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Z r W2al June 7, 1988 AGS Job No. 87048-2 Page 2 measurement was 0.27-foot vertically per 100 feet horizontally (14 feet per mile) . These calculated values are similar to the previous sampling event of June 16, 1987. During that investigation, the measured direction of ground-water flow was south 60 degrees west and the average gradient 0.33-foot vertically per 100 feet horizontally. The shallower ground-water surface and more southerly ground-water flow direction may be attributable to local pumping for agricultural irrigation. Samples of ground water were collected from the air-fluid interface in the monitoring wells for subjective analyses by lowering a Teflon bailer approximately halfway through the interface. The bailer was then retrieved, and the water sample was examined for floating product, sheen, and other subjective ® evidence of hydrocarbon contamination. No floating product, product sheen, or emulsion was noted in samples from the monitoring wells, although a slight product odor was obvious in wells IC -2 and MW-3. Cumulative results of these and previous subjective analyses are presented in Table 1. ® t'f Approximately three well volumes of ground water (30 gallons) were purged from monitoring wells MW-1 through MW-4 using a submersible pump. Recharge to the wells was relatively rapid. Ground-water samples for laboratory analysis were then collected from the monitoring wells by lowering a clean Teflon bailer through the air-water interface to a point immediately below the ® top of the water column. The bailer was then recovered and the sample slowly transferred to laboratory-cleaned, 4o-milliliter glass volatile organic analysis vials. Concentrated hydrochloric acid was added to each sample as a preservative. Sample containers were then labeled and immediately placed in iced storage. Chain of Custody Records were initiated by the sampler ® and accompanied the samples to the analytical laboratories. Copies of these records are attached to this report. The ground-water samples were analyzed for total volatile hydrocarbons and the volatile hydrocarbon constituents benzene, ethY lbenzene, toluene, and total xylene isomers by Environmental Protection Agency Method 602 at Applied GeoSystems' laboratory in Fremont, California. The results of these and previous analyses are summarized in Table 2. Variations of contaminant concentrations with time are shown on Plates P-4 through P-7. Copies of the laboratory Analysis Reports are attached to this report. --------------- ® APP1149d GeOSYWOms