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a. <br /> �. 2.0 Site Investigations, Monitoring, and Remediation <br /> Lr-ft-C The Stockton Service Center site has been the subject of several investigations, <br /> studies, monitoring, and remedial designs since the USTs were removed in 1987 and <br /> 1989. Three separate soil and groundwater investigations,have been performed at <br /> the site by three consultants. Groundwater monitoring has been implemented at the <br /> site since 1989. A remedial action feasibility study and two remedial action plans <br /> were prepared. The investigations, monitoring,feasibility study, and remedial designs <br /> are summarized in the following sections. <br /> 2.1 Investigations <br /> In 1987 the District removed the first of three USTs, a 1,000-gallon leaded <br /> gasoline UST, from the Stockton Service Center. Petroleum hydrocarbons in excess <br /> of detection limits were detected in the soil beneath the east end of the tank. A soil <br /> L' and groundwater assessment performed by Kleinfelder, Inc. (Kleinfelder) in May and <br /> October 1989 revealed petroleum hydrocarbons in excess of detection limits in soil <br /> and groundwater in the vicinity of the former tank location. This assessment <br /> included the installation of three groundwater monitoring wells, MW-1, MW-2, and <br /> w <br /> MW-3 and four soil borings, B-1, B-2, B-3, and B-4. Benzene, toluene, ethylbenzene, <br /> and xylenes (BTEX) and total petroleum hydrocarbons (TPH) constituents were <br /> detected in boring B-1, downgradient of the former UST location, and in boring B-2, <br /> %.' near the former UST location. BTEX and TPH were also detected in MW-1, <br /> downgradient of the former UST. Organic lead was not detected in any of the soil <br /> 1,0 samples. The water samples were not analyzed for lead. Petroleum hydrocarbons <br /> were not detected in samples from the other borings and monitoring wells. <br /> 4 Groundwater was determined to flow towards the southwest. Kleinfelder <br /> recommended removing the two remaining USTs, installing three to five additional <br /> wells southwest (downgradient) of the USTs, and initiating quarterly groundwater <br /> monitoring. The results of the Kleinfelder assessment are summarized in Appendix <br /> C, Tables C-1 and C-2. <br /> �,. In September 1989, the District removed the two remaining USTs. These tanks <br /> were reported to contain unleaded gasoline and leaded gasoline. No indications of <br /> rt.. <br /> leakage from these tanks were observed and no petroleum hydrocarbons in excess <br /> of detection limits were found in the soil beneath the tanks. These two USTs were <br /> replaced with two aboveground tanks. <br /> LN <br /> 96R7 Fast Bay Municipal Utility District <br /> 40429700.fcr 4 Final Closure Report <br />