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Septic Permit History in the Vicinity Based on a review of septic permits on file at the San Joaquin County Environmental Health Department for nearby properties, septic systems in the area utilize leach lines, leach lines with seepage pits, leach lines with sumps, or filter beds. The septic permits can be found in Appendix 4 of this report. Expected On -Site Maximum Septic Tank Usage Maximum expected usage on the Site would be from the existing and proposed residences. 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 fall of 2018 and spring of 2019 were the most recent available from this source. According to an analysis of these maps (Plates 4 and 5), ground water elevation is approximately 18 to 26 feet below mean sea level; ground water flows down to the northeast at a rate of approximately 12 feet per mile. Given that the ground elevation of the Site is approximately 63 feet above mean sea level, the depth to water below the Site is estimated to be approximately 81 to 89 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. According to the nitrate map (Plate 6), three wells within a half -mile radius of the subject Site have been tested for nitrate. Nitrate was detected in two of these wells at concentrations between 0.1 and 5.0 mg/L-N, and in the third at a concentration between 5.1 and 10 mg/L-N. According to the DBCP map LOGE 2212 Page 3