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• The longer the effluent remains near the surface, the more biologic treatment may occur. In a situation where permeable soils exist to the depth of the aquifer, it is possible that any remaining surface contaminants may be transported to the first saturated zone of the aquifer. Groundwater Analysis Depth and Gradient Live Oak reviewed ground-water elevation information available from the San Joaquin County Flood Control and Water Conservation District to determine the ground-water levels near the Site. Data from the spring and fall of 2016 were the most recent available from this source (Plates 6 and 7). According to an analysis of these maps, the ground-water elevation in the area is approximately 49 to 55 feet below mean sea level. The ground-water flow is to the east or southeast at a rate of approximately four to eight feet per mile. Given that the ground elevation of the Site is approximately 43 feet above sea level, based on the County ground water maps the depth to ground water below the Site is estimated to be 92 to 98 feet below ground surface. Potential Ground Water Contamination Issues • The Nitrate Loading Study is not intended to be an investigation into ground-water contamination sources, and no such investigation was conducted. Many sources can contribute to ground water contamination, including leaking underground storage tanks, agricultural activities, dairies and cattle ranches, septic systems, and storm water infiltration. Agricultural activities and the use of septic systems in the area are known ground-water contamination sources with the potential to impact the Site. Live Oak reviewed the San Joaquin County Environmental Health Department's Water Well Data Table dated March 10, 2009 for nearby addresses that have been tested for nitrate and dibromochloropropane (DBCP). Eight wells were identified in a search of addresses within approximately one mile of the subject Site. All of the wells had been tested for nitrate; it was detected in seven of the wells at concentrations from 0.4 to 43.08 mg/L-NO3 (equivalent to 1.8 to 9.6 mg/L-N). Three of the wells had been tested for DBCP; it was not detected in any of the three. The Maximum Contaminant Level (MCL) set by the US EPA for nitrate as NO3 is 45 mg/L (10 mg/L-N). The MCL for DBCP is 0.2 ug/L. On-Site Wells A new domestic well is located on the Site, but it has not yet been connected to a power supply. • LOGE 1902 Page 3