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' 09 August 2000 <br /> AGE-NC Project No 96-0229 <br />' Page 4 of 5 <br />' samples of the actual ground water conditions in those wells <br /> - The Increase of ground water elevations of approximately 5 feet between January 2000 and <br /> April 2000 is probably attributed to the seasonal fluctuation pattern <br /> - The dissolved BTEX and MTBE plume is at least 25 feet thick in the area of MW-1 and <br /> MW-2, with depth, the dissolved BTEX and MTBE plume apparently grades from lower <br />' concentrations to higher concentrations <br /> TBA was detected in water samples collected from wells MW-4, MW-7 and MW-8 at <br />' concentrations as high as 75 µg/1 Due to abnormally high laboratory reporting limits at <br /> MW-1 and MW-6, TBA may also be present at MW-1 and MW-6 at concentrations below <br /> the laboratory determined detection limits <br />' - The highest MTBE concentration was encountered in ground water samples collected from <br /> the deeply drowned well MW-1 (screened 48 to 53 feet bsg) and from the downgradient well <br /> MW-7 (screened 20 to 40 feet bsg), Implying that MTBE-Impact may be present <br /> crossgradient to downgradient of the site at deeper depths <br /> - The elevated concentrations of petroleum hydrocarbons detected in samples collected from <br /> wells MW-1, MW-2, MW-3 and MW-6 Indicate that these wells are within or near the <br /> dissolved petroleum hydrocarbon "core area"of the plume (Figure 4) <br /> I - The lateral extent of petroleum hydrocarbon-Impacted ground water has not been delineated <br /> to the north-northwest and north-northeast <br /> The vertical extent of MTBE-Impacted ground water has not been delineated In the area of <br /> MW-1 or downgradient In the area of MW-6, MW-7 and MW-8 <br /> 5.0. RECOMMENDATIONS <br />' Based upon data collected during Apirl 2000, AGE recommends <br /> Prepare a work plan for the Installation of deeper ground water monitoring wells located <br /> adjacent MW-6 and MW-7 and one shallow ground water monitoring well located <br /> approximately 100 feet west of MW-8 to further assess the extent of the crossgradient <br /> dissolved petroleum hydrocarbon plume toward the northwest <br /> - Prepare a Feasibility Study Work Plan to assess remedial alternatives for feasibility and cost <br /> to remediate the dissolved petroleum hydrocarbon plume at the site <br /> o Prepare a Corrective Action Plan (CAP), the CAP should Include results of any feasibility _ r <br /> studies to determine appropriate remediation alternatives for the site A receptor survey <br /> Advanced GeoEnvironmental,Inc <br />