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  Synthesis Report on Five Dense, Nonaqueous-Phase Liquid (DNAPL) Remediation Projects (94 pp, 7.54 MB) (EPA/600/R-07/066) May 2007

Dense nonaqueous phase liquid (DNAPL) poses a difficult problem for subsurface remediation because it serves as a continuing source to dissolved phase ground water contamination and is difficult to remove from interstitial pore space or bedrock fractures in the subsurface. Numerous technologies have been developed for DNAPL remediation, but demonstrations of these technologies have had mixed results.

This document summarizes the performance and results of DNAPL removal demonstration projects at five sites with the purpose of informing the hydrogeology and remedial engineering community of the results and lessons learned from these demonstrations. The five projects and the technologies demonstrated for each project are:

  1. Launch Complex 34, Cape Canaveral, Florida – thermally enhanced remediation with resistive heating; thermally enhanced remediation with steam injection/extraction
  2. Dover National Test Site, Dover Air Force Base, Delaware – cosolvent flushing; surfactant flushing; air sparging/soil vapor extraction; cosolvent DNAPL mobilization; complex sugar flushing
  3. Panels 1 and 5, Operable Unit 2, Hill Air Force Base, Utah – surfactant enhanced aquifer remediation
  4. Quarry Site, Loring Air Force Base, Limestone, Maine – thermally enhanced remediation of fractured bedrock with steam injection
  5. Sages Dry Cleaners, Jacksonville, Florida – cosolvent flushing and enhanced bioremediation

Most of the technologies were successful at removing contaminant mass from the subsurface and project performance varied with the degree of project planning and site conditions. The project teams from four of the five technology demonstrations claimed mass removal at approximately 90 percent. Some technology demonstrations removed less than 70 percent. The Loring demonstration, which was conducted in fractured bedrock with limited primary and secondary porosity, removed very little mass from the subsurface (i.e., much less than 10 percent of the target mass).

Each of the projects is discussed and evaluated for success relative to the project objectives and within a financial and regulatory framework that is typical of most contaminated sites. Lessons learned and considerations for future applications based on each project are provided, along with lessons learned for conducting future demonstration projects.


Teri Richardson

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