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ti <br /> i <br /> ameO� <br /> 5.0 CONSTITUENTS OF CONCERN IN GROUNDWATER <br /> The results of on-site and off-site groundwater investigations and groundwater monitoring <br /> described in the CAP indicate the presence of constituents of concern (CDCs) in groundwater <br /> beneath the site and the off-site area (AMEC, 2010a). The CDCs include CVOCs and <br /> petroleum hydrocarbons constituents. The nature and extent of these COCs in groundwater <br /> beneath the on-site and off-site areas are described in detail in the CAP and are summarized <br /> in the following sections. <br /> 5.1 CHLORINATED VOLATILE ORGANIC COMPOUNDS <br /> CVOCs consisting of historically common industrial solvents and their transformation <br /> byproducts are the primary CDCs in groundwater at this site. Concentrations of CVOCs <br /> detected in samples collected during the March 2010 monitoring event are shown on Figure 6. <br /> CVOCs are described in the following subsections in the approximate order of its relative <br /> concentration, frequency, and/or distribution. <br /> 5.1.1 Tetrachloroethene <br /> PCE is the most prevalent CVOC measured in groundwater samples collected from on-site <br /> and off-site monitoring wells (Figure 6). PCE is used as a solvent in various industrial <br /> applications and in dry cleaning of fabrics. PCE degrades in the environment to <br /> trichloroethene (TCE), then to either 1,1-dichloroethene (11DCE) or 1,2-dichloroethene <br /> (12DCE) then to vinyl chloride and finally to ethane. <br /> PCE is in groundwater beneath the site and the off-site area northeast of the site. The <br /> groundwater samples containing the highest concentration of PCE in the site vicinity were <br /> collected from borings on North Hunter Street south of the intersection with East Poplar <br /> Street and from monitoring well cluster MW-5 (Figure 6). <br /> 5.1.2 Trichloroethene <br /> TCE is the second-most prevalent CVOC measured in groundwater samples collected <br /> from on-site and off-site monitoring wells (Figure 6). TCE is used as a solvent in industrial <br /> applications. TCE can be present in groundwater as a degradation product of PCE. TCF_ <br /> degrades to either 11 DCE or 12DCE. TCE is in groundwater beneath the site and the off-site <br /> area northeast of the site. <br /> Groundwater samples containing the highest concentration of TCE in the site vicinity were <br /> collected from borings on North Hunter Street south of the intersection with East Poplar Street <br /> and from monitoring well cluster MW-5 (Figure 6). <br /> AMEC Geomatrix,_Inc, <br /> IM 30000 3290\Archive\13290-49.DOC 6 <br />