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San Joaquin County, as well as state records, indicate that groundwater flows northeastward <br /> beneath the site and occurs at about 40-50 feet below surface <br /> Pacific Bell facility UE042 presently contains three 25,000 gallon diesel UST's which supply <br />' fuel to electric generators <br />' 1.3 Site History <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 gallon and 550 gallon) were removed and <br /> disposed by 1T 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 13,000 ppm In December 1990, the two diesel UST's were closed in place by <br /> rinsing the tanks and filling with a cement slurry <br /> 2.0 Investigative Methodology <br /> PT representatives performed an additional off-site investigation at Pacific Bell Facility UE042 <br /> on San Joaquin Street in Stockton, California, in order to further characterize off-site soil and <br /> groundwater quality downgradient of the former and existing underground storage tank <br /> locations <br /> The off-site investigation included the drilling of six soil borings (Figure 3) The soil boring <br /> g g <br /> locations were identified to examine two potential petroleum hydrocarbon sources. the three <br /> existing 25,000 gallon diesel UST's and the two former diesel tanks (300 and 550 gallon) <br /> previously closed in place Field investigation methods followed the Tri Regional Board <br />' Staff Recommendations for Preliminary Evaluation and Investigations of Underground <br /> Storage Tank Sites, 10 August 1990 The following section describes the procedures that <br />' were used in completing the investigation. <br /> ' 2.1 Drilling Methodology <br /> IT notified Underground Services Alert (USA) two working days before starting any drilling <br /> activities This is ni addition to hiring an independent line locating service to standby on site, <br /> which helped to insure that drilling activities did not encounter any underground utilities. <br /> MZA)3-1 Cr93/ENG/93-0034 jf 2 <br />