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SECTION 3.0 SUMMARY OF PREVIOUS INVESTIGATIONS
<br /> generally decreased in groundwater monitoring wells MW-7 and MW-11, slightly increased in
<br /> MW-12, and increased in MW-10
<br /> 3.2 PREVIOUS GROUNDWATER MONITORING INVESTIGATIONS
<br />' Historical groundwater analytical results are summarized in Table 3-2 Groundwater monitoring
<br /> trends since 1994 are summarized below
<br /> • In 1995, GEOCON performed environmental engineering services that included restoring
<br /> groundwater sampling capability for eight groundwater monitoring wells that were temporarily
<br /> decommissioned A groundwater monitonng/vapor extraction test well VW-1 was also installed
<br /> in 1995 Two vapor extraction test monitoring wells (VM-1 and VM-2) and two new
<br /> groundwater monitoring wells MW-25 and MW-26 were installed by GEOCON in 1996 A
<br /> Corrective Action Plan was prepared in 1996 (GEOCON, 1996)
<br /> ® Groundwater monitoring was performed in 1994 by Nmyo & Moore Groundwater samples
<br />' collected from monitoring wells MW-10, MW-11, MW-12, MW-13, MW-14, MW-16, MW-
<br /> 19, MW-20, and MW-24 were analyzed for TPH-g, TPH-d, and BTEX TPH-g concentrations
<br /> decreased in MW-10, MW-11, MW-13, slightly increased in MW-14, and remained unchanged
<br /> at below the laboratory detection limits in MW-12, MW-19, and MW-20 BTEX concentrations
<br /> increased in monitoring wells MW-10, MW-14, and MW-24, generally decreased in MW-11,
<br />' MW-13, and MW-16, fluctuated (some concentrations slightly increased and some
<br /> concentrations slightly decreased) in MW-12 and MW-19, and remained below detection limits
<br /> in MW-20 during the groundwater sampling performed in 1994 (Nmyo and Moore, 1994)
<br />' • In 1994 Nmyo & Moore abandoned the following momtonng wells due to declining water
<br /> levels MW-1 through MW-8 and MW-10 In addition, eight groundwater monitoring wells
<br /> (MW-9, MW-11, MW-13, MW-14, MW-16, MW-19, MW-20, and MW-24) were temporarily
<br /> decommissioned due to on-site construction activities
<br /> + Three quarters of groundwater monitoring were performed by GEOCON in 1996 Monitoring
<br /> wells MW-9, MW-11, MW-12, MW-13, MW-14, MW-16, MW-19, MW-20, MW-24, and
<br /> VW-1 were sampled for TPH-g, TPH-d, BTEX, and MTBE Groundwater monitoring wells
<br /> MW-25 and MW-26 were sampled during the last quarter of sampling in 1996 Groundwater
<br />' concentrations of TPH-g, TPH-d, BTEX, and MTBE generally decreased from the first to the
<br /> third monitoring event in monitoring wells MW-9 and MW-11, fluctuated in MW-12, MW-13,
<br /> MW-19, MW-20, and MW-24, and increased in MW-14, and MW-16
<br /> • Groundwater monitoring was performed by Professional Service Industries (PSI) in May,
<br /> • September, and December of 1997 Groundwater concentrations of TPH-g, TPH-d, BTEX and
<br /> MTBE continued to decrease in monitoring wells MW-9, MW-11, MW-12, MW-13, MW-14,
<br /> S 1PROjwlO4OtOOO44SHOP701SHOP10SAC6C 3-3 URS Greiner Woodward Clyde
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