SU0006921 - Laserfiche WebLink

Home Browse Search

Project Description-- Report of Composting Site Information Tracy Material Recovery Facility and Transfer Station 30703 5. MacArthur Drive, Tracy, California 95377 ; Site Groundwater Hydrology The San Joaquin County Flood Control and Water Conservation District maintains an annual record of elevation of water in wells in San Joaquin County. For data collect in the Fall 1992 indicates first encountered groundwater beneath the project site occurs in the upper unconfined aquifer at elevation 70 MSL, or at an approximate depth of 90 to 95 feet below the ground surface. Depth to groundwater generally increases to the north- northwest(San Joaquin County, 1993). Limited water level data for selected wells in the project area indicate that water levels vary from year to year, but tend to return to an equilibrium level that reflects the balance between recharge, pumping, and subsurface inflow and outflow. This balance is affected by long-term changes in irrigation pattems and the relative amounts of groundwater and imported surface water used for irrigation. Periods of above-or below-average rainfall and stream flow can cause relatively short-term deviations from the equilibrium water level (San Joaquin County, 1993). There are a number of large irrigation wells in the vicinity of the project site. These wells provide water for agriculture and ranching uses. Irrigation wells typically tap both the lower, confined aquifer, and the upper, unconfined aquifer, drawing water from depths between 50 and 700 feet below the ground surface. The typical absence of sanitary seals, the extent of perforated intervals, and the gravel packing, allow most of these wells to tap both the unconfined and the confined aquifers together. In contrast, most municipal wells produce water primarily from the lower aquifer below the Corcoran Clay. As a result of pumping and drawdown of the deep aquifer, water levels in these deep wells are typically lower than water levels in the shallow wells. Groundwater Quality Limited groundwater quality data for selected wells in the project area is on file at the Department of Water Resources, Sacramento District. Groundwater in the vicinity of the project appears to be generally of good quality, with the exception of total dissolved solids (TDS), which can exceed California Secondary Drinking Water Standards. Water quality in the upper unconfined aquifer is generally worse than the quality in the lower confined aquifer, with higher concentrations of dissolved solids, chloride, boron, and sulfate. These constituents are thought to originate from subsurface inflow of groundwater from the marine sedimentary rocks adjacent to the western edge of the basin. The higher quality of the lower confined aquifer indicates that some of it probably originates from recharge on the eastern side of the valley. Elevated concentrations of nitrate in the upper aquifer are reported to occur in various parts of San Joaquin County, including the Tracy area (San Joaquin County, 1993) . The suspected sources of nitrogen are fertilizer and animal wastes. 11 Edgar&Associates,Inc. Tracy Compost Fac ProjDescO42310