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B ZONE Monitor wells MW2, MW3, MW4, MW5 penetrate both the A and B zones Figure 4B show the gradient determination for the B Zone The B zone gradient and flow direction shows a ridge developed from Country Club Food & Fuel wells MW3 and MW4 to Sanchez well MW613 The current groundwater gradient shows a flow direction to the northwest at a gradient of 0 0012 Minear ft (MW5 to Sanchez MW613) RESULTS OF CERTIFIED ANALYSES OF GROUNDWATER SAMPLES MONITOR WELLS Monitor wells MW2, MW3, MW4, and MW5 penetrated both the A and B zones Contaminants found in these wells would mix with the groundwater of both zones Figure 5A represents the hydrocarbon groundwater plume in the A zone and shows an elongated plume extending west of MW2 out to "Geoprobe" hole P9 were degradation has left only minor TPHg(470 ug/L), Toluene (0 65 ug/L) and tert-Butanol (I I ug/L), the degradation byproduct of MTBE Highest concentrations of TPHg are associated with well MW6A at 13000 ug/L The area that was over-excavated contained temporary piezometers PZ I A and PZ2A and contained the highest concentration of hydrocarbons with 140,000 ug/L and 62,000 ug/L TPHg respectively on January 31, 2003 Figure 5B represents the hydrocarbon groundwater plume in the B zone and shows a similar elongated plume extending west from MW2 out to "Geoprobe" hole P9 where degradation has left only minor amounts of Toluene (0 81 ug/L), Xylenes (0 83 ug/L) and MTBE (1 6 ug/L) Again the highest concentrations are associated with monitor well MW613, 610 ug/L The area that was over-excavated contained temporary piezometers PZ113 and PZ213 with 40,000 ug/L and 16,000 ug/L TPHg respectively on January 31, 2003 Figure 6 illustrates the subsurface lithology and the extent of the A and B zones groundwater plumes within the A and B zones Also shown in cross section is the extent of the over-excavation and residual soil contamination February 28, 2003 RECOMMENDATIONS 1) Carry out the approved workplan to install a 4 inch diameter monitor well within the excavated area, a northern extent cluster monitoring well (A and B zones), north of former well location MW 1 and a down-gradient cluster monitoring well (A and B zones) to document the lateral extent west of probe hole P9, see Figure 3 2) Western Geo-Engineers is currently obtaining encroachment permits from San Joaquin County Public works and drilling permits from San Joaquin County Health 6 Sanchez QM 2nd 2004