ARCHIVED REPORTS_XR0003246 - Laserfiche WebLink

Home Browse Search

30 June 1999 } AGE-NC Project No. 98-0468 ' Page 10 of 12 , 5.4.4. Fuel Oxygenating Compounds MTBE and TBA were the only fuel-oxygenating compounds detected in the ground water samples analyzed (Table 6). MTBE and TBA were only detected in sample MW-4 at concentrations of 660 ug/1 and 32 ug/l, respectively. The reported detection of MTBE in sample MW-4 exceeds the DHS-established secondary MCL of 5.0 ug/l and action level of 13 ug/l for MTBE in ground water. There are no State- or Federal-established MCL or action level for TBA. ' 6.0. SUMMARY AND CONCLUSIONS On the basis of the information reviewed and collected during this investigation, AGE concludes: ' Shallow subsurface soil primarily consists of relatively coarse-grained soil including sand with silt, silty sand/sandy silt, and silty sand from ground surface to approximately,5.5 to ' 8.5 feet bsg. Fine-grain soil consisting of sandy silt, silt, and silty clay.extend beneath the coarse-grain unit to a depth of approximately 18.5 feet bsg. Clayey sand was observed-from, _w 18.5 feet bsg.to the total depth of the boring of 21 feet bsg. ■ ' 3 . . .The depth to ground water at the site was measured at approximately 7.5 to 8 feet bgs. Ground water flow direction is suggest to betothe north-northeast at a gradient of 0.006. ' There were no reported detections of BTEX;TPH-g,or TPH-d in soil samples collected from the five soil borings (Table 5). Fuel oxygenating compound MTBE was detected at ' concentrations of 65,ug/rig and 110 ug/ft in soil samples collected from soil boring M ' 4 at 17.5 and 20 feet bsg, respectively. There were no other reported detections of fuel oxygenating compounds in the soil samples analyzed. • Based on the mobility of MTBE in ground water, the relatively low concentrations of MTBE reported in the soil samples collected from soil boring B-4 (MW-4) may•be indicative of MTBE-impacts to ground water in the soil samples collected from the saturated zone rather ' than MTBE-impacts to soil. • Toluene was detected in ground water sample MW-2 at a concentration of 0.35 ug/l (Table 6). Based on current and previous site investigation results, the extent of TPH-g impact in ground water appears to be delineated.(Figure 4). ' TPH-d ,was detected in groundwater samples B-2 and B-3 and concentrations of 570 ug/l and 130 ug/1, respectively. Based on ground water analytical results, the extent of TPH-d "impacted ground water has not been delineated on the east and west portions of the site. The extent of TPH-dimpact in ground water is illustrated in.Figure 5. f Fuel oxygenating compounds MTBE and TBA-were detected in ground watersample MW-4 Advanced GeoEnvironmental.Inc.