A National Research Council (NRC) committee chaired by Michael Kavanaugh, Ph.D., P.E., a senior principal engineer in Geosyntec's Oakland office, has issued a comprehensive report examining the future of groundwater remediation at thousands of locations throughout the United States.
The report, "Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites," is now available from the National Academies Press. It explains that at least 126,000 sites across the country have contaminated groundwater that requires remediation, and about 10 percent of these sites are considered so complex that their restoration is unlikely to be achieved in the next 50 to 100 years.
"The complete removal of contaminants from groundwater at possibly thousands of complex sites in the U.S. is unlikely, and no technology innovations appear in the near-time horizon that could overcome the challenges of restoring contaminated groundwater to drinking water standards at these locations," Dr. Kavanaugh said.
Among the key findings of the committee:
- The estimated "cost to complete" for sites that have not reached closure to date is between $110 billion and $127 billion. This number is highly uncertain and likely to be an underestimate of future liabilities.
- There are limited data with which to compare remedial technology performance. Additional independent reviews of remedial technologies are needed to summarize their performance under a wide range of site characteristics.
- Consideration of the vapor intrusion (VI) pathway is needed at all sites where volatile organic chemicals (VOCs) are present in the soil or groundwater aquifer. As a precaution, vapor mitigation could be built into all new construction on or near known VOC groundwater plumes.
- New research is needed in many areas to support the shift to long-term management of complex sites, including remediation technology development, tools to better assess VI and monitored natural attenuation, and modeling that can incorporate back-diffusion and desorption.
"At many of these complex sites, a point of diminishing returns will often occur as contaminants in groundwater remain stalled at levels above drinking water standards, despite continued active remedial efforts," Dr. Kavanaugh said. "We are recommending a formal evaluation be made at the appropriate time in the life cycle of a site to decide whether to transition the sites to active or passive long-term management."
The central theme of the committee's report is how the nation should deal with those sites where residual contamination will remain above levels needed to achieve restoration.
"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," Dr. Kavanaugh said.
"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."
At Geosyntec, Dr. Kavanaugh offers clients more than 35 years of consulting experience in the areas of water quality, water treatment, and groundwater remediation. He has served a highly diverse group of private and public sector clients directly, through industry associations, and through attorneys. He is an instructor for the Princeton Groundwater Course and a consulting professor in the Stanford University Civil and Environmental Engineering Department. He also serves on the Board of Directors for the Environmental Law Institute.
To order a copy of the committee's report, visit the National Academies Press. For more information on the findings of the committee, contact Michael Kavanaugh in Oakland at 510-285-2766 or firstname.lastname@example.org.