Alternatives for Ground Water Cleanup (1994) / Chapter Skim
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Executive Summary
Executive Summary
Pages 1-18
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Pump-and-treat systems are the most common technology for ground water cleanup in the United States. The studies indicated that pump-and-treat systems may be unable to remove enough contamination to restore the ground water to drinking water standards, or that removal may require a very long time, in some cases centuries.
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The findings of this report are based on the committee's review of original data from case studies, reports in scientific journals, presentations by experts outside the committee, evaluation of policy documents, and the extensive experience of committee members. COMPLEXITY OF THE CONTAMINATED SUBSURFACE Theoretically, restoration of contaminated ground water to drinking water standards is possible.
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Regardless of the remediation technology chosen, these inherent complexities pose major obstacles to ground water cleanup. PERFORMANCE OF CONVENTIONAL PUMP-AND-TREAT SYSTEMS The committee found that at the majority of contaminated sites, the complex properties of the subsurface environment and the complex behavior of contaminants in the subsurface interfere with the ability of conventional pump-and-treat systems to achieve drinking water standards for contaminated ground water.
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· Cleanup of sites in category 3: Cleanup of sites in category 3 to drinking water standards is possible but is subject to significant uncertainties; partial cleanup may be a more realistic scenario for many such sites. For example, of the 29 sites in Appendix A in category 3, cleanup goals have been achieved at only three.
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The part of the site containing primarily dissolved contaminants might fit category 1 or 2 according to Table ES-1, while the part of the site containing entrapped sources of contamination might fit category 3 or 4. Finally, when using a framework such as Table ES-1, it is important to realize that to some extent the feasibility of ground water cleanup depends on the cleanup goals.
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While no known technology can ensure the achievement of health-based cleanup goals at complex sites, these innovations nevertheless have the potential to increase the effectiveness and reduce the costs of ground water cleanup. Some innovative technologies- including soil vapor extraction, air sparking, and in situ bioremediation of petroleum products are already being implemented.
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CHARACTERIZING SITES FOR GROUND WATER CLEANUP The inability of pump-and-treat systems to reach drinking water standards at many sites to date is not just a function of site complexity and technical limitations; it is also a result of insufficient or inaccurate characterization of the problem prior to cleanup. At several sites the committee reviewed, the cleanup systems failed to contain the contamination (much less clean it up)
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Data collection should continue throughout the life of the ground water cleanup system, and these data should be analyzed regularly to determine whether they are consistent with the current understanding of the site and, if not, whether changes in the remediation plan are necessary. SEWING GOALS FOR GROUND WATER CLEANUP This report documents that the ability of technology to restore contaminated ground water to drinking water standards is uncertain at many sites.
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Thus, a high degree of uncertainty exists, making quantitative assessment of the risks and benefits of various ground water cleanup goals extremely difficult. Like society as a whole, the committee had diverse views about which of the various alternative cleanup goals is most appropriate and whether the current approach of requiring cleanup to drinking water standards at a large number of sites should be changed.
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In the recommendations below, the committee outlines a scenario for dividing contaminated sites into three categories, some of which would require interim objectives and some of which would not. CONCLUSIONS AND POLICY RECOMMENDATIONS In summary, the committee found that at many sites requiring ground water cleanup, some areas will remain contaminated above drinking water standards for the foreseeable future even when the best available technologies are used.
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Although cleanup is possible at some sites, properties of the subsurface and the contaminants may make restoring contaminated ground water to drinking water standards technically infeasible with current technology in reasonable time frames (decades) at a large number of sites.
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In the middle is a group of sites generally represented by categories 2 and 3 in Table ES-1; for sites in this group, attaining healthbased ground water cleanup goals will be difficult or unlikely with current technology but not necessarily impossible over the long term as technology improves. The long-term cleanup goals for sites in this middle group should be temporarily superseded by interim objectives reflecting the capabilities of existing technologies.
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One possibility is to use some of the funds to create an applied ground water research fund to pay for a strong research program for improved ground water cleanup techniques. The other possibility is to use some of the funds to encourage use of innovative cleanup technologies by reimbursing responsible parties for testing these technologies in certain circumstances.
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Existing procedures for setting ground water cleanup goals do not adequately account for the diversity of contaminated sites and the technical complexity of ground water cleanup. Whether goals established under existing procedures adequately protect public health and the environment, or whether they are overprotective or underprotective, is uncertain, as are the costs to society when these goals cannot be achieved.
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