REMEDIATION Summer 2010
In Situ Remediation of PCE at a Site
With Clayey Lithology and a Significant
Smear Zone
Josephine Molin
James Mueller
Donald Hanson
Troy Fowler
Tim Skrotzki
Groundwater at the former Serry’s Dry Cleaning site in Corvallis, Oregon, was impacted by chlo-
rinated volatile organic compounds (CVOCs). The primary CVOCs impacting the site include
tetrachloroethene, trichloroethene, dichloroethene, and vinyl chloride, which were detected at
concentrations up to 22,000, 1,700, 3,100, and 7 μg/L, respectively, prior to treatment. Large sea-
sonal fluctuations in groundwater CVOC concentrations indicated that a significant fraction of the
CVOC mass was present in the smear zone. Field-scale pilot tests were performed for the Oregon
Department of Environmental Quality’s Dry Cleaner Program to evaluate the performance of EHC®
in situ chemical reduction (ISCR) technology. The pilot study involved evaluating field performance
and physical distribution into low-permeability soil using basic Geoprobe® injection tooling. The
testing results confirmed that bioremediation enhanced by ISCR supported long-term treatment
at the site. This article describes the implementation and results of the tests. Performance data
are available from a three-year period following the injections, allowing for a discussion about
sustained performance and reagent longevity. Oc 2010 Wiley Periodicals, Inc.
INTRODUCTION
EHC® combines controlled-release, hydrophilic organic carbon with micro-scale
zero-valent iron (ZVI) for in situ chemical reduction (ISCR) of chlorinated compounds in
groundwater. Following the placement of EHC into the subsurface, various physical,
chemical, and microbiological processes combine to create strongly reducing conditions
that stimulate rapid dechlorination of many oxidized compounds, such as chlorinated
ethenes, ethanes, and other chlorinated solvents. This typically yields safe, rapid, and
effective destruction of targeted contaminants without the accumulation of conventional,
dead-end intermediates.