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Mr. Kenneth Earnest Ultramar Inc. November 23, 1994 Page 2 On September 7 and 8, 1994, confirmation borings CB-4, CB-5, and CB-6 were drilled to a depth of 50 feet at on-site locations. Soil samples were collected from each boring at 5-foot intervals. Confirmation boring CB-6 was angled 35 degrees off vertical in order to collect soil samples beneath the former underground storage tank pit. Soil boring locations are shown in Figure 2. Soils encountered during drilling exhibited poor lateral continuity but can be generally characterized as silty sand from the surface to approximately 10 feet below grade, silt from approximately 10 feet to 20-feet below grade, poorly graded sand or sand containing minor clay, silt or gravel from approximately 20 feet to 50 feet below grade, clay and silt from 50 feet to 60 feet below grade, and poorly grade sand below 60 feet. Ground water was present at depths of approximately 57 to 60 feet. Soil boring logs with detailed lithologic descriptions are presented in Enclosure B. Soil Analytical Results Soil samples collected from each boring at depths of 10, 20, 30, 40, 45, and 50 feet were submitted for laboratory analysis of benzene, toluene, ethylbenzene, total xylenes (BTEX), and total petroleum hydrocarbons (TPH) as gasoline. Analytical results are summarized in Table 1 and copies of the analytical laboratory reports are presented in Enclosure C. Analytical results for the soil samples indicate that detectable concentrations of petroleum hydrocarbons were not present in samples collected from confirmation borings CB-1, CB-2, or CB-3. Detectable concentrations of TPH as gasoline were present in soil samples collected at depths of 20, 30, 40, 45, and 50 feet from confirmation boring CB-4, and from a depth of 45 feet from confirmation borings CB-5 and CB-6. Ground Water Analytical_Results The ground water samples collected from confirmation borings CB-1, CB-2, and CB-3 were submitted for laboratory analysis of BTEX and TPH as gasoline. Analytical results are summarized in Table 2 and copies of the analytical laboratory reports are presented in Enclosure D. Analytical results indicate that petroleum hydrocarbons were not present in detectable concentrations in any of the ground water samples with the exception of the ground water sample collected from confirmation boring CB-1, which contained xylenes at a concentration of 0.61-micrograms per liter. This sample was originally analyzed for BTEX by EPA Method 602, a photoionization method, and was subsequently reanalyzed for BTEX using EPA Method 624, a mass spectrometry method. No BTEX constituents were detected using BPA Method 624. Vapor Extraction Well Installation Confirmation boring CB-4 was completed as soil vapor extraction well VEW-1. Vapor extraction well VEW-1 has three separate 2-inch diameter casings nested within the borehole, with screened • intervals at 15 feet to 25 feet, 27 feet to 37 feet, and 40 feet to 50 feet. Construction details for vapor extraction well VEW-1 are illustrated in Figure 3.