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A� 1i Groundwater Flow Direction/Gradient (deep wells) Possible radial flow around well MW-8/ • 0 006 to 0 0022 ftlft DISCUSSION As discussed in the Site Conceptual Model (SCM), review of the subsurface geology and groundwater well elevation data indicate that although different transmissive (i a sandy) zones have been identified at various depths at this site, these zones appear to be hydraulically connected and likely form one continuous water-bearing zone Groundwater monitoring wells have been screened at three distinct intervals Shallow screened wells VEW-1, VEW-2, MW-2 through MW-7, and MW-15 were screened at various depth intervals between 40 and 70 feet below ground surface (bgs) Samples collected from these wells currently represent groundwater concentrations at first encountered groundwater Deeper screened wells intended to target sandy, more transmissive zones that may represent preferential pathways for petroleum hydrocarbon migration Mid-depth wells MW-16 and MW-18 are screened in sandy zones between 85 and 90 feet bgs Deep wells MW-8 through MW-11 and MW-17 are screened between 94 and 120 feet bgs, within a laterally continuous sandy unit first encountered at approximately 95 to 105 feet bgs Shallow Wells At the time of the third quarter 2004 monitoring event, groundwater was encountered in the shallow monitoring wells at depths ranging from 51 10 to 53 42 feet bgs Well MW-3 is obstructed Groundwater elevations had decreased between 3 05 and 3 61 feet in all shallow wells since the previous monitoring event (May 24, 2004) Groundwater monitoring data were normalized to mean sea level (MSL) and used to prepare a groundwater elevation contour map (Figure 2) The groundwater flow direction on August 23, 2004, was toward the northeast at a gradient of 0 0015 ft/ft Since 1995, groundwater flow in the shallow • wells has consistently been toward the east and southeast TPHG (21,000 pg/L) and benzene (2,600 pg/L) were reported in well VEW-1 Benzene was also reported in well MW-2 (1 8 µg/L) TBA (12 µg/L)was reported in well MW-2 1,2-DCA was reported in wells MW-2 (140 pgtL), MW-5 (3 0 pg/L), and MW-6 (16 µg/L) MTBE, DIPS, ETBE, TAME, or EDB were not reported in any of the shallow wells These analytical results are generally consistent with historical data TPHG, benzene, and MTBE concentrations for samples collected and analyzed during the third quarter 2004 are summarized on Figure 3 Mid-Depth Wells At the time of the third quarter 2004 monitoring event, groundwater was encountered In the mid-depth monitoring wells at depths of 48 92 and 52 77 feet bgs Groundwater levels had decreased 0 39 feet in well MW-16 and 3 43 feet in well MW-18 since the previous sampling event (May 24, 2004) Depth-to-water measurements have been summarized on Figure 4 TPHG, benzene, TBA, and 1,2-DCA were reported in wells MW-16 and MW-18 The highest concentration of TPHG (490 µg/L) was reported In well MW-16 The highest concentrations of benzene (17 µg/Q, TBA (51 pg/L), and 1,2-DCA (91 pg/L) were reported in well MW-18 MTBE, DIPE, ETBE, TAME, or EDB were not reported in any of the mid-depth wells TPHG, benzene, and MTBE concentrations for samples collected and analyzed during the third quarter 2004 are included on Figure 5 Deep Wells At the time of the third quarter 2004 monitoring event, groundwater was encountered in the deep monitoring wells at depths ranging from 52 21 to 53 05 feet bgs Groundwater elevations had decreased . between 2 29 and 3 76 feet in all deep wells since the previous monitoring event (May 24, 2004) P IApachc Plastics%Quarterly reports120041Apache_3Q04 DOC 5TR/47-US