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Mr. Kenneth Earnest Ultramar Inc. November 5, 1993 Page 2 Soil Boring Results Soil samples were collected from each soil boring at 5-foot intervals for classification and for field analysis of petroleum hydrocarbon vapors with an organic vapor meter (OVM). Soils encountered from the surface to a depth of approximately 50 feet were generally poorly graded sand with silt and interbeds of sandy silts and clays. At depths greater than 50 feet, the soils were generally sandy silts and clays with interbeds of poorly graded sand with silt. Soil boring logs containing soil descriptions and OVM readings are included in Enclosure B. Soil samples collected from each boring at approximate 10-foot intervals were submitted for laboratory analysis of benzene, toluene, ethylbenzene, and xylenes, and total petroleum hydrocarbons ('IPH) as gasoline using methods approved by the U.S. Environmental Protection Agency and the California Department of Health Services. TPH as gasoline was detected in only one sample, SB-3-5, at a depth of 26 feet below grade. The concentration was 17 parts per million (ppm). The soil sample collected at a depth of 41 feet from soil boring SB-3 contained xylenes at a concentration of 0.0074 ppm, but did not contain detectable concentrations of other petroleum hydrocarbons. Benzene was not detected in any of the samples collected from the soil borings. Soil sample analytical results are summarized in Table 1 and copies of the certified reports are included in Enclosure C_ Well Installation `= Ground water monitoring wells MW-1, MW-2, and MW-3 were constructed of flinch diameter, flush threaded, Schedule 40 PVC casing to approximately 79 feet below grade. The screen interval extends from 79 to 64 feet below grade. The annular space was filled with No. 3 Lonestar sand from the total depth to 2 feet above the well screen. A 2-foot thick bentonite seal was placed above the filter pack in the wells. The annular space above the bentonite seal was filled with cement grout containing 5 percent bentonite. Well construction details for monitoring wells MW-1, MW-2, and MW-3 are included in Enclosure D. A copy of the monitoring well construction permit is included in Enclosure E. Water Table Elevation Measurements Flow Direction and Hydraulic Gradient Ground water table elevation measurements were recorded on September 8, 1993, and are included in Table 2. The ground water table measurements recorded on September 8, 1993, were used to construct the water table contour map presented in Figure 3. Based on the September 8, 1993, water table measurements, the inferred direction of ground water flow is toward the east-southeast with a hydraulic gradient of approximately 0.01 foot per.foot. Based on the direction of ground water flow, monitoring well MW-1 is the upgradient well, monitoring well MW-2 is located downgradient of the underground storage tanks, pump islands, and monitoring well MW-3 is located crossgradient of the pump islands. Ground Water Sampling and Analytical Results On August 27, 1993, monitoring well MW-3 was sampled and on August 31, 1993, monitoring wells MW-1 and MW-2 were sampled. Each well was surged and purged before sampling. The ground water sample collected from monitoring well MW-3 contained benzene at a concentration of 0.8 parts