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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 measures that 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 measures which require that the 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 measures which requires that the applicant submit a comprehensive onsite grading, drainage, and erosion control plan ("drainage plan") for the project to the 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 these mitigation measures. The project's impact to hydrology and water quality has been identified as a potentially significant impact but will be reduced to a less than significant impact with the incorporation of the mitigation measures. Utilities and Service Systems The proposed project will include installation of an upgraded Industrial Wastewater Treatment Plant ("IWTP") located at the south end of the project site, near the proposed Maintenance Building. The IWTP will collect wash down and stormwater from areas with high potential for contamination, including the crane maintenance pad, the maintenance shop, the diesel fuel storage area, and the fueling and fuel pump areas. This water will be passed through an oil/water separator, and then discharged into a lined evaporation basin. Thus, water from the IWTP will not be discharged offsite, but will be contained in on- site facilities until evaporated. Potential leaching of water from the evaporation pond into the subsurface could carry with it various pollutants, including fuel and lubricant related pollutants, which could degrade groundwater quality and exceed wastewater treatment requirements of the RWQCB. Further, sewage from the existing Union Pacific facility is currently treated by a septic system and leach field located directly south of the existing Maintenance Building. With the proposed expansion, the Maintenance Building and Gate Building will be relocated. Thus, the septic system will also be relocated to serve the new Gate Building and Driver Kiosk to be located near Roth Road, and a new septic system will be constructed to serve the relocated Maintenance Building at the south end of the site. Although the proposed project will not be connected to a public sewer system, the operation of the proposed septic system could result in environmental impacts if not designed to adequately handle sewage generated by the project. In addition, stormwater from the project site will be channeled into a series of on-site stormwater retention and infiltration basins, and will result in no discharge of stormwater from the project site. Construction of the project will therefore result in on-site changes to stormwater flow paths and directions, and to the total volume of stormwater that is currently generated on-site. If these flows were improperly managed, they could result in the erosion and entrainment of soils and sediments on-site, and cause sedimentation within the proposed stormwater retention ponds. Potential impacts from exceedances of wastewater treatment requirements will be less than significant with implementation of mitigation measures which requires that all evaporation ponds be double-lined San Joaquin County PA-0900184 & 185\Union Pacific 11%w Community Development Page 13