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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 the spring and fall of 2021 were the most recent available from this source. According to an analysis of these maps (Plates 4 through 7), depth to water in the area is approximately 50 to 63 feet, and ground water appears to flow generally to the east or southeast in the area at a rate of approximately 2 to 4 feet per mile. 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 October 2021. According to the nitrate map (Plate 8), six wells within a one-mile radius of the subject Site have been tested. Nitrate was detected in three of the wells at concentrations between 0.1 and 5.0 mg/L-N; no nitrate was detected in the remaining wells. Two wells within a one-mile radius of the Site were tested for DBCP (Plate 9); no DBCP was detected in the wells. Nitrate is commonly detected in shallow ground water aquifers of the Central Valley. Application of fertilizers, livestock waste, and untreated septic tank waste can all contribute to nitrate in ground water. Nitrate is mobile and tends to accumulate in shallow ground water zones. Based on work in the Sacramento Valley from the early 1900s, it is estimated that under "natural" conditions, ground water contains nitrate at concentrations of no more than about 3 mg/L-N. Nitrate may be increasing in areas LOGE 2325 Page 3