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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 spring and fall of 2016 were the most recent available from this source. According to an analysis of these maps (Plates 5 and 6), ground water elevation is approximately q to 57#eof-6elow mean sea level; the ground-water flow beneath the Site 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 37 to 38 feet above mean sea level, the depth to water below the Site is estimated to be approximately 87 to 95 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 water was approximately 65 feet in 1983 and 70 feet in 1999. 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. According to the nitrate map (Plate 9), eight wells within a half-mile radius of the subject Site have been tested for nitrate; it was detected in five at concentrations between 0.1 and 5.0 mg/L-N, and in three at concentrations between 5.1 and 10.0 mg/L-N. Six wells within one-half mile of the Site were tested for DBCP (Plate 10); no DBCP was detected in any of the wells. The Maximum LOGE 1919 Page 3