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7C Page 45 Practices (BMPs) for the control of point and non-point source pollutants in stormwater and constitute the Stormwafer Pollufion Prevention Plan (SWPPP). Project grading shail not commence (no grading permit shall be issued by the City} until an NPDES permit is issued, demonstrating that project erosion contro! and stormwater treatment measures, including the project SWPPP, meet SWRCB requirements. The praject shall be required to fiully implement the erasion con#rol and other water quality measures cited in the SWPPP and to monitor these measures during a speci�ied period foflowing completion of project construction. The RWQCB would be responsible for inspecting these measures, typically on an annuai basis, while the sponsor would be responsible for impiementing any remedial measures if the Board indicated that site stormwater quality objectives were not being met. The City Engineering Division would also be responsible for post-construction inspection of all measures that would eventually become part of the maintained infrastructure of the project, including source cantrol and water quality treatment measures. Findings: Implementation of these measures woufd reduce the construction- related soil erosion and sedimentation impacts to a less-than-significanf level. B. lncreased Starmwater Contaminant Laadinq — Poten#ial Violation ofi Water Qualitv Standards Potential Impact 9-2: The propased project would result in incremental increases in the stormwater contaminant loading far some heavy metals, as wel! as oil and grease and pesticide/herbicide residues. Project contaminant input could further impair the already impaired quafity of s#ormwater discharged to Redwood Creek, which has included (from variaus sources in the area} copper, hydrocarbons, PCBs, and DDTs in excess of EPA threshaids. This possible project effect is considered a potentially signifrcant impacf. Mitigation 9-2: Apply the following site-appropriate Best Management Practices (BMPs) or their equivalents as part of the project Stormwater Polfution Preventian Pfan (SWPPP), including measures required to comply with the C.3 regufations adopted as part of the San Mateo Countywide Stormwater Poflution Preven#ion Program (STOPPP), in arder to comply with #he requirements af the NPDES General Permit and imminen# updating of the Municipal Stormwater Permit fiar Redwood City: 1. Integrate start-at-the-source measures for stormwater control and treatment into the project stormwater drainage design. Such measures could include pervious parking lots, infiltration basins, vegetated (grass} swales ("bioswales"), or other measures designed to minimize stormwater runaff (through maximization af local infiltration and detention storage), settle out fine sediments, and filter contaminants. Oil/grease traps, sand filters, or similar in-line filtration systems for starm drain systems should also be considered. Such traps, filters, or sepa�ators must be accompanied by a clean out(maintenance program that ensures acceptable trap efficiencies, specifies appropriate disposal procedures, and reduces the risk that the traps become sinks for polfutants. 2. Institu#e a regular schedule of street and parking !ot sweeping. The frequency of cleaning shall be higher{twice manthiy} during the winter rainy season, yet mairttained ysar-round. Regular cleaning of paved surfaces reduce the "first flush" phenomenon wherein the highest concentration of contaminants are flushed off the surfaces during the early portion of a runoff ev�n#. Cleaning AttylResolReso.1772 24 1213D7