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_ v - <br /> 12 May 1998 <br /> AGE-NC Project No 9570121 , <br /> Page 3 of 5 <br /> In February 1998, the gradient was calculated to be 0 003 ft/ft, or approximately 16 feet per mile <br />' (Figure 3) Generally, ground water monitoring data collected at the site Indicated a northeastg round <br /> wate3 r flow direction Based on a northeast flow direction, wells MW-1, MW-2, MW-4 and MW-8 <br /> are located downgradlent of the former UST area A low ground water elevation was observed at <br />' MW-9 suggesting a southeast ground water flow direction In the southern portion of the site Due <br /> to the relatively flat gradient at the site, any slight variations In ground water measurements could <br />' modify ground water flow direction <br />' 3 2 DISSOLVED OXYGEN MEASUREMENTS <br /> Dur`Ing the February 1998'ground water monitoring event; dissolved oxygen measurements were <br />' recorded after purging monitoring wells Dissolved oxygen measurements ranged from "0 32 <br /> milligrams per liter(mg/1) in MW-3 to 1 10 mg/1 In MW-8 Results of dissolved oxygen in ground <br /> water samples are summarized in Table'No 2 <br /> 3 3 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected In water samples collected from MW-1 through MW-4 and MW-7 at <br />' concentrations ranging up to 91,000 parts per billion (ppb, reported as micrograms per liter) TPH-d <br /> was detected In samples collected from monitoring wells MW-1 through MW-9 at concentrations <br /> ranging up to 18,000 ppb, the laboratory indicated that all TPH-d chromatograms were not typical <br />' of diesel patterns <br />' BTE&X compounds were,detected in samples collected from each well at concentrations ranging <br /> I up to 19,000 ppb (benzene, MW-3) MTBE was detected"utilizing EPA method 8020 in samples <br /> collected from MW-2 and MW-5 at concentrations up to 140 ppb <br /> MTBE was confirmed utilizing EPA method 8260 In,a sample collected from MW-5 at a <br /> concentration Iof 5 ppb TAME,DIPE, TBA and ETBE were not detected in the laboratory analysis <br /> of any ground water samples <br /> Due to instrument-compllcations,the laboratory repotted that the sample holding Mmes expired prior <br /> to the 8260 analysts The laboratory report (Castle Analytical Laboratory Reference Number 1474 <br /> and Onsite Environmental Laboratories, Inc Report Number 3EO38) and chain-of-custody forms <br /> are presented In Appendix B, the results"of the analysis are contained In Table 2 <br /> v <br /> . a <br /> - Advanced GeoEmaronmentel,Inc <br /> ' 1 <br />