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Ms. Linda Turkatte August 22, 1991 Page 2 Free Product Measurements The presence of free product or proalicl she�-n in the monitoring wells was evaluated using procedures described in Enclosure A. An July a 1991, free product was detected in,p9niloring well MW4 (thickness 0.02-foot)and product sheen was observed an ground water samples colift-ted-from monitoring wells MW-3 and MW-9: On August 1,1991,free product was detected is monilming wcl! .MW-4-,thicIm=(WS-foot),but product sheen was not observed on water samples collem-A from the other monitoring wells. Free product and preducl sheen observations are included in Table 1. A Westinghouse pneumatically-operated product-only pump was operating alternately in monitoring wells MW-2 and MW-7 between January and April 1991. Product recovery pumps have been operating in both wells simultaneously since May 1991. Neither free product nor product sheen was detected in monitoring wells MW-2 and MW-7 on July 23, 1991. These wells were not examined for free product or product stem when water levels were met4ured on August 1,1991. The total amount of free product recovered since Mqy 1991 is not known be-cause the pumps have been discharging ground water as well as product. Ground Water Sampling and-Ana!1lical Resnits Ground water samples were collected from monitoring welts MW-I,MW-3,IVIW-5,MW-6,MW-8,and MW-9 on July 23, 1991. Monitoring wells MW-2, MW-4,and MW-7 were not sampled due to the presence of free product or operating product recovery pumps, as described above. Ground water samples were collected using procedures described in Enclosure X Each ground water sample was submitted for analysis of benzene, toluene, ethylbcnzene, xylenes (BTEX), and total petroleum hydrocarbons (TPH) as gasoline, using U.S. Environmental Protection Agency and California Department of Health Services approved methods. The analytical laboratory results for ground water samples collected an July 23, 1991, are summarized in Table 2. Previous results are also provided in Table 2 for comparison. Copies of the certified laboratory reports for the July 1991 sampling event are included in Enclosure B. Analytical test results indicate that detectable concentrations of petroleum hydrocarbon constituents were present in each of the ground water samples collected on July 23, 1991- Concentrations of TPH as gasoline ranged from 120 parts per billion (ppb)(MW-6) to 110,000 ppb (MW-9), and benzene concentrations ranged from 1.1 ppb (MW-6) to 18,000 I.,lb (MW-9). Concentrations of-1wiroleunt hydrocarbon constituents in ground water samples generally increased since the previous sampling event in April 1991; however, concentrations of benzene in samples collected from monitoring wells MW-I and MW-9,and TPH as gasoline in the sample collected from monitoring well MW-9,have decreased.