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4. ENVIRONMENTAL ANALYSIS 4.8 HYDROLOGY AND WATER QUALrrY Mitigation Measure 4.8.4c: Groundwater Extraction Management Plan Following the completion of Mitigation Measures 4.8.1a and lb, the project applicant shall develop a Groundwater Extraction Management Plan (Plan)based on the results of the aquifer testing and the recommendations of the California-certified hydrogeologist. This plan shall outline a required approach and schedule for groundwater pumping during mining operations. .. The groundwater extraction approach and schedule shall provide adequate groundwater supply to meet either a proposed or revised demand while maintaining groundwater discharge rates that do not impact the groundwater aquifer system. As stated above,impacts to the aquifer would occur if excessive, local and regional drawdown were to occur from the proposed project. In addition to groundwater pumping schedules and extraction well operation strategies (i.e.,pumping and storage), the Plan shall include alternate water conservation measures to reduce groundwater demand. The recommendations provided in the plan shall comply with applicable San Joaquin County ordinances and requirements set forth by the RWQCB. The Plan shall become part of the project. Significance after Mitigation: Less-than-Significant. The mitigation measures developed for this impact will verify,prior to project implementation, the magnitude of groundwater resource impacts resulting from the proposed project. These mitigation measures would not permit the project to commence if adverse impacts to groundwater resources are found to occur and also provide a mechanism to correct adverse effects caused by long-term groundwater extraction before and during project implementation. Implementation of these mitigation measures prevent excessive groundwater extraction and its adverse consequences and therefore ensures that impacts related to depletion of groundwater resource remain less-than- significant. Impact 4.85: Reuse of excavated overburden containing clay and silts combined with equipment compaction of the reclaimed mine areas could decrease infiltration of surface water and reduce groundwater recharge from the project site throughout the life of the project and after reclamation. This would be a less-than-significant impact. Under current conditions, the surface soils and underlying aggregate deposits provide a natural recharge system for the water table. The surface water is transmitted downward to the water table, driven by gravity,through pore spaces in the overburden material and then through the more porous,underlying aggregate unit. The infiltration capacity of the soil and rates that water 6. travels through the soil depend on the soil characteristics,rainfall,and topography and level of surface disturbance. Annual irrigation and precipitation contributes water available for percolation and evapo-transpiration under the current land use conditions. The proposed project would alter the surface by stripping away overburden in active mining phases to expose aggregate resources,constructing silt settlement ponds,and replacing the RMC Pacific Veniahs Quany Mining and Redamatiw Project 4.8-31 ESA/203015 Administrative]haft E1R March 20D4