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There are currently no sites for water storage if pumping is required to remove water from the quarry area, except for the county-owned drainage pond. Water within the quarry pits would likely to be turbid, and would introduce sediment if pumped to the Mokelumne River. Groundwater pumping may draw down local water tables, potentially affecting the performance of nearby shallow wells. If water were allowed to stand in the quarry pits, the saturated substratum could present a safety problem for operation of heavy equipment at the site. Saturation would decrease the cohesiveness of the substratum, increasing the possibility of wall collapse within the quarry pits. These impacts are considered potentially significant. Groundwater extraction for project operation could locally impact the groundwater table and affect nearby wells. No definitive information is available to determine the potential for this impact; however, the existing project has utilized groundwater from this well for at least 8 years at an average rate of about 10,000 gallons per day, and no adverse impact on local wells has been identified. 3.2.3 Mitigation Measures The mitigation measures listed below are intended to reduce the potentially significant impacts that would result from project construction to less than significant levels. 1. The potential for change in channel alignment, although insignificant, should be reduced in case of a levee failure during peak streamflow events. The gravel extraction pits shall be left open for as brief a time as possible, particularly during the rainfall season, and the pits shall be aligned perpendicular to the streamf low. 2. The new bridge site shall be constructed so as to minimize constriction of the channel and prevent a decrease in flood carrying capacity of the Mokelumne River that may increase erosion and flood potential. The San Joaquin County Public Works Department and the State Reclamation Board should require the cross sectional area of the channel at the new bridge site to be surveyed to determine that the present channel capacity has not changed since the USGS report. A permit from the State Reclamation Board will be required for relocation of the bridge. The bridge relocation must also comply with requirements of the Federal Emergency Management Agency and the San Joaquin County Flood Prevention Ordinance. 3. An erosion control plan shall be prepared and implemented according to guidelines developed and approved by the San Joaquin County Department of Public Works and the State Reclamation Board. Bridge removal and relocation 36