U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Combining Remedies for More Effective Site Cleanup

This Web page provides examples of the use of multiple technologies (combined or in treatment trains) to develop remedial approaches that address contamination resulting from the release to the subsurface of non-aqueous phase liquids (NAPLs) and other chemical species. These releases often result in a source zone (free-phase, residual, and/or diffusion-based) and an associated dissolved-phase plume (groundwater or soil vapor).

Combining remedy approaches can be a two-part process. The first part ensures that the chosen technology or technologies are the ones best suited for the problem both initially and as the cleanup process evolves. The more complex the problem, the more likely it is that several technologies will be required to address it effectively. Allowing for flexibility in the Record of Decision is a good way to ensure that efficient implementation and transition takes place when needed (Battelle 2010).

The second part of the process is observational. It recognizes that the continued application of a cleanup technology in and of itself changes the subsurface conditions from the conditions that were present when the technology was first applied. Monitoring data need to be evaluated periodically to ensure that the original technology is still the most effective option for the current conditions and is not simply operating as designed.

Combined remedies and/or treatment trains are deployed most effectively when the hydrogeological and chemical contaminant conditions in the subsurface are well defined. EPA has developed the Triad approach to gather data more cost effectively and recommends using tools that provide for high-resolution site characterization.

The case studies below illustrate various approaches for developing combined remedies and treatment trains.

Adapted from:

Battelle Memorial Institute. 2010. Guidance for Optimizing Remedy Evaluation, Selection, and Design, User's Guide. UG-2087-ENV. Naval Facilities Engineering Command, 84 pp.

Planned Combined Remedies or Treatment Trains

Combined remedies or treatment trains were planned, and the remedial action objectives have been reached.

Planned Combined Remedies or Treatment Train and Treatment Ongoing

Components have been implemented, but the process is ongoing as of August 2013, and the final results are not available.

Planned Combined Remedies or Treatment Train with Observational Modification

Original planning provided for combined remedies or treatment trains, but evaluation of monitoring data as the remedy proceeded resulted in the addition (or in some cases subtraction) of technologies.

Observational Modification

Original planning did not involve treatment trains or combined remedies, but evaluation of the monitoring data as the remedy progressed led to the addition of treatment technologies.