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03 September 2002 <br /> AGE-NC Project No 99-0624 <br /> Page 4 of 5 <br /> • Ground water flow direction in the area of wells MW-1 through MW-4 was Inferred to be <br /> towards the south-southwest at an approximate gradient of 0 004 ft/ft Due to the low <br /> hydraulic gradient at the site, slight variations In ground water measurements'or changes of <br /> recharge/discharge of the local ground water could greatly modify the inferred ground water <br /> flow direction <br /> • TPH-g was detected in ground water samples from wells MW-2 and MW-3, the highest <br /> concentration was detected in the sample collected from MW-2 at 740 µg/1 <br /> • Various BTEX compounds were detected in the water samples collected from MW-2 and <br /> MW-3, the MW-2 sample had the highest concentrations <br /> • Utilizing EPA Method 8260M, MTBE was detected from MW-1, MW-2 and MW-3 at <br /> concentrations as high as 11,000 µg/1 (MW-2) <br /> • The elevated concentrations of petroleum hydrocarbons detected in samples collected from <br /> well MW-2 indicate this well Is within or near the dissolved petroleum hydrocarbon "core <br /> area" of the plume (Figure 4) <br /> • During ten consecutive quarterly ground water monitoring events, TPH-g has generally <br /> . fluctuated from MW-2 at concentrations between 140,ug/1 and 8,900,ug/l,significant MTBE <br /> concentrations have fluctuated between 130 µg/1 and 14,000 ug/l The significant <br /> fluctuations in MTBE-impacted ground water combined with the laboratory notations that <br /> all MW-2 sample chromatograms have contained significant unmodified or weakly modified <br /> gasoline could be interpreted as a relatively new release <br /> 5.0. RECOMMENDATIONS <br /> Based upon data collected during May 2002, AGE recommends <br /> • Continued utilization of wells MW-1 through MW-4 for quarterly ground water monitoring <br /> and sampling <br /> • Performance of a receptor survey to locate potential receptors within 2,000 feet of the site <br /> • Preparation of a monitoring well installation workplan to assess petroleum-impacted ground <br /> water near the product lines and current fuel dispensing area and downgradient of MW-2 <br /> • Preparation of a feasibility studies report to evaluate soil and ground water remediation <br /> alternatives at the site <br /> Advanced GeoEnvironmental,Inc <br />