20A - AA FIRST ST BRIDGE REPLACEMENT PROJECT

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LSA ASSOCIATES, INC. INITIAL STUDY/MITIGATED NEGATIVE DECLARATION JULY 2010 FIRST STREET BRIDGE REPLACEMENT PROJECT CITY OF SANTA ANA Mitigation Measures WQ-1 During final design, the City of Santa Ana shall prepare specifications for an Erosion Control Plan, to be included in the bid package that describes the best management practices (BMPs) to be implemented during construction. The BMPs shall include Erosion and Sediment Control BMPs from the California Stormwater Quality Association's Stormwater Best Management Practice Handbook - Construction. The City of Santa Ana shall ensure that the construction contractor implements and maintains the BMPs identified in the Erosion Control Plan during project construction. WQ-2 During final design, the City of Santa Ana shall prepare a Final Water Quality Management Plan (WQMP) that details the Source Control, Site Design, and Treatment Control BMPs to be incorporated into the proposed project. The BMPs shall be consistent with the Orange County Drainage Area Master Plan (DAMP) and City of Santa Ana Local Implementation Plan (LIP) and shall be properly designed, installed, and maintained to target pollutants of concern. The Source Control, Site Design, and Treatment Control BMPs shall include, but not be limited to, common area landscape management, BMP maintenance, storm drain stenciling, slope protection and energy dissipation, minimization of impervious areas and connectivity, a biofiltration swale, and catch basin inserts. B. Substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level (i.e., the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted)? Less than significant impact. The project does not require use of water from a groundwater well or aquifer; therefore, groundwater supplies would not be affected by the proposed project. Historically, groundwater has been encountered between 5 and 28 ft below ground surface (bgs). Groundwater is not anticipated to be encountered during construction of the proposed project; therefore, groundwater dewatering is not anticipated. The project proposes bridge replacement and street widening. These uses currently exist on the site and do not require provision of potable water. Consequently, the proposed project will also not require an additional provision of potable water. The project would result in an addition of 0.30 ac of impervious area on site due to the street widening and thus reducing the amount of area available for groundwater infiltration. The project site is not considered an important area for groundwater recharge due to its high level of development. Therefore, impacts to groundwater supply are considered less than significant, and no mitigation is required. C. Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of stream or river, in a manner, which would result in substantial erosion or sitation on or off-site? Less than significant with mitigation. As discussed in detail in VII1.A., during construction the project would be required to implement an Erosion Control Plan and implement Erosion and 07/25/10 ,P:\DMJ0701\MND\4.0 Environmental Analysis.doc» 4-22 20A-73