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9038OB-SS4 CON-47 <br /> the groundwater. During the drilling of the boreholes, however, the air <br /> rotary exhaust from the borehole was continuously monitored with an Organic <br /> Vapor Analyzer (OVA) for Health and Safety purposes. No such vapors were <br /> found. Downgradient, the groundwater contaminant plumes from Contaminant <br /> Area 1 combine with those from Contaminant Area 2 and extend some distance <br /> beyond the Depot boundaries, as described in Section 4.3.5. <br /> 4.3.6.2 Contaminant Area 2. There are two well clusters in Contaminant <br /> Area 2, a northwest cluster which includes Well LM 62 and a southeast <br /> cluster which includes Well LM 30. The northwest cluster showed both TCE <br /> and PCE at single- to double-digit concentrations (Table 4.3-3) , <br /> distributed relatively uniformly with depth in the uppermost four wells. <br /> The southeast cluster, by contrast, showed about 400 ug/l of PCE in the <br /> shallowest well and single-digit values below that. The tentative <br /> conclusion is that the solvents in the groundwater under the northwest end <br /> of Contaminant Area 2 are derived from Contaminant Area 1, whereas in the <br /> southeast end the source is local . This conclusion is supported by Figure <br /> 4.2-4a, which shows elevated soil gas and soil contaminant levels around <br /> the southeast cluster and relatively clean soil gas and soil over the <br /> northwest cluster. Moreover, Figure 3.1-1 shows that drums were stored on <br /> the southeastern part of Contaminant Area 2. Thus, it appears that the <br /> ti solvents in the groundwater derive from two sources: Contaminant Area 1, <br /> and leaks and spills from drums stored and handled in the southeastern <br /> portion of the area. As in Contaminant Area 1, perched lenses of liquid <br /> solvent may remain in the soil from previous spills and leaks. The <br /> solvents were not, however, detected by the OVA during the installation of <br /> the boreholes. <br /> 4.3.6.3 Contaminant Area 3. There is one well cluster in Contaminant Area <br /> 3. The shallowest well , LM 32, has shown declining levels of both solvents <br /> a <br /> from 1986 to the most recent sampling round in 1988. The 1986 Radian <br /> results gave 210 ug/1 TCE and 320 ug/l PCE; these levels declined to 67 and <br /> 100 ug/l , respectively, in 1988 (Table 4.3-3) . Figure 4.2-5b shows <br /> elevated solvents in the soil and soil gas in the vicinity, and Figure 3.1- <br /> 1 shows drums stored in Contaminant Area 3. Well LM 33 in this cluster, <br /> 4-191 <br />