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07 July 1997 AGE-NC Project No 95-0121 r i IPage 4 of 4 S • The top of the saturated zone was between 4 75 and 14 40 feet above the tops of screen , I intervals in monitoring wells MW-1 through MW-9 Because screened intervals -are r r significantly below the ground water table, analytical results from samples collected in these ' wells may not be representative of actual conditions in the shallow saturated zone • Based upon ground water monitoring well data collected to date, there does not appear to be a consistent relationship between ground water depth and hydrocarbon concentrations (Appendix C) 5-0.- RECOMMENDATIONS Based upon data collected from the site, AGE recommends the following • Based on the consistently high concentrations of petroleum hydrocarbons in MW-7 and the ` prevailing ground water flow direction, at least one additional ground water monitoring well is needed west of MW-7 to fully assess the dissolved petroleum hydrocarbon plume 4 • Based on previous detection of petroleum hydrocarbons in MW-5 and a current screen interval that is approximately eleven feet beneath the top of the saturated zone (a drowned well), at least one additional ground water monitoring well is needed northeast of MW-5 to ' fully assess the dissolved petroleum hydrocarbon plume • Any additional monitoring wells installed at the site should be designed around the current ground water elevation, but able to compensate for the long term rise of ground water I, elevation in the area • A Revised Remedial Action Work Plan for the"core" petroleum-hydrocaibon impacted-area ' was submitted to the PHS-EHD in April 1997 Upon regulatory approval, installation of the - remediation system should commence ' The next quarterly monitoring should be scheduled for August 1997 t 60 LIMITATIONS y s Our professional services were performed using that degree of care and skill ordinarily exercised by environmental consultants practicing in this or similar localities The findings were based upon analytical results provided,by an independent laboratory Evaluation of the hydrogeologic conditions at the site for the purpose of this investigation was made from a limited number of available data points(monitoring wells samples), and subsurface conditions may vary away from these data points No other warranty, expressed or implied, is made as to the professional recommendations contained in this report 4 l