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Expected On-Site Maximum Septic Tank Usage <br /> Maximum expected usage on the Site would be from the current and future residents of <br /> the Site. Septic system design should be based on the San Joaquin County On-Site <br /> Wastewater Treatment Systems Standards (2017) or other engineering <br /> recommendations. <br /> Ground Water Information <br /> Depth and Gradient <br /> Live Oak reviewed ground-water depth and elevation information available from the San <br /> Joaquin County Flood Control and Water Conservation District to determine the ground <br /> water levels near the Site. Data from the spring and fall of 2021 were the most recent <br /> available from this source. According to an analysis of these maps (Plates 4 through 7), <br /> depth to water in the area is approximately 85 to 95 feet, and ground water appears to <br /> flow to the northeast in the general area, at a rate of approximately 3 to 4 feet per mile. <br /> Potential Ground Water Contamination Issues <br /> The Soil Suitability Study is not intended to be an investigation into ground-water <br /> contamination sources, and no such investigation was conducted. Many sources can <br /> contribute to ground-water contamination, including leaking underground storage tanks, <br /> agricultural activities, dairies, septic systems, and storm water infiltration. Agricultural <br /> activities and the use of septic systems in the area are known ground-water contamination <br /> sources with the potential to impact the Site. <br /> Two common ground-water contaminants in San Joaquin County are nitrate and <br /> dibromochloropropane (DBCP). Live Oak reviewed the San Joaquin County <br /> Environmental Health Department's maps of Nitrate — Land Use Data and DBCP— Land <br /> Use Data dated October 2021 (Plates 8 and 9). According to the nitrate map, 24 wells <br /> within a one-mile radius of the subject Site have been tested for nitrate. Nitrate was <br /> detected at concentrations between 0.1 and 5.0 mg/L-N in 16 of the wells, at <br /> concentrations between 5.0 and 10.0 mg/L-N in 4 of the wells, and at a concentration <br /> over 10.0 mg/L-N in one well; no nitrate was detected in the final well. According to the <br /> DBCP map, 11 wells within a one-mile radius of the Site have been tested for DBCP. No <br /> DBCP was detected in 10 of the wells; DBCP was detected at a concentration between <br /> 0.01 and 0.2 pg/L in the remaining well. <br /> LOGE 2312 Page 3 <br />