ARCHIVED REPORTS XR0000721 - Laserfiche WebLink

Home Browse Search

Ms. Marla Guensler Exxon Company, U.S.A. September 14, 1993 Page 2 Approximately 500 cubic yards of soil were removed from the site in December 1991 by Dillard Trucking, Inc., to two landfills: The Chemical Waste Management facility in Kettleman City, California, and the Browning-Ferris Industries(BFI)landfill on Vasco Road in Livermore, California. Approximately 1,300 cubic yards of soil were removed from the site in May and June 1992 by Dillard Trucking, Inc., to the BFI landfill in Livermore, California. There are currently four ground water monitoring wells at the site. The depth to ground water in these wells has generally ranged from approximately 11 to 15 feet below grade, and the inferred direction of ground water flow has consistently been toward the northeast. The most recent analyses of ground water samples indicates that detectable concentrations of petroleum hydrocarbons were present in samples collected from monitoring wells MW-5 and MW-6. For example benzene was detected in MW-5 at 79 parts per billion (ppb) and in MW-6 at 0.9 ppb. A summary of quarterly monitoring results may be found in the Quarterly Ground Water Monitoring Report, First Quarter 1993, prepared by Delta, May 4, 1993. Purpose The purpose of this investigation was to identify the lateral extent of petroleum hydrocarbons in soil beneath the site. This was necessary because soil samples collected from the sidewall at the southwest corner of the former underground gasoline storage tank excavation, and from the east and south sidewalls of the former pump island excavation contained petroleum hydrocarbons. Soil Borings On July 15, 1993, two soil borings were drilled near the southwest corner of the former fuel storage tank excavation, and six soil borings were drilled east and south of the former pump island excavation, in order to evaluate the extent of petroleum hydrocarbons in soil at those locations. Ground water was present in the monitoring wells at approximately 12 feet below grade; therefore, each soil boring was advanced to approximately 10 feet below grade. Soil samples were collected from each boring at 5-foot intervals. Methods used to drill and sample the soil borings are described in Enclosure A. Locations of the soil borings are shown in Figure 2. i Soils encountered in the borings generally consisted of silty clay or clayey sand to approximately 8 to 11.5 feet, underlain by clay to the maximum depth of drilling. Soil boring logs are presented in Enclosure B. Soil Sample Analytical Results Soil samples were analyzed in the field for the presence of organic vapors using a photoionization detector (PID). The PID readings are recorded on the soil boring logs in Enclosure B. The soil samples were submitted to a California-certified laboratory for analyses of concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) and TPH as gasoline. In addition a soil sample collected from the stockpiled drill cuttings was analyzed for concentrations of BTEX, TPH as gasoline, and .` organic lead. Analytical test results are summarized in Table 1 and copies of the analytical laboratory reports are presented in Enclosure C.