Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites (2013) / Chapter Skim
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Although many hazardous waste sites at military facilities have been closed with no further action required, meeting goals like drinking water standards in contaminated groundwater has rarely occurred at many complex DoD sites. It is probable that these sites will require significantly longer remediation times than originally predicted and, thus, continued financial demands for monitoring, maintenance, and reporting.
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Since the most recent NRC report in 2005, better understanding of technical issues and barriers to achieving site closure have become evident. The following questions comprised the statement of task for this Committee, which considered both public and private hazardous waste sites.
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Nonetheless, the Committee used these data to estimate the number of complex sites, the likelihood that sites affect a drinking water supply, and the remaining costs associated with remediation. At least 126,000 sites across the country have been documented that have residual contamination at levels preventing them from reaching closure.
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Remaining sites include some of the most difficult to remediate sites, for which the effectiveness of planned remediation remains uncertain given their complex site conditions. Furthermore, many of the estimated costs do not fully consider the cost of long-term management of sites that will have contamination remaining in place at levels above those allowing for unlimited use and unrestricted exposure for the foreseeable future.
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There are several alternatives to traditional cleanup goals, like technical impracticability waivers, that can allow sites with intractable contamination to move more expeditiously through the phases of cleanup while still minimizing risks to human health and the environment. The chapter also discusses sustainability concepts, which have become goals for some stakeholders and could impact the remedy selection process.
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CURRENT CAPABILITIES TO REMOVE/CONTAIN CONTAMINATION Chapter 4 updates the 2005 NRC report on source removal by providing brief reviews of the major remedial technologies that can be applied to complex hazardous waste sites, particularly those with source zones containing dense nonaqueous phase liquids (NAPLs) like chlorinated solvents and/or large downgradient dissolved plumes.
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There is a clear need for publically accessible databases that could be used to compare the performance of remedial technologies at complex sites (performance data could be concentration reduction, mass discharge reduction, cost, time to attain drinking water standards, etc.)
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, potentially leading to a determination that the existing remedy at some hazardous waste sites is no longer protective of human health and the environment. Modification of EPA's existing CERCLA five-year review guidance would allow for more expeditious assessment of the protectiveness of the remedy based on any changes in EPA toxicity factors, drinking water standards, or other riskbased standards.
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Management of residual contamination to reduce the exposure risks via the vapor intrusion pathway is challenged by the highly variable nature of exposure, as well as uncertain interactions between subsurface sources and indoor background contamination. Existing protocols for assessing monitored natural attenuation and
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Although the Committee did not attempt a comprehensive assessment of research needs, research in the following areas would help address technical challenges associated with long-term management at complex contaminated sites (see Chapter 6 for a more complete list) : • Remediation Technology Development.
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BETTER DECISION MAKING DURING THE LONG-TERM MANAGEMENT OF COMPLEX GROUNDWATER CONTAMINATION SITES The fact that at most complex groundwater sites drinking water standards will not be attained for decades should be more fully reflected in the decision-making process of existing cleanup programs. Thus, Chapter 7 provides a series of recommendations that will accelerate the transition of sites to one of three possible end states: (1)
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Regulators and federal responsible parties should work with members of existing advisory groups and technical assistance recipients to devise models for ongoing public oversight once remedies are in place. Such mechanisms may include annual meetings, Internet communications, or the shifting of the locus of public involvement to permanent local institutions such as public health departments.
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