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BUILDING 16 FORMER USTs GROUND WATER INVESTIGATION WORK PLAN PORT WEST COMPLEX, ROUGH AND READY ISLAND, PORT OF STOCKTON The soil samples collected from the excavation of USTs 16-1 and 16-2 revealed petroleum hydrocarbons up to 1,900 milligrams per kilogram (mg/kg) of TPHg, 9.7 mg/kg of toluene, 9.5 mg/kg of ethyl benzene, and 6.1 mg/kg of xylenes. MTBE was detected in three soil samples up to 0.13 mg/kg. The grab ground water sample revealed TPHg at 25,000 micrograms per liter (µg/1),benzene at 270 µg/1, toluene at 790 µg/1, xylenes, at 3,700 µg/1, and MTBE at 8,900 µg/l. The soil samples collected from the excavation of UST 16-3 revealed petroleum hydrocarbons up to 0.24 mg/kg of benzene, 0.14 mg/kg of toluene, 0.005 mg/kg of ethyl benzene, 0.066 mg/kg of xylenes, and 0.056 mg/kg of MTBE. The grab ground water sample revealed TPHg at 82,000 µg/l,benzene at 800 µg/1, toluene at 7,600 4g/1,xylenes, at 8,300 µg/1, and MTBE at 57,000 µg/1. The soil samples collected from the excavation of the pipelines and dispensers revealed petroleum hydrocarbons up to 2.9 mg/kg of TPHg, 0.15 mg/kg of benzene, 0.32 mg/kg of toluene,0.007 mg/kg of ethyl benzene, 0.18 mg/kg of xylenes, and 1.9 mg/kg of MTBE. 2.4.2 Soil and Ground Water Investigation A soil and ground water quality investigation was performed in August 1999. Ten borings were advanced (Bl through B10). Four soil samples were collected from 4.5 feet to 8 feet bgs, ten shallow grab ground water samples were collected from approximately 5 feet bgs, and five grab ground water samples were collected from 14 feet bgs. The samples were analyzed for TPHg,BTEX, fuel additives including MTBE, and lead. Of the four soil samples (B1, B3, B7,B8), only the B3 sample collected adjacent to the excavation of the 16-1 and 16-2 USTs revealed measurable concentrations of petroleum hydrocarbons (Table 4). This sample revealed 1.5 mg/kg toluene, 0.49 mg/kg ethyl benzene, and TPHg at 150 mg/kg, which the laboratory reported as not resembling the gasoline standard. MTBE was reported in three samples up to 0.17 mg/kg. Seven of the ten shallow ground water samples did not reveal petroleum hydrocarbons above the detection limit(Table 5). Benzene and toluene were reported in only one sample, B7, at 1.4 µg/1 and 0.91 µg/1, respectively. Ethyl benzene and xylenes were detected in three ground water samples up to 4.3 µg/1 and 19.1 µg/l, respectively. MTBE was detected in six borings up to 590 µg/1, and one boring at 7,900 µg/1. These samples describe conditions in the shallow sandy fill material at the Site. Figure 14 and 15 posts the analytical results for TPHg and MTBE for the shallow grab ground water samples. Four of the five deeper grab ground water did not reveal petroleum hydrocarbons above the detection limit(Table 6). Only the duplicate grab ground water sample collected at B5 revealed TPHg at 58 µg/1 and toluene at 0.52 µg/1. MTBE was detected in three samples up to 2.4 µg/1. These samples describe conditions in the native silts and clays underlying the Site. Figure 16 posts the analytical results. Environmental Risk Services,Corp.