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Expected On-Site Maximum Septic Tank Usage Maximum expected usage on the Site would be from the current and 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 spring and fall of 2016 were the most recent available from this source. According to an analysis of these maps (Plates 4 and 5), ground water elevation is approximately 47 to 50 feet below mean sea level. Ground water appears to flow to the east or southeast at a rate of four to seven feet per mile. Given that the ground elevation of the Site is approximately 35 feet above mean sea level, the depth to water below the Site is estimated to be approximately 82 to 85 feet. San Joaquin County experienced its highest recent ground-water levels in 1983 and 1999. Maps of ground-water levels were reviewed for this study (San Joaquin County Flood Control and Water Conservation District, 1983 and 1999); depth to ground water was approximately 58 to 62 feet for these years (Plates 6 and 7). 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 8 and 9). According to the nitrate map, six wells within a half-mile radius of the subject Site have been tested for nitrate. One of these wells was found to contain nitrate at a concentration between 0.1 and 5.0 mg/L, three were found to contain nitrate at a concentration between 5.1 and 10 mg/L-N, and one was found to contain nitrate at a concentration over 10 mg/L-N; no nitrate was LOGE 20-03 Page 3