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C r ASSOVATIL O C I ATE S INC On January 8, 1998, an ATC geologist supervised the advancement of one soil boring to 41.5 feet below ground surface (bgs). A site plan showing the location of soil boring SB 1 is included as Figure 2. Soil samples were collected at five foot intervals and submitted for analysis of total petroleum hydrocarbons as gasoline and diesel (TPHg and TPHd) by EPA Method 8015; and volatile organic compounds (VOCs) by EPA Method 8260. A Hydropunch groundwater sampling probe was advanced in the soil boring and a groundwater sample was collected. The groundwater sample was analyzed for TPHg, TPHd, VOCs, and halogenated volatile organic compounds (HVOCs) by EPA Method 801018020. Subsequent to the sample collection, the open sampling hole was tremie grouted to the surface with neat cement. Petroleum hydrocarbon constituents were detected in soil samples collected from boring SB 1. The highest reported constituent concentrations were observed in the soil sample collected at 5.5 feet bgs. The petroleum hydrocarbons appeared to attenuate rapidly with depth as indicated greatest by soil sample from 35.5 feet bgs, which contained only trace levels of isopropylbenzene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene. Trace amounts of petroleum hydrocarbon constituents were also detected in the groundwater sample collected from soil boring SB 1, On September 13, 1998, ATC personnel supervised the excavation of the impacted backfill material, approximately 85 tons, located in the former UST location. The excavated backfill material was immediately transported to Forward Inc. landfill in Stockton. Confirmation soil samples were collected from the excavation sidewall and bottom and analyzed for TPHg, TPHd, total petroleum hydrocarbons as Stoddard solvents (TPHss, EPA Method 8015), benzene, toluene, ethylbenzene, and xylenes (BTEX, EPA Method 8020). Confirmation samples from the bottom of the excavation and the north sidewall contained TPHss at concentrations ranging from 1,000 ppm to 4,500 ppm. The excavation was limited by buildings to the south and west of the former UST location. The excavation was backfilled with clean crushed rock from eighteen feet to five feet bgs. The remaining five feet was backfilled with clean Class II aggregate base material to the surface. On September 16 and 17, 1998, ATC personnel supervised the advancement of three soil borings to approximately 57 feet bgs. The borings were completed as groundwater monitoring wells MWI, MW2, and MW3 to evaluate the lateral extent of petroleum hydrocarbon impacted groundwater. ATC also supervised the advancement of one soil boring to approximately 70 feet bgs to evaluate the vertical extent of petroleum hydrocarbon impacted soil. This boring was grouted to the ground surface upon completion. ATC personnel developed and sampled wells MW1, MW2, and MW3. Based on the analytical results and field observations, the soil and groundwater beneath the location of the former 1,000-gallon UST are impacted by TPHss. Groundwater and soil samples collected from wells MW1 and MW2 indicate that impacted soil and groundwater have been defined to the north and east of the former UST. The soil samples from boring SB2 indicate the vertical extent of impacted soil is limited to less than 65 feet bgs. The extent of impacted groundwater and soil to the south and west is unknown. w:1172951reportslwkp 1299.doc 2