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4. ENVIRONMENTAL ANALYSIS 4.8 HYDROLOGY AND WATER QUALITY - Measures to mitigate this impact involve source control and leak containment to reduce the potential that a petroleum or fuel spill would reach surface or groundwater. In addition,media that is impacted by petroleum fuel is to be removed from the site. The prescribed mitigation would limit the opportunity for hazardous materials to contact surface water and groundwater and _ would ensure that water quality impacts associated with petroleum fuel releases remain less-than- significant. Mitigation Measure 4.8.2: Implement Mitigation Measure 4.11.2. Significance after Mitigation: Less-than-significant Impact 4.83: Excavation that disturbs and/or truncates the existing groundwater well shafts on the project site could increase the potential for contaminants to enter and pollute the groundwater through the wells. This would be a significant impact without mitigation prescribed as part of this EIR. The proposed project converts agricultural lands to an open quarry to depths of approximately 100 feet. Since agricultural operations have occupied this area for many years,there is a possibility that unused,unidentified, or abandoned groundwater wells remain within the boundaries of the property. Unidentified useable or abandoned groundwater wells remaining on the proposed project site after project implementation could be damaged or truncated by excavation equipment. A truncated or improperly abandoned groundwater well would act as a _ preferential pathway to the underlying aquifer allowing surface water, sediment, and surface- bome contaminants to degrade water quality. According to the Significance Criteria,above, a significant impact would occur if the project resulted in a condition that would lead to groundwater quality degradation. There are five known wells located within the project boundaries,three agricultural wells and two domestic wells. The proposed project would continue use of two of the agricultural wells and one of the domestic well. The two unused wells, as well as other that may not yet be identified, would not be operated as part of the project and therefore,could be either truncated or destroyed _ during quarry operations. As part of the proposed project,the project applicant would decommission unused wells. Mitigation for this impact(Mitigation Measure 4.8.3)ensures that unused or abandoned wells would be properly destroyed and water quality impacts associated _ with truncated or undiscovered, open wells would remain less-than-significant. Mitigation Measure 4.83: Prior to the commencement of excavations,the project _ applicant shall conduct a comprehensive well survey to locate,identify,and confirm all existing groundwater wells on the project site. Information for well locations shall be obtained,if available,from DWR,San Joaquin County,Stanislaus County,and the former property owners. Groundwater wells that will not remain in operation shall be properly destroyed and removed in accordance with the DWR Well Standards. The well RMC Pacific Vemalis Quany Muting and Reclamation Pmject 4.8-24 ESA/203015 Admmisba w D=ft P1R Mamh 2004