ARCHIVED REPORTS_XR0007917 - Laserfiche WebLink

Home Browse Search

tUpdated Site Conceptual Model and Third Quarter 2003 Monitoring and Remediation Report Cleaziu and Abatement Order No 5-00-707 EAI Project No 1232 i5.0 DISCUSSION 5.1 Ground Water Elevation Contour Maps Ground water beneath the sites has been segregated into shallow and deep zones hereinafter referred to Hydro-Strati graphic Units A and B respectively, or simply Unit A and Unit B Two deeper units, Unit C and Unit D, are also associated with the sites (Section 2 0) The wells that are located on the former Wards site are generally screened in Unit B with the exception of well MW-81) which is screened in Unit D Figures 8 and 9 present ground water elevation contour maps for Hydro-Stratigraphic Units A and B Unit A wells are screened across the water table, generally between 30 to 50 feet bgs Unit B wells are generally screened between 50 and 70 feet bgs (Figures 8 and 9) ' Five additional wells are screened across Hydro-Stratigraphic units deeper than Units A and B as follows Two wells are screened in Unit C (MW-23S and MW-24S) and three wells (MW- 81), MW-23D and MW-24D) are screened in Unit D (Section 2 0) It is EAI's opinion that Units C and D are hydraulically connected and represent the same unit 5.2 Ground Water Flow Direction and Magnitude Since the RIW was taken out of operation in August 2000, ground water flow direction in Hydro-Stratigraphic Units A and B has consistently been toward the east The current gradient as measured from Unit B is approximately 0 001 foot/foot 5.3 Monitoring Well Hydrographs Figures 4 through 7 present TPH-G and benzene concentration plus ground water elevation verses time for ground water monitoring wells MW-2, MW-3, MW-11 and MW-12, respectively A general decline in TPH-G and benzene concentrations has been observed since ground water monitonng was initiated Ground water elevation over the same period of time has risen approximately 20 feet on average 5.4 TPH-G and Benzene Isoconcentration Maps ' Figures 10 and 11 present TPH-G Isoconcentration maps for Units A and B Figure 10 indicates that no Unit A wells had detectable TPH-G concentration above the laboratory detection limit In Unit B, the highest concentration of TPH-G was in well MW-11 (15,000 lig/L) Figures 12 and 13 present Unit A and Unit B benzene Isoconcentration maps, respectively Benzene was detected in Unit A wells MW-14A (1 3 pg/L) and MW-18 (0 58 pg/L) dunng the August 2003 sampling event The highest Unit B benzene concentration was in monitoring well MW-11 at 5,300 lig/L (Figure 13) 13HM WORD 1232RO351 -7-