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O +1 i 14 May 2000 AGE-NC Project No 95-0137 Page 3 of 4 hydraulic gradient were detennmed by contouring the ground water elevation data on a scaled map of the RFS site (Figure 3) The ground water flow direction in the former UST area was locally variable,but generally toward the north The gradient is indeterminant in the area east of the of the former USTs The gradient on the Jimco Truck Stop truck wash area was calculated to be of 0 0075 toward monitoring well MW-7, as presented in Jimco Truck Stop Quarlerl3 Report - January 2000, dated 14 February 2000 and prepared by AGE Historically, ground water flow direction at the site has vaned from north to northwest The depth to ground water measurements from the vapor extraction wells on the site may not be fully compatible with those from the monitonng wells due to the limited the screen intervals of the former Most of the data for the ground water contours are from wells with screen intervals that terminate at approximately 30 feet bsg,while the vapor N%ell screens terminate at approximately 20 feet bsg The ground water elevation in well V\V-2A is abnormally low for reasons not understood Figure 3 illustrates the contoured relative ground water elevations as measured on 12 January 2000 32 ANALYTICAL RESULTS OF GROUND WATER SAMPLES Petroleum hydrocarbons were reported in all wells sampled during the Tanuary 2000 monitonng event Benzene was reported in four of nine wells sampled at concentrations ranging from 1 1 micrograms per liter(pg/l, VW-1b)to 520µg/l (MW-2) Toluene, ethylbenzene and/or xylenes were reported in eight of nine wells sampled at concentrations ranging from 0 54 ,ugll (toluene, VW-1b) to 840 ,ug/l (ethylbenzene, VW-1a) TPH-g was reported in eight of nine samples at concentrations as high as 9,400 pg/l (VW-1 a) TPH-d was reported in each NN ell sampled at concentrations as high as 16,000 �g/l (VW-2a) MTBE was reported in the ground vv ater sample collected from VW-1 a by EPA method 8020 at a concentration of 27 ,ug,'] MTBE was reported in the ground\%ater sample collected from well MW-3 by EPA method 8260 at a concentration of 4 0 pgll DIPE and TBA were also reported in various samples collected dunng the January 2000 monitoring event at concentrations up to 6 9 ,ug/] and 83 �zg/l. respects ely ETBE and TAME were not reported in samples collected from the site Aiial�nical results from ground water samples for each moivtonng event analyzed by EPA Methods 8015 Modified and 8020 are summanzed in Table 2 Anal)qical results for ground water samples analyzed by EPA Method 8260 Modified are sunmzanzed in Table 3 A copy of the laboratory report (NIA] Lab ID Numbers 29092 through 29100), quality assurance and quality control (QA/QC) and chain-of-custody form are included in Appendix B Adicnced GeoEn+ironmenlal Inc