Alternatives for Ground Water Cleanup (1994) / Chapter Skim
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6 Setting Goals for Ground Water Cleanup
6 Setting Goals for Ground Water Cleanup
Pages 213-254
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From page 213... ...
However, in a number of cases, existing ground water cleanup goals cannot be met with current technologies. In other cases, achieving these goals will require extraordinary amounts of time (decades to centuries)
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From page 214... ...
However, although drinking water standards are the most commonly used cleanup goals, for any one chemical the cleanup goal may vary depending on the state in which the site is located and whether it is a CERCLA or a RCRA site. Table 6-1 shows a sampling of the range of concentrations that have been used as ground water cleanup goals under current policy.
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From page 215... ...
is that ground water cleanup goals should meet chemical-specific "applicable or relevant and appropriate requirements" from other regulations, known as ARARs. Ground water that could be used for drinking must meet federal requirements under the Safe Drinking Water Act (known as maximum contaminant levels, or MCLs; see Table 6-1)
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From page 218... ...
at 99 Superfund sites, lower concentrations at 23 Superfund sites, and higher concentrations at 13 sites; at 32 sites, the goals were based on risk levels in the 10 - to 10-6 range.1 Although a range of cleanup goals is possible, as a practical matter federal drinking water standards serve as ceilings for ground water cleanup goals at most sites for the contaminants for which MCLs have been developed. Of the approximately 300 ground water remedial actions selected in the Superfund program between October 1, 1987, and September 30, 1991, the cleanup goal was to achieve drinking water standards through pumping and treating at 270 sites (EPA, 1992~.
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From page 219... ...
The key factor that the EPA considers in granting an ACL is whether it will protect public health at the point of exposure, i.e., whether contaminant concentrations will be reduced to ensure adequate public health protection at the nearest drinking water well. The EPA is increasingly recognizing that attaining drinking water standards is not feasible at certain types of sites and has drafted a guidance document to clarify the policy regarding technical impracticability of ground water cleanup at CERCLA and RCRA sites (EPA, 1993b)
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From page 220... ...
On the other hand, even when strict cleanup goals are not technically achievable, their existence may provide an incentive against further pollution and may encourage development of cleanup technologies that better protect public health. In the debate over whether strict ground water cleanup goals are appropriate, given the limitations of technology and the high costs, various interest groups have advocated goals ranging from complete restoration to restricting use of the ground water, as shown on Figure 6-1 and explained below.
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From page 222... ...
One benefit of using detection limits or background levels as cleanup goals is the elimination of the need for government agencies to define explicitly an "acceptable" risk level. Rather, using detection limits or background levels implies that cleanup is accomplished to the fullest extent measurable with today's technologies.
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From page 223... ...
Partially Restricted Use Goals Some who believe that the current ground water cleanup program is too costly have advocated using partially restricted use goals, shown in the middle of Figure 6-1. Under this scenario, cleanup goals would correspond to the expected use of the water.
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From page 224... ...
Data indicate that at nearly one-third of Superfund sites, existing private, community, and public drinking water supply wells have been closed or restricted because of contamination (Wells, 1992~. Three options are possible to prevent exposure in these situations: wellhead treatment, point-of-use treatment, and development of alternative water supplies (see Box 6-1 and Box 6-2~.
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From page 225... ...
Unfortunately, the decision is not so simple. The selection of ground water cleanup goals from among the variety of options discussed above is a political process involving debates about several factors, summarized in Table 6
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The following discussions focus on health and ecological risks of ground water contamination and the
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From page 227... ...
costs and benefits of cleanup because these factors are at the center of national policy debates over cleanup goals. The chapter then addresses the question of whether current ground water cleanup goals should change, given the committee's conclusions about the capabilities of technology and the available evidence on health risks, ecological risks, and cleanup costs.
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From page 228... ...
Studies of people living near contaminated sites are the more relevant approach because occupational groups are usually exposed at higher levels and through different pathways third populations exposed through contaminated ground water. However, there are serious limitations to undertaking epidemiologic studies at hazardous waste sites, undermining their ability to answer questions about health hazards.
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From page 229... ...
ologic investigations of hazardous waste sites are usually small, a situation that may result in risks going unobserved because the statistical power of the study is too low. While studying large populations would be preferable, communities surrounding waste sites are usually small.
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· Confoundingiactors and sources of bias: The results of epidemiologic studies may be confounded by factors other than contaminant exposure that are themselves associated with the disease under study. For example, some hazardous waste sites may be located in industrialized and highly polluted areas.
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From page 231... ...
Unfortunately, the ability to conduct conclusive epidemiologic studies at hazardous waste sites such as that in Hardeman County is extremely rare. As a result, when one analyzes the existing body of epidemiologic evidence as a whole, the public health implications of ground water contamination from hazardous waste sites are unclear.
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Recent congressional testimony by the Agency for Toxic Substances and Disease Registry (ATSDR) describes studies by both the ATSDR and other researchers suggesting that reproductive problems may be associated with drinking contaminated water or living near hazardous waste sites (Johnson, 1993~.
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Although observations in humans are more relevant for predictions of risk in human populations, toxicologic data from animal studies are essential in quantitative risk assessment in circumstances where direct human information is not available which is the situation at the majority of hazardous waste sites. Evaluating the Evidence: Risk Assessment Epidemiologic and animal studies provide information about the types of health problems that may occur from exposure to hazardous chemicals, but they may be insufficient to determine the likelihood that health problems will occur in a given exposed population.
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" Table 6-3 shows the connection between the above four steps of the risk assessment process and information from epidemiologic research, animal studies, and field measurements. Risk assessments of ground water contamination have several limitations.
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in the United States. For example, as discussed in this chapter, for chemicals for which no drinking water standard exists, cleanup goals at Superfund sites are based on a site-specific risk assessment.
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Nevertheless, the absence of documentation of health risks cannot be used as proof that exposure and adverse health effects have not occurred. Given the scientific uncertainties associated with epidemiology and risk assessment, public policymakers should err on the side of caution in setting ground water cleanup goals.
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From page 237... ...
The researchers concluded that alteration of soil acidity and of soil aluminum, sodium, and heavy metal concentrations caused by ground water contamination likely predisposed trees to deteriorate, with severe drought acting as the final trigger for deterioration and tree death. In another example, involving a wetland, researchers observed direct and severe ecological effects as a result of ground water contamination with a highly alkaline leachate from an on-site lagoon at a Massachusetts hazardous waste facility.
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From page 238... ...
Probably the most comprehensive review of the ecological impacts of ground water contamination on surface water ecosystems is an EPA analysis of the nature and extent of ecological risks at Superfund sites (EPA, 1989~. Of 52 Superfund sites evaluated, 30 (including 14 landfills and 16 surface impoundment lagoons)
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From page 239... ...
Changing cleanup goals can have a significant impact on cleanup costs. However, like the health and ecological risks of various levels of ground water contamination, the costs of reaching various cleanup goals are highly uncertain at both the national and site levels.4 National Cleanup Costs A widely cited national study published by the University of Tennessee in 1991 concluded that the costs of cleaning up all hazardous waste sites nationwide could drop by approximately one-third if cleanup goals are made less stringent or could increase by approximately one-half if cleanup goals are made more stringent (Russell et al., 1991; Abelson, 1992~.
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From page 240... ...
If one presumes that 70 percent of the total cost of hazardous waste site remediation represents ground water cleanup, then the best-guess cost in present value terms is $200 billion under current policy. If one presumes that 50 percent of the cost applies to ground water cleanup, then the best-guess cost is $140 billion under current policy.
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From page 241... ...
Site-Level Cleanup Costs Simple computations for a hypothetical site provide further indication of how changes in cleanup goals can affect cleanup costs. For this hypothetical illustration, consider an aquifer containing a 190-millionliter plume of the common contaminant TCE at an average concentration of 1,000 ~g/liter.6 If the site will be cleaned up using a conventional pump-and-treat system that will treat the effluent with an air stripper and a granular activated carbon filter, then Table 6-5 shows estimates for the time and cost required to achieve various cleanup goals, ranging from 80 to 99.99 percent TCE removal.
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The curves begin at a goal of 80 percent contaminant removal. As the figure demonstrates, increasing the removal efficiency to 99.99 percent substantially increases cleanup costs.
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· · 90% removal 1 ,000,000 0 1 2 3 4 5 Retardation Factor 6 7 8 9 10 FIGURE 6-3 Cost of operating a pump-and-treat system as a function of the contaminant's retardation factor, which indicates its tendency to sorb to solid material in the aquifer. The figure illustrates that cleanup costs can increase substantially when contaminants sorb.
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From page 244... ...
(It is important to note that if the in situ bioremediation system cannot reach the required cleanup goal in the predicted time, its life cycle costs may increase to the point where the costs are similar to those associated with conventional pump-and-treat systems.) These hypothetical computations show that changing ground water cleanup goals from 80 or 90 percent contaminant removal to nearly 100 percent contaminant removal can have a substantial effect on cleanup costs at the site level.
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From page 245... ...
No studies have attempted to compare differences in the dollar value of benefits received for different national ground water cleanup goals. Further, at the time this report was prepared only one study assessing the total national economic benefits of restoring ground water was available, and this study was controversial.
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From page 246... ...
· The fact that individuals are not actually required to pay their bid may affect the result of the study, although where there are well-defined related markets the magnitude of this bias seems small (Brookshire and Coursey, 1987~. · Individuals may offer the same bid for cleaning up one hazardous waste site, all related hazardous waste sites, or all hazardous waste sites in a region (Kahneman and Knetsch, 1992)
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From page 247... ...
In the EPA study of the national benefits of ground water cleanup, the 900 survey respondents indicated that, on average, they would be willing to add $7.08 to their monthly water bills for the next 10 years to clean up ground water.9 With approximately 100 million households in the United States, this estimate indicates an aggregate willingness to pay $8 billion per year for 10 years. Table 6-7 shows the present value of this annual willingness to pay using various discount rates for a 10-year period.
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From page 248... ...
Given the high level of uncertainty in the risks and economic damage created by ground water contamination, the committee believes that whether changes are needed in the policies for setting long-term cleanup goals can only be decided through policy debates; science can influence these debates, but value judgments must be the deciding factors. At the same time, however, the committee strongly believes that because existing ground water cleanup goals cannot be at
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From page 249... ...
They preserve the values that public policymakers believed were important when the nation's ground water cleanup programs were first implemented. CONCLUSIONS Based on an assessment of current ground water cleanup goals in light of the capabilities of ground water cleanup technologies, along with a review of the risks, costs, and benefits associated with ground water
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From page 250... ...
· The health risks of ground water contamination from hazardous waste sites are uncertain, but this uncertainty does not provide justification for changing long-term cleanup goals. The inadequate documentation of health risks derives from the general absence of information on human exposure to contaminated ground water and lack of information on the adverse effects of ground water contamination on humans.
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1992. Remediation of hazardous waste sites.
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1990a. Corrective action for solid waste management units at hazardous waste management facilities.
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1987. Evaluating health effects of exposure at hazardous waste sites: a review of the state-of-the-art, with recommendations for future research.
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Presented at Third Intemational Conference on New Frontiers for Hazardous Waste Management, Pittsburgh, Pa., September 10-13, 1989. Silbergeld, E
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