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• Live Oak inspected the on-site soil near the proposed new residential area on January 17, 2018. The surface and near-surface soils were found to be sandy silt. Mass Transport Soil Properties The soil type will allow limited infiltration of water through the surface soils. 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 ranges from two to nine feet below mean sea level, depending on the season; the ground-water flow is to the north or north-northeast at a rate of approximately one to two feet per mile. Given that the ground elevation of the Site is approximately 10 to 12 feet above sea level, based on the County ground water maps the depth to ground water below the Site is estimated to range between 12 to 21 feet. 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). Two wells were identified at addresses within approximately one-half mile of the subject Site. One of the wells had been tested for DBCP; it was not detected in the sample. Both the wells had been tested for nitrate; it was detected in the samples at concentrations of 71.0 and 132.0 mg/L-NO3. 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 µg/L. Based on the available information, it • LOGE 1802 Page 3