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August 19, 1988 AGS Jab No. 86091-6 Page 2 were inconsistent with those from the other wells and were excluded from the gradient calculation. After initial water-level measurements were taken, samples of ground water from the air-fluid interface were collected for subjective analysis by lowering approximately half the length of a clean Teflon bailer through the interface. The bailer was then retrieved and the water sample examined for floating produce•', sheen, and other subjective evidence of hydrocarbon contami- nation. No floating product, product sheen, or emulsion was noted in samples from the monitoring wells, although a slight product odor was dete--ted in well MW-1. Results of these and previous subjective analyses are summarized in Table 1. I The monitoring wells were purged prior to sampling with an electric submersible pump. Monitoring wells MW-1, MW-2, and MW-3 are 4-inch-diameter wells, and 165 to 20o gallons of ground water were removed from each. Wells MW-4 and MW-5 are 2-inch-diameter wells, and 60 to 65 gallons were removed from each, The water was pumped to 55-gallon DOT drums which were temporarily stored on the site. The purged water was subsequently removed from the drums, hauled to Beacon's refinery in Hanford, California, and treated in a waste-water separator. After purging, ground-water samples were collected from the wells by lowering the bottom of a clean Teflon bailer to a point approximately 3 feet below the air-water interface. The bailer was then retrieved and the sample transferred to laboratory-cleaned, 40-milliliter glass volatile organic analysis vials. G-incentrated hydrochloric acid was added as a preservative. A Chain of Custody Record was initiated by the field geologist and accompanied the samples to Applied GeoSystems' analytical laboratory in Fremont, California. A copy of that record is attached to this letter report. The samples were analyzed for total petroleum hydrocarbons by the Environmental Protection Agency (EPA) Method 8015 (modified for � gasoline) and the volatile hydrocarbon constituents benzene, athylbenzene, toluene, and total xylene isomers by EPA Method 602. Applied GeoSystems' laboratory is certified by the State of California for these analyses. Copies of the laboratory Analysis Reports are attached to this letter report. The results of the laboratory analyses, summarized in Table 2 , indicate that the benzene concentration in ground-water samples collected from monitoring wells MW-1, MW-2, and MW-4 exceeded the maximum level for drinking water recommended by the California Department of Health Services (DHS) . The concentration of the other volatile constituents in these wells have increased in comparison to previous analyses but were below the maximum levels for drinking water recommended by the DHS. The benzene