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09 January 2006 <br /> . AGE-NC Project No. 95-0137 <br /> Page 3 of 4 <br /> I <br /> The distribution of dissolved 1,2-DCA is depicted in Figure 4. No additional contaminants of <br /> ' concern were detected in the ground water samples. The analytical results are summarized in Tables <br /> 2 and 3. A copy of the laboratory report (CTEL Project Number CT214-0511140), quality <br /> assurance/quality control (QA/QC)report, and chain of custody form are included in Appendix C. <br /> Documents confirming the upload of soil and ground water laboratory reports in electronic <br /> deliverable format (EDF) files and depth to water measurements to GeoTracker are included in <br /> Appendix D. <br /> I4.0. SUMMARY AND CONCLUSIONS <br /> Based on the data collected from the site, AGE finds: <br /> ' The g average depth to round water increased approximately 0.5 feet between the third and <br /> p <br /> fourth quarter 2005 ground water monitoring events.The ground water flow direction varied <br /> from south to north across the site, at a nearly flat hydraulic gradients ranging from <br /> approximately 0.0803 ft across the former UST release area. <br /> Dissolved petroleum hydrocarbon concentrations on-site and directly down-gradient of the <br /> I . p Y Y <br /> former UST area were below detection limits in the fourth quarter 2005, except for TPH-d. -Y� 6 <br /> .Diesel was not detected in on-site samples for approximately two-annual monitoring cycles`-A o <br /> with detections in well MW-4 never greater than 1,000 micrograms per liter. Additionally; <br /> .4� the detections of TPH-d did not occur in samples from well MW-2 and MW-3, the former <br /> �U" UST location and the prior location of the most significant detections of TPH-d detections. <br /> A new,source of TPH-d may have discharge near or off the site. <br /> • Dissolved 1,2-DCA concentrations generally have been declining. 1,2-DCA has not been <br /> detected in wells MW-1 and well MW-2 for six and five consecutive quarters,respectively. <br /> ' However, the concentrations in well MW-4, MW-9, and MW-10 remain and are currently <br /> undefined by the monitoring well network. 1 <br /> • The detections of 1,2-DCA in wells MW-4, MW-9, and MW-10 are above the DHS's <br /> Maximum Contaminant Level (MCL) of 0.5 µg11 in drinking water. The lateral extent of <br /> dissolved 1,2-DCA is undefined west and down-gradient of the site, beyond the recently <br /> Iinstalled ground water monitoring wells. -' <br /> 5.0. RECOMMENDATIONS <br /> Based on the findings of the environmental activities recounted in this report and previous <br /> investigations, AGE recommends: <br /> Advanced GeoEnvironmental,Inc. <br /> 1 ' <br />