ARCHIVED REPORTS XR0001584 - Laserfiche WebLink

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' 24 October 1997 AGE-NC Project No 95-0235 Page 10 of 11 • Soil samples collected at 25 feet bsg during installation of monitoring wells MW-4 and MW- ' 5 did not contain detectable concentrations of TPH-g or BTE&X • The ground water flow direction is generally toward the northeast in the former tank pit ' excavation area, but appears to be toward the northwdst overall due to a northwest/southeast trending trough of lower ground water elevation cutting across the property • The ground water elevation at the site is higher than the tops of the screened intervals in ' monitoring wells MW-1, MW-2 and MW-3 • The ground water sample collected from MW-2 was the most highly impacted by ' hydrocarbons _ • The most highly impacted soil was encountered In MW-2 within the scieened interval (41 5 ' feet bsg) during well Installation This contamination may represent the capillary fringe zone near the time of the hydrocarbon release • Ground water sampled from MW-I and MW-2 may not be in direct communication with the ' ground water sampled from MW-4 and MW-5 due to completion of the former in only the lower clay-rich intervals (See Figure 8 - Geologic Cross Section A-A ) Therefore the analytical results from MW-2 may be representative of the most impacted ground water, which is not the shallowest ground water • Contoured TPH-g concentrations resemble the contoured ground water elevations Benzene concentrations follow the trend of TPH-g concentr`atlons The current up-gradient and down-gradient extent of hydrocarbon-impacted ground water ' has not been delineated The current cross-gradient extent of impacted shallow ground water is delineated by monitoring wells MW-4 and MW-5 I 12 0. RECOMMENDATIONS Based on the findings of the environmental activities recounted in,this report, AGE recommends ' Continued quarterly monitoring of the ground water monitoring wells on-site'should be performed f ' Installation of three additional ground water monitoring wells, two north of MW-2 In the apparent down-gradient direction and a shallowly completed well near MW-2 The two down-gradient wells should be dual completed to monitor both the current high water level, ' as monitored In wells MW-4 and MW-5,and the former lower water level monitored in wells MW-1 and MW-2 Installation of a shallow completion well near MW-2 will yield reliable hydrocarbon concentrationsinshallow ground water under the current regime of high ground Adtiunced CcoEnvironmental,Inc