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i • Mr. John Jackson San Joaquin County Environmental Health Department 28 June 2004 Page 2 Area 15 was originally developed in the early 1900s and redeveloped in the 1950s for use as part of the Chase Chevrolet auto repair facility(Figure 2). Because of the current construction at the Site, the Site is vacant with no former buildings present. Two former UST locations with releases of petroleum hydrocarbons have previously been identified. Groundwater monitoring has been taking place in 16 groundwater monitoring wells which were destroyed in March 2004 under pcnmit from the SJCEHD. The B-6 UST is located to the east of the historical Auto Body Shop in the vicinity of soil borings 15B-6 and 15B-9 and former groundwater monitoring well MW-12. Boring 15B-6 had total petroleum hydrocarbons as gasoline (TPHg) concentrations ranging up to 13,000 milligrams per kilogram (mg/kg) and total petroleum hydrocarbons as diesel (TPHd) concentrations ranging up to 520 mg/kg. Boring 15B-9 had TPHg concentrations ranging up to 8,500 mg/kg with TPHd concentrations below detection limits (<400 mg/kg). (Remedial Investigation Report, Treadwcll &Rollo, 24 August 2000). The site is part of the Banner Island redevelopment project, and the DISC is overseeing hazardous materials issues in soil and water for the project. In March 2004, the DTSC determined that remedial action (excavation)was required for soil around borings 1513-6 and 1513-9. The excavation remedy was performed in accordance with the DTSC approved Final Remedial Action Plan (RAP) (Treadwell &Rollo, August 2001) and Remedial Design and Implementation Plan (RDIP) (Treadwell &Rollo, 2004). Excavation and offsite disposal is intended to be the final remedy for this area. Beginning in March 2004, implementation of the RDIP began at the Banner Island redevelopment project. Under the chosen remedial action alternative, all soil exceeding the RAP Remedial Action Objectives (RAOs) was removed and disposed of off-site at an approved disposal facility. During the Area 15, B-6 excavation, the UST associated with former Chase building was exposed just north of the northern side of the former building concrete slab (Figure 3). The presence of the UST was previously unknown as were it's former contents. UST REMOVAL AND SAMPLING 9th On 30 March 2004, a metal, single-walled, open top I 0-gallon UST was discovered during the excavation activities associated with the remedial action soil excavation at Area 15 boring B-6. The UST was noticed when a tooth of the excavator bucket exposed a portion of the side of the tank. The excavation work was halted and the UST investigated. The Treadwell &Rollo geologist notified the City, Stockton Fire Department(SFD), SJCEHD, and DISC. Thorpe immediately applied for permits to remove the UST through the SJCEHD UST removal permit process. On 2 April 2004, Mr. John Jackson, inspector for the SJCEHD, and Mr. Kent Miller, fire inspector for the SFD were present for the UST removal. Because the UST was full of soil and