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i URS Ms Margaret Lagono Page 5 San Joaquin County Environmental Health Department June 27, 2003 1995 Destruction of Well W-6 During construction of a Boston Chicken in the vicinity of well W-6, a contractor destroyed well W-6 This well was properly abandoned in May 1995 by a contractor hired by Boston Chicken 1997 Closure Request Based on low influent concentrations into the SVE and GWE systems, and the low to nondetectable concentrations of hydrocarbons in groundwater beneath the site, a request for site closure was subrrutted to the San Joaquin County Environmental Health Department in 1996 The County granted closure in 1997 and concurrence was received by the Regional Water Quality Control Board-Central Valley Region (RWQCB-CVR) A "No Further Action" letter was not provided because ARCO did not want to destroy the site wells since it was anticipated that they might be used in the future 1998 Off-Site Well Destruction Wells W-4, W-5, W-7, W-8, W-10, W-11, and W-12 were destroyed under permit in 1998 (Secor, 1999a) No additional off-site wells remain On-site wells were maintained for possible use in future site investigations 1999 UST Removal Two 12,00-gallon USTs, one 6,000-gallon gasoline UST, and the associated piping and dispensers were removed from the site on June 16, 1999 Two of the excavated USTs appeared to be in good condition, with no apparent holes or cracks noted during the removal activities One of the tanks had some holes around the pull-rings caused by the excavator during the removal of the tank(Secor, 1999b) Seven soil samples were collected from the bottom of the UST pit beneath each former UST location The tank pit was approximately 13 to 14 feet below ground surface (bgs) Eight soil samples were collected beneath the dispensers, and ten soil samples were collected beneath the product The location of the soil samples on the map in Attachment G(Secor, 1999b) Soil samples were analyzed for TPHg, BTEX, and methyl tert-butyl ether (MtBE) by Department of Health Services (DHS) Leaking Underground Fuel Tank (LUFT) Method, fuel oxygenates (tert-butyl {� alcohol [TBA], MtBE, di-isopropyl ether [DIPE], tertiary amyl methyl ether [TAME], ethyl tertiary butyl ether [ETBE], ethylene dibromide [EDB], and 1,2-dichloroethane [1,2-DCA]) by EPA Method 8260, and total lead by EPA Method 6000/7000 Series Methods (Secor, 1999b) 1 Soil samples identified TPHg contamination in only one of the seven UST samples collected at a concentration of 5 15 mg/kg BTEX was not detected beneath the USTs MtBE was detected in five of i i K 1WprocessU5 BP ARCO\004341Closure Request\Station 434 Closure Doc doc