3400 RIVERFRONT BLVD BASE FILE 2020-07-15

Stormwater Pollution Prevention Plan 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. 3.1.3 Element#3—Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. The specific BMPs for flow control that shall be used on this project include: No BMPs to be implemented No No BMPs are planned to control flow rates because the project is not creating any new impervious surface. Alternate flow control 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 NPDES Permit or the Construction Stormwater General Permit(Appendix D). To avoid potential erosion and sediment control issues that may cause a violation(s),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,the project must comply with Minimum Requirement 7 (Ecology 2005). In general, discharge rates of stormwater from the site will be controlled where increases in impervious area or soil compaction during construction could lead to downstream erosion, or where necessary to meet local agency stormwater discharge requirements. However based on the nature of the work, discharge rates are not expected to increase. 3.1.4 Element#4—Install Sediment Controls All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged to an infiltration facility. The specific BMPs to be used for controlling sediment on this project include: • Silt Fence (BMP C233) • Storm Drain Inlet Protection(BMP C220) 6