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Numerous attempts were made to access desired drilling locations, however, due to overhead <br /> obstructions and impenetrable foundation gravels and concrete, the desired drill depths could <br /> not be achieved Refusal was reached in five locations Three soil borings were completed <br /> to depths ranging between 3 0 to 6.0 feet below the basement floor, with soil samples <br /> collected at the maximum depth achieved No vadose wells were constructed, as bonngs of <br /> sufficient depth were unattainable <br />' Where applicable, field investigation methods followed the Th-Regional Board Staff <br />' Recommendations for Preliminary Evaluation and Investigations of Underground Storage <br /> Tank Sites, 10 August 1990. The following section describes the procedures that were used <br /> in completing the investigation. <br /> 2.1 Drilling Methodology <br /> i <br /> IT notified Underground Services Alert (USA) two working days before initiating any drilling <br />■ activities. This, in addition to studying utility maps and the contracting of an independent <br /> line locating service, helped insure that drilling activities did not encounter any underground <br /> utilities Each day, prior to field work, the field geologist conducted a tailgate safety meeting <br /> to ensure proper site safety precautions were identified and also to conform to the IT site <br /> y specific Health and Safety Plan <br /> A concrete saw was used to core 4" diameter holes in the basement floor to facilitate access <br /> to the subsurface. The bonngs were drilled by Powercore representatives (C-57 license, <br /> #607550) on July 8, 1994 All drilling was performed using a skid mounted hydraulic impact <br /> hammer with a remote power unit. Before advancing to another drill site, the downhole <br /> drilling equipment was steam cleaned to prevent cross-contamination between boreholes <br /> All nnsate generated by steam cleaning was containerized in the facility basement. The <br /> hydraulic drilling method generated soil cores which were examined, and together with the <br /> concrete cores contatnenzed in 55-gallon drums as generated These drums are stored with <br /> those containing equipment decontamination waters, pending future disposal 'Three boreholes <br /> were completed to the depths of 6.0 feet (VW-1), 3.0 feet (VW-2), and 5.0 feet (VW-3) <br /> MZ/09-06-94/UST/940138 mer 4 <br />