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r 'ktw � ;�`s,$� � ,:c �"; a �/�, _•.'yiw. ,'+. fir.. ✓,�t f �' .s� � RF�.tas , cfi��' dam: <br /> T6 <br /> s y}y1'�'�r�' vtt �,.,�fH.✓.'a�6sl�t � if� FI`���a�s�.- �,..,c•r ;�a�' � �.• ,: y^'��`='•, „y:. _. �d,iy� }��-'i�+s� y_�`�'Y �L��`'y� r.���.t'�, r ...1' .�� ti . �� ".f <br /> JY <br /> r� <br /> r: <br /> Y, <br /> f <br /> 275 Grantline Rd. Page 2 of 7 <br /> underneath this strata lies 4 feet of light to medium dark tannish- <br /> brown, damp, slightly plastic clay; this layer is followed by at <br /> least 4 feet of moist grayish-tan to tannish-brown, very fine- <br /> grained clayey sand that contains occasional. pebbles. Groundwater <br /> was first encountered at a depth of appproximately 10.5 feet below <br /> grade and stabilized at a depth of 8.5 feet after 5 hours. Based <br /> on the surface topography, a very low groundwater qradient is <br /> assumed. It is estimated that the direction of groundwater flow is <br /> to the northeast. <br /> SITE BACKGROUND AND HISTORY <br /> The current business activity- at the site is a video sales and <br /> rental shop. It was reported to TECC that the site was formerly <br /> used as a retail gasoline service station. Approximately 60 feet <br /> of underground product line were connected to the underground fuel <br /> "Yanks with a product dispenser area (pump island) located on the <br /> southern portion of the property. According to interviews with the <br /> present tenant, the (UST's) were removed some time in 1971 and had <br /> last been us-Dd to store gasoline. There were no known details of <br /> the tanks removal, contents or disposal, nor were any as-built <br /> plans available. On July 18, 1989 , TFCC collected 4 soil oamples <br /> of the soil/water interface (vadose zone) along the perimeter of <br /> the area where the UST's were thought to have been. The sampling <br /> locations are shown as circles in the attached Figure 1. <br /> Analytical results did not indicate any concentrations of purgeable <br /> halocarbons above test method detection limits (see TFCC proposal <br /> dated 3/15/90) . TPH(as gasoline) was detected in 2 of the 4 soil <br /> samples analyzed but in concentrations only slightly above test <br /> method detection limits. A concentration of 370 ppm oil and Grease <br /> was detected in the soil sample from Boring #2, the most <br /> northeasterly location and the farthest location away from the <br /> waste oil pit. <br /> A 250-gallon UST that had last contained oil and grease had not <br /> bee; removed in 1971 and .remained on site until December 6, 1989 . <br /> On that date, TFCC removed and disposed of the waste oil tank in <br /> accordance with the San Joaquin .County Health District: tank removal <br /> guidelines. Groundwater was encountered at a depth of <br /> approximately 8.5 to 9 .0 feet below surface grad-. <br /> SOIL EXCAVATION AND DISPOSAL <br /> On July 11, 12 and 13, 1990, TECO excavated an estimated 220 cubic <br /> yards of oil and grease-contaminated soil from the area around and <br /> under the removed waste oil tank (see attached Figure 1) . The <br /> soils were removed based on visual appearance of the soils. Soil <br /> contamination_ appeared as a dark gray stain from a depth of 6.5 <br /> feet to 10 fee:: below grade. Soil samples were taken immediately <br /> - - above the groundwater interface, about 8 to 9 feet below grade. <br /> Groundwater was first encountered at a depth of approximately 10.5 <br /> , <br />