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I ' 16 May 2001 . AGE-NC Project No 96-0229 Page 4 of 5 ' • Monitoring wells MW-1 and MW-IOB 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, but is not Impacted in the down-gradient area of MW-10B (50 to 55 feet ' bsg) ' • The dissolved TPH-g, BTEX and MTBE plume is at least 25 feet thick in the area of MW-1 (screened 48 to 53 feet bsg) and MW-2 (screened 25 to 45 feet bsg) ' • MTBE was detected in the sample collected from well MW-i (screened 48 to 53 feet bsg) in deeper ground water, but was not detected in the samples collected from shallow water ' on-site wells MW-2 (located 5 feet from MW-1), MW-3 or MW-4, Implying that an undelineated MTBE and DIPE-Impact maybe present crossgradient to downgradient of the site at deeper depths ' • The greatest concentrations of off-site dissolved MTBE were detected in downgradient wells MW-6 at 210µg/1, MW-7 at 580 /ug/l and MW-8 at 42 4g/l ' • Increasing TPH-g, BTEX and MTBE were reported in water samples collected from MW-6 Further downgradient at MW-7, TPH-g and BTEX concentrations decreased, while MTBE '• concentrations Increased The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-1, MW-2, MW-3 and MW-6 indicate that these wells are within or near the dissolved petroleum hydrocarbon "core area"of the plume (Figure 4) Based on maps depicting the estimated extent of dissolved TPH-g and MTBE(Figures 4 and 5),the horizontal extent of the dissolved hydrocarbon plume has not been defined north of MW-7 an northwest of MW-2,the vertical extent of hydrocarbon-impacted ground water has not been delineated in any direction S.Q. RECOMMENDATIONS IBased upon data collected during March 2 00 1, AGE recommends ` • A work plan for cone penetrometer testing(CPT)was approved by the PHS-EHD on 02 May 10AI +0 r, _+i, .. +1, 1k....___+_1 ,� ,.,,,� +�„+ F+t,e i,,,Y,o Do,..i„.,,Y TCT !'1 LVV1 LV illi Lllbl assessL111r 11V11L,V11l.Ci1 aL1LL Vel L1VLL1 VxL1ri1L Vl L11V p1L1111V L Vllllllla VU1 `.lea,l1LLp Fund pre-approval, AGE anticipates start-up of CPT investigation some time in June 2001 1 • 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 a Preparation of a corrective action pian (CAP), the CAP should include results of any feasibility studies to determine appropriate remediation alternatives for the site Advanced GcoEnvironmenlal,Inc