At least 126,000 sites across the U.S. have contaminated groundwater that requires remediation, and about 10 percent of these sites are considered "complex," meaning restoration is unlikely to be achieved in the next 50 to 100 years due to technological limitations, says a new report titled Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites from the National Research Council. The report adds that the estimated cost of complete cleanup at these sites ranges from $110 billion to $127 billion, but the figures for both the number of sites and costs are likely underestimates.

The U.S. Department of Defense has already spent approximately $30 billion in hazardous waste remediation to address past legacies of its industrial operations. DOD sites represent approximately 3.4 percent of the total active remediation sites, but many of these sites present the greatest technical challenges to restoration with very high costs. Therefore, the agency asked the National Research Council to examine the future of groundwater remediation efforts and the challenges facing the U.S. Army and other responsible agencies as they pursue site closures.

The report is organized around five key inquiries:

  1. Size of the Problem. At how many sites does residual contamination remain such that site closure is not yet possible? At what percentage of these sites does residual contamination in groundwater threaten public water systems?
  2. Current Capabilities to Remove Contamination. What is technically feasible in terms of removing a certain percentage of the total contaminant mass? What percent removal would be needed to reach unrestricted use or to be able to extract and treat groundwater for potable reuse? What should be the definition of "to the extent practicable" when discussing contaminant mass removal?
  3. Correlating Source Removal with Risks. How can progress of source remediation be measured to best correlate with site-specific risks? Recognizing the long-term nature of many problems, what near-term endpoints for remediation might be established? Are there regulatory barriers that make it impossible to close sites even when the site-specific risk is negligible and can they be overcome?
  4. The Future of Treatment Technologies. The intractable nature of subsurface contamination suggests the need to discourage future contaminant releases, encourage the use of innovative and multiple technologies, modify remedies when new information becomes available, and clean up sites sustainably. What progress has been made in these areas and what additional research is needed?
  5. Better Decision Making. Can adaptive site management lead to better decisions about how to spend limited resources while taking into consideration the concerns of stakeholders? Should life cycle assessment become a standard component of the decision process? How can a greater understanding of the limited current (but not necessarily future) potential to restore groundwater be communicated to the public?

"The central theme of this report is how the nation should deal with those sites where residual contamination will remain above levels needed to achieve restoration," Michael Kavanaugh, chair of the committee that wrote the report and a principal with Geosyntec Consultants in Oakland, CA, stated. "In the opinion of the committee, this finding needs to inform decision making at these complex sites, including a more comprehensive use of risk assessment methods, and support for a national research and development program that leads to innovative tools to ensure protectiveness where residual contamination persists. In all cases, the final end state of these sites has to be protective of human health and the environment consistent with the existing legal framework, but a more rapid transition will reduce life-cycle costs. Some residual contamination will persist at these sites and future national strategies need to account for this fact."

The committee said that if a remedy at a site reaches a point where continuing expenditures bring little or no reduction of risk prior to attaining drinking water standards, a reevaluation of the future approach to cleaning up the site, called a transition assessment, should occur. The committee concluded that cost savings are anticipated from timelier implementation of the transition assessment process but funding will still be needed to maintain long-term management at these complex sites.

The report is available at http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=14668.