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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 60 to 90 feet below mean sea level. Ground water appears to flow to the northeast at a rate of approximately 4 to 60 feet per mile, depending on the season. 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 115 to 145 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 (Plates 7 and 8). According to the nitrate map, 15 wells within a one -mile radius of the subject Site have been tested for nitrate. Eight of these wells were found to contain nitrate at concentrations between 0.1 and 5.0 mg/L, five were found to contain nitrate at concentrations between 5.1 and 10.0 mg/L, one was found to contain nitrate at a concentration over 10.0 mg/L, and no nitrate was detected in the final well. According to the DBCP map, eight wells within a one -mile radius of the Site have been tested for DBCP. No DBCP was detected in any of 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 no more then about 3 mg/L-N. Nitrate may be increasing in areas with LOGE 2208 Page 3