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Project 113-26-04,05,Page 2 November 17,1995 R� . Site UST History There are currently four active USTs at the site Two 10,000 gallon gasoline USTs were removed from the property on March 3, 1988 Groundwater was observed at 7 feet BGS (below ground surface) The tank excavation was de-watered and groundwater grab samples were obtained by Kleinfelder personnel prior to the installation of three new USTs measuring 12,000 gallons each, along with one 550 gallon waste oil tank- The grab groundwater samples contained TPH as gasoline at 86 and 59 parts per billion (ppb) and benzene, toluene, ethylbenzene, xylenes (BTEC) constituents from hundreds of ppb up to hundreds of ppm (Table 1 Soil and Groundwater Sample . ) About 400 yards of contaminated soil was removed from the tank pit Confirmation soil samples from the tank pit walls showed 22 and 30 parts per million (ppm) TPH as gasoline In 1988, USTs were also removed from the property across Holly Drive to the west (2421 Holly Dr ) from the site Soil samples from about 9 feet BGS (2-3 feet below the static groundwater level) gave N D (not detected) results for TPH as gasoline and BTEX with detection limits of 1 ppm and 10 ppb, respectively A groundwater grab sample contained 130 ppm TPH as gasoline with BTEX in the 10's of ppm range A June 30, 1988 letter from the County requested further investigation and site assessment Another station existed across Holly Dr and across Grant Line Rd (10 West Grant Line Rd ) to the southwest from the subject property It was discovered from a local tank removal contractor that USTs had been removed and that gasoline contaminated soil was present there Three groundwater monitoring wells (MW-1, 2, 3) were installed at the site in April, 1988, and a fourth well (MW-4) in May, 1988 Groundwater sampling and analyses from May 1988 showed TPH-gasohne at 140 µg/L and benzene at 2.7 µg/L in MW-4 (Table 1) Groundwater monitoring was performed by Parker Environmental Services in September, 1992 Approximately 0 06 feet of free standing gasoline was measured upon the groundwater in MW-4, which is immediately north of the tanks near the store front MW-2 had a soil blockage at six feet BGS MW-1 and MW-3 contained low to moderate levels of TPH as gasoline and BTEX The blockage in MW-2 was pushed to the bottom of the well by Parker Environmental Services in December, 1992 • A passive skimmer was installed in MW-4 by Parker Environmental Services on February 11, 1993, to collect floating product No free product was collected in the skimmer during the monitoring period Seven small diameter soil cores were advanced under the direction of Parker Environmental Services in March, 1993 Continuous soil cores were obtained, and undisturbed soil samples obtained from between 6 and 7 feet below ground surface Parker Environmental Services, 190 East 7th Street, Pittsburg, CA 94565-2317 Phone (510) 439-1024 Fax (510) 439-2566