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Workplan for Supplemental Investigation <br /> 2005 Navy Drive, Stockton, CA <br /> January 2, 2013 <br /> Page 5 of 12 <br /> 2.1 Contaminant Fate and Transport <br /> It is highly unusual to find DCE at a site without at least one of its parent <br /> compounds, trichloroethylene (TCE) or tetrachloroethylene (also known as <br /> perch loroethylene (PCE). Both of these "parent compounds" are used as industrial <br /> degreasers and in auto repair shops, several of which were observed to be in close <br /> proximity to the subject property. As the schematic on the following page shows, the <br /> production of DCE is typically a consequence of the removal of one chlorine atom <br /> from TCE. The DCE breaks down to vinyl chloride (VC) in soils or groundwater <br /> lacking in oxygen (anaerobic condition) or under methanogenic environments, <br /> neither of which exist in the shallow groundwater, which explains the absence of <br /> detectable VC. The DCE can also by-pass the VC step and form ethene which then <br /> breaks down to carbon dioxide and water (Pankow and Cherry 1996) <br /> DCE is not typically used by itself except in very specialized manufacturing plants <br /> which were not observed in the vicinity of the subject site. <br /> Risk-Based Decisions, Inc. <br />