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,1 20 June 1996 AGE-NC Project No 95-0137 Page 3 of 4 ' consistently shallow gradient During April 1996, the ground water gradient was calculated to be 0 0007 ft/ft, with a northwesterly flow direction 4 2 PETROLEUM HYDROCARBON-IMPACTED GROUND WATER TPH-g was detected in we]Is MW-1, MW-2 and MW-3 at concentrations of 90, 2,300 and 350 parts per billion(ppb,reported as micrograms per liter) TPH-d was detected in wells MW-1 through MW- 3 and MW-5 at concentrations up to 4,000 ppb (MW-3) ' Benzene was detectedMW-2 in samples from MVS 2 and MW-4 at concentrations of 220 and 0 41 ppb, ' respectively, toluene was detected only in MW-2 at a concentration of 12 ppb Ethyl benzene and xylenes were detected in samples collected from MW-2 and MW-3 at concentrations as high as 190 ppb (xylenes, MW-2) Analytical results of ground water samples are summarized in Table 2 The laboratory report (AAL Batch No 96-0419-030) and chain-of-custody are included in Appendix B 5 0. CONCLUSIONS AND RECOMMENDATIONS The highest concentration of dissolved hydrocarbons detected during the April 1996 sampling was 1 in MW-2, located at the northern portion of the site The lowest concentrations of petroleum hydrocarbons were detected in wells MW-4 and MW-5, west and south of the former UST areas Concentrations of hydrocarbons to each well decreased between January and April 1996, except for MW-3, which had increased hydrocarbon concentrations MTBE was detected in MW-4 at 12 ppb, and in MW-5 at 1 ppb The water sample from MW-I was not analyzed for MTBE, and the samples from MW-2 and MW-3 had nondetectable MTBE concentrations, but also had higher method detection limits than MW-4 and MW-5 ' Additional assessment will be required at the site to determine the lateral extent of impacted soil and ground water A work plan for additional assessment north and west of the site is presently being prepared by AGE Upon approval by the PHS-EHD and the neighboring property owners,field work will be scheduled Feasibility studies should be initiated at the site to determine the most suitable corrective action Upon completion of the assessment and feasibility studies, a Corrective Action Plan (CAP) should be prepared, if necessary The next quarterly monitoring at the site should be scheduled for July 1996 A survey of the property ' is also scheduled to be completed in July 1996 to determine the precise locations of all monitoring wells and property lines at the north end of the site r