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yUJ�U�-JJ4 �UIV-40 <br /> 4.3.6.1.1 The western part includes the shallow Well LM 24, which <br /> showed 760 ug/l PCE in 1986. The concentration steadily, reaching 15 ug/l <br /> in 1989 (Table 4.3-3) . The upgradient well , LM 42, has never shown TCE or <br /> PCE above detection limits, and of the westerly cross-gradient wells, LM 1, <br /> LM 75, LM 78, and LM 88, only LM 1 was found to contain PCE in 1988, at <br /> 0.6 ug/1 , just above the detection limit. The generally downgradient <br /> wells, LM 4, LM 15, and LM 27A, have never shown TCE or PCE; this could be <br /> due to the groundwater mounding under the ponds, however, as discussed in <br /> Section 4.3.5.4.7. The soil gas samples (Figures 4.2-1 and 4.2-2) <br /> similarly show elevated PCE (and no TCE) in the vicinity of LM 24. Results <br /> from the soil sampling are spotty, probably reflecting the relatively high <br /> detection limits in soils (Figure 4.2-3a) . The source of the PCE found in <br /> this area is most likely a series of historic, undocumented spillage <br /> associated with the degreasing of locomotives and possibly other vehicles <br /> and equipment for maintenance and repair. <br /> 4.3.6.1.2 The eastern part of Contaminant Area 1 generally shows more <br /> widespread areas of contamination than the western part. Well LM 25, just <br /> north of the recoup facility in Building 26, has consistently contained <br /> about 500 ug/l of TCE (but little or no PCE) . Well LM 61, just south of <br /> the sanitary settling ponds, and about 400 feet north of LM 25, has <br /> consistently shown both TCE and PCE, in the 13 to 85 ug/l range. Wells LM <br /> 2 and LM 3, downgradient from LM 61 (considering the effects of the <br /> groundwater mounding discussed in Section 4.3.5.4.7) , have consistently <br /> shown both TCE and PCE. in the 8.1 to 20 ug/1 range. Soil gas solvent <br /> concentrations are elevated for both TCE and PCE (Figures 4.2-1 and 4.2-2) , <br /> and Soil Boring SB 42, just north of Building 237, gave the highest <br /> concentration of PCE found on the site, 960 ug/kg. Many of the other soil <br /> borings in the area showed PCE above the detection limit of 50 ug/kg. The <br /> three activities suspected of contributing solvents to the soil and <br /> groundwater include the former recoup facility in Building 26, asphalting <br /> equipment cleaning to the north of Building 237, and the storage of drums <br /> as shown on Figure 3.1-1. Also, there may be small amounts of liquid <br /> solvent perched on a discontinuous clay layer that continues to release to <br /> 4-190 <br />