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WIN r 275 Grantline Rd. Page 2 of 7 underneath this strata lies 4 feet of light to medium dark tannish- brown, damp, slightly plastic clay; this layer is followed by at least 4 feet of moist grayish--tan to tannish-brown, very fine_, grained clayey sand that contains occasional pebbles . Groundwater was first encountered at a depth of appproximately 10.5 feet below grade and stabilized at a depth of 8.5 feet after 5 hours. Based on the surface topography, a very low groundwater gradient is assumed. It is estimated that the direction of groundwater flow is to the northeast. SITE BACKGROUND AND HISTORY The current business activity at the site is a video sales and rental shop. It was reported to TECO that the site was formerly used as a retail gasoline service station. Approximately 60 feet of underground product line were connected to the underground fuel tanks with a product dispenser area (pump island) located on the southern portion. of the property. According to interviews with the present tenant, the (UST's) were .removed some time in 1971 and had last been used to .store gasoline. There were no known details of the tanks. removal, contents or disposal, nor were any as-built plans available. On :July 18,1989, TECO collected 3 soil samples of the soil/water interface (vadose zone) along the perimeter of the area where the UST's were thought to have been. The sampling locations are shown as circles in the attached Figure 1. Analytical results did not indicate any concentrations of purgeable halocarbons above test method detection limits (see TECC proposal dated 3/15/90) . TPH(as gasoline) was detected in. 2 of the 4 soil samples analyzed but in concentrations only slightly above test method detection limits. A concentration of 370 ppm Oil and GreaseIIIM . was detected in the soil sample from Boring #2; the most northeasterly location and the farthest location away from the waste oil pit. A 2507gallon UST that had last contained oil 'and grease had not been removed in 1971 and remained on site until December 6, 1989. On that date, TECO remo:ad and .disposed of the waste oil tank :in accordance with the San Joaquin County Health District tank removal guidelines. Groundwater was encountered at a depth of approximately 8.5 to 9 .0 feet below surface grade. ----- -:_-:__: - . .._:.. SOIL.-EXCAVATION_AND...DISPOSAL.._._.. .. On. July 11, 12 and 13, 1990, . TECC excavated an fastimated 220 cubic yards of oil and grease-contaminated soil from the area around and under the removed. waste oil tank (see attached. Figure 1) . The soils were removed based on visual appearance of .the soils. Soil contaminationappearedas a dark gray stain from a depth of 6.5 feet -to 10 feet below grade. Soil samples were taken immediately above the groundwater interface, about 8 to 9 feet below grade. Groundwater was first-encountered at a depth of approximately 10.5 ' ,_