Introduction of Relatively High Conductivity Material and the Effects on TCE Degradation and Remediation

Wednesday, April 22, 2009: 11:05 a.m.
Agave Ballroom (Hilton Tucson El Conquistador Golf & Tennis Resort )
Danielle R. Moss , Geology, Miami University, Oxford, OH
Jonathan Levy, Ph.D. , Geology, Miami University, Oxford, OH
Michael Proffitt , Ohio EPA, Dayton,, OH
Brian Hiles , Miami University, Cincinnati, OH
Miami University owns a former Nike missile base site, CD-78 in Oxford, Ohio.  Previous activities on site led to groundwater contamination by trichloroethene (TCE) and its related degradation products, dichloroethene and vinyl chloride.  TCE concentrations are highly variable, with concentrations in 2002 as high as 486 μg/L.  The abandoned missile silos filled up with contaminated groundwater due to the high water table, thus providing a potential exposure pathway.  In November 2007, the silos were purged and demolished by implosion, then subsequently filled with a relatively high hydraulic conductivity material compared to the surrounding geologic medium.  Prior to silo destruction, it was believed that natural attenuation of the compounds was a sufficient course of action.  However, the silo removal could change the groundwater flow directions and geochemistry.  More data are needed to determine if natural attenuation is still the best course of action.

We documented the current site conditions and plan to develop a groundwater-flow and contaminant-transport model of the system.  Groundwater flow rates and directions will be determined.  Groundwater samples will be analyzed for basic geochemistry and for chlorinated hydrocarbons by gas chromatography/mass spectrometry.  Results since the silo destruction will be compared to previously-collected data.  Changes in groundwater flow and geochemistry resulting from the silo destruction could affect the degradation rate of TCE and its products.  We hypothesize that changes in the flow paths and increases in the oxidation-reduction potential and dissolved oxygen content have diminished the effectiveness of natural attenuation due to a change to more aerobic conditions.  The applicability of phytoremediation as an alternative to natural attenuation at this site will also be assessed.