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1� contain impermeable pond liners to directly prevent infiltration of pond water to groundwater, and thereby also prevent the migration of potential groundwater pollutants into the subsurface,as could otherwise occur if infiltration were not prevented. Failure of the proposed lining, however,could result in significant impacts to groundwater quality. Further, siting of the proposed stormwater infiltration basins in areas where existing surface or subsurface contamination is located could result in the further migration of such contamination, deeper into the subsurface, potentially resulting in increased rates of groundwater degradation. In particular, infiltration facilities sited within the former cheese production facility wastewater pond areas could result in the mobilization of additional nitrate and total dissolved solids (salts)into underlying groundwater,resulting in increased pollutant levels within groundwater underlying the project site and adjacent areas. The proposed onsite stormwater system would be sufficient to contain a 100-year storm event at the project site,with nearly 10 acre-feet of additional storage available Industrial wastewater would also be treated and evaporated onsite, with no discharge to surface waters required. Therefore,implementation of the proposed project would result in installation of sufficient onsite stormwater and drainage control facilities to handle anticipated runoff rates without discharging water from the project site, and without contributing to downstream or offsite flooding. However, finalized designs for the proposed stormwater basins have not yet been completed and so the project could increase the potential for flooding, erosion,or siltation onsite and offsite due to altered drainage patterns as a result of the increased level of facility operations, or result in increased stormwater flows that could exceed the drainage system capacity. The project would make a cumulatively considerable contribution to significant cumulative impacts related to hydrologic resources and flooding. Findings The County finds that, pursuant to Section 15091(a)(1) of the CEQA Guidelines, changes or alterations have been required in or incorporated into the project, which mitigate or avoid potential impacts associated with erosion and/or siltation, on or offsite flooding, exceedances of storm drainage system capacity and additional sources of polluted runoff as identified in the Final EIR.The County further finds that the change or alteration in the project or the requirement to impose the mitigation as a condition of project approval is within the jurisdiction of the County to require,and that this mitigation is appropriate and feasible. Facts in Support of Findings Potential impacts from the failure of impermeable liners in proposed evaporation ponds,designed to prevent infiltration of pond water to groundwater, will be less than significant with implementation of Mitigation Measure HYDRO-1,which would require that all ponds be double-lined with impermeable material and fitted with an automatic leak detection system between the two layers of impermeable material. Monitoring for leak detection shall be completed (automatically) on a continuous basis throughout the duration of project operations. In the event a leak is detected,the applicant shall ensure the pond is drained and not used until the liner is repaired and shall notify appropriate response and regulatory agencies. Potential impacts from the siting of the proposed stormwater infiltration basins in areas where existing surface or subsurface contamination is located will be less than significant with implementation of Mitigation Measure HAZARDS- 2, which requires that applicant shall ensure the completion of remediation of soils conditions within such ponds under the regulatory oversight of the RWQCB. Potential impacts associated with flooding, erosion, or siltation onsite and offsite due to altered drainage patterns as a result of the project will be less than significant with implementation of Mitigation Measure HYDRO-2, which requires that the applicant submit a comprehensive onsite grading,drainage, and erosion control plan ("drainage plan' for the project to the San Joaquin County Public Works Department for approval,and ensure that all recommendations of the drainage plan are implemented. The project's contribution to cumulative hydrology and water quality impacts will be less than significant with implementation of Mitigation Measure HYDRO-3, which in turn requires the implementation of Mitigation Measures HYDRO-1 and HYDRO-2. Findings of Fact/ 12 November 2012 Statement of Overriding Considerations