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03 January 2002 • AGE-NC Project No 96-0229 Page 4 of 5 towards the northeast at an approximate gradient of 0 01 ft/ft or less • Due to the low hydraulic gradient at the site, slight variations in ground water measurements or changes of recharge/discharge of the local ground water could greatly modify the inferred Iground water flow direction • Monitoring wells MW-I and MW-1 OB are "drowned", and yield samples representative of deeper ground water conditions Deeper ground water in the area of MW-1 (48 to 53 feet bsg) is impacted by TPH-g, BTEX, MTBE and DIPE, deeper ground water in the area of downgradient well MW-1OB is impacted by MTBE • MTBE was detected in the sample collected from well MW-1 (screened 48 to 53 feet bsg) in deeper ground water, but was not detected in the samples collected from shallow water I on-site wells MW-2 (located 5 feet from MW-1) and MW-4, implying that an undelineated MTBE and possibly DIPE-impact may be present crossgradient to downgradient of the site at deeper depths (Figure 5) ' The greatest concentrations of off-site dissolved MTBE were detected In downgradient wells MW-6 and MW-7, low concentrations of dissolved MTBE were detected at wells MW-8, � . MW-9, MW-10A and MW-10B, a trend of increasing off-site MTBE concentrations has been noted since March 2001 Increasing TPH-g, BTEX and MTBE were reported in water samples collected from wells MW-1, MW-2 MW-3, MW-9 and MW-IOA, increasing TPH-g was reported from MW-7 and increasing MTBE was reported from MW-6 and MW-10B, suggesting that the plume of MTBE-Impacted ground water has shifted towards the northeast • The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-1, MW-2,MW-3, MW-6 and MW-7 indicate that these wells are within or near the dissolved petroleum hydrocarbon"core area"of the plume (Figure 4) 5.0. RECOMMENDATIONS Based upon data collected dunng September 2001, AGE recommends • Preparation of a feasibility study work plan to assess remedial alternatives for feasibility and cost to address the dissolved petroleum hydrocarbon plume at the site • Preparation of a corrective action plan (CAP), the CAP should include results of any feasibility studies to determine appropriate remediation alternatives for the site • • Performance of a receptor survey to locate potential receptors within 2,000 feet of the site, results of the receptor survey should be Included in the CAP ' Advanced GeoEnviron mental,Inc I