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4.Environmental Analysis r groundwater flow direction and gradients can, in some cases, result in a noticeable effect to local recharge and the natural radial flow to wells within the same aquifer. Potential Project-Related Effects r The proposed project would excavate material to depths just above the water table and would not extend into or below the groundwater. Considering this plan, it is unlikely that groundwater r. would be exposed in the active mining areas during normal mining operations and under existing groundwater conditions. However, if the regional groundwater levels gradually rise due to a seasonal or long-term, regional increase in groundwater levels, the groundwater could eventually inundate the bottom of the active mining phase. Inundation could expose groundwater to evaporative losses, hinder mining operations,contribute to slope instability,or limit equipment access. Long-term increases of groundwater levels could inundate the bottom of the completed, reclaimed mining phases depending on the depth of cover placed over the mined area during ` reclamation. If this were to occur,the surface soils in the reclaimed phases would become saturated and, depending on the reuse(i.e.,agriculture or grazing), could result in unfavorable soil conditions. Although this would not necessarily constitute an impact under CEQA (see Significance Criteria, above), it could be considered long-term flooding and adversely affect the proposed mining and reuse plans. r Groundwater seepage and inundation within the active or reclaimed mining phase could cause a groundwater quality issue as surface water and pollutants commingle with the incoming _ groundwater. Because of the size of the excavation and volumes of incoming groundwater, the degradation would be localized in areas where surface pollutants are present and are allowed to enter the water.Furthermore, the amount of unpolluted surface and groundwater would likely be sufficient to dilute pollutant loads to below regulatory action levels. However,if a large concentrated spill of a potential pollutant(i.e., chemicals related to mining operations including fuel, oil,grease, and sediment)occurs and is not contained,the resultant plume could degrade the �. surface water and migrate into the groundwater. Furthermore, if high volume groundwater pumping were to occur near or adjacent to the mine excavation, contaminated surface water could be drawn from the pit to the extraction well. Impact Analysis r„ Project mining would occur to an approximate depth of 70 to 120 feet below the surface. The proposed project is designed to limit all mining excavations to above the groundwater table at the time of mining. Proposed excavation depths are partly based on the groundwater depth when the r. Applicant developed the proposed mining plan. The analysis performed for this EIR included a review of geologic exploratory logs and long-term California Department of Water Resources(DWR) groundwater records to evaluate the water table and the potential for groundwater fluctuations. The data indicates that the approximate groundwater elevation of the unconfined zone ranges from 57 to 85 feet above msl at the project site or equivalently, at depths of 83 to 120 feet below the surface. Groundwater depths observed r RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.8-22 ESA/203015 Draft Environmental Impact Report May 2006