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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 spring and fall of 2016 were the most recent available from this source. According to an analysis of these maps (Plates 5 and 6), ground water elevation is approximately 25 to 40 feet above mean sea level. Ground water appears to flow to the east, northeast, or southeast, the ground-water gradient beneath the Site could not be determined due to an unmapped area to the west. Given that the ground elevation of the Site is approximately 90 feet above mean sea level, the depth to water below the Site is estimated to be approximately 50 to 65 feet. San Joaquin County experienced its highest recent ground-water levels in 1983 and 1999. Maps of ground-water levels were reviewed for this study (San Joaquin County Flood Control and Water Conservation District, 1983 and 1999); however, the Tracy area was not mapped during these years. 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, five wells within a half-mile radius of the subject Site have been tested for nitrate. Three of these wells were found to contain nitrate at a concentration greater than 10 mg/L-N, one contained nitrate at a concentration between 5.1 and 10 mg/L-N, and one contained nitrate at a concentration between 0.1 and 5.0 mg/L-N. According to the DBCP map, two wells within a half-mile radius of the Site have been tested for DBCP; no DBCP was detected in either well. On-Site Wells The Site receives water from a community well. No well permits were identified for the Site from among the files of the San Joaquin County Environmental Health Department. LOGE 20-01 Page 3