incorporation of sustainability metrics in remedial decision making appears likely.
Although technologies capable of removing substantial amounts of contaminants from groundwater have evolved significantly over the last 40 years, our ability to predict remediation performance, and its associated groundwater quality improvement, with adequate certainty is limited. Additional questions must be answered before management of sites can proceed in a way that is protective in an era of limited financial resources. The following questions guided the work of this NRC committee.
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?