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Soil Sampling Report - Chevron Service Station #9-3232, Stockton, CA April 28, 1999 Gasoline UST Removal and Sampling On March 11 , 19992 three 10,000-gallon single-walled fiberglass gasoline USTs were uncovered and removed by Wendt. Upon removal, the USTs were visually inspected for evidence of failure. Holes were not observed in the gasoline USTs. The USTs were removed from the site and disposed of by Ecology Control Industries (ECI) of Richmond, California Limits of the former UST excavation are shown on Figure 2. Backfill materials in the former gasoline UST excavation consisted primarily of pea gravel. Perched water was encountered in the UST excavation following UST removal. Per the direction of Mr. Michael Kith, prior to compliance soil sampling, one water sample, labeled TK-Water, was collected from the perched water in the gasoline UST pit by the use of a disposable bailer. Six soil samples, labeled TKl -N, TKl -S, TK2-N, TK2-S, TK3 -N, and TK3 -S, were then collected from beneath the northern and southern ends of the gasoline USTs at approximate depths of 14 feet bgs. Due to discoloration and hydrocarbon odor noted in the soil beneath the middle gasoline UST, and to further characterize the soil condition, one additional soil sample, labeled TK2-N(21), was collected from beneath the location of sample TK2-N at a depth of approximately 21 feet bgs, and two additional soil samples, labeled TK-2S(19) and TK2-S(21), were collected from beneath sample location TK2-S at depths of approximately 19 and 21 feet bgs, respectively. Native soil beneath the USTs consisted of sand to a depth of approximately 19 feet below ground surface (bgs) and silt between 19 feet bgs and the maximum depth explored (approximately 21 feet bgs). Soil sample locations are shown on the attached Figure 2 . Following UST removal, soil sampling and excavation activities (prior to new UST installation) no water was present in the UST pit. Three 10,000-gallon new double-wall fiberglass gasoline USTs will be installed in the former UST pit by Wendt. All soil and water samples collected from the former gasoline UST pit were analyzed for Total Petroleum Hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX), methyl tert-butyl ether (MtBE) by EPA Method 8020, and oxygenate compounds by EPA Method 8260. TPHg was detected in soil samples TK2-S and TK2-S(19) at concentrations of 1 .3 and 680 ppm (reported by the laboratory as gasoline and unidentified hydrocarbons C6-C12), respectively, and in soil sample TK2-S(21) at a conccentration of 51 ppm (reported by the laboratory as gasoline and unidentified hydrocarbons >C7). Benzene was not detected in any of the soil samples from the gasoline UST pit. MtBE (EPA method 8020) was not detected in additional soil samples TK2-N(21 ), TK2-S(19) and TK2-S(21), and was detected in all initial soil samples (collected from beneath the gasoline USTs at depths of 14 feet bgs) at concentrations ranging between 0. 17 and 1 . 2 ppm. Oxygenate compounds (EPA Method 8260), except for MtBE, were not detected in any of the soil samples from the gasoline UST pit. MtBE (EPA Method 8260) was not detected in soil sample TK2- N(21), but was detected in all other soil samples at concentrations ranging between 0. 11 and 0. 97 ppm. The grab groundwater sample (TK-Water) contained xylenes at a concentration of 0. 97 ppb. Oxygenate compounds were not detected in sample TK-Water, except for MtBE (EPA Method 8260) detected at a concentration of 6 ppb. 346463 .03 2