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Ile SECTION 3.0 SUMMARY OF PREVIOUS INVESTIGATIONS
<br /> MW-16, MW-19, MW-20, MW-24, VW-1, MW-25, and MW-26 Concentrations of TPH-d,
<br /> toluene, and xylenes fluctuated and concentrations of TPH-g and benzene decreased in VM-2
<br /> • Four quarters of groundwater monitoring were conducted by PSI in 1998, and one quarter in
<br /> 1999 Two monitoring wells, VW-1 and MW-26, were abandoned following the collection of
<br /> groundwater samples due to the recent construction of the maintenance building Groundwater
<br /> concentrations of TPH-g, TPH-d, BTEX and MTBE were not detected above the laboratory
<br /> detection limits in groundwater morutonng wells MW-16 and MW-25 during 1998 TPH-d
<br /> were detected in the following nine monitoring wells MW-9, MW-11, MW-13, MW-14, MW-
<br /> 24, VW-1, VM-1, VM-2, and MW-26 TPH-g were detected in the following seven monitoring
<br /> wells MW-12, MW-13, MW-14, MW-20, VW-1, VM-1, and VM-2 BTEX were detected in
<br /> seven MW-12, MW-13, MW-14, MW-19, VW-1, VM-2, and MW-26 A concentration of
<br /> MTBE was detected in one well (VW-1) by EPA Method 8020 (PSI, 1999)
<br /> ® QuarterlY groundwater monitoring events were performed by NinYo and Moore in June and
<br /> September 1999 Between the two events, concentrations of TPH-g decreased from 500 to 450
<br /> pg/L in MW-13, increased from 3,700 to 8,820 µg/L in VM-1, and decreased from 64,000 to
<br /> 18,200 pg/L in VM-2 Concentrations of TPH-d increased from below the laboratory detection
<br /> limit of 100 µg/L to 700 4g/L in VM-1, and from below the laboratory detection limit to 900
<br /> µg/L in VM-2 Concentrations of benzene decreased from 471 to 85 gg/L in MW-13, increased
<br /> from below the laboratory detection limit of 0 3 µg/L to 3,890 pg/L in VM-1, and increased
<br /> from 2,250 to 7,920 pg/L in VM-2 Concentrations of MTBE were not detected in the
<br /> groundwater samples analyzed during both monitoring events
<br /> In summary, 21 groundwater monitoring wells and three vapor monitoring wells have been
<br /> installed at the Shop 10 site between 1987 and 1996 Ten of the groundwater monitoring wells and
<br />' two vapor monitoring wells are currently located onsite and are included in the current groundwater
<br /> monitoring program, including the routine groundwater monitoring and analysis for TPH-g, TPH-d,
<br /> BTEX, and MTBE EIeven of the groundwater monitoring wells and one vapor monitoring well
<br /> have been abandoned at the Shop 10 site
<br /> S IPROJ lO4O100044SHOP101SHOP10SADOC 3-4 URS Greiner Woodward Clyde
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