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1 3 <br /> Medium-grained, well-sorted sand was encountered in each boring at <br /> a depth of approximately 75 feet. Water was encountered in the <br /> borings at approximately 70 feet. <br />' 4.2 Groundwater Measurements <br /> Based on groundwater depth measurements, the groundwater flow <br /> direction at the site was calculated to be S 70 W. Groundwater <br /> elevation contours are shown in Figure 3 . Contour spacing yields a <br /> groundwater gradient of 0. 0073 ft/ft. <br />' 4.3 Field Evidence of Contamination <br /> Evidence of soil contamination was encountered during drilling. <br /> Soil samples emitted slight to strong hydrocarbon odors in Boring <br /> #2 , but little or no odor in Borings #3 and #4 . Hydrocarbon vapors <br /> were also detected by the organic vapor meter (Appendix A) , and <br /> were used to select samples for laboratory analysis. No field <br /> evidence of groundwater contamination was detected during drilling <br /> or sampling. <br /> 4.4 Laboratory Results <br /> Only one soil sample collected during the installation of the <br /> monitoring wells contained detectable hydrocarbons. A benzene <br /> concentration of 0. 0079 mg/kg was detected at a depth of 45 feet in <br /> MW-2 , just south of the tank pit. This concentration is just <br /> slightly above the detection limit of 0. 005 mg/kg. Slightly higher <br /> concentrations of hydrocarbons were detected in Boring #1 to a <br /> depth of 55 feet (see GeoAudit report dated 16 November 1992) . Soil <br /> sample analyses are summarized in Table 3 . The laboratory report <br /> and chain of custody are attached in Appendix A. <br /> A low benzene concentration was also detected in the water sample <br /> from MW-2 . A concentration of 3 .7 Ag/1 was reported, along with a <br /> slightly lower xylene concentration of 1. 1 µg/1 . Both <br /> concentrations are only slightly above detection limits. The water <br /> sample analyses are summarized in Table 4 . The laboratory results <br /> and chain of custody are attached in Appendix B. <br /> I5.0 CONCLUSIONS & RECOMMENDATIONS <br /> 5. 1 Boil Conditions <br /> The site is underlain to a depth of approximately 70 feet by <br /> relatively fine-grained material ranging from sandy silt to silty <br /> sand. Below 70 feet, fine to medium-grained sand is present. This <br /> material is relatively porous and permeable, and at present, forms <br /> the shallowest water-bearing zone at the site. <br /> 4 <br />