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12 June 1996 <br /> • AGE-NC Project No 95-0130 <br /> Page 4 of 5 <br />' 4.0. FINDINGS <br /> 41 RELATIVE GROUNDWATER ELEVATION AND GRADIENT <br />' The relative elevation of round water in each well was calculated b subtracting the round water <br /> g Y g g <br />' depth from the surveyed relative casing elevation (Table 1 - Ground Water Elevations) Ground <br /> water depths at the site ranged from 50 30 to 51 35 feet Groundwater at the site rose an average of <br /> 3 80 feet between January 1996 and April 1996 <br />' Ground water is currently 5 to 10 feet above the tops of the screen intervals of monitoring wells <br /> MW-1 through MW-4, and is approximately 0 5 feet below the top of the screen interval of MW-5 <br />' Ground water flow direction at the site is generally toward the southeast at an approximate gradient <br /> of 0 006 ft/ft, or 32 feet per mile (Figure 3 -Relative Ground Water Elevations Map) <br /> 42 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected insam round water les from well MW-2,MW-3, and MW-5 at concentrations <br /> g P <br /> of 860 parts per billion (ppb, reported as micrograms per ]iter), 150 ppb, and 13,000 ppb, <br />' respectively <br />' Benzene was detected in ground water samples from wells MW-2 through MW-5 at concentrations <br /> of 83 ppb, 2 7 ppb, 2 8 ppb, and 2,000 ppb, respectively Toluene, ethyl benzene and xylene were <br /> detected in wells MW-2, MW-3 and MW-5 at concentrations ranging from non-detect to 1,000 ppb <br />' MTBE was detected in ground water samples collected from MW-2 and MW-4 at concentrations <br /> of 58 ppb and 0 53 ppb,respectively The analytical results of ground water samples are summarized <br />' in Table 2 The laboratory report (CAL Laboratory No 742) and chain-of-custody are included in <br /> Appendix B <br /> 5 0. CONCLUSIONS & RECOMMENDATIONS <br />' Ground water flow direction and gradient has remained relatively constant at the site over the past <br /> year Monitoring well MW-5 is located up-gradient of the UST area, while monitoring well MW-4 <br />' is located down-gradient <br /> During April 1996, TPH-g concentrations in well MW-2 increased, while TPH-g concentrations in <br /> wells MW-3 and MW-5 decreased BTE&X concentrations increased in wells MW-2 and MW-4, <br />