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w N.i' Ultramar, Inc. December 21, 1998 UST Closure Report Page 2 Beacon Station No. 492 Vapor extraction was resumed between June and September, 1992. Analytical results of vapor samples indicated that Total Petroleum Hydrocarbons as Gasoline (TPHg) in the vapor stream had been reduced to below laboratory detection limits. In October 1992, RESNA drilled and sampled three borings to confirm that removal of petroleum hydrocarbons was complete. Petroleum hydrocarbons were not detected in the ten soil samples submitted from the borings. Based on corrective action efforts and the findings of the chemical analyses, San Joaquin County issued a letter(dated October 17, 1996) stating that, "...no further action related to the underground storage tank release is required." SITE DESCRIPTION The subject site is located at 470 North Main Street in Manteca, California, southeast of the intersection of North Main Street and Alameda Street (see Figure 1). Site improvements include a station building (cashier and retail sales), dispenser islands with a canopy, underground storage tanks, and surface pavements (see Figure 2). UST REMOVAL Three 10,000 gallon-capacity underground gasoline storage tanks (T-1, T-2, and T-3) were exhumed by JNS Construction, Inc., on November 5, 1998. Prior to removal of the USTs, tank contents were pumped from the tank, and the tanks were inerted with dry ice. The UST removals were observed by Mr. Steve Sasson of the San Joaquin County Environmental Health Division (the County), Mr. Ron Waddle of the Manteca Fire Department, Mr. Joseph Aldridge of Ultramar, Mr. John Vagt of Ultramar, and Mr. John Pfeiffer of BSK. A fourth UST (T-4), approximately 400 gallons in capacity, was discovered while JNS was preparing the site for installation of the new dispenser islands. The UST was not in use and its existence was unknown until it was uncovered. The UST contained some water, and a water sample was collected from the UST for analysis. The removal of T-4, on November 13, 1998, was observed by Mr. Sasson of the County, Mr. Waddle of the Manteca Fire Department, Mr. Steve Coodey of Ultramar, and Mr. Jeffrey Yeazell of BSK. Prior to removal, approximately 30 gallons of water was pumped from the UST into a DOT-approved 35-gallon drum. On removal, the three 10,000-gallon USTs were observed to be in good condition with minor pitting,but no obvious holes. The 400-gallon UST had an approximately one-inch diameter hole in the bottom of it. The USTs were transported by KVS Transportation, Inc. to the UCI facility in Richmond, California for processing. Soil removed during excavation to expose the USTs was stockpiled at the area indicated on Figure 2. Following removal of the 10,000-gallon USTs, one sample from each end of the tanks (two per tank) were obtained from soil formerly underlying the USTs. Samples were obtained from depths of approximately 13.5 to 15 feet below ground surface (bgs). Following removal of the