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Expected On -Site Maximum Septic Tank Usage Maximum expected usage on the Site would be from the future residents of the Site. Septic system design should be based on the San Joaquin County On -Site Wastewater Treatment Systems Standards (2017) or other engineering recommendations. Ground Water Information 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 fall of 2017 and the spring of 2018 were the most recent available from this source. According to an analysis of these maps (Plates 4 and 5), ground water elevation is approximately 10 to 12 feet below mean sea level. Ground water appears to flow to the northeast at a rate of approximately 9 to 15 feet per mile. Given that the ground elevation of the Site is approximately 59 feet above mean sea level, the depth to water below the Site is estimated to be approximately 69 to 71 feet. Potential Ground Water Contamination Issues The Soil Suitability 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, 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. Two common ground -water contaminants in San Joaquin County are nitrate and dibromochloropropane (DBCP). Live Oak reviewed the San Joaquin County Environmental Health Department's maps of Nitrate — Land Use Data and DBCP — Land Use Data dated February 20, 2019 (Plates 6 and 7). According to the nitrate map, eight wells within a one -mile radius of the subject Site have been tested for nitrate. Four of these wells were found to contain nitrate at concentrations between 0.1 and 5.0 mg/L-N, three wells were found to contain nitrate at concentrations between 5.1 and 10.0 mg/L- N; the remaining well had a concentration over 10 mg/L-N. According to the DBCP map, six wells within a one -mile radius of the Site have been tested for DBCP. DBCP was detected in one of the wells at a concentration between 0.01 and 0.2 ug/L; it was detected at concentrations over 0.2 µg/L in the remaining five wells. LOGE 2145 Page 3