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URS Ms Margaret Lagono Page 3 San Joaquin County Environmental Health Department June 27, 2003 Soil samples were collected from the borings and one groundwater sample was collected from each well and analyzed for total fuel hydrocarbons and fuel-related volatile organic compounds Soil samples identified contamination up to the following concentrations total fuel hydrocarbons, 11,400 milligrams per kilogram (mg/kg), benzene, 4,200 micrograms per kilogram (gglkg), toluene, 638,000 gg/kg, xylenes, 164,000 gg/kg Groundwater samples identified contamination at the following maximum concentrations total fuel hydrocarbons, 2817 mg/L, benzene, 14,000 gg/L, toluene, 25,000 gg/L, xylenes, 16,000 Ag/1L(B&C, 1987b) Sampling results are presented in Attachment F Free product was identified in wells W-2 and W-3 Free product was removed from the wells during this investigation and was recommended to continue on a bi-weekly basis until the remediation system is installed at the site (B&C, 1987b) November 1987 Site Investigation The November 1987 site investigation included drilling two borings and converting both of the borings into groundwater monitoring wells (W-7 and W-8) (Attachment E) Soil samples were collected from the borings and analyzed for total petroleum hydrocarbons by Modified EPA Method 8015 and benzene, toluene, and xylenes (BTX) by EPA Method 8020 Soil samples did not identify analytes at or above the reporting limits (B&C, 1988) Groundwater was sampled from wells W-1 through W-8 and analyzed for total petroleum hydrocarbons by Modified EPA Method 8015 and BTX by EPA Method 602 Total petroleum hydrocarbons were identified in three of the eight samples at concentrations up to 343 9 mg/L BTX was identified at the following maximum concentrations benzene, 6,200 Rg/L, toluene, 5,300 gg/L, and xylene, 13,000 µg/L Groundwater from the five off-site wells was again sampled in February 1988 and analyzed for BTX by EPA Method 602 No analytes were detected at or above the reporting limit with the exception of one detection of benzene (2 µg/L) in W-5 (B&C, 1988) Analytical laboratory results are presented in Attachment F Free product was removed from wells W-1, W-2, and W-3 on a biweekly basis from July 22, 1987 to November 25, 1987 A total of 30 5 gallons were removed during this time Significant recharge of free product did not return in these wells after November 25, 1987 (B&C, 1988) June 1988 Well Installation Wells W-2A and W-2B (Attachment E) were installed in the vicinity of well W-2 during June 1985 to determine whether groundwater contamination had migrated vertically Based on the analytical results from this well cluster, fuel-contaminants did not migrate vertically into well W-2B, which is screened in a deeper part of the aquifer (Attachment F) i K 1WprocessV5 BP ARC010043410osure Requestl5tation 434 Closure Doc doc