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On-Site Wells Two wells are currently located on the Site. Six well permits were identified for the Site from among the files of the San Joaquin County Environmental Health Department: • May 1973 permit for pump replacement at well. • July 1973 permit for pump repair at well. • November 1977 permit for new domestic well. The well is depicted to the south of the old well, which was reportedly "abandoned by owner & proper." • November 2015 permit for new domestic well. The permit notes that a grout seal to 180 feet was required due to DBCP contamination. • November 2015 permit for new irrigation well; a similar grout seal was installed. • September 2016 permit for destruction of old well. The well permits have been included in Appendix 4. Water Sample Mr. Bavaro provided the results of a water sample collected from his domestic well on February 23, 2016 and analyzed by Far West Laboratories of Riverbank, California (Appendix 5). Nitrate plus nitrite were detected in the sample at a concentration of 7.1 mg/L-N. Nitrite was not detected above the reporting limit of 0.4 mg/L-N. Far West Laboratories indicated that nitrite is not typically detected in well water, and it is reasonable to assume that the entire detection consists of nitrate (personal communication, February 25, 2019). DBCP was not detected in the sample. 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 13.5 mg/L-NO3 (3 mg/L-N). Nitrate may be increasing in areas with concentrations of 24.75 mg/L-NO3 (5.5 mg/L-N) or more (Hull, 1984). The US EPA has set the Maximum Contaminant Level (MCL) for nitrate as nitrogen at 10 mg/L. 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 common health effect of nitrates in water is methemoglobinemia, or blue baby syndrome, which results in reduced oxygen supply to vital tissues. Pregnant women and certain others can also develop methemoglobinemia. Symptoms include a bluish LOGE 1907 Page 4