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� a r Ms. Linda Turkatte May 29, 1991 Page 2 Waler level measurements made; on April 1991, indicate an inferred direction of ground water flow toward the nuith-northeast (Figure 4). The ground water gradient beneath the site averages approximateiy 0.03 foot per foot. Free Product Measurements Free product measuo.-ments were recorded from monitoring wells MW-2,MW-3,MW-4,and Nil-on February 15,March 7,and April 26,1991. Included in Table 1 are observations and product thicknesses. Free product was detected in monitoring wells MW-3 and MW-7 in February and March 1991,but oniy a sheen was detected in April 1991 in both monitoring wells. Monitoring well MW-2 contained up to 1.31 feet of free product(Maria:7,1991)and monitoring well MW-4 contained approximately 1 foot of free product during the April sampling event. A subjective analysis for a ground water sample collected from each well was perfermee, during each sampling event according to methods described iri Enclosure A. Figure 5 illustrates the inferred extent of product beneath the site. Ground Water Sampling and Anal-i7ieal Results On April 26, 1991,ground water samples were collected from monitoring wells MW-1,MW-3 MW-5, MW-6,MW-7,MW-8,and MW-9. Ground water samples were collected using procedures described in ,Enclosure A. Foch ground water sample was Submitted for analysis of benzene,toluene,ethylbenzene, xylenes (BTEX), and total petroleum hydrocarbons;(TPH) as gasoline using U.S. Environmental Protection Agency and California Department of Health Services approved methtv!:. The analytical laboratory results for ground water samples collected on April 26, 1991 are sumtn'w1zed in Table 2. Previous results are also provided in Table 2 for comparison. Copies of the certified laboratory reports for April 1991 are included ip.Enclosure B. Analytical laboratory results indicate an increase in the concentrat;on of benzene from January to April 1941 in ground water.samples collected from monitoring well MW-5 and a decrease in benzene concentration in ground wa!er sampleb collected from monitoring wells MW-1, MW-8, and MW-9. Ground water samples collected from monitoring well MW-6 have not contained detectable concealrations of benzene for six consecutive sampling events. Free-Phase Product Recovery A Westinghouse pncumatica!!�-operatcd product-only pump was operating alternately in monitoring wells MW-2 and MW-7 between January and April 1991. On March 7, 1991, the pump was removed from monitoring well MW-7 and placed in MW-2. The product level in monitoring well MW-7 has dropped from 1.05 feet in November 1990 to a heavy sheen iz April 1991. An additional pump was purchased in May 1991 so that monitoring wells MW-7 and MW-2 could be subjected to free product i recovery simultaneously.