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. 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 are hydraulically connected and form one continuous water-bearing zone The monitoring well network, as currently installed, was intended to target these sandy, more transmissive zones and potential migration pathways Groundwater monitoring wells have been screened at two distinct intervals Upper zone wells, MW-1 through MW-7, are screened in sandy zones between 46 5 and 70 feet below ground surface (bgs), to monitor petroleum hydrocarbon impact to the uppermost 15 to 20 feet of the water-bearing zone Lower zone wells, MW-8 through MW-12, are screened between 94 and 115 feet bgs, within the laterally continuous sandy unit first encountered at approximately 95 to 105 feet bgs At the time of the first quarter 2004 monitoring event, groundwater was encountered in the monitoring wells screened within the upper zone at depths ranging from 48 09 to 49 98 feet bgs Well MW-3 is obstructed Groundwater was encountered in the monitoring wells screened within the lower zone at depths ranging from 49 18 to 50 78 feet bgs Groundwater elevations increased approximately 1 70 to 2 22 feet in upper zone wells (VEW-1, MW-2, MW4 through MW-7), and increased 1 69 to 2 12 feet in lower zone wells (MW-8 through MW-12) since the November 10, 2003 event Groundwater monitoring data were normalized to mean sea level (MSL) and used to prepare groundwater elevation contour maps In the upper zone, the groundwater flow direction on February 23, 2004, was toward the east-southeast at a gradient of 0 001 ft/ft A groundwater elevation contour map for the upper zone is shown on Figure 2 The water level measured in well MW-5 appeared to be anomalous and was not used in contouring Since 1995, groundwater flow in the upper zone has consistently been toward the east and southeast In the lower zone, groundwater flow during the first quarter 2004 was toward the south-southeast at an average gradient of 0 008 ft/ft A groundwater elevation contour map for the lower zone is shown on Figure 3 Groundwater flow in the lower zone has historically been toward the south and east In the upper zone wells, THPG and benzene were reported in wells VEW-1, VEW-2, and MW-2 The highest concentration of TPHG (130,000 gg/L) was reported in wells VEW-1 and VEW-2, and the highest concentration of benzene (1,300 gg/L) was reported in VEW-2 TBA was reported in wells MW-2 (41 µg/L) and MW-5 (7 1 pg/L) 1,2-DCA(3 9 ug/L) was reported in well MW-5 MTBE, DIPE, ETBE, TAME, or EDB were not reported in any of the upper zone wells The concentrations reported for well VEW-1 were anomalously high compared to historical data Analysis of a second VOA from this sample returned similar results (refer to Table 1) Additional monitoring is required to evaluate if this large increase represents a change in well conditions In the lower zone wells, TPHG and benzene were reported in wells MW-8 and MW-9 The highest concentration of TPHG (53,000 ltglL) and benzene (500 µg/L) were reported in well MW-9 TBA was reported in wells MW-8 (34 µg/L) and MW-11 (7 9 pg/L) 1,2-DCA(1 9 ltg/L) was reported in well MW-11 MTBE, DIPE, ETBE, TAME, or EDB were not reported in any of the lower zone wells TPHG, benzene, and MTBE concentrations for samples collected and analyzed during the first quarter 2004 are included on Figure 4 SJCEHD has requested that all peaks detected in the analyses be reported A copy of the laboratory tentatively identified compounds (TIC) report is attached Tentatively identified compounds were reported for wells MW-2, MW-8, MW-9, VEW-1, and VEW-2- Results of the TIC analysis are summarized in Table 3 P\Apache Plastics\Quarteriy reports\20MApache_1Q04 DOC 5Tl2ATU5