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Mr. Randall Stephenson January 27, 1994 Page 2 Soil Borings Soil samples collected from the borings consisted of silty clay, clayey silt, sandy silt, and silty sand. For example, samples collected from the soil boring for monitoring well MW-1 indicated the following vertical soil sequence: from below the asphalt to 21 feet below grade, the soil encountered consisted of silty clay, from 21 to 45.5 feet, a sandy silt unit was encountered; under the sandy silt, a silty sand is present to 70 feet; from 70 to 82 feet, a sandy silt was encountered; and from 82 to 90 feet (the total depth of the boring), silty clay was encountered. Contacts between soil types were sharp. Soil boring logs containing detailed descriptions of soil conditions encountered in each boring are included in Enclosure B. Ground water was encountered in the soil borings at depths ranging from 79 to 80 feet below grade. Soil Sample Analytical Results A portion of each soil sample collected from the soil borings was sealed in a plastic bag and allowed to reach ambient air temperature. The headspace of the bag was then screened in the field with a photoionization detector (PID). The highest PID reading for each sample was recorded on the right-hand side of the boring logs (Enclosure B). Selected soil samples collected from above the water table in each soil boring were submitted to a California-certified laboratory for analyses. A total of nineteen soil samples were analyzed for BTEX and TPHg. Soil sample analytical results are summarized in Table 1. Copies of certified analytical reports are contained in Enclosure E. Soil samples collected from the boring for monitoring well MW-2 contained benzene at concentrations ranging from less than 0.0050 milligrams per kilogram (mg/kg) to 0.22 mg/kg. TPHg concentrations ranged from less than 1.0 mg/kg to 7.7 mg/kg in soil samples collected from the boring for monitoring well MW-2. All other soil samples collected from monitoring wells N1W-1 and MW-3 did not report detectable concentrations of benzene and TPHg. Ground Water Level Measurements Depth to ground water measurements were made in each monitoring well on December 15, 1993 (Table 2). Ground water was present at depths ranging from 79.39 to 80.22 feet below the top of the monitoring well casings. Water level measurements on December 15, 1993, indicated an inferred direction of ground water flow toward the northeast as illustrated on Figure 3. The calculated ground water gradient on this date was less than 0.01 foot per foot. LRPT057.ECD ACTON+ MICKELSON • van DAM, INC. Consulting Scientists, Engineers,and Geologists