SITE INFORMATION AND CORRESPONDENCE_FILE 1

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samples analyzed from borings U-J (1.7 ppm at 26.5 feet bgs) and U-K (130 ppm at 41.5 feet bgs). TPHg were detected in soil samples analyzed from borings U-3 (330 ppm at 46.5 feet bgs), U-L(19,000 ppm at 45.5 feet bgs), and U-M (5 10 ppm at 45.5 feet bgs). GSI performed a limited environmental site assessment (ESA) of the properties in the vicinity of the subject site. The ESA identified a former station located at 448 East Miner Avenue, south of the subject site. Historical groundwater data indicate that this former station is upgradient of the subject site. Environmental information related to the soil and groundwater conditions beneath this former service station were not obtained during the ESA. To further assess on-site and off-site subsurface conditions, GSI installed three additional on-site groundwater monitoring wells(U-4 through U-6)and two off-site groundwater monitoring wells(U-7 and U-8), drilled two additional on-site exploratory soil borings (U-N and U-O), and installed one on-site vapor extraction well (UV-1) in August 1995 (Figures 2 and 3). TPHg or benzene were not detected in soil samples collected from borings U-5 through U-7 or U-O. TPHg was detected in the soil sample collected from boring U-N at 25 feet bgs (1.7 ppm). TPHg and benzene were detected in the soil sample collected from well boring U-4 at 10 feet bgs (41 and 0.011 ppm, respectively). TPHg was detected in the three soil samples collected from well boring UV-1 at 25, 35, and 40 feet bgs at concentrations ranging from 3,400 to 20,000 ppm. Benzene was detected in the soil samples collected at 35 feet (99 ppm) and 40 feet bgs (15 ppm) in boring UV-1. In May 1997, GSI conducted a search of Department of Water Resources files in Sacramento, California for domestic and municipal supply wells located within a 0.5-mile radius of the subject site. Twelve sites with wells were identified within the area searched. Six sites were identified as domestic water supply wells, four sites as municipal water supply wells, and two sites as industrial water supply wells. The nearest downgradient well (municipal) is located approximately 1,580 feet from the subject site. In August 1997, GSI installed off-site groundwater monitoring well U-9 in an attempt to delineate the downgradient edge of the dissolved plume (Figure 3). Petroleum hydrocarbons were not detected in the three soil samples from the well boring that were submitted for analysis. The groundwater sample from the well initially contained TPHg (990 ppb), benzene (130 ppb), and MTBE (12 ppb). Quarterly monitoring and sampling of the groundwater monitoring wells began in August 1994. At the time wells U-1 through U-3 were installed in August 1994, groundwater was measured at approximately 48 feet below ground surface (bgs). Groundwater in well U-9 is currently measured at approximately 32 to 33 feet bgs (August 31, 1997), a rise of 15 to 16 feet. Groundwater flow during this period has been to the northeast. Dissolved concentrations of TPHg or benzene have been detected in wells U-1 through U-4 and U-7 through U-9. Most recent data indicates wells U-1 and U-3 contain dissolved concentrations of TPHg and benzene.