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29 March 1996 <br /> AGE-NC Project No 95-0125 <br /> Page 2 of 5 <br /> 2 3 MONITORING WELL INSTALLATION AND SAMPLING <br /> Between 1987 and 1992, a total of ten ground water monitoring wells were installed at the site by <br /> Groundwater Technology, Inc (GTI) No petroleum hydrocarbons were detected in soil samples <br /> collected during installation of the wells <br /> Ground water was sampled on eight 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 Histoncal ground water depth at the site has varied between 5 and 10 feet below surface <br /> grade (bsg) The prevailing ground water flow direction has been to 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 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 ten feet bsg <br /> Discrete soil samples were collected at depths of five, seven and ten feet bsg In addition to soil <br /> samples, a grab ground water sample was obtained from one probe boring Petroleum hydrocarbons <br /> were detected in soil samples collected during the investigation Results of the investigation were <br /> detailed in AGE quarterly report, dated 25 September 1995 <br /> 25 EXCAVATION OF HYDROCARBON-IMPACTED SOIL <br /> On 20 and 21 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 maintenance <br /> building Water was encountered in the excavation at a depth of approximately 8 feet below surface <br /> grade A total of eleven soil samples were collected from the sidewalls and floor of the excavation, <br /> under the direction of Ms Margaret Lagono of the PHS-EHD TPH-g was detected in soil samples <br /> collected from the sidewalls of the excavation at concentrations as high as 1,600 ppm (7-East) <br /> Toluene, ethylbenzene and xylenes were detected in excavation soil samples at concentrations ranging <br /> from 0 0072 ppm(toluene, 3-East) to 100 ppm (xylenes, 7-East) Benzene was not detected in any <br /> of the samples collected Under the authorization of the PHS-EHD, approximately 44 tons (32 cubic <br /> yards) of pea gravel and crushed rock were placed on the bottom of the excavation The pea gravel <br /> and crushed rock was used to fill the excavation above the free standing water in the excavation The <br /> excavation was then backfilled using clean fill sand, approximately 240 cubic yards and 14 cubic yards <br /> of gravel was used to cover the excavation Results of the excavation were detailed in AGE quarterly <br />