5
Conclusions and Recommendations

The Navy's Environment Challenges

This report is the culmination of efforts to help the Navy solve problems in its Environmental Restoration Program. The goals of the first phase of the study were to review the ASTM RBCA standard guides and other relevant methodologies and consider their implementation at Navy facilities. As stated in Chapter 2, the ASTM standard guides and the EPA guidance to which they were compared are risk-based methodologies that contain elements of both risk assessment and risk management. Risk management is considerably more difficult to conduct than risk assessment because it involves issues that go beyond purely scientific considerations. This fact was reflected in discussions with Navy personnel, who characterized their risk assessment process as relatively straightforward, but their risk management decision-making process as complex, variable, and unstructured. The major hurdles the Navy Environmental Restoration Program is struggling to overcome are summarized below.

Cost Control

Environmental remediation competes with the Navy's obligations to maintain a seaworthy and battle-ready fleet. Because of the balanced budget agreement, there is a direct trade-off between money spent on hazardous waste site cleanup and money spent on other Navy activities. As a result, the Navy's budget for performing cleanup of hazardous waste sites is limited. The combined Defense Environmental Restoration Account and BRAC funding for FY97 was $549 million, and the Navy is under pressure from Congress to reduce that figure in future years.



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--> 5 Conclusions and Recommendations The Navy's Environment Challenges This report is the culmination of efforts to help the Navy solve problems in its Environmental Restoration Program. The goals of the first phase of the study were to review the ASTM RBCA standard guides and other relevant methodologies and consider their implementation at Navy facilities. As stated in Chapter 2, the ASTM standard guides and the EPA guidance to which they were compared are risk-based methodologies that contain elements of both risk assessment and risk management. Risk management is considerably more difficult to conduct than risk assessment because it involves issues that go beyond purely scientific considerations. This fact was reflected in discussions with Navy personnel, who characterized their risk assessment process as relatively straightforward, but their risk management decision-making process as complex, variable, and unstructured. The major hurdles the Navy Environmental Restoration Program is struggling to overcome are summarized below. Cost Control Environmental remediation competes with the Navy's obligations to maintain a seaworthy and battle-ready fleet. Because of the balanced budget agreement, there is a direct trade-off between money spent on hazardous waste site cleanup and money spent on other Navy activities. As a result, the Navy's budget for performing cleanup of hazardous waste sites is limited. The combined Defense Environmental Restoration Account and BRAC funding for FY97 was $549 million, and the Navy is under pressure from Congress to reduce that figure in future years.

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--> Over the last five years, there has been a trend at Navy facilities toward spending more money on cleanup and less on the study phase that precedes cleanup. The Navy feels this is a move in the right direction in terms of justifying the large amounts of money spent (Department of the Navy, 1998). However, for the most part, the true fiscal requirements of cleanup exceed the budget allocated to the Navy for that purpose. This is because most of the technological solutions are expensive, especially for sites containing highly recalcitrant compounds. The monetary pressures brought on by the waste cleanup process are not unique to the Navy. General experience in environmental remediation indicates that considerable resources have been spent remediating sites over long periods of time with little to show in terms of percent contaminant removal or risk reduction (NRC, 1994). The CERCLA process, which the Navy uses for 66 percent of its hazardous waste sites, is complicated and lengthy, and is perceived by some in the Navy as being too expensive. The Navy is seeking alternative strategies that will save money in cleaning up both petroleum and non-petroleum sites. Other risk-based methodologies, such as ASTM RBCA, in which the focus is shifted from treatment technologies to engineering and institutional controls, were perceived as a less expensive way to close sites. The variability between state RBCA programs makes it difficult to assess the validity of these perceptions. However, a recent report summarizing data from 18 states suggests that RBCA could lower cleanup costs for petroleum underground storage tanks by as much as 36 percent (Environmental Information, Ltd., 1997). Timely Site Close Out A second problem confronting the Navy is the need to close sites more quickly. As discussed in Chapter 1, pressure to close out sites is coming mainly from communities and developers in areas adjacent to BRAC facilities. Developers are eager to convert the land to other uses, and community members want to maintain the employment levels that existed when the base was active. There is also DOD-wide pressure for the military to complete all necessary environmental remediation. Meeting its cleanup obligations as soon as possible is viewed by the military as an opportunity to focus its resources on objectives relating to national security (Eikenberry, 1998). The average time needed to complete the CERCLA process has been 10.6 years from initial site investigation to construction of a remedy (GAO, 1998). The Navy has increasingly used removal actions (interim remedial actions) to eliminate sources of contamination before a complete RI/FS is accomplished, thereby accelerating the CERCLA time line. Unfortunately, these actions are effective only if removal of contaminated soils, tanks, and pipes eliminates risk to potential receptors. Very often, enough residual contamination in the soil or tank spillage has leached to the ground water to form a secondary source of contami-

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--> nation. In such cases, removal actions have accomplished important long-term benefits by preventing the contaminant pool from growing, but an RI/FS is still needed to facilitate cleanup or containment of the secondary source. In the same way that other risk-based approaches were perceived as possibly saving the Navy money, they were also thought to accelerate the site closure process. (Experience with the ASTM RBCA methodology in Oklahoma to date has not indicated any increase in the number of sites closed per year.) Conflicting Regulatory Requirements Responsible parties like the Navy are faced with multiple regulatory problems. A plethora of federal, state, and local agencies are responsible for the protection of public health and the environment. Empowered by different legislative mandates, each operates with a program-or agency-specific bias. Environmental statutes and regulations are inconsistent across the nation, often differing between agencies within a state. For example, each of the nine Regional Water Quality Control Boards in California operates as an independent regulatory body with its own cleanup criteria for contamination from underground storage tanks. The result is a conflicting regulatory maze for the regulated community. Responsible parties operating at the national level, like the Navy, would benefit greatly from a consistent risk assessment process and risk management strategy that could be modified to satisfy the various oversight agencies. Adoption of a carefully designed risk-based methodology could be one way of providing such consistency. Conservative Regulatory Approaches Some of the regulatory agencies responsible for cleanup oversight at waste sites use conservative assumptions regarding the level of cleanup. This conservatism stems partially from uncertainties in the risk assessment process that force the agencies to adopt safety margins. One result of this conservatism, however, is that responsible parties may feel they are being asked to continue cleanup beyond that required to achieve maximum risk reduction. Responsible parties may also perceive the conservatism of regulatory agencies as being inconsistent with the current limitations in cleanup technology. Complexity of Naval Facilities Chapter 1 described many of the features of Navy bases that differentiate them from a typical hazardous waste site. The magnitude of the Navy's environmental liability is extremely high because of the tremendous complexity associated with its installations. Most Navy facilities are large and contain multiple types of hazardous waste sites. In individual sites there may be a variety of toxic

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--> The coastal location of the recently capped McAllister Point Landfill in Newport, Rhode Island, aptly demonstrates it susceptibility to multiple contaminant migration pathways and ecological receptors. Courtesy of the U.S. Navy. substances, many unidentified and most in unknown quantities because of accidents, outdated management practices, or a lack of recordkeeping. The location of many naval facilities along coastlines introduces potential pathways of contaminant migration and potential human and ecological receptors that are not characteristic of inland facilities. The complexity of most naval facilities suggests that the cleanup of waste at these facilities will be difficult, potentially expensive, and time consuming. Eleven Criteria for A Risk-Based Methodology The Navy's request for this study reflected the challenges outlined above. The perception by many involved in the environmental cleanup business is that CERCLA is slower and more expensive than other risk-based approaches to cleanup. The committee recognizes the attraction of a new risk-based approach to the Navy Environmental Restoration Program, but remains cautious in recommending its use at Navy facilities. This is because risk-based approaches are more likely than source removal or technology-based approaches to result in remedies that leave contamination in place. The committee agrees that risk-based

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--> solutions can have significant short-term benefits. However, it does not believe that the long-term ramifications of leaving contamination in place are sufficiently considered in the methodologies that were reviewed. If a risk-based approach to environmental remediation is to be used at naval facilities, it must overcome the weaknesses that characterize solutions in which contamination is left in place. Based on its review of federal, state, and other risk-based methodologies, interviews with and presentations from Navy personnel, previous NRC reports, and the expertise of its members, the committee has identified 11 important criteria for a risk-based methodology that addresses hazardous waste sites at Navy facilities. These criteria outlined below take into account the complex characteristics that distinguish Navy facilities from other types of hazardous waste site complexes. 1.   An effective risk-based methodology should facilitate prioritization of contaminated sites at individual installations. One of the strengths of a risk-based approach noted in Chapter 3 is the ability to prioritize sites based on their relative risk. This feature is especially important at facilities harboring multiple waste sites. Ranking of sites based on their relative risk can help determine which sites pose immediate threats to human health and the environment, which sites should be cleaned up first, and how much money should be devoted to individual sites. This process should be relatively simple so that its use early in the remediation process can be expedited. Thus, prioritization does not have to occur with the same risk assessment and risk management paradigms that characterize a comprehensive methodology. However, initial data collected for the priority-setting analysis should be easily incorporated into an expanded framework. 2.   It should provide a consistent mechanism for addressing all types of sites. The Environmental Restoration Program of the Navy must be able to encompass low risk sites that contain simple, well identified chemicals, as well as high risk sites characterized by multiple, recalcitrant chemicals and unfavorable hydrogeological conditions. Thus, if the Navy adopts a risk-based methodology for environmental remediation, it must include a systematic approach for conducting site investigations of differing complexity. A risk-based methodology that facilitates the evaluation of both simple and complex sites should allow for the replacement of conservative, generic cleanup goals with less conservative but more site-specific cleanup goals when appropriate. Site-specific cleanup goals ensure that carefully considered and effective solutions are brought to bear on well-defined problems, minimizing the potential for the misallocation of limited resources. On the other hand, when time and resources cannot allow for protracted studies to generate site-specific information, generic cleanup goals should be available that reflect a level of conservatism consistent with the lack of knowledge about the site.

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--> 3.   It should provide guidance on data collection needed to support the development of site-specific cleanup goals. Because risk-based approaches may suggest remedies in which some contamination is left in place, extensive site characterization and data collection must accompany their use to ensure that they are truly protective of human health and the environment. Currently, there are methods to characterize sources and pathways with known levels of confidence that will bolster the scientific defensibility of the resulting risk estimate. A satisfactory risk-based methodology will provide guidance for setting data collection methods and data quality objectives. It will suggest ways to conduct an initial site assessment that will aid in prioritization of sites, as well as methods of site characterization that can be used to generate site-specific cleanup goals. Consistency in the methods for conducting site characterization is essential for multi-state responsible parties like the Navy. 4.   It should provide for integrated assessment of sites affecting the same human or ecological receptors. At large facilities containing multiple hazardous waste sites with complex chemical mixtures, such as military bases and Superfund sites, the risk from exposure to contamination may derive from multiple sources. A risk-based methodology must be able to assess quantitatively all of the sources that affect individual human or ecological receptors. First, it must include cumulative risk assessment, which evaluates the effects on potential target receptors of multiple chemicals and multiple exposure pathways originating from a single waste site. Second, an integrated assessment of sites must be conducted to determine the overall facility-wide risk encountered by potential target receptors. As discussed in Box 5-1, an integrated assessment of the potential risks posed by multiple waste sites has not traditionally been performed at naval facilities. 5.   It should encourage early action at sites (a) where the risk to human health and the environment is imminent and (b) for which the risks are demonstrably low and remediation is likely to be more rapid and inexpensive. A risk-based methodology will allow for source removal and pathway interruption to eliminate risk to potential receptors before the remedial option has been chosen. It will also facilitate rapid action at sites that are easy and inexpensive to remediate, as defined by the nature of the contaminants present and the affected subsurface (NRC, 1994). If all contamination is not removed as a result of these early actions, the methodology should evaluate the long-term consequences of removal actions and pathways interruptions with long-term monitoring. If such monitoring shows that contamination remains above acceptable risk levels, further remedial action, such as the implementation of engineering or institutional controls, may be necessary. Although interim removal was never intended to bypass the normal timeline for cleanup under either the EPA or ASTM RBCA methodologies, in practice re-

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--> moval actions often become the only actions taken at a site because of time and money constraints (see Criterion 8). 6.   It should consider relevant uncertainties. This report has emphasized the significant uncertainties in risk-based approaches to remediation, e.g., model and data uncertainty, lack of understanding concerning ecological or environmental risk, uncertainty in dose-toxicity relationships, and incomplete knowledge about the enforceability of institutional controls. This uncertainty directly translates to uncertainty in risk estimates, associated cleanup levels, and the effectiveness of the proposed solutions. A quantitative risk-based methodology will allow for the explicit consideration of these uncertainties and suggest options for reducing these uncertainties. For uncertainties that cannot be reduced, the methodology should allow for the use of stochastic modeling approaches, such as the Monte Carlo simulation, rather than deterministic models, in order to represent the degree of uncertainty associated with the risk estimates. 7.   It should provide a mechanism for integrating the selection of the remedial option with the establishment of remedial goals. It should also provide quantitative tools for developing risk management strategies. A risk-based methodology provides guidance for calculating the risk of a hazardous waste site (with risk assessment), setting goals for the cleanup process, and determining methods for meeting those goals. This process is sometimes conducted sequentially, with the setting of cleanup goals preceding the selection of a remedial option. In many instances, however, there are no remedies technologically capable of meeting those goals, which can significantly confound the process if cleanup goals are immutable. A risk-based methodology should allow flexibility in setting cleanup goals and selecting remedies by using an interative approach during which the responsible party and oversight agencies cycle back and forth between these issues. Currently, the selection of remedial options is qualitative, and relies on the limited guidance embodied by the nine criteria in the NCP (or other similar criteria, as found in the ASTM RBCA standard guides). At least three of the nine criteria, short- and long-term effectiveness of the remedy and cost, are amenable to quantitative analyses. The committee acknowledges that ''cookbook" solutions for conducting remedy selection are not workable. However, it believes that quantitative tools for evaluating multiple remedial options can be developed to improve the remedy selection process. Such tools are likely to balance effectiveness and cost and consider risk reduction per dollar of expenditure. 8.   It should have options to revisit sites over the long-term. Risk-based approaches to the management of contaminated sites must have the ability to quantify and control future risks, both short-term and long-term. Thus, a risk-based methodology may call for future evaluations of risk if site conditions change

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--> BOX 5-1 Using Risk for the Cleanup of USTs at North Island Naval Air Station A type of risk-based methodology, the Risk-Based Cleanup Index, was prepared for the Navy by Bechtel National, Inc., to address closure of underground storage tanks (USTs) at North Island Naval Air Station (Bechtel National, Inc., 1997). A general description of North Island Naval Station can be found in Box 1-1. A total of 190 individual USTs have been identified at North Island, including tanks currently in use, closed and abandoned tanks, and tanks planned for upgrading or replacement. This index addressed the closure of petroleum tank sites containing gasoline diesel fuel, marine diesel, and the jet fuels JP-4 and JP-5. It expressly excluded tanks containing Chlorinated compounds, acids, metals, and non-petroleum products that met the criteria for classification as non-RCRA hazardous waste. A detailed description of this study is beyond the scope of this report. However, a summary of the key points is relevant to Criterion 4 of a risk-based methodology. Because the ground water beneath North Island has been declared unsuitable for drinking water, human exposure to contamination was limited to inhalation of volatile organics and to exposure from dissolved contaminants that migrate to San Diego Bay or to the Pacific Ocean. Calculations of environmental risk indicated little potential exposure of human occupants to volatile organic contaminants present in ground water. Thus the methodology focused on ecological receptors in the waters surrounding North Island. over time. Internal DOD and Navy guidance, as well as CERCLA and the other regulatory processes that govern Navy cleanup, are flexible enough to allow site decision makers to adapt to changing site conditions. But the standard practice, encouraged by the pressure to close out sites, is not sufficiently flexible. In the committee's experience, many remedies consist of single actions, such as one remedial action or removal action. This approach may be acceptable when the source of contamination can be completely removed with currently available technologies. However, it is likely to be inappropriate when contamination remains on site after the remedy is in place. The affected public and regulatory agencies may be more willing to accept short-term decisions that appear to leave sources in place if they believe responsible parties are willing to take additional future action. Therefore, the Navy would be best served by a flexible risk-based method-

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--> Contaminant transport by ground water to the marine environment was the main pathway by which pollutant sources were assumed to reach potential receptors. Ground water flow models and estimated biodegradation rates were used to calculate allowable concentrations (cleanup goals) for target indicator compounds present in petroleum at the individual UST locations (BTEX, naphthalene, and polynuclear aromatic hydrocarbons). These allowable concentrations were back calculated from compliance limits set for petroleum-based contaminants in the North Island aquifer. In determining these cleanup levels, the Navy did not analyze the cumulative impacts of all USTs on potential receptors, but instead examined each tank in isolation. This runs counter to the committee's recommendation that any risk-based methodology used by the Navy should perform an integrated risk assessment of all sites affecting the same human or ecological receptors. It is not known whether an integrated assessments of sites would have made a difference in the cleanup levels generated at North Island. However, considering each site separately may lead to situations where no actin is taken at individual sites even though the overall facility-wide risk is significant. ology that simultaneously addresses short-term and long-term risk. Box 5-2 presents two common scenarios at Navy facilities that illustrate why risk-based approaches should include options to revisit sites over the long-term. This criterion for revisiting sites over the long-term applies to both active and BRAC facilities. It should be noted that in some circumstances, current DOD policy relieves the Navy of responsibility for performing additional cleanup activities on BRAC facilities that have been transferred to the private sector. For example, a future change in land use by the new owner, if it goes against a stated deed restriction or institutional control, does not require the DOD to return and provide additional cleanup. However, the military will return to conduct additional cleanup if (1) the selected remedy is no longer protective (because of its failure), (2) new contamination is discovered, or (3) regulatory agencies require

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--> BOX 5-2 Revisiting Sites over the Long Term Dense nonaqueous phase liquids A frequent scenario at Navy facilities is ground water contaminated with dense nonaqueous phase liquids (DNAPLs). Existing technologies, such as pump-and-treat systems, are robust enough to control plume migration, but in most cases they cannot bring contamination down to risk-based regulatory goals. in such cases, remedies should be designed to accomplish short-term goals, such as containment, while the responsible parties and others support the research and development of remedial technologies that can more completely or more cost-effectively reduce contamination to acceptable risk levels (NRC, 1994). Land Fills A typical problem at most Navy bases is the presence of one or more landfills, usually an unlined pit containing household garbage, landscape refuse, construction debris, and industrial chemicals, such as waste oils or paints in 55-gallon drums. Often very little is known about what was buried and what remains that could potentially pose a threat if a drum were to start leaking. A "one-shot" solution might have to be extremely costly or intrusive to guard against that worst case scenario. However, an approach that allows sites to be revisited over time could guard more effectively against evolving risks. If regulators and the public are confident that the Navy (or other responsible party) is monitoring such sources as leaking drums and pathways of contaminant migration (or other new signs of risk), and has a plan in place to respond quickly to such evidence, the response can be both more protective and less costly. additional cleanup (Department of Defense, 1997). Any risk-based methodology adopted by the Navy should contain provisions for revisiting sites under these circumstances. 9.   It should be implemented in a public setting with all stakeholders involved. Implementation of any risk-based methodology adopted by the Navy should take place in a public forum. The assumptions and relevant science used during the risk assessment process and the proposed remedies, along with all relevant value judgments, must be presented to and understood by interested

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--> stakeholders. To facilitate public scrutiny and debate, the methodology must be explicit, scientifically defensible, and traceable. Fortunately, the Navy already has policies requiring public involvement in its remediation activities through Restoration Advisory Boards (though some stakeholders feel these policies are unevenly implemented). This criterion for a risk-based methodology should not be as difficult for the Navy to implement as it could be for other responsible parties. 10.   Its guidance document should undergo both external, independent scientific peer review and public review. Any proposed risk-based methodology must be the product of rigorous and broad external scientific peer review. All interested stakeholders must be allowed to review the risk-based approach, and supporting policies, during a public comment period prior to its implementation. Adoption of any methodology developed by a limited stakeholder group will insert potentially misleading biases into the remediation process. It also discourages (perhaps inadvertently) the pursuit of improved risk-based methodologies. 11.   It should comply with relevant state and federal statutory programs for environmental cleanup. Cleanup of contaminated Navy sites is governed by a variety of regulatory agencies and state and federal environmental statutes. Any risk-based methodology adopted by the Navy must comply with relevant laws and regulations, including CERCLA and RCRA. The methodology must be flexible enough to incorporate the regulatory policies of the states and the EPA, including all relevant generic cleanup criteria that have been developed. Comparing ASTM RBCA to the Eleven Criteria The Navy asked that the ASTM Risk-Based Corrective Action standard guides be evaluated for possible implementation at Navy facilities. The committee has reviewed the documents (Chapter 2) and discussed their strengths and weaknesses (Chapter 3). This section reviews ASTM RBCA with respect to the specific criteria outlined above. The following assessment of the ASTM publications is based on a strict reading of the guides. It does not imply that the RBCA approach could not be modified to take some of these criteria into account. Most states have modified the ASTM petroleum RBCA standard guide to some extent prior to implementation for cleanup of USTs. Prioritization of Sites ASTM RBCA allows for the ranking of sites by risk. As stated in Chapters 2 and 3 in this report, prioritization is accomplished during the initial site assess-

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--> ment and classification. Table 1 in petroleum RBCA describes the necessary site characteristics that lead to classifications of immediate threat, short-term threat, long-term threat, or no demonstrable threat. This information can be used to direct immediate response actions and prioritize sites for cleanup. The ASTM document stresses that Table 1 is only an example. The prioritization method can be modified according to the user, and it may include additional levels of prioritization. Consistent Mechanism for Addressing All Site Types The tiered approach of ASTM RBCA is a systematic mechanism that is applicable to both low and high risk sites. In addition, generic cleanup standards can be replaced with site-specific cleanup levels given the appropriate data collection. The tiered approach expedites the closure of low risk sites that are relatively simple, while allowing high risk sites to undergo more intensive site characterization. Data Collection and Site Characterization At many Navy facilities, there are hazardous waste sites with unknown types of contaminants. Any risk-based methodology adopted by the Navy should require data collection sufficient to delineate unidentified sources of contamination. Petroleum RBCA lists the types of data that may be collected as part of a tier 1 or tier 2 evaluation, but it does not require that these data be collected. Chemical RBCA greatly improves on petroleum RBCA by (1) adding to the types of data that are collected; (2) making data collection mandatory; and (3) requiring the development of data quality objectives. Users are referred to other ASTM documents and EPA guidance for developing data quality objectives. The discussion of site characterization in chemical RBCA is only minimally adequate. Users would greatly benefit from more information on data quality objectives, monitoring methods, appropriate sample size, and performance criteria for data collection methods. Integrated Risk Assessment The petroleum RBCA standard guide makes no mention of either cumulative risk assessment or integrated risk assessment. Chemical RBCA calls for cumulative risk assessment during a tier 2 evaluation; however, the standard guide does not define cumulative risk. It is not clear whether both multiple exposure pathways and multiple chemicals are considered and whether their effects are additive or combined in some other fashion. An integrated assessment of multiple sites that affect target receptors is not part of either RBCA standard guide. This type

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--> of analysis is likely to increase considerably the complexity of any risk-based methodology. Early Action ASTM RBCA does allow for source removal actions and actions to interrupt pathways of contaminant migration. Once an early action is completed, the user returns to Site Classification and Initial Response Action, and then to a tier 1 evaluation (see Figure 2-3). This refunneling of sites back into the main cleanup process ensures that early actions do not lead directly to site closure. Care must be taken by oversight agencies to ensure that the methodology is not abused by allowing interim remedial actions to lead directly to site closure. For low risk sites for which remediation is expected to be inexpensive and timely, the tier 1 evaluation can expedite site closure. If chemical concentrations at such sites are below generic cleanup levels found in the look-up table, a tier 1 evaluation can lead directly to site closure. Uncertainty The ASTM RBCA methodology does not adequately consider uncertainty in the data and the models of fate and transport used in the risk assessment process. This pertains to data on the concentrations of the chemicals of concern, data used to develop the dose-response models, and the actual models of fate and transport. The standard guides do not require that the user determine the uncertainty of the data collected; all data are assumed to be error-free. An assessment of the variability of certain parameters, such as hydraulic conductivity and individual response to toxicants, is not required. The ASTM RBCA approach to modeling is inherently deterministic and ignores the myriad of very real uncertainties associated with subsurface modeling that are enumerated in Chapter 4. The use of conservative model parameters in no way characterizes the uncertainty in model output. Uncertainty in transport model parameters due to soil heterogeneity could be incorporated into ASTM RBCA by using a Monte Carlo analysis. The ASTM documents do suggest using Monte Carlo techniques as part of a tier 3 analysis. Evidence from state programs implementing the petroleum RBCA standard guide indicates that most contaminated sites never reach tier 3 because of the costs associated with conducting extensive site characterization, so this suggestion is rarely realized. Monte Carlo analysis should be suggested for tier 2 evaluations as well as tier 3. None of the qualitative uncertainties associated with risk management are mentioned in ASTM RBCA. Chapter 4 in this report discusses several important unknowns in both technical and non-technical remedial options that can seriously hamper remedy selection. A more thorough discussion of these uncertainties and suggestions for assessing and reducing them are needed.

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--> A comprehensive assessment of uncertainty will increase the complexity of a risk-based methodology, and a high degree of expertise may be required to adequately implement such a methodology. Nonetheless, given the pervasiveness of uncertainty in risk assessment and risk management, a quantitative risk-based methodology must incorporate a more thorough evaluation of uncertainty than can be found in the ASTM RBCA methodology. Linking Cleanup Goals and Remedial Options ASTM RBCA is a flexible, iterative risk-based methodology that allows the user to cycle between deciding on the cleanup level and choosing the remedial option. Under RBCA, remedial options can be considered at each tier evaluation. If remedial options are not technically capable of reaching the cleanup levels developed for that tier, then more site-specific cleanup goals are generated as part of a higher tier evaluation. ASTM RBCA lacks a quantitative, consistent method for choosing remedial options based on their effectiveness and cost. The petroleum RBCA standard guide provides virtually no guidance on choosing the remedial option, while chemical RBCA states only what criteria must be considered (similar to the nine criteria of the NCP). It should be noted that ASTM is producing other documents relating to specific remedial options, such as a standard guide for the use of natural attenuation at petroleum release sites. In addition, the RBCA standard guides specifically discuss the use of institutional controls as remedial options. While similar guidance for the other types of remedial options would be beneficial, what is needed most is a quantitative method for analyzing various remedial options during each tier evaluation. Revisiting Sites over the Long Term Petroleum RBCA provides almost no guidance on how long monitoring should be conducted to ensure protection of public health, nor does it discuss how the risk at a hazardous waste site can be assessed at a later date. This stems from the long-held assumption that petroleum products biodegrade relatively quickly in the natural environment (Bouwer and Zehnder, 1993). However, the discovery of MTBE in many petroleum mixtures has demonstrated the fallacy of this assumption. The absence of wording about long-term monitoring in petroleum RBCA is a significant weakness. Chemical RBCA, on the other hand, addresses each of these issues in a more satisfactory manner. The purpose of long-term monitoring is clearly stated as "(1) demonstrating the effectiveness of the chosen remedial option, (2) confirming an improvement in conditions over time, and (3) verifying model assumptions and conditions." Chemical RBCA discusses the very real possibilities of ineffective remedial

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--> In preparation for transfer of the property to the private sector, considerable cleanup was conducted at the Derecktor's Shipyard located at the Newport Naval Education and Training Center. Courtesy of the U.S. Navy. options and future changes in land use, although the wording is not as strong as might be desired. If long-term monitoring demonstrates that the remedial option is ineffective, the user should either reevaluate the remedy or return to the applicable tier evaluation. Similarly, if future land use changes during the implementation of a remedial option, the user may return to the applicable tier evaluation. Chemical RBCA does not, however, mention what to do when changes in land use occur after the remedial action is complete and after site closure. A somewhat surprising feature of chemical RBCA related to long-term considerations of risk is the inclusion of Figure 2 (see Figure 2-5 in Chapter 2) in a tier 1 evaluation. This figure allows for a preliminary assessment of the completeness of the pathways connecting sources to receptors. Depending on how the figure is interpreted, demonstrating a break in that pathway can lead to site closure before concentrations of chemicals of concern are compared to generic cleanup levels. This is problematic because in the absence of any control strategies, currently incomplete exposure pathways may be completed at some point in the future. If interpreted in this way, this figure negates many of the improvements of this document over the petroleum RBCA standard guide.

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--> Broad Stakeholder Participation in Implementation Public involvement during implementation of petroleum RBCA is minimal. During the site classification, petroleum RBCA requires that the appropriate authorities, property owners, and potentially affected parties be notified of the risk posed by the contamination. Chemical RBCA, on the other hand, mentions public involvement during the collection of site assessment information, following site classification, and during remedy selection (although public involvement still does not appear at explicit points in the RBCA flowchart). The appendixes of chemical RBCA contain detailed information on potential public involvement activities. External Scientific Peer Review and Public Review Both ASTM standard guides were designed and approved by a limited group of stakeholders. Petroleum RBCA was the product of negotiations between the oil industry, state regulatory programs, members of ASTM, and the EPA. Chemical RBCA was created by oil and chemical industries, a small number of state regulatory agencies, members of ASTM, and the EPA (which officially abstained from voting for approval of the standard guide). Environmental advocacy organizations were not involved in the design of either standard guide. Nor did the ASTM RBCA standard guides undergo external scientific peer review, although they did win approval in the ASTM consensus balloting. Because the general public and the scientific community were not given an opportunity to comment on the standard guides before being approved by ASTM, it is likely that the methodologies reflect biases that might not have been present if these groups had been involved at an earlier stage. Compliance with Current Statutory Guidelines Both of the ASTM RBCA standard guides outline a framework that encompasses all aspects of the cleanup process, from initial site discovery to eventual site closure. Depending on the particular regulatory environment, only portions of the methodology may be amenable to adoption by state and federal environmental cleanup programs. The ASTM petroleum RBCA standard guide is being adopted by many states as the regulatory framework for their UST programs. Because USTs are regulated primarily under RCRA, which does not mandate any specific cleanup framework, integration of petroleum RBCA has been successful in many states. Most states have made modifications to the RBCA framework that reflect particular state laws and regulations regarding cleanup of USTs. The implementation of chemical RBCA for contaminated sites regulated under RCRA may be accomplished with similar ease. Especially for Brownfields sites and voluntary cleanup efforts, the chemical RBCA framework may be an attractive way for state hazardous waste programs to become more standardized.

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--> At 66 percent of its hazardous waste sites the Navy uses CERCLA, a federal statute that dictates a specific cleanup framework. The integration of RBCA into the CERCLA framework is not at all clear. For example, in circumstances where ground water must be restored to drinking water quality because of other statutes (ARARs), the tiered approach of RBCA could not be used to generate site-specific cleanup levels that were greater than MCLs. State environmental laws would also have to be consulted prior to the use of chemical RBCA. Some state laws are more stringent than the corresponding federal laws and contain non-degradation or resource conservation provisions that would eliminate any risk-based methodology from consideration. To its credit, the chemical RBCA standard guide, unlike the petroleum RBCA standard guide, repeatedly stresses that it is a voluntary methodology meant to complement state and federal regulatory programs rather than replace them. It suggests strongly that the appropriate regulatory authorities should be contacted to assist users with a myriad of technical policy decisions that would have to precede its use at the state level. Unfortunately, the standard guide does not present an example of how the methodology could be integrated with existing regulations, suggesting that this is a formidable task. Recommendations The committee recognizes that consideration of risk as well as resource conservation is an important element of environmental remediation. The high costs associated with environmental remediation combined with limited financial resources mean that all sites cannot be cleaned up to background levels. A consideration of risk is an important and pragmatic way to help determine which sites should be cleaned up. Risk-based approaches are more likely than source removal or technology-based approaches to result in remedies that leave contamination in place. This can lead to a variety of problems that have been described in detail, including the appearance of previously unidentified compounds or pathways after site closure, less interest in the development of innovative technologies for source removal, a reliance on institutional controls, and a loss of public support and trust. Unless a risk-based approach is formulated to prevent these problems, the committee does not believe that such an approach can provide a long-term solution to environmental contamination at Navy facilities. Use of the ASTM RBCA Standard Guides The ASTM RBCA standard guides are a strong attempt to provide a uniform risk-based approach to environmental remediation. The chemical RBCA standard guide is an improvement over the petroleum RBCA standard guide because

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--> of the increased attention given to ecological risk assessment, cumulative risk, the selection of the remedial option, long-term monitoring, and the establishment of a RBCA program at the state level. In fact, if the Navy currently were using RBCA programs based on the petroleum standard guide, the committee would recommend that it adopt the chemical standard guide in its place. Despite these improvements, however, the committee does not recommend the adoption of either the petroleum or chemical RBCA standard guides at Navy facilities unless they are modified to satisfy the 11 criteria outlined above. As currently written, the ASTM RBCA methodology does not satisfy all 11 criteria listed above as characteristics of an effective risk-based methodology. Petroleum and chemical RBCA fall short in their guidance on site characterization and cumulative risk assessment. The methodology does not integrate the effects of multiple sites on individual receptors. Although some consideration of uncertainty is present in the methodology, an explicit assessment of uncertainty is suggested only during a tier 3 evaluation, which would encompass very few cleanups. Uncertainties associated with remedial options are not discussed at all. Chemical RBCA includes a preliminary assessment of source, pathways, and receptors that might allow site closure prior to any tier evaluation. Although criteria for remedy selection are provided in chemical RBCA, no quantitative framework is suggested for balancing those criteria. ASTM RBCA was drafted by a limited group of stakeholders and did not undergo independent, external scientific peer review or public review. Finally, its successful integration into such existing statutory programs as CERCLA is unclear. There are several practical reasons to recommend against the use of ASTM RBCA at Navy facilities. One of the advantages of ASTM RBCA is the perceived time and cost savings associated with its use at petroleum USTs. It may be true that minimal treatment of low risk sites, such as leaking petroleum USTs, could generate cost savings. These benefits of ASTM RBCA are less likely to accrue to the Navy because of the complexity of its hazardous waste sites. Navy sites contain mixtures of such contaminants as fuels, chlorinated solvents, metals, and other organic compounds. Often, neither the quantity nor the type of contamination is known, especially for landfills. The array of potential receptors surrounding naval facilities is particularly broad because of their proximity to coastlines and their location in densely populated areas. Navy facilities are located throughout the country, and are thus subject to oversight by a wide range of regulatory agencies, many of which may have inconsistent requirements for environmental remediation. These complexities make it unlikely that significant time and cost savings would follow implementation of ASTM RBCA. Two other practical considerations are: (1) Federal Facilities Agreements at naval facilities on the National Priorities List would have to be altered to reflect the use of ASTM RBCA. This reopening of a negotiated legal document could delay cleanup efforts and introduce considerable public opposition; and (2) the use of a new methodology will involve retraining personnel. Earlier attempts to

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--> use ASTM RBCA were opposed by some Navy personnel, who described the methodology as too complicated for widespread implementation. However, this challenge will accompany the adoption of any legitimate risk-based approach, not just the ASTM standard guides. Although not necessarily the intention of its authors, it is clear that the ASTM RBCA approach is attractive because it is perceived by responsible parties to be a short cut to cleanup that will lead to faster site closure. This perception is partially due to examples in both ASTM standard guides in which site closure is obtained relatively quickly and with minimal cleanup efforts. Our analysis indicates that most (not all) of the states have developed a short-term view of risk, increasing the possibility that ASTM RBCA might be misinterpreted to allow for premature site closure. The committee is reluctant to advocate fully a risk-based methodology that is perceived as supporting a no-cleanup alternative. A Risk-Based Approach After reviewing the problems in its Environmental Restoration Program, it is clear that the Navy would benefit from a consistent approach to environmental cleanup at all sites across the country. The committee's evaluation of existing risk-based approaches, the type of approach specifically desired by the Navy, did not reveal a methodology the committee could fully endorse for use at Navy facilities. Recognizing the merits of risk-based environmental remediation and a significant increase in its use across the country, the committee recommends that the Navy develop a risk-based methodology for its Environmental Restoration Program that incorporates the following 11 criteria: Prioritization of contaminated sites at individual installations. Provision of a consistent mechanism for addressing all types of sites. Guidance on data collection needed to support the development of site-specific cleanup goals. Integrated assessment of sites across entire installations affecting the same human or ecological receptors. Early action at sites (a) where the risk to human health and the environment is imminent and (b) for which the risks are demonstrably low and remediation is likely to be more rapid and inexpensive. Consideration of relevant uncertainties. Integration of the selection of the remedial option with the establishment of remedial goals. Provision of quantitative tools for developing risk management strategies. Revisiting of sites over the long-term. Implementation in a public setting with all stakeholders involved. Both external, independent scientific peer review and public review for the guidance document.

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--> Compliance with relevant state and federal statutory programs for environmental cleanup. These criteria overcome many of the weaknesses associated with the use of risk-based methodologies. In particular, if a risk-based methodology gives sufficient attention to long-term risks (Criterion 8), the presence of potentially dangerous unidentified compounds and the use of institutional controls become less problematic. Public trust in such an approach is likely to be greater because of the continued involvement of the responsible party in long-term monitoring and enforcement of institutional controls. The development of innovative technologies for removing sources of contamination may still be slowed, but risk-based methodologies have been shown to spur the development of other technologies that accomplish pathway interruption and long-term monitoring. Because of the diversity of Navy facilities and sites within those facilities, the committee suggests developing a broad framework that can be customized for use at individual facilities. A possible starting point for constructing this framework could be the ASTM RBCA methodology, but this is not a requirement. If the ASTM RBCA methodology is used as a guide, care should be taken to avoid the weaknesses currently found in the ASTM standard guides. The framework must be flexible enough to work with existing state and federal environmental statutes. Any risk-based approach must be capable of gaining the approval of the EPA and its state counterparts. To identify weaknesses and make improvements, the committee recommends pilot testing the methodology at one facility before commencing its widespread use. The 11 criteria identified as important for any-risk-based approach to environmental remediation, as well as the problems identified by Navy personnel, point to several avenues for further study. First, the process by which the remedial option is chosen requires significant analysis, explanation, and refinement. One possible study could expand on Criterion 7. The goal of this study would be to develop quantitative analytical tools to assist with remedy selection by evaluating the cost and effectiveness of remedies (including long-term maintenance of engineering and institutional controls). As currently envisioned by the committee, one tool would be based on the paradigm of optimizing risk reduction per dollar spent for a suite of available remedial options. Another important aspect of an effective risk-based approach is its ability to assess risk over the long-term. Improving long-term monitoring at sites in which contamination is left in place will be critical to the use of a risk-based approach. Such monitoring is critical to ensure the effectiveness of chosen remedies and to reduce uncertainty in risk assessment. Techniques that allow for successful, efficient monitoring of the site's responses to natural processes, treatment technologies, containment technologies, and institutional controls should be the focus of such efforts.

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--> Assessing and reducing uncertainties in both risk assessment and risk management should accompany the implementation of a risk-based approach to environmental remediation. Formal considerations of uncertainty must be incorporated into a risk-based methodology in an understandable and convenient way. It will be important for the Navy to develop guidelines aimed at remedial project managers for (1) using more sophisticated analytical techniques during risk assessment, (2) reducing the uncertainty associated with site characterization and treatment technologies, (3) conducting uncertainty analyses when appropriate, and (4) enforcing a wide variety of institutional controls. Success Metrics The committee has observed that on-site project managers in the Environmental Restoration Program often strive to meet vague or inconsistent goals regarding the level of cleanup required to close a site. This is partly because, until recently, few people in management positions in regulated or regulatory agencies had spent much time determining what site completion actually meant. As described in Chapter1 and in Figure 1-3 of this report, the Defense Environment Security Office has recently clarified ''terminology for work after remedial design" (Office of the Deputy Under Secretary of Defense, 1998). This apparently new terminology represents a step forward compared to the vague concepts of "completion" and "close-out." The definition of "response complete" makes it clear that monitoring is often required beyond the operation and maintenance stage. The DOD's recent clarification of site completion milestones is a significant step in the right direction. The committee recommends that the inter-agency task force on site completion (Air Force/Army/Navy/EPA, 1998) reach consensus on processes that use or adapt that terminology. It further recommends that project managers for regulatory agencies and the military be quickly apprised of the terminology and associated goals. As currently employed, the site completion track of the DOD's cleanup program focuses too heavily on site closeout as its metric of success. The committee feels that metrics of success should reflect the characteristics of individual sites. For those sites where closeout may never be feasible because of the type of contaminants present and the ineffectiveness of source removal technologies, the committee recommends that the Navy put more emphasis on "response complete" as the most important metric of success. "Response complete" more adequately addresses progress at sites where contamination remains in place by rewarding the effective operation of the remedial option(s). The military might even consider developing multiple "response complete" milestones or replacing "response complete" with one or more "response taken" milestones. In this way, progress toward long-term monitoring, containment, and enforcement of institutional controls would be considered an achievement, even though additional re-

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--> sponses would still be recognized as necessary. Developing improved metrics of success for sites in which contamination remains in place could go a long way toward increasing the public acceptance of risk-based approaches to environmental remediation. References Air Force/Army/Navy/EPA Working Group. 1998. The Road to Site Close-out (Working Draft). Washington, D.C. Bechtel National, Inc. 1997. Risk-Based Cleanup Index for the Closure of Underground Storage Tanks at Naval Air Station, North Island, San Diego County, California. Bouwer, E. J., and A. J. B. Zehnder. 1993. Bioremediation of Organic Compounds—Putting Microbial Metabolism to Work. Trends Biotechnol. 11:360–367. Department of Defense. 1997. Responsibility for Additional Environmental Cleanup after Transfer of Real Property. Memorandum dated 7/25/97 from R. Noel Longuemare, Acting Under Secretary of Defense, to the Assistant Secretary of the Army, the Assistant Secretary of the Navy, the Assistant Secretary of the Air Force, the Deputy Under Secretary of Defense, (Environmental Security), the Deputy Under Secretary of Defense (Industrial Affairs and Installations), and the Director of the Defense Logistics Agency. Washington, D.C. Department of the Navy. 1998. Department of the Navy Environmental Restoration Plan for Fiscal Years 1998–2002. Chief of Naval Operations, Arlington, Va. Eikenberry, S. 1998. Naval Facilities Engineering Service Center. Personal communication. Environmental Information, Ltd. 1997. Underground Storage Tank Cleanup. Environmental Information Ltd. Minneapolis, Minn. General Accounting Office (GAO). 1998. Superfund: Times to Complete Site Listing and Cleanup. GAO/T-RCED-98-74. National Research Council (NRC). 1994. Alternatives for Ground Water Cleanup. National Academy Press. Washington, D.C. Office of the Deputy Under Secretary of Defense (Environmental Security). March 1998. Management Guidance for the Defense Environmental Restoration Program.