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San Joaquin County, as well as state records, indicate that groundwater flows northeastward <br /> beneath the site Groundwater monitoring wells at the site confirm that the groundwater table <br /> rexists approximately 42 feet beneath the site and flows in a northeasterly direction Pacific <br /> Bell facility UE042 presently contains one 25,000-gallon diesel UST which supplies diesel to <br /> stand by generators <br /> 3.0 Previous Investigative Work_ <br /> The county and city have few records of the site The site had been owned by AT&T from <br /> the mid-1940's until 1963 when a grant deed was issued to Pacific Bell <br /> The vent and fill lines for two diesel USTs (300 gallons and 550 gallons) were removed and <br /> disposed by IT representatives in May 1990 Several borings were hand bored beneath the <br /> tanks in June 1990 and total petroleum hydrocarbons expressed as diesel were found in the <br /> soil as high as 22,000 ppm In December 1990, the two diesel UST's (located beneath the <br /> basement floor in the center of the facility) were closed in place by rinsing the tanks and <br /> filling with a cement slurry <br /> In December 1991, IT installed three monitoring wells in the streets around the site In the <br /> soil samples analyzed, no total petroleum hydrocarbons as diesel was observed, however, in <br /> the upgradient boring, (MW-3), TPH as gasoline was observed (7 4 ppm) Benzene, toluene, <br /> ethyl benzene, xylenes (BTEX) were identified in soil samples in MW-2 (downgradient) and <br /> MW-1 (upgradient) <br /> BTEX constituents were not observed in any of the groundwater samples collected during the <br /> initial sampling, however, the groundwater samples from MW-1 and MW-2 contained 130 <br /> ppb and 52 ppb TPH as diesel, respectively Analysis of groundwater samples, collected <br /> during nine consecutive quarterly sampling events, revealed no detectable petroleum <br /> hydrocarbons <br /> In February 1993, IT installed six off-site soil borings to further examine the extent of <br /> petroleum hydrocarbon migration from the site Analysis of soil samples from these <br /> boreholes revealed no detectable petroleum hydrocarbons Analysis of groundwater samples, <br /> collected from the boreholes, revealed no detectable diesel concentrations No detectable <br /> volatile hydrocarbons were encountered in the groundwater samples collected from borings <br /> M7Jo4-06-95/UST/95-0089 2 <br />