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Soil Boring Report — former Chevron Station #9-3232, Stockton CA July 27 1999 - million (ppm). Benzene was detected in one sample at a concentration of 0. 81 ppm . Lead was detected in three of the five soil samples at concentrations of 5 and 6 ppm. The soil sample collected beneath the waste oil UST remote fill pipe contained TPHg (3 ppm). Total Petroleum Hydrocarbons as diesel (TPHd) were also detected in this sample at a concentration of 350 ppm, along with Oil and Grease (O&G) at a concentration of 1 ,700 ppm and trichloroethane (TCE) at a concentration of 0.037 ppm . In October 1998, GR installed three groundwater monitoring wells (MW- I through MW-3). The soil samples analyzed from well borings MW4 and MW-3 did not contain detectable concentrations of TPHg, benzene, toluene, ethylbenzene, and total xylenes (BTEX) or methyl tert-butyl ether (MtBE) with the exception of the sample from boring MW-3 at 49.5 feet bgs. This sample contained TPHg and benzene at concentrations of 52.6 and 0.901 ppm, respectively. Samples from 10 to 25 .5 feet bgs in boring MW-2 did not contain TPHg, BTEX or MtBE. However, TPHg and benzene were detected in the samples from 30.5, 40.5 and 50.5 feet bgs. TPHg concentrations ranged from 2.94 to 593 ppm, and benzene concentrations ranged from 0. 184 to 6.4 ppm. On November 4, 1998, groundwater was recorded at depths between 31 .93 and 36.07 feet below top of well casing. The flow direction was to the southwest at a gradient of 0.05 ft/ft. Groundwater samples from each of the wells contained concentrations of TPHg and BTEX. Well MW-2, located downgradient of the dispenser islands had the highest concentrations of TPHg (120,000 parts per billion, or ppb) and benzene (23,000 ppb). Fuel oxygenate compounds were not detected in any of the groundwater samples. The gasoline and waste oil USTs were removed on March 11 , 1999. Petroleum Hydrocarbons were not detected in the samples collected beneath the dispenser island or the product piping. TPHg was detected in soil samples collected beneath the middle gasoline UST. The highest concentration was detected in the sample from beneath the southern end of the middle tank at 19 feet bgs (680 ppm). A sample from 21 feet bgs in this area contained only 51 ppm of TPHg. MtBE was detected in eight of the nine soil samples collected beneath the gasoline USTs at concentrations between 0. 11 and 0.96 ppm. Benzene was not detected in any of the samples from beneath the gasoline USTs. One soil sample from 10 feet beneath the waste oil UST contained TPHg (2.0 ppm), TPHd (810 ppm), tetrachloroethane (0.5 ppm), and O&G (2,700 ppm). After additional excavation of the waste oil UST pit, a sample from 17 feet bgs in this area did not contain TPHg, TPHd, or tetrachloroethane, but did contain O&G (79 ppm). A soil sample from the opposite end of the waste oil UST pit at 10 feet bgs contained O&G (110 ppm). A groundwater sample from the gasoline UST pit did not contain TPHg or benzene, but did contain MtBE (6.0 ppb). FIELD ACTIVITIES To further evaluate the distribution of residual petroleum hydrocarbons, GR advanced four soil borings to depths up to 70.5 feet bgs by Geoprobe and hollow-stem augers. Field work was performed in accordance with GR's Site Safety Plan #346463 .04, dated April 21 , 1999 . GR Field Methods and Procedures are included in Appendix B . Underground Service Alert was notified prior to beginning site activities, and a private subsurface utility locating service was contracted to locate subsurface utilities on the subject site. Geoprobe activities were performed by Fisch 346463 .04-2 2