Enhanced Attenuation: Chlorinated Organics

While there are remedial strategies being used in combination with monitored natural attenuation (MNA), there has been no guidance or “process” available regarding when or how to implement these strategies at contaminated chlorinated organic sites. The ITRC Enhanced Attenuation: Chlorinated Organics (EACO) Team has developed a new decision-making framework, which not only defines the enhanced attenuation (EA) concept but also incorporates a well-defined process as a site management tool. The EACO Team and the DOE MNA/EA for Chlorinated Solvents project team formed a partnership in 2004. The team also included members from five state regulatory agencies; industry; federal agencies, including the Department of Energy and Environmental Protection Agency; academia; and stakeholders. A technical and regulatory guidance document, “Enhanced Attenuation: Chlorinated Organics (EACO-1)” along with Internet-based training was completed in April 2008.

EA is a site management tool that provides a decision-making framework and incorporates a “bridge” between MNA and remedial technologies. Three important features of EA are the evaluation of mass balance, defined as the relationship between mass loading and attenuation capacity of an aquifer; a decision framework that provides guidance for site decisions; and a “toolbox” of potential EA technologies, known as “enhancements.” One of the most important products of the team is the decision flowchart, which provides a clear and concise pathway so that regulators and others have guidance for the evaluation of the overall site conceptual model and the incorporation of a phased approach for site rehabilitation. The EA approach is consistent with the current regulatory environment, and it is anticipated that this new remedial framework and decision process will accelerate the environmental cleanup progress on a national scale and may reduce overall costs, while still providing protection to human health and the environment. The team is currently monitoring remedial activities nationwide to document the use and importance of EA as a site management tool.