20A - AA FIRST ST BRIDGE REPLACEMENT PROJECT

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LSA ASSOCIATES, INC. INITIAL STUDYIMITIGATED NEGATIVE DECLARATION JULY 2010 FIRST STREET BRIDGE REPLACEMENT PROJECT CITY OF SANTA ANA Less than significant impact with mitigation. Construction. During construction activities, excavated soil would be exposed, and there would be an increased potential for soil erosion due to rainfall/runoff and wind compared to existing conditions. The disturbed soil area during construction of the project would be approximately 0.33 ac. In addition, chemicals, liquid products, petroleum products (such as paints, solvents, and fuels), and concrete-related waste may be spilled or leaked and have the potential to be transported via storm runoff into receiving waters. Dewatering of groundwater is not anticipated during construction. Construction impacts would be minimized through implementation of Erosion and Sediment Control Best Management Practices (BMPs), as well as BMPs that control other potential construction-related pollutants. As specified in Mitigation Measure WQ-1, an Erosion Control Plan would be prepared for the proposed project and would specify the specific BMPs, such as sand bags, to be implemented during construction. The Erosion Control Plan would ensure the implementation and maintenance of BMPs to reduce or eliminate sediment, pollutants adhering to sediment, and other nonsediment pollutants in storm water as well as non-storm water discharges. Operation. Pollutants of concern during operation of a transportation facility include sediments, trash, petroleum products, metals, and chemicals. Because the project would widen First Street and the First Street Bridge, it would result in a permanent increase of impervious surfaces and a permanent increase in runoff and pollutant loading. The project would increase the impervious surface area by approximately 0.30 ac compared to the existing roadway facility. An increase in impervious area would increase the volume of runoff during a storm, which would more effectively transport pollutants to receiving waters. Proposed conditions would follow the drainage pattern of the existing conditions. Currently there are no Treatment BMPs within the project area, and runoff from the project area is untreated. In order to prevent degradation of receiving water quality with construction of the proposed project, the City would implement Source Control, Site Design, and Treatment Control BMPs, consistent with the Orange County Drainage Area Management Plan (DAMP) and the City's Local Implementation Plan (LIP). Implementation of these BMPs is specified in Mitigation Measure WQ- 2. Proposed Source Control BMPs include common area landscape management, BMP maintenance, storm drain stenciling, and slope protection and energy dissipation. Proposed Site Design BMPs include minimizing impervious areas and connectivity. Proposed Treatment Control BMPs include a biofiltration swale and catch basin inserts. The proposed Treatment Control BMPs would target sediment, heavy metals, organic compounds, trash and debris, oil and grease, and bacteria and viruses. The biofiltration Swale would be located in the southwest portion of the project area, within the landscaped area. The catch basin inserts would be installed in the existing catch basins located on the east side of North Harper Street and West First Street and on the south side of West First Street and North Gunther Place. With incorporation of construction and postconstruction BMPs, as specified in Mitigation Measures WQ-1 and WQ-2, impacts related to waste discharge requirements and water quality standards would be reduced to less than significant levels. 07/25/10 ,TA\DMJ0701\MND\4.0 Environmental Analysis.doc» 4-21 20A-72