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B ZONE <br /> Monitor wells MWI, MW2, MW3, MW4, MW5 penetrate both the A and B zones <br /> Figure 4B show the gradient determination for the B Zone utilizing only the cluster wells <br /> RIB, MW613 and MW713 The flow direction is relatively flat (0 0013 ft/linear ft) and to <br /> the northwest <br /> RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES <br /> MONITOR WELLS <br /> Monitor wells MW1, MW2, MW3, MW4, and MW5 include and are open to both the A <br /> and B zones Contaminants found in these wells would mix with the groundwater of both <br /> zones <br /> Figure 5A represents the hydrocarbon groundwater plume in the A zone and shows an <br /> elongated plume extending west of MM2 out to "Geoprobe" hole P9 were degradation <br /> has left only minor TPHg(470 ug/L), Toluene (0 65 ug/L) and tert-Butanol (I 1 ug/L), the <br /> degradation byproduct of MTBE <br /> Figure 5B represents the hydrocarbon groundwater plume in the B zone and shows a <br /> similar elongated plume extending west from MW2 out to "Geoprobe" hole P9 where <br /> degradation has left only minor amounts of Toluene (0 81 ug/L), Xylenes (0 83 ug/L) and <br /> MTBE (1 6 ug/L) <br /> Figure 6 illustrates the subsurface lithology and the extent of the A and B zones <br /> groundwater plumes within the A and B zones <br /> RECONMENDATIDNS <br /> 1) Destroy wel I MW I <br /> 2) Install temporary Piezometers for pump test <br /> 3) Conduct pump test <br /> 4) Start dewatering of A zone oen week prior to over-excavating gasoline contaminated <br /> soils <br /> 5) Over-excavate former UST - piping and dispenser areas to approximately 24 feet <br /> bgs Backfill excavation with pea gravel, road base and resurface with asphalt <br /> 6) Submit a report of findings/results <br /> 6 QM 4th 2002 <br />