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1 <br /> 31 January 1997 <br /> AGE-NC Project No 95-0125 <br />' Page 3 of 7 <br />' Based upon the shallow depth to ground water at the site, the PHS-EHD required a subsurface <br /> investigation of the former UST areas <br />' 23 MONITORING WELL SAMPLING HISTORY <br />' Between 1987 and 1992, a total of ten ground water monitoring wells were installed at the site by <br /> Groundwater Technology, Inc (GTI) Petroleum hydrocarbons were detected in one soil sample <br /> (Sample MW-6A) analyzed during installation of the wells This sample was collected from below <br />' the level of the water table and was saturated with the ground water from the site The results of the <br /> investigation were detailed in the GTI Problem Assessment Report, dated 16 July 1990 <br />' Ground water was sampled oneig t occasions between 1987 and 1995 Field observation of selected <br /> monitoring wells were performed on an infrequent basis between 1993 and 1994 by representatives <br /> of LSD Historical ground water depth at the site has vaned between 5 feet and 10 feet below surface <br /> grade (bsg) The prevailing ground water flow direction has been toward the northwest <br /> Petroleum hydrocarbons have been detected in ground water only in the vicinity of the former <br /> dispensers Previous sampling events have established an ellipse-shaped ground water plume, <br /> extending from MW-2 at the south to near MW-5 at the north The center of the plume has <br /> apparently remained near MW-6 (GTI Quarterly Report, dated 3 March 1992) <br /> 24 LIMITED SUBSURFACE INVESTIGATION <br /> On 26 June 1995, five soil probe borings were advanced at the site to a depth of 10 feet bsg <br /> Discrete soil samples were collected at depths of 5 feet, 7 feet and 10 feet bsg In addition to soil <br /> samples, a grab ground water sample was obtained from probe boring P5 Petroleum hydrocarbons <br /> were detected in soil samples collected during the investigation Petroleum hydrocarbons were <br /> detected in one soil samples analyzed from probe boring P3 Petroleum hydrocarbons were not <br /> detected in any other soil samples analyzed nor the grab ground water sample collected from probe <br /> boring P5 Results of the investigation were detailed in AGE Quarterly Report, dated 25 September <br /> 1995 <br /> 25 EXCAVATION OF HYDROCARBON-IMPACTED SOIL <br /> On 20 and 2I December 1995, approximately 285 cubic yards of hydrocarbon-impacted soil were <br />. excavated from the former UST area Excavated soil was stockpiled on-site, north of the <br /> maintenance building Water was encountered in the excavation at a depth of approximately 8 feet <br />