75B - PH ADOPT RESO FOR PR NO 15-6827

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NT MENTS INITIAL STUDY/MITIGATED NEGATIVE DECLARATION FAIRVIEW BPIOGE REVLACEM REST TO STREET BEET) PROJECT L S A MAY 2020 (9Tx STREET To ANTx STREET) L, OLEGT SANTA ANAL CALIFOPHIA permit, groundwater would be tested and treated (as necessary) prior to release to surface waters to ensure that discharges do not exceed water quality limits specified in the permit. Therefore, with implementation of Mitigation Measures HYDRO-1 and HYDRO-2, the proposed Project would not violate any water quality standards or waste discharge requirements or otherwise substantially degrade surface or groundwater quality. Therefore, impacts would be less than significant with mitigation incorporated Expected pollutants of concern during operation of the proposed Project include suspended solids/sediment, nutrients, heavy metals, pathogens (bacteria/viruses), pesticides, oil and grease, toxic organic compounds, and trash and debris. The pollutants of concern for the Project are metals and oil and grease. The proposed Project would increase impervious surface area by approximately 8,500 sf (approximately 0.2 ac), which would increase the volume of runoff during a storm and more effectively transport pollutants to receiving waters. In addition, an increase in impervious surface area would increase the total amount of pollutants in the storm water runoff, which would increase the amount of pollutants discharged to downstream receiving waters. In order to avoid impacts to water quality during Project operation, the proposed Project would need to prepare and implement a Final (design -level) WQMP that specifies the Low Impact Development (LID) BMPs, Source Control BMPs, Site Design BMPs, and/or Treatment Control BMPs to be incorporated into Project design to reduce the discharge of pollutants of concern to the maximum extent practicable. LID BMPs mimic a project site's existing hydrology by using design measures that capture, filter, store, evaporate, detain, and infiltrate runoff, rather than allowing runoff to flow directly to piped or impervious storm drains. Source Control BMPs are preventative measures that are implemented to prevent the introduction of pollutants into storm water. Site Design BMPs are storm water management strategies that emphasize conservation and use of existing site features to reduce the amount of runoff and pollutant loading generated from a project site. Treatment Control BMPs are structural BMPs designed to treat and reduce pollutants in storm water runoff prior to release to receiving waters. Currently, proposed BMPs include a vegetated swale adjacent to Fairview Street in the Fairview Triangle rest area. Additional treatment BMPs to treat runoff from the bridge deck may be incorporated into the bridge design at a later date during final design and will need to be sized to treat runoff from new impervious surface. According to the Draft WQMP prepared for the proposed Project, proposed nonstructural Source Control BMPs include right-of-way landscape management, right-of-way litter control, right -of way catch basin inspection, and street sweeping. Structural source control BMPs include use of efficient irrigation systems and landscape design, water conservation, smart controllers, and source control. Mitigation Measure HYDRO-3 requires preparation of a Final WQMP that refines the BMPs during final design, consistent with the requirements above. The BMPs would target and reduce constituents of concern from transportation facilities in compliance with the North Orange County MS4 Permit requirements. In addition, infiltration of storm water could have the potential to affect groundwater quality in areas of shallow groundwater. Pollutants in storm water are generally removed by soil through absorption as water infiltrates. Therefore, in areas of deep groundwater, there is more absorption R:\WKE1702\ISMND\Fina1 ISMND\Fairview Street Bridge Final ISMND7,05S SS 1 3-57