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W <br />H <br />IT CORPORATION <br />2.0 DRILLING AND WELL INSTALLATION <br />/ The initial drilling program conducted on February 27, 1985 was a site <br />assessment to provide basic subsurface soil and hydrogeologic informa- <br />tion at the station. Four boreholes (DH -1, DH -2, DH -3 and DH -4) were <br />drilled and backfilled during this phase of the investigation, at the <br />locations shown in Figure 2.1. All four borings were drilled with a <br />truck -mounted drilling rig equipped with 8 -inch hollow -stem, continuous - <br />flight augers. <br />r" <br />The objective of the second drilling program was to determine the extent <br />of the hydrocarbon plume discovered during the initial drilling phase. <br />On-site work was conducted on March 26, 1985 and March 29, 1985. During <br />this time, four borings were drilled at the locations shown in <br />Figure 2.1. These borings (MW -1, MW -2, MW -3, and MW -4) were drilled <br />with a truck -mounted drill rig equipped with 8 -inch hollow -stem augers <br />to a depth of 20 feet. All four borings were completed as vadose wells <br />of the type shown on the individual boring logs, Plates 2 through 12. <br />The third drilling program was intended to install three wells to the <br />ground water table to determine if the ground water has been contami- <br />nated and the direction of ground water flow. Drilling for this phase <br />was conducted on May 29, 1985, during which time three ground water <br />monitoring wells MW -5, MW -6, MW -7 were installed to a depth of 50 feet <br />at the locations shown in Figure 2.1. These wells were drilled with a <br />truck -mounted CME -55 drill rig, equipped with a 6 -inch O.D. continuous - <br />flight, hollow -stem auger. <br />2.1 SOIL SAMPLING <br />Undisturbed sail samples were collected in every borehole at 5 -foot <br />intervals using a 2 -inch I.D. California sampler and field tested for <br />hydrocarbon contamination using aGX-3A explosive- _gas __analyzer.__ --The <br />procedures for taking soil samples and field hydrocarbon testing are <br />described in Attachment 1, included with this report. For each boring <br />with a lower explosive limit (LEL) reading of 10 percent or greater, the <br />F <br />