ARCHIVED REPORTS_XR0008001 - Laserfiche WebLink

Home Browse Search

Updated Site Conceptual Model and Fourth Quarter 2002 Morutormg and Remed,atmn Report Cleanup and Abatement Order No 5-00-707 EAI Project No 1232 5.0 DISCUSSION 5,1 Ground Water EIevation Contour Maps Ground water beneath the sites has been segregated into shallow and deep zones hereinafter referred to Hydro-Stratigraphic 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 (see Section 2 0) The wells that are located on the foriner Wards site are generally screened in Unit B with the exception of well MW-8D 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 Note during the current gauging event, several of the ground water elevation data points were inconsistent with historic ground water elevation data These inconsistent data points were not used in constructing the ground water elevation maps (Figures 8 and 9) Five additional wells are screened across Hydro-Strati graphic 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 (see 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-Strati graphic Units A and B has consistently been toward the east The current gradient as measured from Unit B is approximately 0 003 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 monitoring 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 an Figures Fig 10 d 11 present TPH-G isoconcentration maps for Units A and B Figure 10 indicates that no Unit A wells had a detectable TPH-G concentration above the laboratory detection limit for the fourth quarter 2002 In Unit B, the highest concentration of TPH-G was in well MW-3 (17,000 pg/L) Figures 12 and 13 present Unit A and Unit B benzene isoconcentration maps, respectively Benzene was detected in Unit A in two wells during the December 2002 sampling event (MW- BHM WORD 1232Ro2D1 -$- ENVIRONMENT4L.4UDIT, INC p