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Expected On -Site Maximum Septic Tank Usage Maximum expected usage on the Site would be from the current residents of the Site, as well as any new residents of Parcel 2 in the future. 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 2018 and the spring of 2019 were the most recent available from this source. According to an analysis of these maps (Plates 5 and 6), ground water elevation is approximately 20 to 30 feet below mean sea level. Ground water appears to flow to the northeast at a rate of approximately three feet per mile in the fall; the rate could not be calculated for the spring map. Given that the ground elevation of the Site is approximately 55 feet above mean sea level, the depth to water below the Site is estimated to be approximately 75 to 85 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, 20 wells within a mile of the Site were tested for nitrate (Plate 7). Nitrate was detected in 14 of the wells at concentrations between 0.1 and 5.0 mg/L-N, in three of the wells at concentrations between 5.1 and 10.0 mg/L-N, and in one of the wells at a concentration over 10 mg/L- N; no nitrate was detected in the final well. Within a mile of the Site, 11 wells were tested for dibromochloropropane (DBCP) (Plate 8). No DBCP was detected in 10 of the wells; it was detected in the final well at a concentration between 0.01 and 0.2µg/L. LOGE 2150 Page 3