75A - PH BRISTOL ST MEMORY LN PROJECT

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ENVIRONMENTAL IMPACT REPORT ADDENDUM Bristol Street and Memory Lane Intersection Improvements — Proiect No. 17-6883 3.9 HYDROLOGY AND WATER QUALITY This section corresponds with the following 1990 FEIS/EIR, Section IV, Environmental Consequences and Mitigation Measures, subsections: • Subsection C, Erosion Impacts; • Subsection D, Floodplain/Floodivay Encroachment; and • Subsection F, Water Quality. Would theprojeetr a) Violate any water quality standards or waste discharge requirements? Under Section 402 of the Clean Water Act (CWA), the EPA has established regulations under the NPDES program to control direct storm water discharges. Should 1.0 acre or more of site disturbance occur, those activities would be subject to the NPDES program for the Santa Ana Regional Water Quality Control Board. The proposed Project would only impact approximately 0.39 acres, which is less than the 1.0 -acre threshold. Thus, the Project would not be subject to NPDES requirements, as potential waste discharge would be nominal. Furthermore, the Project would be required to comply with the 1990 FEIS/EIR Mitigation Measure C-2, involving the placement of straw or other suitable materials over uncovered soils, as needed, during street construction activities, further reducing the amount of erosion occurring at the Project site. Regarding operations, the Project would not increase the capacity of the roadway or the number of vehicles using the Project area. Therefore, impacts to water quality would be similar to those identified in the 1990 FEIS/EIR. Certified 1990 FEIS/EIR Mitigation Measures: Refer to 1990 FEIS/EIR Mitigation Measure C-2 Mitigation Measures: No additional mitigation measures are required. 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 (e.g., the production rate of pre-existing nearby wells would drop to a level that would not support existing land uses or planned uses for which permits have been granted)? The proposed Project would not result in increased water consumption and would not deplete groundwater supplies. No impact to groundwater supplies would result from the proposed Project. Impacts in this regard would not be greater than that previously analyzed in the 1990 FEIS/EIR. Certified 1990 FEIS/EIR Mitigation Measures: No 1990 FEIS/EIR mitigation measures are applicable. Mitigation Measures: No additional mitigation measures are required. C) Substantially alter the eeisting drainage pattern of the site or area, including through the alteration of the course of a strewn or river, in a manner that would result in substantial erosion or siltation on- or off-site? The proposed Project would only nominally increase the paved/impervious areas of the Project site. This nominal increase would not result in a substantial increase in erosion or siltation on- or off-site. Further, implementation of 1990 FEIS/EIR Mitigation Measure C-2 would reduce any potential erosion/siltation impacts during construction. Thus, impacts in this regard would not be greater than that previously analyzed in the 1990 FEIS/EIR. Certified 1990 FEIS/EIR Mitigation Measures: Refer to 1990 FEIS/EIR Mitigation Measure C-2 Mitigation Measures: No additional mitigation measures are required. Draft I November 2017 3-17 Environmental Consequences 75A-46