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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 spring and fall of 2021 were the most recent available from this source, covering the area of the Site. According to an analysis of these maps (Plates 5 through 8), depth to water in the area is approximately 75 to 85 feet, and ground water appears to flow generally to the north or northeast in the area at a rate of approximately 20 to 24 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. Five dairies are located within two miles of 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 9), eight wells within a one-mile radius of the subject Site have been tested. Nitrate was detected in two of the wells at concentrations between 0.1 and 5.0 mg/L-N, in three wells at concentrations between 5.1 and 10.0 mg/L-N, and in three wells at concentrations over 10 mg/L-N. Seven wells within a one-mile radius of the Site were tested for DBCP (Plate 10); DBCP was detected between 0.01 and 0.2 µg/L in two of the wells and over 0.2 µg/L in two of the wells; no DBCP was detected in the remaining three 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 than about 3 mg/L-N. Nitrate may be increasing in areas with concentrations of 5.5 mg/L-N or more (Hull, 1984). The US EPA has set the Maximum Contaminant Level (MCL) for nitrate at 10 mg/L-N. Although nitrate is a naturally occurring compound necessary for plant growth, it can cause health problems when present at high levels in drinking water. The most LOGE 2307 Page 3