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1 r 07 June 2004 AGE-NC Project No 02-0926 ' Page 10 of 1 i Ground water flow was inferred to be towards the north-northeast under a gradient of approximately 0 016 foot/foot Figure 6 illustrates the contoured ground water elevations as measured on 17 February 2004 45 ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in the ground water sample collected from well monitoring well MW-3 at a concentration of 100 µg/1 1,2-DCA was detected in the ground water samples collected from wells ' MW-1 and MW-3 at concentrations of 14 µg/1 and 95 pg/l, respectively An iso-concentration map depicting the approximate distribution of dissolved TPH and 1,2-DCA is presented in Figures 7 and S,respectively No other target analytes were detected at or above laboratory detection limits in the ground water samples analyzed The hydrocarbon impact to ground water is shown in Figure 9 with an approximation of the extent of contamination The analytical results of water samples collected on 17 February 2004 are summarized in Table 4 The laboratory report(CTEL Project No CT214-0402091),QA/QC report '• and chain-of-custody form are included in Appendix G ' 5 0. SUMMARY AND CONCLUSIONS The following conclusions were drawn from the results of this investigation • Silty clays and clayey silts and clays are encountered throughout the majority of each boring to approximately 50 feet bsg Fine-grained sand with clay and silt is encountered to the ' northwest and southeast at 5 feet bsg and at 20 to 25 feet bsg in the vicinity of MW-2 More fine sand with clay and silt is encountered beyond 50 feet bsg • One or more target analytes were detected in soil samples collected from B4, B5 and B6 ' 0 The lateral extent of petroleum-hydrocarbon impacted soil is mostly defined in all directions with exception to the east,on city of Stockton property One or more of the constituents TPH- ' g, BTEX and lead were detected in samples B4-35 and B6-45 and B6-55 at very low levels The vertical extent of petroleum hydrocarbon-impacted soil Is not defined at the former UST area, though soil is defined at depth away from the UST area ' The highest concentrations of dissolved hydrocarbons detected in grab ground water samples occurred in the sample from B5, collected in the former tank area When comparing grab ground water samples with samples collected from permanent ground monitoring wells, a ' significant reduction is observed The highest concentration of dissolved hydrocarbons detected in the monitoring well ground water samples occurred in monitoring well MW-3, ' which is located up-gradient of the UST area Advanced GeoEnvironmental,Inc i 1