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December 22 , 1988 Page 3 Project 156-117 . 1 Three exploratory borings (DH-1 , DH-2 , DH-3 ) were drilled on the subject site ( locations are shown on the Site Plan, Figure 2 ) . All borings were drilled using a truck mounted drill rig equipped with eight-inch diameter hollow stem augers . Undisturbed soil samples were obtained from the borings at two and one half foot intervals beginning just below ground surface and continuing to the bottom of the boring . Soil samples for laboratory analysis were obtained using a Modified California sampler and were contained within two inch diameter brass liners, wrapped in foil , capped at both ends , labeled, kept refrigerated, and transported to a State-certified laboratory under appropriate chain-of-custody documentation . Borings DH-1 , DH-2 , and DH-3 were terminated approximately ten to twelve feet below the first encounter of ground water , and converted to monitoring wells (MW-1 , MW-2 , MW-3 ) as follows : Two inch diameter, threaded, PVC well casing was installed through the hollow stem augers with the bottom fifteen feet of the casing being factory slotted ( slot size 0 . 02 inch ) to allow the inflow of ground water. The annular space around the slotted interval of each well was backfilled with coarse sand to act as a filter to screen out fine grained sand and silt that may clog the slotted interval . A one foot thick bentonite seal was placed on top of each sand pack filter . A cement surface seal was placed into the remaining annular space of each well . Each well head was secured inside a locking vault and encased in a traffic- rated, water-proof christy box, to protect against damage and unauthorized access . Well construction details are presented in Appendix A. The wells were developed to ensure that ground water representative of the aquifer was flowing through the slotted intervals . The wells were developed using a bottom check- valve bailer . Electrical conductivity, pH, and temperature of the discharge water was monitored during development . Upon stabilization of the above parameters following the removal of ten well volumes , water samples were obtained. The ground water samples withdrawn from each well were carefully decanted into 40 ml , amber glass volatile organic analysis (VOA) vials , until a positive meniscus was formed. A Teflon-lined screw cap was used to seal each vial . After capping , the vials were inverted and tapped to verify that no air bubbles were present . Ground water samples were also collected in one liter , amber glass bottles , and one half liter , plastic bottles . Samples of the shallow ground water to be tested were labeled, immediately placed in a refrigerated container, and transported to a State-certified laboratory accompanied by appropriate chain-of-custody documents . GBetacAssociates . Inc.