Environmental Cleanup at Navy Facilities: Risk-Based Methods (1999)

Over the past two decades, a massive effort has been under way in the United States to remediate sites at which hazardous materials threaten the environment and human health. Two recent National Research Council reports (NRC, 1994, 1997) have documented the magnitude of the problem by describing the sources of ground water and soil contamination, the number of contaminated sites, and types of contaminants commonly found at these sites. The U.S. Environmental Protection Agency (EPA) currently estimates that 217,000 sites exist where soil and/or ground water may require remediation to overcome the adverse impacts of past military, industrial, agricultural, and commercial operations (EPA, 1997). Cost estimates for hazardous waste site remediation over the coming decades range from $187 billion (EPA, 1997) to as high as $750 billion (Russell et al., 1991), depending on the assumptions made.

The main impetus for remediation of waste sites has been the enactment of federal hazardous waste statutes in the late 1970s and early 1980s. The two most noteworthy, the Resource Conservation and Recovery Act (RCRA) of 1976 (42 USC 6901) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980 (42 USC 9601), set overarching national soil and ground water cleanup policy by prescribing priorities and decision frameworks. The federal laws establish minimum standards, and most states have adopted their own versions of these laws. Thus, the regulations that are used to enforce environmental laws vary from state to state and may be more prescriptive or more stringent than their federal counterparts (for example, the Washington State version of CERCLA, the Model Toxic Control Act of 1989).

The Navy's cleanup mission is enormous in scope (Figure 1-1). As of September 30, 1997, the Navy's Environmental Restoration Program encompassed

Figure 1-1

Department of the Navy sites classified by phase category. "BRAC" refers to the Base Realignment and Closure Act. SOURCE: Department of the Navy, 1998.

4,448 sites at 269 installations throughout 32 states and territories. Of the 4,448 sites, 1,966 sites were in a study phase, 629 sites were being remediated, and 1,853 sites were considered to require no further action. During FY97, the Navy spent a total of $549 million on environmental cleanup activities at its sites.

Of the 4,448 sites identified by the Navy, 998 sites are at facilities slated for closure under the Base Realignment and Closure (BRAC) program. CERCLA requires that the Navy clean up all environmental contamination on property to be transferred to non-federal entities or certify that appropriate remedial actions are in place. There is significant political pressure for property transfer, mainly from the communities in which the bases are located. Community members are eager to maintain the rates of employment that were present during operation of these facilities, while developers and local governments are hoping to capitalize on the large amounts of land that will become available. Cleaning up the closing bases is not only a legal obligation but also a necessity for economic redevelop-

ment of the property. Furthermore, for the sites that have been cleaned up, whether under the BRAC program or at active bases, the Navy faces a major challenge in certifying to regulators, potential purchasers, and lenders that the property is in compliance.

Due to the considerable scientific uncertainties associated with conditions in the subsurface environment, cleanup of contaminated soil and ground water poses a great challenge to the Navy. Remediation of contaminated ground water (which is present at more than 80 percent of Navy sites¹) under CERCLA and RCRA regulations usually means cleanup to maximum contaminant levels (MCLs) when available. Soil cleanup goals are sometimes based on the most restrictive use of the land, such as residential development. However, achieving these standards may not be practical at many locations due to the inherent complexities of the subsurface and the lack of effective treatment technologies. For example, the 1994 NRC report Alternatives for Ground Water Cleanup—the most comprehensive available assessment of ground water remediation—reviewed ground water cleanup systems at 77 sites and determined that regulatory standards had been achieved at only 8 of them. Further, the study found that at 42 of the 77 sites it would be unlikely for regulatory standards to be achieved in the future with conventional technologies. The study provided a matrix for determining the degree of difficulty of cleaning up contaminated ground water based on site hydrogeological conditions and contaminant characteristics. Sites in category 1 are easiest to clean up, while those in category 4 are most difficult.

Navy facilities span the entire range of complexity encountered in ground water and soil cleanup. For example, more than three-quarters of BRAC sites have locations where fuel (petroleum hydrocarbons) has leaked underground. As long as the hydrogeology is relatively simple, these sites belong to categories 1 and 2 in the matrix, which are the easiest to clean up according to Alternatives for Ground Water Cleanup. More than half of the BRAC facilities have some locations that are contaminated with chlorinated solvents, a recalcitrant class of compounds that would automatically place a site under category 3 or 4, indicating a difficult cleanup scenario. It is likely that most Navy facilities will include some contamination that can be cleaned up now with available technologies, but it is also likely that alternative management strategies and remedial technology innovation will be required to address the remaining contamination.

Since the costs of remedial measures required to achieve background or other conservative cleanup levels are high, and in many cases no existing technologies have been proven to achieve these low levels (NRC, 1994), alternative policies are being developed for site cleanup. Remediation policy is shifting toward increased use of risk-based decisions to establish cleanup goals and reduce the

amount of engineering effort required at sites. Short-term monetary cost savings and a swift return of properties to beneficial uses can be gained by using containment, long-term monitoring, and institutional controls to eliminate exposure pathways. This can be attractive when compared to expending huge sums of money on soil and ground water remedial technologies, which often remove only a small fraction of the contamination. However, risk-based approaches may not address harm to the underlying natural resources and may delay actual cleanup, thereby passing the contamination problem on to future landowners. This report evaluates the use of risk-based methodologies for closing waste sites at Navy facilities, recognizing that this approach could result in site management strategies that eventually cause unanticipated harm to human health and the environment.²

The introductory chapter of this report provides a brief overview of the current regulatory framework for environmental remediation, the characteristics of the contamination at Navy sites, and the pressing cleanup challenges facing the Navy. The report reviews and critiques risk-based approaches including EPA policies, American Society for Testing and Materials (ASTM) standard guidelines, and individual state regulations. Uncertainties in source, pathway, and receptor characterization are discussed, as are uncertainties in potential remedial options that are critical components of an effective risk analysis. Finally, the report recommends whether to use a risk-based methodology for cleaning up hazardous waste sites. Although this report centers on the environmental restoration challenges of the Navy, many of the challenges facing other potentially responsible parties are similar, and therefore the findings should also be relevant to a broader universe of sites and facilities.

This report was prepared by the Committee on Environmental Remediation at Naval Facilities, which was appointed by the National Research Council to provide guidance to the Navy on how it should cope with the technical challenges and costs surrounding its Environmental Restoration Program. The committee consisted of 15 members having expertise in environmental engineering, hydrogeology, soil science, geochemistry, ground water modeling, statistical sampling of ground water, toxicology, risk assessment, law, public health, and public participation/stakeholder involvement. Members came from academia, government, and the private sector. The committee met four times over a nine-month period to review technical information and deliberate policy issues. In conducting its study, the committee consulted a variety of stakeholders involved in site remediation, including federal and state regulators, managers of contaminated Navy sites, industry groups, and citizen groups.

Ground water contamination resulting from human activities has been a problem in the United States for the past 150 years. It was not until the early 1970s that this problem gained nationwide attention. A major catalyst for this increased awareness was the relocation of residents living adjacent to 21,800 tons of waste buried in the Love Canal hazardous waste landfill in Niagara Falls, New York. The waste had the potential to adversely affect the health of hundreds of people, including children at a neighborhood school built at the site. As a direct result of Love Canal, Congress passed CERCLA to clean up abandoned hazardous waste sites across the country. With CERCLA, Congress appropriated $1.6 billion to the cleanup, a sum that gave the law its famous nickname—Superfund. RCRA had been previously passed to prevent shoddy waste disposal practices, and in 1984 it was expanded to include corrective action as well.

Since the passage of these federal laws, environmental remediation of hazardous waste has undergone numerous changes in terms of the goals and expectations of these activities. The philosophy underlying both CERCLA and RCRA was in the tradition of resource conservation, which dictates that sites affected by anthropogenic wastes should be cleaned up to their original pristine condition. This concept, which places inherent value in the soil and ground water, strives for complete cleanup of the resource because it enables unrestricted use of the resource. The motivation for enacting RCRA and CERCLA was not strictly limited to the concept of resource conservation. It also emanated strongly from the risks to human health posed by environmental contamination. However, in the late 1970s and early 1980s, a formal distinction between resource conservation and risk was not made, as it was assumed that any degradation of the environment entailed risk.

RCRA and CERCLA outlined legal frameworks for identifying contaminated sites, assessing the liability associated with the sites, and cleaning them up. It soon became clear that cleanup would be a difficult undertaking. In 1980, there was virtually no proven technology available to clean up contaminated soils and ground water in situ. This problem was compounded by the thousands of sites requiring remediation. Although considerable progress has been made in the last 20 years, there are still many contaminated sites for which no technologies can achieve complete removal of contaminants. (For extensive reviews of the present capabilities of cleanup technologies for soil and ground water contamination, see NRC, 1994, 1997.)

In addition to technical limitations, significant fiscal limitations to the complete removal of contamination have become apparent. Depending on the amount of contamination and the type of affected media, cleanup activities at individual hazardous waste sites can range from several thousand dollars to tens of millions of dollars for the more recalcitrant contaminants in unfavorable hydrogeologic settings. During the 1980s, these fiscal limitations received considerable atten-

tion, and distinctions between resource conservation and other types of cleanup goals became a topic for public debate.

What has evolved in response to such concerns is a broad range of cleanup goals, from resource conservation to technology-based goals to goals based on the immediate risk to humans and the environment ("risk-based" goals). As shown in Figure 1-2, the choice of a cleanup goal determines whether reuse of the resource is more or less restricted. The goal of resource conservation is to return sites to unrestricted uses. Other cleanup goals, such as technology-based goals or risk-based goals, may result in more restricted uses of the land following such remedial activities as partial cleanup and containment.

Risk-based approaches to cleanup, as defined by the committee, view environmental contamination solely in terms of human health and ecological risk. Depending on the apparent risk, such an approach may lead to full-scale remedial activities (such as complete removal of the contaminant source), or it may lead to limited actions (such as containment measures). The distinguishing factor between this and other approaches is that risk-based approaches are more likely than technology-based approaches and resource conservation to result in remedies that leave contamination in place. Thus, risk-based approaches do not place inherent value in soil and ground water resources, unless human or ecological health is directly threatened by contamination of those resources.

For responsible parties such as the Navy, regulatory agencies, and the public, the decision of which environmental approach to embrace must take technical, fiscal, and social issues under consideration. For example, if resource conservation and unrestricted use is the goal, then environmental contamination will be cleaned up regardless of present or projected health risks to humans or wildlife. This can involve large capital costs associated with cleaning up environmental contamination, as well as non-monetary costs if, for example, cleanup activities

Figure 1-2

The range of possible ground water cleanup goals and the associated uses of the resource.

lead to the destruction of wildlife habitat. On the other hand, adopting a risk-based approach is more likely to result in some contamination being left in place, which may restrict future use of the resource. There may be fewer direct monetary costs associated with this approach, but there are other significant costs associated with the monetary value of the contaminated natural resources, with increased long-term monitoring efforts, and with potential future exposure to contamination and associated personal injury or property damage. Approaches that take multiple viewpoints into account are also foreseeable. One such approach might focus on maximizing the health benefits of dollars available for environmental remediation (risk-based approach) while minimizing the loss of natural resources (resource-conservation approach).

The technical and fiscal limitations of hazardous waste cleanup have led to a general shift away from resource conservation toward the use of risk-based approaches for prioritizing cleanup operations. Perhaps the best example to date of ranking hazardous waste problems based on risk has to do with the cleanup of underground storage tanks (USTs) of fuel. In the 1980s, many states took on significant environmental liability by committing themselves to remediating leaking USTs with funds from gasoline taxes. Since that time, the number of USTs has increased relative to the resources available for cleanup, compelling the states to informally prioritize their UST cases (EPA, 1995). Because USTs are regulated under RCRA-UST, which does not specify national cleanup levels or administrative procedures, the states have developed cleanup goals and procedures for leaking USTs that can vary tremendously. This inconsistency in cleanup goals among the state programs was recognized by the ASTM, which formed a committee to develop a standardized method for assessing the risk of petroleum hydrocarbons that could be customized and used by all states.

Much of the impetus for adoption of a uniform standard regarding cleanup of USTs came from potentially responsible parties that faced liabilities under both CERCLA and RCRA, including the states and the petroleum industry. These groups clearly saw that by transferring emphasis from resource conservation to human risk, it was possible to decrease their overall liability. The state UST programs and the petroleum industry, therefore, had similar interests in developing risk-based approaches for petroleum hydrocarbon contamination, and much of the technical input to the ASTM RBCA standard guide came from these organizations.

At the present time, many states have formally adopted a risk-based approach for managing soil and ground water contaminated with petroleum hydrocarbons. As discussed in Chapter 2, there is a trend toward adopting a risk-based approach for other environmental contaminants (such as chlorinated solvents, industrial chemicals, pesticides, and metals). The degree to which RBCA can be applied to non-petroleum hydrocarbons has not yet been established. In light of the recent creation of the ASTM RBCA standard guide and its rapid adoption by many

states, the Navy requested that the NRC evaluate its use for cleaning up contamination at naval facilities.

In 1986, the Superfund Amendments and Reauthorization Act (SARA, PL 99-499) brought all military facilities under the authority of the Superfund Program. From that point on, the Navy's environmental cleanup occurred as part of the Environmental Restoration Program. Cleanup activities under the Environmental Restoration Program are dictated by a variety of regulatory programs, with most following CERCLA guidelines (Department of the Navy, 1998). At some individual sites, the military uses RCRA guidelines for cleanup rather than CERCLA. If the major contaminants at a site are exclusively petroleum hydrocarbons, RCRA-UST is the primary regulation followed. Both RCRA and RCRA-UST have milestones and terminology that are similar to CERCLA milestones and terminology.

The most contaminated military facilities in the country are on the National Priorities List (NPL). At these facilities, the Department of Defense (DOD) negotiates a Federal Facilities Agreement (FFA) with the EPA and its state counterpart to define roles and responsibilities, establish a mechanism for dispute resolution, and set cleanup milestones, thereby establishing clear EPA enforcement authority. A certain subset of military bases have been slated for closure under BRAC, with the goal of returning the land to the private sector. For BRAC facilities on the NPL, both cleanup and land transfer are supervised by the EPA.

When a military facility is not on the NPL, the EPA no longer has regulatory authority over the cleanup process (although the DOD almost always follows CERCLA guidelines when designing and implementing cleanup [Department of the Navy, 1998]). In these cases, most states sign statewide Defense State Memoranda of Agreement (DSMOA), which are similar to FFAs but contain no project milestones. Thus, enforcement under DSMOAs can be relaxed compared to enforcement under FFAs. (For example, in the San Francisco Bay area, regulators have less leverage at non-NPL bases, such as the Alameda Naval Air Station, than at NPL-listed Moffett Naval Air Station, because there is no FFA defining enforceable milestones at Alameda.) However, at BRAC facilities not on the NPL, the EPA is involved in the transfer process as dictated under CERCLA Section 120. Thus, unlike at other non-NPL facilities, the EPA has regulatory authority at non-NPL BRAC facilities, along with state environmental regulators.

It is evident from the above that the Navy operates its Environmental Restoration Program in a complex regulatory environment. Depending on the level of

contamination, the type of contamination, and whether a facility is active or closing, a variety of federal, state, and regional authorities play a role in ensuring compliance from the Navy.

The phases of environmental cleanup are essentially the same under the CERCLA, RCRA, and RCRA-UST scenarios. The first phase of the cleanup is called the preliminary assessment/site inspection (PA/SI). It involves identification of problem areas and review of existing site characterization data. Based on the information from the PA/SI, the property receives an initial ranking based on the degree of hazard presented using the Hazard Ranking System (HRS) (Federal Register, 1990). If the property receives a score of 28.5 or greater, usually the entire facility is placed on the NPL.

If the site inspection reveals contamination at the facility, a more detailed remedial investigation (RI) is conducted for one or more sites. The RI typically involves the installation of ground-water monitoring wells and/or soil sampling to identify the degree and scope of contamination. Current EPA guidance requires that a human health risk assessment and an ecological risk assessment be conducted, which, at the majority of sites, involves a quantitative assessment. Information from the remedial investigation is used to conduct a feasibility study (FS) to determine what the ultimate remedy should be to address the contamination. The factors that must be evaluated when choosing a remedy are discussed in the National Contingency Plan (NCP) (40 CFR 300). The chosen remedy is supported by a record of decision (ROD) for NPL sites or a decision document for non-NPL sites.

Once the ROD is approved, implementation of the remedy (or cleanup) begins. During remedial design (RD), technical specifications are prepared. This is followed by remedial action (RA), during which construction, operation, and implementation of the final remedy occur. Further guidance on remedial action has recently been provided by DOD management (Office of the Deputy Under Secretary of Defense, 1998) to clarify ''terminology for work after remedial design," as illustrated in Figure 1-3. Remedial action-construction (RA-C) is the period during which the final remedy is put in place. The end date signifies that the construction is complete, all testing has been accomplished, and the remedy will function properly. The phase remedial action-operations (RA-O) is the period during which the remedy is in place (RIP) and is operating to achieve the cleanup objective identified in the ROD or equivalent agreement. Response complete (RC) signifies that the remedy is in place and the required RA-O phase has been completed. If there is no RA-O phase, then the RA-C end date will also be the RC date.

Response complete does not necessarily mean that the contamination has been eliminated. When contamination is left in place, long-term monitoring and

Figure 1-3

Milestones of the Defense Environmental Restoration Program. SOURCE: Office of the Deputy Under Secretary of Defense (Environmental Security), 1998.

institutional controls may be required. Under CERCLA, where significant contamination is left in place that has the potential to cause a risk to human health and the environment, five-year reviews are typically required along with continued monitoring. Similarly, under RCRA, post-closure care is required, which usually lasts for a minimum of 30 years where significant ground water contamination is involved. The subsequent monitoring that is required beyond "response complete" is termed long-term monitoring (LTM). LTM is reserved for monitoring once a site is "response complete," and should not be used to refer to monitoring after "remedy in place." After LTM demonstrates that the site no longer poses a significant risk to human health and the environment, the site can be closed.³ Site closeout relieves the potentially responsible party of any further remedial activity at the site.⁴

Environmental cleanup at BRAC facilities follows the same time line outlined above, except that the ultimate goal is transfer of the facility to local governments, the private sector, or other federal agencies. The BRAC base closure process requires the DOD to close military facilities within a specified time frame

but not necessarily to transfer the land within that time frame. BRAC facilities do not have to reach site closeout prior to the time the bases are closed or transferred. They are only required to reach RIP and RA-O at the time of transfer to non-federal ownership. The entire facility does not have to achieve RIP; the transfer of certain parcels that have achieved RIP is allowed.

There are several success measures for BRAC and non-BRAC facilities used under the Environmental Restoration Program. The 1998 Defense Management Guidance lists both RC and RIP as measures of merit for both sites and entire facilities. The July 1997 Defense Planning Guidance Goals (FY 1999–2003) for BRAC facilities also target RIP and RC, stating that 75 percent of installations and 90 percent of all sites "will have remedial systems in place or responses complete" by the end of FY 2001. From the committee's experience, Navy managers also perceive site closeout to be an important metric of success.

Another important metric for active bases and former defense sites is risk reduction (Office of the Deputy Under Secretary of Defense, 1998). This refers specifically to the priority-setting process "Relative Risk Site Evaluation Framework" (Anderson and Bowes, 1997) that allocates funding in the Environmental Restoration Program. This framework qualitatively ranks sites according to risk by grouping sites into high, medium, and low risk categories. Information on contaminant sources, exposure pathways, and human and ecological receptors is used to assign sites to categories. Risk reduction is measured when sites are moved from the high or medium risk categories to lower categories. This framework is only used to request and allocate DOD cleanup funds and does not play a role in the CERCLA decision-making process.

The risk-reduction metric fits well with the stated goals of the Environmental Restoration Program. However, it is not clear whether this simple evaluation method, which was designed to hold down assessment costs and time and encouraging the understanding (and support) of external stakeholders, is precise enough to serve this purpose.

Navy project managers report another metric that they say comes from regulatory agencies—the signing of the ROD or other decision document formalizing the remedy for an operable unit. This apparently is not a formal metric but rather the culmination of the study process and a key milestone in most Federal Facility Agreements.

Contaminant distributions at naval facilities are complex and varied. Of the 4,448 individual sites listed in the Environmental Restoration Program, 857 are

classified as RCRA sites, 751 as UST sites, and 2,840 as CERCLA sites. It is important to note that under Navy terminology, an individual UST site can contain more than one underground storage tank. In addition, the total volume of an individual tank may exceed one million gallons.

Navy facilities span a broad spectrum of land use ranging from rural residential to urban residential, transportation support, and heavy industry. This varied land use has resulted in a complex and diverse set of contamination events and sources. In many cases, Navy facilities represent intact communities providing full residential, recreational, and urban services to their occupants. Virtually all types of contamination associated with urban centers can be found at Navy installations. These include such sources of soil and water contamination as municipal solid waste landfills, wastewater treatment plants, and underground storage tanks for automobile and truck fuels. Additional contamination can be associated with larger scale transportation activities, such as the transport and storage of marine and aviation fuels. Industrial activities (e.g., aircraft and ship maintenance) release waste solvents and heavy metals and often result in the creation of "industrial" solid waste landfills. Contamination at many Navy facilities can result from personnel training activities (e.g., "fire pits," where fire fighting techniques have been practiced, and target ranges). Finally, contamination can emanate from golf courses and other recreational facilities, as well as landscape maintenance at Navy complexes.

With such diverse activities giving rise to contamination at naval facilities, the array of contaminant types is extremely large, ranging from fuels and solvents to metals, pesticides, and household cleaners.⁵ Although contaminant mass and concentration data for individual waste sites are collected at each Navy facility, there is no central compilation of comprehensive data. In an attempt to provide some overview of contaminant distributions, information compiled from the Navy is presented in Table 1-1. These data represent all hazardous waste sites in the United States and its territories, as reported by the Navy.

Organic contaminants are the most common contaminants found at Navy facilities. Petroleum, oil, and lubricants (POLs) and hydrophobic organic contaminants (HOCs) exist at over half of all installations, and pesticides are found at almost one quarter. Metals are also frequent contaminants. In most cases, multiple contaminants are present. It is not possible to determine from readily available data if the contaminants exist as mixed wastes or if they are present at separate sites in a given installation.

To gain some idea about the magnitude of contamination at Naval facilities, the committee studied maximum concentration data from seven sites across the

country. Characterization of these sites cannot go beyond the most general terms because of the wide range of contaminants and reported concentrations. Similar to the data found in Table 1-1, these sites contain predominantly POL-related contaminants, halogenated organic compounds, pesticides, and heavy metals, with the greatest total mass of contaminants probably being POLs.

The characteristics of a particular Navy facility, the North Island Naval Air Station in San Diego, California, are given in Box 1-1. The wide variety of contaminants, the unique hydrogeologic conditions, and the many regulatory authorities present at North Island demonstrate the highly variable environment in which cleanup takes place.

Like other responsible parties, the Navy is faced with environmental cleanup responsibilities that take time, resources, and attention away from its principal mission. Many top decision makers view cleanup as a discretionary expense that

competes with readiness, modernization, and other military goals at a time when overall budgets are declining. The Navy is seeking ways to reduce the financial dimension of that obligation without increasing measurable risk to human or ecological receptors.

At closing bases, the Navy is also subject to political pressure to prepare property for transfer in a much more timely fashion, though state and local stakeholders often differ among themselves over whether to emphasize stringency of cleanup or timeliness of reuse. At closing bases, there is often tension over the level of cleanup, with the Navy urging limits on reuse as a way to cut cleanup costs, and the recipients, who do not pay for cleanup, wanting more stringent cleanup goals to enable greater flexibility in future use. Closures typically force the Navy to spend more money, or at least to expend funds faster, than at comparable active bases.

An interesting feature of the Navy's cleanup costs common to many multisite facilities is that the cleanup budget is disproportionately allocated to the most contaminated sites. According to data provided by Navy personnel, 59 percent of sites undergoing the Relative Risk Site Evaluation were ranked as high risk.⁶ However, the cost of cleanup at these sites comprised 81 percent of the total cleanup cost. Low risk sites, on the other hand, comprised 25 percent of the sites but only 8 percent of the cost. This distribution of costs among Navy sites, which was expected and is appropriate, suggests that management and response at high risk sites is critical for controlling overall cleanup costs. The Navy has not completed an analysis of how cost estimates might vary if alternative remediation strategies for high risk sites were employed.

Like other responsible parties with broad national exposure, the Navy seeks standardized treatment from regulatory agencies. Each of the states (and recognized Indian tribes) have both sovereign and delegated authority to develop and enforce their own hazardous waste regulations. Some areas of the country are more sensitive to environmental issues than others. Some areas are more dependent on ground water, or have scarcer water supplies, than others. Some areas are willing to relax environmental standards to achieve other goals, such as job creation. It is, therefore, unrealistic to expect a unitary national regulatory framework, but it is possible to standardize terminology and process.

The Navy has made progress in this area. Compared to the other armed services, the Navy is concentrated in a relatively small number of states. This has made it possible to establish interstate regulatory cooperation, such as the efforts

of the Naval Facilities Engineering Command Southwest Division to set priorities for projects among states. Furthermore, in many communities the Navy has been successful in establishing Restoration Advisory Boards (RABs), which facilitate the consideration of diverse local concerns at bases undergoing cleanup. In general, these efforts have made cleanup operations more consistent across regions.

North Island contains one CERCLA site, 17 RCRA corrective action sites, and 3 RCRA underground storage tank sites (which include 190 individual USTs). These contain a range of heavy metals (As, Cr, Cu and Pb), PCBs, and volatile and semi-volatile organic compounds. Because the facility is mainly used for maintenance and repair of aircraft, a large proportion of the waste includes jet fuels and solvents. Most of the sites at North Island have been evaluated with the Navy's Relative Risk Site Evaluation model, indicating 10 high risk sites, 5 medium risk sites, and 4 low risk sites. Remedial activities mainly consist of studies, with only 9% of all sites response complete and 18% undergoing active cleanup. SOURCE: Department of the Navy, 1998.

The Navy's concentration in port cities creates more demands on its cleanup programs than on those of the other armed services. Naval bases have released contaminants into terrestrial, freshwater, estuarine, and marine environments that historically provide food for human consumption. Because contamination has occurred across this broad spectrum of environmental compartments, the need for and complexity of ecological risk assessments is great. Such ecological risk assessments must give consideration to a wide range of transport mechanisms and biological receptors.

Naval aircraft carrier U.S.S. Carl Vinson passing the battleship Missouri. Naval shipyards are often located in areas with multiple human and ecological receptors.

Courtesy of the U.S. Navy.

Many closing Navy bases comprise valuable waterfront real estate. Potential future users, including developers of housing and other uses calling for high levels of cleanup, are eager to obtain the property. On the other hand, many Navy bases have released contaminants into aquifers that are nonpotable because of saltwater intrusion, reducing demands for remedial action.

As previously noted, the primary contaminants found at Navy facilities, in terms of the overall numbers of affected sites, are petroleum products, oils, and lubricants (POLs). However, almost all naval facilities are also significantly contaminated with other organic contaminants, such as chlorinated solvents, heavy metals, and pesticides, that have different mobility and extremely long environmental half-lives in terrestrial, aquatic, and marine media (Department of the Navy, 1998). Treatment and removal of these compounds is far more problematic, and in some instances, no available technology is capable of reducing contaminant levels to meet health-based standards. In cases where the technology is available, it is sometimes costly to implement. Consequently, the types of con-

tamination found at naval facilities present both technological and fiscal challenges that the Navy must address.

In addition to the recalcitrance of many chemicals found at Navy facilities, a single waste site may contain a mixture of contaminants that interact in unknown ways with each other and with potential human and ecological receptors. The Navy must have some mechanism for assessing the cumulative risk posed by multiple chemicals present at individual sites. Finally, large numbers of sites present at a single facility greatly increase the complexity of interactions that are possible between potential sources and human and ecological receptors. A facility-wide assessment of risk must be able to integrate the effects of multiple individual waste sites.

The DOD's plan to close additional bases early in the next century presents a final dilemma. Most remedial decisions at bases undergoing closure over the past decade have been made with knowledge that the base was closing and sometimes with reuse plans in place. The new closures, however, will take place at bases where remedies may have been chosen without knowledge that the base was closing. Transferees may insist that many cleanup agreements be reconsidered to accommodate potential changes in land use. Similar changes in land use may also occur at bases that remain active, as the Navy modifies its uses of major parcels of property to meet its evolving requirements.

In all cases where contamination remains in place after remedial actions are complete, there is tension over the permanence of the response. Any effort to base cleanup standards on risk, as measured today, must take into account this long-term uncertainty. The CERCLA cleanup process is sufficiently flexible to allow for the integration of information over time. In practice, however, remedial options tend to be permanent because site managers are influenced by pressures to clean up as quickly and inexpensively as possible. Greater discussion of long-term considerations during risk-based cleanup and the DOD's current obligations at closing facilities is found in Chapter 5.

In closing, multiple parties are urging the Navy to reduce the costs of its Environmental Restoration Program, while others insist that the program maintain adequate protection of human health and the environment. These factors, combined with the recent popularity of the ASTM Risk-Based Corrective Action standard guide for Petroleum Release Sites, have led the Navy to consider implementing a new risk-based methodology for cleanup of all their hazardous waste sites. As this report will demonstrate, risk-based methodologies have strengths and weaknesses that restrict their implementation at complex sites. This report reviews existing risk-based methodologies, describes their strengths and weaknesses, and makes recommendations to the Navy for their use in certain circumstances.

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