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(Plate 7), three wells within a half -mile radius of the Site have been tested for DBCP; it was detected in all three of the wells at concentrations over 0.2 ug/L. 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. On -Site Wells A domestic well is currently located on the Site. Two well permits were identified for the Site from among the files of the San Joaquin County Environmental Health Department: • February 1996 permit for new domestic well. The total depth is listed as 280 feet, with a grout seal at 200 feet. This permit refers to the subject Site. • June 2015 permit for pump replacement at domestic well. This permit appears to refer to the adjacent house to the east. These permits have been included in Appendix 4 of this report. Water Sample Live Oak collected a water sample from the domestic well on the Site on February 14, 2022. The sample was analyzed for nitrate and dibromochloropropane (DBCP) per San Joaquin County Environmental Health Department policy. As required by the laboratory, the sample was collected in a plastic container and two glass vials for nitrate and DBCP analysis, respectively. Trip blanks were also utilized. The sample was placed on ice and transported under chain of custody to FGL Environmental, Stockton. Nitrate was detected in the sample at a concentration of 6.7 mg/L-N. DBCP was detected at a concentration of 0.81 ug/L. The laboratory analytical results are attached as Appendix 5 of this report. The document notes that the concentration of DBCP detected was above the calibration range for the instrument; the test result should be understood to include some degree of experimental error/uncertainty as a result of this calibration problem. 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 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. LOGE 2212 Page 4