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Mr. Duncan A. Austin - 2 - 25 January 2012 • In a 21 December 1993 letter, San Joaquin County Environmental Health Department stated that no further action was required regarding the removal of one of the underground fuel tanks. • In 2008, 26 soil samples from 13 borings were analyzed in which organochlorine compounds were not detected, 5 samples contained chlorinated herbicides at concentrations substantially below CHHSLs and EPA RSLs, hand-held photo ionization detectors did not identify any vapors from any of the samples, and diuron was not detected. Twelve of these 26 soil samples were also analyzed for polynuclear aromatic compounds, which were not detected. • In 2008, grab groundwater samples detected diuron and dichlorobenzene above water quality objectives in the sump and drainage basin areas. Other volatile organic compounds, total petroleum hydrocarbons, organophosphate pesticides, organochlorine pesticides and chlorinated herbicides were not detected. • Since at least 2008, the soil has been cultivated with safflower and other crops. • In 2009, monitoring wells were installed and four quarters of monitoring did not detect volatile organic compounds, pesticides or herbicides. Extent defined: Yes Threat to Groundwater: Groundwater occurs at 8 to 10 feet below ground surface and does not contain pollutants. There does not appear to be a threat to groundwater. Threat to Human Health: • Dermal Contact Hazard: The remaining residual concentrations are substantially below health protection screening levels for dermal contact. Therefore, there does not appear to be a threat to human health through dermal contact at the site. Public Review: On 9 August 2011, 30-day public notice was distributed to neighbors and interested parties. One neighbor expressed concern that groundwater pollutants could be in their on-site drinking water well. On 14 September and 21 September, two domestic water wells downgradient from Trinkle and Boys were analyzed for carbamate urea compounds, chlorinated herbicides, volatile organic compounds, nitrate and dissolved metals. No pollutants associated with Trinkle and Boys were found, although some dissolved metals were detected. The concentrations detected were below the Maximum Contaminant Level, which is considered safe for drinking water, and the concentrations were similar in both domestic water wells. This suggests that these metals are associated with the native aquifer formation. Summary: Based on the above evaluations the Central Valley Water Board staff concurs with Trinkle and Boys that the remaining residual concentrations of pesticides at the site do not appear to present either a threat to water quality, human health, or the biota.