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Depth to Groundwater(deep wells) _ 49 70 to 50 66 feet below top of well casing Groundwater Flow Direction/Gradient (deep wells) Northeast/0 0011 ft1ft 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 are 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 fourth quarter 2005 monitoring event, groundwater was encountered in the shallow monitoring wells at depths ranging from 48 91 to 51 10 feet bgs Well MW-3 is obstructed Groundwater elevations had decreased between 0 06 and 0 34 feet in all shallow wells except for MW-2, which increased 0 01 feet since the previous monitoring event (August 15, 2005) 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 was generally to the east at an average gradient of 0 0006 Rift Since 1995, groundwater flow in the shallow wells has consistently been toward the east and southeast(except for the first quarter 2005, flow was toward the east-northeast) TPHG and benzene were reported in wells VEW-land VEW-2 Benzene was also reported In well MW-2 The highest concentration of TPHG (110,000 pg/L) was reported in well VEW-2 and the highest concentration of benzene (2,500 pg/L) was reported in well VEW-1 1,2-DCA was reported in wells MW-2 (57 }µg1Q, MW-5 (1 4 pg/L), and MW-6 (29 uglL) MTBE, DIPE, ETRE, TAME, TBA, or EDB were not reported in any of the shallow wells The laboratory noted that the pH levels reported in wells VEW-1, VEW-2, and MW-5 were above the EPA recommended limit of 2 As the reported results appear to be consistent with historical data, it appears that the elevated pH has not affected data quality These analytical results are generally consistent with historical data TPHG, benzene, and MTBE concentrations for samples collected and analyzed during the fourth quarter 2005 are summarized on Figure 3 Mid-Depth Wells At the time of the fourth quarter 2005 monitoring event, groundwater was encountered in the mid-depth monitoring wells at depths of 49 60 and 50 12 feet bgs Groundwater levels had decreased 0 17 feet In well MW-16 and increased 0 06 feet in well MW-18 since the previous sampling event (August 15, 2005) Depth-to-water measurements have been summarized on Figure 4 TPHG (530 gg/L), benzene (11 µg&), 1,2-DCA(11 µg/L), and TBA(52 µg/L)were reported In well MWA8 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 fourth quarter 2005 are included on Figure 5 • K(Apache PlasticslQuarterly repons12005\Apache_4Q05 DOC STRATUS