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10/17/2007 14:36 FAX 2094683163 SJC_COMM_DEV R 008/013 '%./ other contaminants(such as gasoline and oils). As further noted in the measure,if monitoring results in a determination that Project dewatering activities have adversely affected groundwater quality,all dewatering activities will cease,and a detailed analysis will be performed by a licensed engineer in conjunction with a certified hydrogeologist to identify the likely cause of contamination. This analysis will conform to American Society for Testing and Materials(ASTM)standards,and will include recommendations for reducing or eliminating the source or mechanisms of contamination. Based on this analysis,the Operator will select and implement measures to control contamination,with a performance standard that groundwater quality must be returned to baseline conditions, The County and the Central Valley RWQCB will be the lead agencies involved in matters of groundwater quality degradation. A second measure,Mitigation Measure GW-Ib,"Maintain Well Offsets,"requires the project proponent to maintain minimum San Joaquin County Health Department offsets between the mine and adjoining property lines to ensure that all nearby water supply wells are appropriately distant from potential sources of contamination. Health department offsets are considered sufficient to shield down-gradient wells from any microbiological contamination. A third measure,Mitigation Measure GW-3,"Monitor and Report Groundwater Levels; Implement Measures to Maintain Groundwater Levels as Necessary,"reiterates the requirement for the applicant to establish a network of on-site sentinel and off-site monitoring wells to monitor baseline,or background,water level cbm-4detistics to detect any groundwater level impacts caused by the Project. The sentinel wells would be located on the project parcel and would be designed to detect impacts before they spread beyond the parcel boundaries. Off-site monitoring wells,which may include existing water supply wells,would be used to provide an ongoing,continuous baseline record to complement the monitoring at the sentinel sites. As further noted in the measure,if the groundwater monitoring resulted In a determination that the Project was adversely affecting groundwater levels,by reducing them such that local well owners were affected by a reduction in well production,the following measures would be implemented,listed in general order of implementation: • Limit the depth of excavation,as determined by San Joaquin County,until corrective measures are approved by San Joaquin County and implemented by the Operator. • Lower a well pump for any well where groundwater levels are reduced by the mining activities. • Deepen any well where lowering of a well pump is infeasible to maintain well capacity. • Replace any well for which all preceding measures fail to mitigate loss in well capacity. • Provide an alternative water supply to any property where the preceding measures fail to mitigate loss in well capacity or water supply caused by the mining activities.