ARCHIVED REPORTS_XR0008818 - Laserfiche WebLink

Home Browse Search

01 March 2004 AGE-NC Project No 99-0645 Page 8 of 11 and VW3 The lowest vacuum was measured in MW-3,approximately 30 feet west of the extraction point and screened much lower in the stratigraphy at the site,however,sufficient induced vacuum was observed in the monitoring wells to demonstrate that a vertical connection may exist across the vertically separated layers at the site During the deeper soil vapor extraction pilot test (06 October) the greatest induced vacuum was measured in the observation point nearest the extraction well,at 0 45 inches of water in well MW-1R The lowest vacuum was measured in VW2 and VW 1B, approximately 20 feet west of the extraction point and screened above the lower stratigraphy at the site Again, sufficient induced vacuum was observed in the monitoring wells and also in the upper soil vapor extraction wells,to demonstrate that a vertical connection may exist across the vertically separated layers at the site AGE plotted in a loganthmic scale,the maximum vacuum measured at the observation points during the pilot test versus the distance from the extraction well The effective radius of influence was determined by drawing a best-fit line though these data points to correlate distance to vacuum data At a vacuum potential of 0 10 inches of water,the radius of influence is approximately 30 feet for the lower screened well(VW 1 A)and radius of influence is approximately 40 feet for the upper screened well(VW 1 B),at an induced vacuum potential of 10 inches of water,the radius of influence is 20 feet for well VW 1A and approximately 25 feet forwell VW 1B Further,a vacuum potential of 10 0 inches of water the radius of influence is less than 10 feet Based on the United States Environmental Protection Agency(EPA)-prepared document,How to Evaluate Alternative Cleanup Technologies For UST sites the radius of influence is considered to be the distance from the extraction well at which a vacuum of at least 0 1 inches of water is observed Based upon an effective vacuum potential of 0 1 inches of water, the calculated effective radius of influence at the site will be 30 feet up to almost 40 feet for the upper screened vapor well The majority of the residual impacted soil would be collected within the 40 foot radius of influence Appendix C depicts the effective radius of influence i 3 5 GROUND WATER GRADIENT AND FLOW DIRECTION Ground water elevation, flow direction and gradient were determined from field data collected on 06 October 2003, the contaminant impact to ground water was quantified from the ground water laboratory data Depth to ground water at the site ranged from 95 09 feet to 95 34 feet below the monitoring well casing tops The ground water elevation in each well was calculated from this data The ground water elevations from well MW-2 and MW-3 were 49 90 feet and 49 86 feet below mean sea level(MSL) The average decrease of 4 feet from the July 2002 monitoring event is depicted in Table 4 The ground water flow direction was estimated to flow toward the northwest,however,the well head elevation for MW-1R has not been resurveyed Figure 4 illustrates the contoured ground water Advanced GeoEnvsronmentni,Inc