ARCHIVED REPORTS XR0000745 - Laserfiche WebLink

Home Browse Search

r , 10 September 1996 AGE-NC Project No. 95-0106 Page 7 of 8 monitoring well MW-1 at concentrations of 1,500 ppm, 8.3 ppm, 8.4 ppm, 28 ppm, 15 ppm and 55 ppm, respectively. Analytical results of soil boring samples are summarized on Table 2. The laboratory report(MAI Laboratory ID 66514 through 66517) and chain-of-custody are in Appendix F. 4.5. GROUND WATER ELEVATION AND GRADIENT The ground water elevation in each well was calculated by subtracting the depth to ground water from the surveyed casing elevation (Table 3). Monitoring well casing elevations were surveyed relative to monitoring well MW-1. Ground water gradient on 09 July 1996 was calculated to be 0.0045 ft/ft(23.76 feet per mile) directed N 16° E. The relative ground water elevation at the site is illustrated in Figure 3 - Relative Ground Water Elevation. 4.6. LABORATORY RESULTS OF GROUND WATER SAMPLES The highest concentrations of hydrocarbons were detected in wells MW-1 and MW-4, located down- gradient (north) of the former UST excavation; TPH-g was detected at concentrations as high as 18,000 ppb (TPH-g, MW-4). Benzene was detected at concentrations of 190 ppb and 590 ppb in MW-1 and MW-4, respectively. The maximum toluene concentration detected was 960 ppb, encountered in MW-1. The maximum ethylbenzene and total xylenes concentrations of 700 ppb and 2,100 ppb, respectively, were encountered in MW-4. Neither TPH-g nor BTE&X were detected in the ground water samples from MW-2 and MW-3. MTBE was detected in samples collected from wells MW-1, MW-2 and MW-4,at concentrations of 41 ppb, 16 ppb and 100 ppb, respectively. Analytical results of ground water samples are summarized on Table 4. The laboratory report (MAI Laboratory ID 66629 through 66632) and chain-of-custody are in Appendix G. 5.0. CONCLUSIONS AND RECOMMENDATIONS 5.1. CONCLUSIONS The following conclusions were drawn from the results of this investigation: • Hydrocarbon-impacted soil has been encountered at depths of 6 to 10 feet bsg, coinciding with the capillary fringe or saturated zone.