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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 (Plates 5 and 6). The Site is beyond the mapped area for both years; the closest ground-water contours are at sea level and ten feet below sea level. The ground-water flow direction and gradient could not be calculated. No ground water was encountered by Live Oak during the drilling of the two shallow percolation test borings discussed later in this report. Given that the ground elevation of the Site is approximately sea level, based on the maps reviewed and our field observations, the depth to water below the Site is estimated to range from four to 10 feet. Ground water depth and flow direction in the Delta islands is highly dependent on seasonal pumping and irrigation in the area. 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 immediate vicinity of the Site was not mapped during these years. The closest mapped contours indicated a ground-water depth of ten feet (Plates 7 and 8). 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 9), no wells within a one-mile radius of the subject Site have been tested for nitrate. The closest wells to the Site, located two to four miles away, were found to be non-detect for nitrate or have nitrate at a concentration between 0.1 and 5.0 mg/L-N. According to the DBCP map (Plate 10), no wells within a one-mile radius of the subject Site have been tested for nitrate. The closest wells to the Site, located two to four miles away, were found to be non-detect for DBCP. The Maximum Contaminant Level (MCL) set by the US EPA for nitrate is 10 mg/L-N; the MCL for DBCP is 0.2 ug/L. LOGE 20-08 Page 3