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DNAPL Removal Key to Accelerated, Less Expensive Remediation

Map showing the location of a chlorinated ethene plume
Map showing the location of the total chlorinated ethene plume and monitoring wells at Submarine Base Kings Bay, Georgia. The map showes the location of the plume prior to a series of in situ oxidation source-removal actions. Figure 17 from USGS WRIR 03-4057.

Pools of dense non-aqueous phase liquids (DNAPLs) in the subsurface can serve as a long-term source for dissolved contaminant plumes at many contamination sites. Debates regarding whether partial removal of these pools contributes to effective cleanup technology were calmed when Toxics Program scientists, in conjunction with the U.S. Navy, demonstrated that the near-complete removal of a DNAPL pool in the subsurface by engineered methods facilitated the rapid collapse of a chlorinated solvent plume at the Submarine Base Kings Bay, Georgia. The removal was achieved by in situ chemical oxidation with Fenton's reagent that was injected into the subsurface through an array of injection wells. The removal of the DNAPL at Kings Bay has lowered the estimated time for site remediation from 35 years or more (with the previous pump-and-treat system) to approximately 5 years, and lowered the estimated remediation costs from $30 million to $5 million. Similar cost savings could be realized at other sites contaminated with chlorinated solvents, a common DNAPL, using the same approach to removing DNAPL that is acting as a long-term source of contamination.

"Providing leadership in the assessment of long-term results of environmental remediation and the development of modern methods for waste disposal is a role that appears to be particularly fitting for attention by the USGS."
-- 1996 National Research Council publication: Hazardous Materials in the Hydrologic Environment - The Role of the U.S. Geological Survey

USGS involvement with the Fenton's reagent injection at Kings Bay was to

  • locate the source area with direct push technology and field gas chromatograph methods,
  • determine the source-area contaminant concentration that could remain after the Fenton's test based on the natural attenuation capacity of the system, and
  • monitor the microbial population at the site before, during, and after Fenton's treatment to observe how contaminant degradation was affected by the treatment.

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Other Chlorinated Solvent Remediation Related Activates

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