. Alternate soil stabilization BMPs are <br /> included in Appendix C as a quick reference tool for the onsite inspector in the event the BMP(s) <br /> listed above are deemed ineffective or inappropriate during construction to satisfy the <br /> requirements set forth in the General NPDES Permit (Appendix D). To avoid potential erosion <br /> Iand sediment control issues that may cause a violation(s) of the NPDES Construction <br /> Stormwater permit (as provided in Appendix D), the Certified Erosion and Sediment Control <br /> I Lead will promptly initiate the implementation of one or more of the alternative BMPs listed in <br /> Appendix C after the first sign that existing BMPs are ineffective or failing. <br /> I The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain <br /> exposed and unworked for more than 7 days during the dry season (May 1 to September 30) <br /> and 2 days during the wet season (October 1 to April 30). Regardless of the time of year, all <br /> I soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on <br /> weather forecasts. <br /> I6 16580.006.doc <br />