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(I I September 14, 1988 r AGS Job No. 86102-3 Page 2 previous sampling events. The data indicate that the ground- water surface has dropped an average of 2.01 feet compared to the last measurement. 61N After the 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 past the interface. The bailer was then retrieved and the water sample examined for floating product, �q emulsion, sheen, or other subjective evidence of hydrocarbon contamination. No floating product or emulsion was noted in samples from the monitoring wells, although a slight product sheen was noted in well Mw-1. Cumulative results of these and previous subjective analyses are summarized in Table 1. Ground-water monitoring wells Mw-1, MW-2, and Mw-3 were purged prior to sampling with an electric submersible pump. Approximately 330 gallons of ground water were pumped from each well. The water was pumped into 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. Recovery in the wells was relatively rapid. After ground water was allowed to recover to static levels, samples were collected by lowering the top of a clean Teflon bailer through the air- water interface to a point approximately 3 feet below the Einterface. The water was then transferred to laboratory-cleaned, C C!I liliter glass volatile organic analysis vials. Concentrated 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 ground-water samples were analyzed for total petroleum hydrocarbons (TPH) by Environmental Protection Agency (EPA) Method 8015 (modified for gasoline) and the volatile hydrocarbon constituents benzene; ethylbenzene, toluene, and total xylene ].sobers (BETX) by EPA Method 602. Applied GeoSystems' laboratory is certified by the State of California for these analyses. Ccpies of the laboratory Analysis Reports are attached to this letter report. -- - ; -- The-results-of-the- analyses f summarized-inTable 2, indicate-that --- - -- _---- -- -- --- the concentration of benzene in ground-water samples collected J from monitoring wells Mw-1, MW-2, and Mw-3 exceeded .the maximum levels for drinking water recommended by the California Department of Health Services (DHS) . The concentration of toluene and total xylene isomers in the sample collected from .4ppiiea� GeoSYSAMs