FEATURE
Will Risk-Based Cleanup Work at Navy Facilities? Process requirements include attention to long-term risk, public involvement, enforcement, and use of uncertainty analysis. LAURA EHLERS
National Research Council (NRC) report released this March (i) assesses new riskbased methods that could be used for managing waste site cleanup at Navy facilities. The report, Environmental Cleanup at Navy Facilities: Risk-Based Methods, suggests that the Navy should develop formal uncertainty analysis methods for contaminated-site risk assessment. It further stresses mat if risk-based methods give sufficient attention to long-term risks, remedies in which contamination remains on site should become less problematic. "Public trust in such a risk-based approach is likely to be greater if the responsible party continues to be involved via long-term monitoring and enforcement of institutional controls," said Lenny Siegel, a member of the NRC committee that developed the report.
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The methods examined by the NRC committee were evaluated on the basis of consideration of 11 criteria (see box on next page) that any risk-based cleanup method adopted by the Navy in its Environmental Restoration Program should satisfy. The selected criteria, although somewhat specific to the needs and challenges of the Navy, are also applicable to most large, multisite responsible parties, including other branches of the military, federal agencies, and large private companies. "Of the eleven criteria, considerations of uncertainty and longterm risks are particularly important," noted NRC committee chairman Edward Bouwer. The NRC panel focused mainly on EPA's Superfund, or Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) process, © 1999 American Chemical Society
which is risk-based, and on Risk-Based Corrective Action (RBCA), as developed by the American Society for Testing and Materials (ASTM) (2, 3). CERCLA was included in the analysis because it is used at 66% of all contaminated Navy sites. As a federal statute, "CERCLA is the standard to which all other methodologies should be compared," states the report. As a result of its considerations, the NRC committee in its report recommends against the adoption of the ASTM RBCA approach at Navy facilities, unless the process is modified to satisfy all the criteria that were identified. "Perceived time and cost savings associated with the [current] use of ASTM RBCA at petroleum underground storage tanks are less likely to accrue to the Navy because of the complexity of its hazardous waste sites," the report notes. A survey of state cleanup programs by the NRC panel revealed that most states have developed a shortterm view of risk, suggesting that state decisions to adopt ASTM RBCA have not weighed the significant weaknesses associated with this method, a mistake the report urges the Navy not to make. The scenario The Navy conducts one of America's largest hazardous waste cleanup programs. As of 1998, more than 4000 individual sites required cleanup at Navy facilities in 37 states and territories, with more sites being discovered every year. Although many of the Navy's waste sites contain relatively easy-to-clean petroleum compounds, a comparable amount contain more recalcitrant chemicals, such as metals, chlorinated solvents, and pesticides—compounds that are often difficult to remove from contaminated soil, sediment, and groundwater. In many cases, no treatment technology exists that can clean sites to meet relevant regulatory requirements. Unique conditions at these types of facilities include • extremely high levels of contamination at some sites; • chemical mixtures with unknown constituents; • a wide variety of human and ecological receptors (due to facility proximity to coastal areas); • a wide range of activities that generate waste; and • the rushed deadline by which some facilities are expected to close and thus have approved cleanup activities under way. As at many hazardous waste sites, cleanup at Navy facilities is both expensive and time-consuming. Where technology is available, depending on the selected remedy, the cost of treating these sites can range from hundreds of thousands to millions of dollars per site, with no guarantee that complete cleanup will be achieved. The U.S. Government Accounting Office currently estimates that the time from site discovery to the initiation of a cleanup remedy is 10.6 years (4). The slow cleanup pace has members of Congress grumbling about the perceived lack of progress in the Navy's cleanup program. "We need help moving the Environmental Restoration Program forward with Congress, which is currently frustrated by the low number of cleanups and site closures," said Stephen Eikenberry, director of the Naval Facilities Engineering Service Center. It is not surprising, therefore, that the Navy is look-
Eleven criteria for any risk-based method adopted by the Navy These 11 criteria identified by the National Research Council committee were used as a basis for evaluating risk-based methods after cleanup of hazardous waste sites. • An effective risk-based method should facilitate prioritization of contaminated sites at individual installations. • It should provide a consistent mechanism for addressing all types of sites. • It should provide guidance on data collection needed to support the development of site-specific cleanup goals. • It should provide for integrated assessment of sites affecting the same human or ecological receptors. • It should encourage early action at sites where the risk to human health and the environment is imminent and at sites where the risks are demonstrably low and remediation is likely to be more rapid and inexpensive. • It should consider relevant uncertainties. • It should provide a mechanism for integrating the selection of the remedial option with the establishment of remedial goals. • It should have options to revisit sites over the long term. • It should be implemented in a public setting with all of the stakeholders involved. • Its guidance document should undergo both external, independent, scientific peer review and public review. • It must comply with relevant state and federal statutory programs for environmental cleanup.
ing for a cost-effective decision-making framework that will allow sites to be closed in a reasonable time frame. Although the Navy's cleanup budget totaled $549 million in fiscal year 1997 (5), environmental restoration in the Navy must compete with other programs for funding. Budgets for fiscal years 1997 and 1998 have decreased from previous years, and given this limited funding, the Navy's goal is to conduct cleanup projects that will achieve the greatest possible reduction of risk to human health and the environment at the lowest possible cost. Other large, multisite responsible parties also are looking for cleanup solutions. Since 1995, the widely popular ASTM RBCA method has been adopted by many state programs for the cleanup of underground storage tanks of fuel. The method's attraction lies in the simple and consistent framework that it uses to organize cleanup activities for all types of contamination and contaminated media. "EPA has not specifically endorsed ASTM RBCA over all other [cleanup] methodologies [for petroleum]. However, the agency supports efforts to improve the understanding and use of risk-based decision making in general, of which RBCA is an excellent example," said Steven McNeely, of EPA's Office of Underground Storage Tanks. As of October 1998, 14 states have adopted some form of ASTM RBCA for cleanup of underground storage tanks of fuel, and 27 more are approaching full implementation. A second RBCA method, which addresses chemical contamination other than petroleum, has been developed by ASTM but has not yet AUGUST 1, 1999/ENVIRONMENTAL SCIENCE 8. TECHNOLOGY / NEWS • 3 2 1 A
sites are either in study or cleanup phases (see figure on the left). Sites at facilities slated for closure unSite cleanup status der the Base Realignment and Closure Act (BRAC) Department of Navy sites are classified by phase category. BRAC refers to have a slightly lower percentage of being "response Base Realignment and Closure Act. complete" than sites at active bases. Environmental remediation at BRAC facilities is on a fast track compared with cleanup at active bases because of the legal requirement to quickly transfer BRAC facilities to nonmilitary owners. In addition to the time and money constraints facing the Navy, the Environmental Restoration Program is plagued with other problems unique to large, multisite responsible parties. Navy officials routinely cite inconsistent and overly strict regulatory practices from state to state, which, in their eyes, tend to complicate the cleanup process and discourage standardization across the country. Part of this problem stems from the inevitable location of Navy facilities in coastal areas. These localities often harbor more environmentally susceptible receptors, denser human populations, and more fate-andbeen implemented at the state level (3). (Through- transport pathways for contaminant migration than out this article, the term ASTM RBCA refers to both inland areas. The broad range of contaminants found at Navy sites and the sometimes poor record keepmethods, which are almost identical.) The NRC report finds the ASTM RBCA method to ing associated with these sites make cleanup of Navy be remarkably similar to CERCLA, with some nota- facilities a challenge. ble exceptions. Most important, because ASTM RBCA The Navy is not alone in its desire for more costcontains more risk-management options at multi- effective, feasible methods to combat multiple conple stages during cleanup, there is a general percep- tamination problems. The past 15 years have wittion that it is faster and more standardized than nessed a major shift in cleanup philosophy at many CERCLA. These advantages, however, are balanced by levels, within regulatory agencies, among responsimultiple weaknesses. "As currently written, ASTM RBCA ble parties, and in the development of cleanup techdoes not satisfy the criteria required of an effective risk- nology. Goals have migrated from complete cleanup based method for the Navy," the report states. or resource conservation—the impetus for the maIn summary, the NRC committee credits the ASTM jor environmental laws of the 1970s—to more riskRBCA method with allowing for site prioritization, based approaches that will allow some contaminaconsistency in cleanup for varying site types, data col- tion to remain in place. These changing priorities lection, and early action at low-risk and immediate have fueled the development of newrisk-basedmethresponse sites. It also notes that the tiered ap- ods such as ASTM RBCA. proach of ASTM RBCA allows the user to iterate between setting cleanup goals and selecting remedia- Making comparisons tion options. However, according to the NRC report, The NRC committee compared the ASTM RBCA integrated assessment of multiple sites is not men- method with the CERCLA process and found similartioned, and discussion of uncertainty analysis is ities and differences. Although not always viewed as viewed as entirely inadequate. Options to revisit sites such, CERCLA is risk-based because it uses both risk over the long term are also not apparent, although assessment and risk management to determine cleanup there is some discussion of the goals of long-term goals and appropriate remedies. CERCLA (see figure on monitoring. "Because the general public and the sci- next page) and ASTM RBCA (see figure on page 324A) entific community were not given an opportunity to describe the entire cleanup process from site discovcomment on RBCA before being approved by the ery to site closure. Both also advocate the use of risk ASTM, it is likely that the methods reflect biases that assessment to determine the inherent level of risk might not have been present if these groups had been posed by a contaminated site and to set cleanup involved at an earlier stage," the report states. The goals. The mathematical fate and transport equareport further notes that ASTM RBCA does not out- tions suggested by each method are the same, and line clear opportunities for public participation dur- they suggest equivalent acceptable risk levels. Each ing implementation and was not designed by a wide method outlines important and similar criteria that range of stakeholders. Finally, integration of ASTM must be taken into account when selecting the reRBCA into existing state and federal laws, particu- medial option during risk management. larly CERCLA, is not at all clear. The most significant difference between the methods is that ASTM RBCA is more systematic than CERCLA because it uses a common framework—a tiered Cleanup challenges Since its inception in 1990, the Navy Environmen- approach—for addressing all types of contamination. tal Restoration Program has dealt with a large case- Under ASTM RBCA's tiered approach, site conditions load of waste sites. More than 50% of all discovered are compared with either generic or site-specific 3 2 2 A • AUGUST 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / N
cleanup levels, and, depending on die results, die site may be closed, cleaned up, or further characterized and analyzed. This approach allows risk management decisions to occur at multiple points during the ASTM RBCA process. The CERCLA process, on the other hand, is more linear in nature. Whether CERCLA uses a tiered approach depends on the type of contamination present; the nature of the contaminated media; and the presence of generic screening levels and other legal requirements in individual states. Another important difference between the two methods is that CERCLA has a preference for source removal. "The preamble to the National Contingency Plan makes it clear that EPA has a strong preference for treatment technologies [source removal] over engineering and institutional controls," notes the NRC report. The ASTM RBCA approach gives equal consideration to source removal, engineering controls such as containment, and institutional controls. The multiple differences between CERCLA and ASTM RBCA have led to a general perception that the RBCA process is faster and less costiy than the CERCLA process.
The CERCLA process The Superfund (CERCLA) risk-based approach for identifying and cleaning up sites is a multistep process that allows for community involvement and public comment. At any point in the CERCLA process, the responsible defense component can take immediate action to respond to immediate risks.
Methodological weaknesses According to the NRC report, potentially rapid site closeout under ASTM RBCA, or any purely risk-based method, comes at a significant price. "Their most significant weakness," states the report, "is that risk-based methods are more likely than source removal to leave contamination in place because of their reliance on engineering and institutional controls." Leaving contamination in place complicates waste site cleanup, if, for example, unidentified and potentially harmful substances remain on site—the discovery of methyl-rerf-butyl ether (MTBE) in groundwater at petroleum waste sites across the country highlights concerns about leaving contamination in place as part of the cleanup remedy. Risk-based methods, in addition to potentially leaving contamination in place, are also characterized by multiple uncertainties. Because these are so numerous and pervasive, the NRC report categorized them into two groups: risk assessAUGUST 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 3 2 3 A
ASTM RBCA for petroleum release sites The American Society for Testing and Materials' Risk-Based Corrective Action (ASTM RBCA) approach involves a three-tiered evaluation process for establishing a remedial action program. (Courtesy ASTM)
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TABLE 1
Risk assessment uncertainties The reliability of a risk assessment can be affected by uncertainties associated with contaminant sources, pathways of contaminant migration, and potential receptors. Sources
Contaminant pathways and transport
Receptors
• Lack of information on source location(s)
• Unknown pattern of subsurface heterogeneity
• Limitations of the dose-response models — extrapolation of hazard and toxicity
• Poorly known history of contaminant releases
• Complexities due to natural and anthropogenic stresses
• Unknown variability in mass or concentration distributions of contaminants
• Inability to define and characterize physical, chemical, and biological fate and transport processes
• Complexity in the chemical composition of contaminants
• Limitations of models of contaminant fate and transport processes • Difficulties in estimating parameters for contaminant fate and transport models
data — insufficient data to identify hazards or dose-response relationship — model selection — parameter estimation for dose-response model • Problems characterizing exposure and outcome — identification of toxicants — identification of target population over time —variability in receptors
ment uncertainty and risk management uncertainty. During the risk assessment process, uncertainties arise when characterizing the contamination source, pathways of contaminant migration, and receptor populations (see Table 1 above). At many hazardous waste sites—including many Navy facilities—there are poor records of waste disposal, making it difficult to know the original mass and time-release history of contamination. Aquifer heterogeneities can greatly complicate flow paths and degradation processes that affect contaminants in both unsaturated and saturated soils. Variability in receptor responses to contaminants can be extreme: For many nonpetroleum contaminants such as MTBE toxicological data are limited a source of u n c e r t a i n t y t h a t c a n n o t b e addressed on the timescale of most cleanup efforts The NRC report stresses the importance of assessing and reducing these uncertainties through the use of quantitative, formal uncertainty analysis. Use of conservative cleanup goals to deal with uncertainty "does not convey the degree of confidence in the risk estimate, and it provides no information about how likely that risk may be," the report notes. Although formal uncertainly analysis can reveal the relative magnitude of sources of uncertainty and help target resources toward reducing the greatest uncertainties, most responsible parties and regulatory agencies have shied away from uncertainty analysis bec a u s e of t h e scientific e x p e r t i s e n e e d e d a n d requirements for extensive site characterization data. This response the report argues has undoubtedly led to an overestimation of risk at some hazardous waste sites: "Quantifving uncertainties may save money in the long run [bv correctly estimating risk] even though the cost of modeling and data collection to quantify uncertainties up front may be high " In addressing uncertainty in risk management, the NRC report focuses mainly on the reliability of cleanup remedies. The success of many treatment technologies depends on aquifer heterogeneities that often preclude contact between contaminants and
cleanup fluids, such as air and water. Previous NRC reports found that pump-and-treat systems, the most common source removal technology used at contaminated sites, are highly unlikely (as little as 10%) to achieve regulatory requirements for cleanup (6, 7), although when used for containment rather than source removal, pump-and-treat system effectiveness is considerably more certain. Institutional controls are also described by the report as highly uncertain because of poor enforcement, and several suggestions are made for improvement: "The most important requirement is that institutional controls be reliable in the long run, when the present-day stakeholders are gone," states the report. According to Laura Hunter of the San Diego Environmental Health Coalition, "Effective enforcement of institutional controls relies on memory, which is often short-term at the Navy due to high personnel turnover."
References (1) National Research Council. Environmental Cleanup at Navy Facilities: Risk-Based Methods; National Academy Press: Washington, DC, 1999. (2) American Society for Testing and Materials. Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites (E 1739-95). In Annual Book ofASTM Standards; ASTM: West Conshohocken, PA, 1998. (3) American Society for Testing and Materials. Standard Provisional Guide for Risk-Based Corrective Action (PS 10498). In Annual Book ofASTM Standards; ASTM: West Conshohocken, PA, 1998. (4) Superfund: Times to Complete Site Listing and Cleanup; GAO/ T-RCED-98-74; U.S. General Accounting Office, U.S. Government Printing Office: Washington, DC, 1998. (5) Chief of Naval Operations. Department of the Navy Environmental Restoration Plan for Fiscal Years 1998-2002. Department of the Navy: Arlington, VA, 1998. (6) National Research Council. Alternatives for Ground Water Cleanup. National Academy Press: Washington, DC, 1994. (7) National Research Council. Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization. National Academy Press: Washington, DC, 1998.
Laura Ehlers is a senior staff officer of the National Research Council's Water Science and Technology Board. AUGUST 1, 1999/ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 3 2 5 A
