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17 January 1997 <br /> AGE-NC Project No 95-0121 <br /> Page 4 of 5 <br /> • The overall increase of detectable hydrocarbons concentrations at the site may be related to <br /> the overall rise in ground water elevations causing washing of impacted soil within the <br /> capillary fringe or lower vadose zone <br /> • The ground water surface was between one and eleven feet above the top of screen intervals <br /> in monitoring wells MW-1 through MW-8 Because screened intervals are below ground <br /> water levels, analytical results from samples collected in these wells may not be representative <br /> of shallow aquifer conditions <br /> • Further assessment northeast of MW-4 and west of MW-7 will be necessary to determine the <br /> lateral extent of dissolved hydrocarbons ground water and to monitor possible migration of <br /> the plume as a result of ground water migration <br /> • The overall increase of detectable hydrocarbons concentrations in downgradient monitoring <br /> point MW-8, crossgradient monitonng points MW-1, MW-5 through MW-7, and upgradient <br /> monitoring point MW-9 is suggestive of an unstable dissolved hydrocarbon plume <br /> 4 2 RECOMMENDATIONS <br /> Based upon data collected from the site, AGE has the following recommendations <br /> • At least two additional monitoring wells should be installed at the site one well should be <br /> considered for installation northeast of MW-4, a second well should be considered west of <br /> MW-7 <br /> • Any additional monitoring wells installed at the site should be completed to allow for the <br /> extreme fluctuation of ground water elevation in the area <br /> • A revised Remedial Action Work Plan for remediation at the site within the "core" area will <br /> be submitted to the PHS-EHD shortly Upon regulatory approval, installation of the <br /> remediation system should commence <br /> • The next quarterly monitoring should be scheduled for February 1997 <br /> 5.0. LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or similar localities The findings were based upon <br /> analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic <br /> conditions at the site for the purpose of this investigation are made from a limited number of available <br /> data points (i a borings, monitonng wells), and subsurface conditions may vary away from these data <br />