ARCHIVED REPORTS_XR0010583 - Laserfiche WebLink

Home Browse Search

i 13 November 2002 • AGE-NC Project No 97-0249 ' Page 4 of 5 ' 4.0. SUMMARY AND CONCLUSIONS The implications from the September 2002 ground water monitoring event are as follows I • Ground water flow direction was generally inferred to be west to southwest at an approximate gradient of 0 006 (Figure 3) I • Due to the low gradient at the site, slight variations in ground water measurements or changes of recharge/discharge of the local ground water could greatly modify the inferred I ground water flow direction • Ground water flow direction at the site may have been influenced by pumping of domestic water well DW-1 • The ground water elevation at the site was within the screened intervals of wells MW-1 through MW-6 which should yield samples fully representative of shallow ground water Iconditions • Ground water elevation at the site appeared to have decreased an average 6 55 feet between the June 2002 and the September 2002 ground water monitoring events (Table 1) • The lateral extent of the dissolved petroleum hydrocarbon plume is not known toward the south, southwest, west, northwest and north of the area bound by wells MW-1 through ' MW-6, the vertical extent on the site is not known in any direction (Figures 4, 5 and 6) • The elevated petroleum hydrocarbon concentrations detected in water samples collected from I wells MW-1, MW-2 and MW-3 (screened between 5 and 25 feet bsg) suggest that these wells may be screened within or near a "core area" of a dissolved petroleum hydrocarbon plume(Figures 4 and 5) Historically,the area of greatest dissolved petroleum hydrocarbon- impact was encountered in the samples from wells MW-3 and MW-6 and lower petroleum hydrocarbon concentrations were detected from in-between well MW-1 • The historical distribution of MTBE concentrations in Three B's Truck Plaza wells MW-1, MW-2,MW-4,MW-6 and Flag City Chevron well MW-7 have suggested the possibility of two separate dissolved MTBE-plumes (Figure 6) 5.0. RECOMMENDATIONS IBased upon data collected during September 2002, AGE recommends ' 1 Continued quarterly ground water monitoring at wells MW-1 through MW-6, the next quarterly ground water monitoring event is tentatively scheduled for September 2002 Advanced GeoEnvironmental,Inc