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List of Reports & Abstracts

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Automated downhole monitoring at Southwest Harbor (WHS 2005)

Pilot testing of a permanganate injection system (WHS 2005)

Evaluating ASR using Columbia River water (WHS 2005)

Anatomy of a Sinking Chlorinated Solvent Plume (WHS 2003)

Comparison of Actual Evapotranspiration Estimates to a Soil Moisture Budget and Plant Growth (WHS 2003)

Hydrogeologic Characteristics of the Columbia River Basalts near Goldendale, Washington (WHS 2003)

Geology of the Brightwater Tunnel corridor (NGS 2004 / GSA 2003)

Abstract

Pilot Testing of Permanganate Injection at Low Concentration to Restore a Solvent-Impacted Drinking Water Aquifer

Presented at the 5th Annual Washington Hydrogeology Symposium, April 12–14, 2005, by Dave Heffner and Chip Goodhue

Routine testing in 1998 of a water supply well at a maintenance facility in Lewis County, Washington, indicated the presence of chlorinated hydrocarbons, primarily tetrachloroethene (PCE) and trichloroethene (TCE), at concentrations above federal maximum contaminant levels (MCLs) in drinking water. The subsequent remedial investigation identified a plume of affected groundwater extending nearly 2,000 feet northward from the site, and comprehensive testing of water supply wells detected chlorinated hydrocarbons in five off-site drinking water wells. An area of soil in the central portion of the facility was identified as the primary source of chlorinated hydrocarbons in groundwater, and 700 tons of affected soil were excavated and removed as an interim action in 2002. Although the interim action is expected to have eliminated the source of chlorinated hydrocarbons, numerical transport modeling predicts that it may take 60 years for concentrations of TCE within the entire plume to attenuate below MCLs. In addition to the lengthy post-interim action restoration time frame, groundwater modeling indicates that migration of affected groundwater may result in a future surface water cleanup level exceedance at a nearby river, and could also impact additional off-site drinking water wells.

In situ chemical oxidation of dissolved PCE/TCE using permanganate was pilot tested as a potential means of reducing the aquifer restoration timeframe and assuring that unacceptable impacts to surface water and additional drinking water wells will not occur. Permanganate-amended groundwater was circulated between an extraction well and a reintroduction well at a flow rate of approximately 12 gallons per minute. Additional wells installed between and downgradient of the extraction/reintroduction well pair were monitored to assess contaminant destruction, permanganate persistence, and effects on subsurface conditions. The pilot test was notable for the relatively large well spacing and low permanganate injection concentration being tested. Both of these test parameters (large well spacing and low chemical usage) must be successfully demonstrated in order for full-scale application of this technology to be economically viable at this site.