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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 4 and 5), ground water elevation is approximately zero to 20 feet above mean sea level; the ground- water flow beneath the Site is to the north or northwest at a rate of approximately 18 to 20 feet per mile. Given that the ground elevation of the Site is approximately 130 to 132 feet above mean sea level, the depth to water below the Site is estimated to be approximately 110 to 132 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. According to the nitrate map (Plate 6), four wells within a half-mile radius of the subject Site have been tested for nitrate; it was detected in three at concentrations greater than 10.0 mg/L-N, and in the fourth at a concentration between 5.1 and 10.0 mg/L-N. According to the DBCP map (Plate 7), two wells within one-half mile of the Site were tested for DBCP; no DBCP was detected in either well. The Maximum Contaminant Level (MCL) set by the US EPA for nitrate is 10 mg/L-N; the MCL for DBCP is 0.2 �tg/L. Much of the nearby land to the southeast of the Site is agricultural; elevated nitrate levels in the area likely derive from fertilizer application on these properties. LOGE 1922 Page 3