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Introduction: DOE's Groundwater and Soil Contamination Problem

The Department of Energy (DOE) faces monumental challenges in restoring the environment at installations that were part of the U.S. nuclear weapons production complex. Cleaning up these installations is the most costly environmental restoration project in U.S. history (Harden, 1996). DOE has spent between $5.6 billion and $7.2 billion per year on environmental management over the past several years for decontamination and decommissioning of nuclear reactors and other facilities, characterization of the types and locations of contaminants in the environment, and stabilization or removal of contaminants (GAO, 1997; Betts, 1998). The department projects that environmental management activities between now and 2070 will cost a total of $147.3 billion in 1998 dollars (DOE, 1998).

One important component of DOE's environmental management problem is the cleanup of groundwater and soil that were contaminated as a result of the range of activities associated with nuclear weapons production. Plumes of contaminated groundwater totaling an estimated 1.8 × 109 m3 are migrating beneath DOE facilities, and an estimated 75 × 106 m3 of soil are contaminated (DOE, 1997). DOE estimates that remediation of these resources will cost more than $15 billion in 1998 dollars (DOE, 1998).

Despite the large amount invested in DOE environmental management, progress on groundwater and soil remediation has been slow. Cleanup of most groundwater and soil contamination sites is in the early stages (EPA, 1997). Nontechnical factors—including management problems, inadequate incentives for DOE contractors, and regulatory obstacles—have contributed to the slow pace of ground-



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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants 1 Introduction: DOE's Groundwater and Soil Contamination Problem The Department of Energy (DOE) faces monumental challenges in restoring the environment at installations that were part of the U.S. nuclear weapons production complex. Cleaning up these installations is the most costly environmental restoration project in U.S. history (Harden, 1996). DOE has spent between $5.6 billion and $7.2 billion per year on environmental management over the past several years for decontamination and decommissioning of nuclear reactors and other facilities, characterization of the types and locations of contaminants in the environment, and stabilization or removal of contaminants (GAO, 1997; Betts, 1998). The department projects that environmental management activities between now and 2070 will cost a total of $147.3 billion in 1998 dollars (DOE, 1998). One important component of DOE's environmental management problem is the cleanup of groundwater and soil that were contaminated as a result of the range of activities associated with nuclear weapons production. Plumes of contaminated groundwater totaling an estimated 1.8 × 109 m3 are migrating beneath DOE facilities, and an estimated 75 × 106 m3 of soil are contaminated (DOE, 1997). DOE estimates that remediation of these resources will cost more than $15 billion in 1998 dollars (DOE, 1998). Despite the large amount invested in DOE environmental management, progress on groundwater and soil remediation has been slow. Cleanup of most groundwater and soil contamination sites is in the early stages (EPA, 1997). Nontechnical factors—including management problems, inadequate incentives for DOE contractors, and regulatory obstacles—have contributed to the slow pace of ground-

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants water and soil cleanup at DOE sites and are reviewed briefly in Chapter 5 of this report. However, technical problems also have limited DOE's progress and are the principal focus of this report. Technologies for remedying many of the types of soil and groundwater contamination problems found at DOE facilities are in the early stages of development. This report focuses on three key categories of contaminants commonly found in soil and groundwater at DOE installations: (1) metals, (2) radionuclides, and (3) dense nonaqueous-phase liquids (DNAPLs), which are oily liquids that are denser than water. The report evaluates the technical options available for cleaning up these classes of contaminants. It also assesses DOE's programs for developing new remediation technologies to address these problems. Although the recommendations in the report are designed for DOE, the bulk of the information will be useful well beyond DOE. DNAPLs and metals are common contaminant classes at all contaminated sites, not just those owned by DOE. This report was prepared by the National Research Council's (NRC's) Committee on Technologies for Cleanup of Subsurface Contaminants in the DOE Weapons Complex. The NRC appointed the committee in 1997 at the request of DOE to review technologies for characterizing, containing, and cleaning up metals, radionuclides, and DNAPLs in groundwater and soil. The committee included experts in hydrogeology, environmental engineering, geochemistry, soil science, and public health from academia, consulting firms, private industries, and public interest groups. During the course of its two-year study, the committee met six times to gather information and prepare this report. The committee also visited cleanup managers at three DOE installations: Lawrence Livermore National Laboratory in Livermore, California; the Savannah River Site in Aiken, South Carolina; and the Hanford Site in Richland, Washington. The committee's conclusions are based on a review of relevant technical literature; the expertise of committee members; and briefings to the committee by DOE managers, site cleanup contractors, Environmental Protection Agency (EPA) staff, and experts in site cleanup technologies from academia, federal laboratories, consulting firms, and industries. DOE asked the committee to address five specific tasks: identify and evaluate the complexity of subsurface conditions and contamination, focusing on metals, radionuclides, and DNAPLs, at selected DOE sites with geologic and hydrologic conditions that are representative of other sites across the weapons complex; review and assess current EPA metal, radionuclide, and DNAPL

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants remediation guidelines, including risk-based end points, in reference to assessment of developing technologies; review and assess developing technologies for application to characterization, containment, and cleanup of subsurface metal, radionuclide, and DNAPL contamination; describe areas of uncertainty in the identified technologies; and provide recommendations, as appropriate, on applications of subsurface remediation technologies for metals, radionuclides, and DNAPLs. In addition to these tasks, which primarily involve a technical evaluation of remediation technologies and the performance standards they must meet, the committee conducted a limited review of DOE's program for developing new subsurface remediation technologies. This program is critical for ensuring that effective technologies are in the pipeline for addressing DOE groundwater and soil contamination problems that existing technologies cannot resolve. This chapter outlines the magnitude of the groundwater and soil contamination problem at DOE facilities and briefly describes risks posed by this contamination, as currently understood. Understanding the nature of the problem is the first step in developing solutions; thus, this chapter provides an important context for understanding the technical evaluations in the later chapters of the report. Chapter 2 reviews the required cleanup goals for ground-water and soil contamination at DOE installations. Understanding these goals is important because they determine the performance standards, or ''end states,'' that remediation technologies must achieve. Chapters 3 and 4 provide the bulk of the technical review in this report. Chapter 3 assesses the availability of technologies for characterization, remediation, and containment of radionuclides and metals in the subsurface, and Chapter 4 provides a similar assessment for DNAPLs. Chapter 5 evaluates the success of DOE's efforts to develop and deploy new technologies for metal, radionuclide, and DNAPL remediation and recommends future directions for DOE work in this area. Chapter 6 recommends strategies to improve DOE's program for developing groundwater and soil remediation technologies. LIMITATIONS OF CONVENTIONAL GROUNDWATER AND SOIL CLEANUP TECHNOLOGIES The limitations of conventional technologies for cleaning up contaminated groundwater and soil, whether at DOE installations or else-

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants where, are now widely known among those involved in environmental restoration (NRC, 1994, 1997). The conventional method for cleaning up contaminated ground-water is called "pumping and treating." Pump-and-treat systems operate by pumping large amounts of contaminated water from the subsurface via a series of wells, treating the water at the surface to remove contaminants, and then either reinjecting the water underground through a second set of wells or disposing of the water off-site. At large contaminated sites being cleaned up under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as "Superfund"), this is still the predominant remedy, being used as the sole cleanup technology at 89 percent of sites with groundwater contamination (EPA, 1998). However, as has now been widely documented, these systems are often ineffective in restoring contaminated groundwater to regulatory standards because the flushing action created by pump-and-treat systems often is not sufficient to dislodge all of the contamination from the subsurface (NRC, 1994; MacDonald and Kavanaugh, 1994). Contaminants may diffuse into inaccessible regions of the subsurface or adhere to sub-surface geologic materials. Small globules of DNAPL contaminants may become entrapped in the porous materials of the subsurface. The physical heterogeneity of the subsurface and the difficulties in characterizing this heterogeneity complicate delivery of treatment fluids to contaminated areas. All of these factors limit the ability to remove contaminants from the subsurface with pump-and-treat systems. In a 1994 review of pump-and-treat systems at 77 sites, the NRC found that cleanup goals had been achieved at 8 of the sites and were highly unlikely to be achieved at 34 of them (NRC, 1994). As discussed in more detail in Chapter 5, pump-and-treat systems, despite their limitations, are the predominant remedy at DOE sites where active cleanup is under way under the CERCLA program. Without the development of new technologies, then, it is highly unlikely that DOE cleanups will achieve regulatory standards for contaminated groundwater. The conventional method for cleaning up contaminated soil is to excavate the soil and then either treat it to remove the contaminants or dispose of it in a specially designed landfill. Often, the treatment involves incineration. Although excavation removes contamination from the area of interest, there are major problems with the method. First, excavation can temporarily increase the risk of human exposure to contamination, both for site workers and for nearby residents who may be exposed to fugitive dusts. Second, excavation destroys the native ecosystem. Plants may be unable to grow unless new topsoil is added to the site after excavation. Third, treatment of

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants excavated soil often involves incineration, and the public often objects to incineration because of the perceived potential for release of hazardous air pollutants when the soil is combusted (NRC, 1997). Fourth, digging up and disposing of tons of soil can be costly at sites where excavation is difficult, off-gas treatment is required, special health and safety measures are needed to protect workers, or the soil requires special disposal. As described in Chapter 5, excavation is the leading remedy being used to clean up soil at DOE's CERCLA sites. Development of new technologies could significantly reduce DOE's soil cleanup expenses and help to avoid problems associated with the destruction of native ecosystems and incineration. DOE'S PROGRAM FOR DEVELOPING GROUNDWATER AND SOIL CLEANUP TECHNOLOGIES DOE's Office of Environmental Management, which is responsible for overseeing cleanup at all of the department's contaminated installations, has long recognized the limitations of conventional technologies for cleaning up contaminated groundwater and soil, as well as for addressing other environmental concerns at DOE sites. Recognizing these technological limitations, the Office of Environmental Management in 1989 established the Office of Technology Development to develop technologies for DOE contamination problems for which good technical solutions are lacking. This office was later renamed the Office of Science and Technology (OST) and given expanded responsibilities. As the unique challenges posed by ground-water and soil cleanup became apparent, OST established a division devoted solely to the development of groundwater and soil cleanup technology. This division is now known as the Subsurface Contaminants Focus Area (SCFA). Because SCFA is the only unit within DOE with the primary mission of developing better solutions for contaminated groundwater and soil, the technical assessments and recommendations in this report are particularly relevant to SCFA. SCFA prioritizes and provides funding for technology development efforts concerning containment of buried wastes and remediation of groundwater and soil contamination. DOE's Savannah River Site in Aiken, South Carolina, is responsible for administering the SCFA program. SCFA groups its technology development projects into four categories, known as "product lines": (1) source-term containment, (2) DNAPL remediation, (3) source-term remediation, and (4) metals and radionuclides. (A listing of projects currently funded under these product lines can be found at http://www.envnet.org/scfa.) SCFA's budget has been cut in recent years, reflecting congres-

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Figure 1-1 The SCFA budget over time. Source: Budget data provided by SCFA. sional dissatisfaction with the OST program as a whole (described in detail in Chapter 5). Congress cut the OST budget from a high of $410 million in 1995 to $274 million in 1998. SCFA's budget was cut from a high of $82.1 million in 1994 to a level of $14.7 million in fiscal year 1998 (see Figure 1-1). Congress earmarked $5 million of the $14.7 million appropriated in 1998, effectively leaving SCFA with a budget of $9.7 million. The earmarked funds were directed to the Western Energy Technology Center in Butte, Montana. In the field of hazardous waste site cleanup, SCFA's 1998 budget of $9.7 million is a very small amount. Cleanup of a single private-sector CERCLA site costs an average of $24.7 million (CBO, 1994). Recent DOE cost projections have estimated that between 1997 and 2070, the department will spend $15 billion on cleanup of contaminant "release sites" (areas where contaminants were released and subsequently infiltrated soil and, often, groundwater) (DOE, 1998). This amount converts to annual expenses of approximately $770 mil-

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants lion, when a discount rate of 5 percent is assumed. SCFA's 1998 budget represents about 1 percent of this spending. In fiscal year 1999, SCFA's budget was boosted to $25 million, but this is still a relatively small amount compared to the average cost of cleaning up a site. Further, the large budget swings have interfered with program planning. DIMENSIONS OF DOE'S SUBSURFACE CONTAMINATION PROBLEM Understanding the locations, types, and risks of contaminants present in the DOE weapons complex is the first step in determining remediation technology development needs. Whether a given process will be effective in cleaning up subsurface contamination at a specific site depends on the hydrogeology of the site, the characteristics of the contaminants, and the acceptable risk levels for the site. As described below, DOE's information on these dimensions of its subsurface contamination problems is incomplete. Locations of DOE Facilities Figure 1-2 shows the locations of DOE installations and other facilities at which DOE is responsible for environmental cleanup. Appendix A lists these facilities and their roles in nuclear weapons production. In total, DOE is charged with cleanup of 113 installations in 30 states (Probst and McGovern, 1998). DOE has identified approximately 10,000 individual contaminated sites within these facilities; continuing investigations may reveal further contamination (EPA, 1997). Five of the installations shown on Figure 1-2 account for the majority (64 percent) of DOE's total projected costs for cleanup (EPA, 1997). These installations are the Rocky Flats Environmental Technology Site, the Idaho National Engineering and Environmental Laboratory, the Savannah River Site, the Oak Ridge Reservation, and the Hanford Site. These five facilities were essentially massive factories involved in nearly every phase of nuclear weapons production, from nuclear materials processing to weapons assembly (CERE, 1995). Table 1-1 shows the estimated volume of groundwater, soil, and sediment contamination at these major facilities. (These estimates are likely to change as DOE continues work to characterize its contaminated sites.) Box 1-1 describes the activities that led to environmental contamination at DOE installations. In addition to cleaning up these major installations, DOE is responsible for cleaning up a large number of other facilities—some

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Figure 1-2 Contaminated facilities in the DOE complex. Source: DOE, 1997. owned by DOE and some not—that played smaller roles in the nuclear weapons production process. These other facilities include key DOE research laboratories, such as Los Alamos and Lawrence Livermore, and also a number of smaller operations that at one time or another were used for the processing of nuclear weapons materials. Twenty-four of the installations are former uranium processing facilities where DOE is cleaning up mine tailings and residual groundwater and soil contamination; these operations are part of what is known as the Uranium Mill Tailings Remediation Control Act (UMTRCA) project (EPA, 1997).

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants The geologic settings of contaminated sites in the DOE complex are highly variable. DOE installations are located in all major geographic regions of the United States. Table 1-2 shows the geologic and climatologic variability at several of the larger DOE facilities. Site geology, including characteristics of the geologic medium and depth to groundwater, is important for two reasons. First, site geology affects travel times and pathways for contaminant migration in the subsurface. Second, it can be the key factor in determining the performance of a technology designed to clean up subsurface contamination.

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Table 1-1 Contaminants and Volume of Groundwater, Soil, and Sediment to Be Cleaned up at Major DOE Installations Installation Examples of Contaminants of Concern Estimated Groundwater Volume (m3) Estimated Soil and Sediment Volume (m3) Savannah River Site TCE, PCE, aluminum, zinc, arsenic, cadmium, chromium, lithium, mercury, lead, tritium, strontium-90, cesium-137 and 139, cobalt-60 3.1 × 108 8.6 × 106 Hanford Site Tritium, cobalt, strontium, cesium, technetium, plutonium, uranium, carbon tetrachloride, nitrates, iodine, chromium, mixed waste, transuranic waste 2.0 × 107 6.4 × 107 Oak Ridge Reservation Asbestos, petroleum hydrocarbons, PCBs, radionuclides (uranium-235 and depleted uranium), mixed waste, strontium-90, cesium-137, cobalt-60, tritium, heavy metals, nitrates, organic solvents, beryllium compounds, mercury, cadmium 4.6 × 106 4.3 × 105 Rocky Flats Plutonium, americium, uranium, VOCs, PAHs, beryllium (soils); nitrates, metals, solvents (groundwater); radionuclides, metals, VOCs, PCBs (surface water) 1.2 × 106 3.2 × 105 Idaho National Engineering and Environmental Laboratory Heavy metals, PCBs, acids, asbestos, solvents, low-level radioactive waste, transuranic waste 7.6 × 105 6.5 × 105 NOTE: PAH = polycyclic aromatic hydrocarbon; PCB = polychlorinated biphenyl; PCE = perchloroethylene; TCE = trichloroethylene; VOC = volatile organic compound. SOURCE: EPA, 1997.

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants BOX 1-1 Origins of Groundwater and Soil Contamination at DOE Facilities Groundwater and soil contamination at DOE installations dates from the start of the Manhattan Project to develop nuclear weapons, beginning in 1942. Initially the responsibility of the U.S. Army Corps of Engineers, stewardship of the nation's nuclear arsenal was transferred to the Atomic Energy Commission in 1946 and to the newly created DOE in 1977. DOE inherited responsibility not only for maintaining and increasing the nation's nuclear weapons arsenal, but also for cleaning up the legacy of environmental contamination associated with nuclear weapons production. The bulk of contamination at DOE installations is a result of nuclear weapons production (DOE, 1997), although some contamination is a by-product of DOE's work on civilian nuclear power projects for the Atoms for Peace program and on nuclear-powered submarines for the Navy. Weapons production processes that ultimately led to groundwater and soil contamination include uranium mining, milling, and refining; isotope separation; fuel and target fabrication; weapons component fabrication; weapons testing; and most important, chemical separations, in which spent nuclear fuel rods and targets were dissolved to extract uranium and plutonium (DOE, 1997). Many of the contaminants released during the manufacturing of nuclear weapons, including DNAPLs and metals, are similar to those released by major manufacturers of durable goods, such as automobiles and airplanes. However, DOE facilities have the added hazard of radioactive contaminants, which are generally not used in other industries. Like other industries, DOE frequently disposed of wastes in landfills, lagoons, or underground injection wells, and spills of these by-products were not uncommon. These practices ultimately led to widespread groundwater and soil contamination across the weapons complex. At DOE facilities, the contamination problem was exacerbated by the veil of secrecy and the resultant lack of environmental oversight associated with the nuclear weapons production program (CERE, 1995; DOE, 1997). In part because of policies designed to preserve the secrecy of the nuclear weapons production process, DOE and its predecessor agencies were exempt from environmental laws for most of the nearly five decades between World War II and the end of the Cold War. Dumping of radioactive and hazardous wastes in unauthorized or improperly designed landfills was not uncommon. At Hanford, for example, environmental auditors have discovered unauthorized burial pits—unlined holes dug in the ground—where radioactive wastes were dumped and where no official records of the dumping were maintained (D'Antonio, 1993). Certain geologic and geochemical characteristics of a site can decrease or increase the migration rates of organic and inorganic contaminants. For example, as described above, DNAPLs can become entrapped in the pore spaces of geologic materials or can sorb (attach) to soils underground, slowing transport. Alternatively, the presence of fractures in the subsurface geologic formation can speed the rate of DNAPL transport. Some geologic formations, such as clayey sand

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants dertaken numerous studies to characterize groundwater and soil contaminants in the weapons complex (see, for example, DOE, 1992, 1996a; EPA, 1997). However, the nature and extent of groundwater and soil contamination remain poorly understood at many sites. Tables 1-3 and 1-4 list the most frequently encountered or highest-priority metal, radionuclide, and DNAPL contaminants in groundwater and soil as identified by some of the studies. As is clear from the tables, different studies have reached different conclusions about which Table 1-3 Metals and Radionuclides in Contaminated Groundwater and Soil at DOE Installations         Riley and Zachara, 1992d Rank EPA, 1997a SCFAb INEEL, 1997c Metals Radionuclides Groundwater 1 Uranium Technetium-99 Tritium Lead Tritium 2 Tritium Chromium(VI) Uranium Chromium Uranium-234, 235, 238 3 Thorium Uranium Strontium-90 Arsenic Strontium-90 4 Lead Tritium Technetium Zinc Plutonium-238, 239, 240 5 Beryllium Mercury Chromium Copper Cesium-137 6 Plutonium   Cesium-137 Cadmium Cobalt-60 7 Radium   Beryllium Barium Technetium-99 8 Mercury   Lead Nickel Iodine-129 9 Arsenic   Thorium Mercury   10 Chromium   Plutonium Cyanide   Soil 1 Uranium Cesium-137 Cesium-137 Copper Uranium-234,235, 238 2 Tritium Uranium Strontium-90 Chromium Plutonium-238, 239, 240 3 Thorium Strontium-90 Uranium Zinc Cesium-137 4 Lead Plutonium Plutonium Mercury Tritium 5 Beryllium Radium Cobalt-60 Arsenic Strontium-90 6 Plutonium Chromium(VI) Americium Cadmium Thorium-228, 230, 232 7 Radium Mercury Tritium Lead Cobalt-60 8 Mercury Thorium Thorium Nickel Technetium-99 9 Arsenic   Lead Barium Iodine-129 10 Chromium   Chromium Cyanide   a The data set includes 86 DOE installations and other locations where characterization and assessment of groundwater and soil have not been completed. The data set does not make separate rankings of contaminants in groundwater and soil. b SCFA developed this ranking based on mobility, prevalence, and toxicity (Jim Wright, Savannah River Site, personal communication, 1997). c This data set is not inclusive across the weapons complex but includes the major waste units identified at about 60 sites in 1995 and 1996. The data were validated in 1997 through review of published references. d The data set includes 91 waste sites at 18 DOE facilities.

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Table 1-4 Chemicals Present as DNAPLs in Contaminated Groundwater and Soil at DOE Installations   Source of Information Rank INEEL, 1997a DOE, 1992b Groundwater 1 Trichloroethylene (TCE) 1,1,1-TCA 2 Dichloroethylene (DCE) 1,2-DCE 3 Perchloroethylene (PCE) PCE 4 Vinyl chloride 1,1-DCA 5 Trichloroethane (TCA) Chloroform 6 Chloroform 1,1-DCE 7 Dichloroethane Carbon tetrachloride 8 Carbon tetrachloride 1,2-Dichloromethane Soil 1 TCE TCE 2 Polychlorinated biphenyls 1,1,1-TCA 3 DCE PCE 4 PCE Dichloromethane 5   Carbon tetrachloride 6   Chloroform 7   Freon 8   1,2-DCA 9   1,1,2,2-Tetrachloroethane 10   Chlorobenzene a This data set is not inclusive across the weapons complex but includes the major waste units identified at about 60 sites in 1995 and 1996. The data were validated in 1997 through review of published references. b The data set includes 91 waste sites at 18 DOE facilities. contaminants are most prevalent or highest priority. Nevertheless, all studies indicate that uranium, technetium, strontium-90, and tritium are commonly detected radionuclides; chromium is generally the key metal contaminant; and trichloroethylene (TCE) and other solvents are commonly encountered DNAPLs. A precise ranking of key contaminants of concern, based on either risk or prevalence, is not possible, given the limitations of existing data. Complicating the design of treatment systems for many DOE sites is the presence of mixtures of contaminants. In a survey of 91 DOE waste sites, for example, Riley and Zachara (1992) found that mixtures of two or more compounds were present at 59 (65 percent) of the sites. In soils, the most frequently occurring mixtures were metals combined with radionuclides, but various combinations of metals

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants and radionuclides with organic contaminants were also observed at some sites. In groundwater, the most common mixtures were metals and chlorinated hydrocarbons. Risks of Groundwater and Soil Contamination at DOE Installations Risks to human health and the environment are the basis for laws requiring the remediation of subsurface contaminants at DOE installations. Remediation technologies must be designed to reduce these risks. Risk, in addition to geologic and contaminant characteristics, is thus the third dimension of the subsurface contamination problem that must be understood in order to determine which types of new remediation technologies are needed most. Quantitative information on health and ecological risks of groundwater and soil contamination at DOE installations is limited. Conduct of comprehensive risk assessments at DOE installations is complicated by the difficulty in characterizing contaminant transport pathways and doses potentially received by people and ecosystems near the installation. Exposure to groundwater and soil contaminants from DOE installations might occur through multiple possible pathways (see, for example, Figure 1-3). Characterizing the locations and concentrations of subsurface contaminants and their transport along pathways to potential receptors has proved to be a daunting task. In general, quantitative assessments of the full risks posed by each installation's contamination have not been conducted, with the exception of studies at Fernald and, to a lesser extent, Oak Ridge (CERE, 1995). Available quantitative risk information is generally limited to studies of discrete contaminated sites within each installation, usually conducted as part of the cleanup process under CERCLA. The aggregate nature of risks from each facility, given all the sites within a facility, is unknown (CERE, 1995). The most comprehensive study to date of risks posed by contamination at DOE facilities was conducted by the Consortium for Environmental Risk Evaluation (CERE), organized by Tulane and Xavier Universities at DOE's request. This study, completed in 1995, was part of a broader DOE effort to prioritize site cleanup activities according to health and ecological risks. CERE reviewed existing health and ecological risk studies at six major DOE installations: Hanford, Idaho National Engineering and Environmental Laboratory, Oak Ridge, Rocky Flats, the Savannah River Site, and Fernald. Boxes 1-2 and 1-3 summarize some of the groundwater and soil contamination risks at these installations, according to CERE's study.

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Figure 1-3 How people could have been exposed to radioactive materials from Hanford. Source: T echnical Strategies Panel, Hanford Environmental Dose Reconstruction Project, 1994. CERE was unable to quantify the magnitude of the health risks posed by DOE installations. CERE concluded that groundwater and soil contamination appear to present little or no immediate hazard to most populations neighboring DOE installations. However, Native Americans living near Hanford are currently at risk, and there is potential for significant future risks if the contamination is left uncontrolled and restrictions on facility access are lifted. CERE's report advises, ''Without careful management, there could be significant risks to workers, to the public and nearby tribes ... from plutonium, spent nuclear fuel, and nuclear wastes currently stored at DOE installations'' (CERE, 1995). Just as the CERE study was unable to quantify the magnitude of the human health risks posed by the weapons complex as a whole, it was unable to place quantitative bounds on the level of ecological

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants BOX 1-2 Health Risks of Subsurface Contamination at Select DOE Installations The Consortium for Environmental Risk Evaluation, in a 1995 study, reported the following information about health risks due to subsurface contamination at select DOE installations. Hanford Site. At Hanford, there is a potential risk to Native Americans who are allowed, through treaty rights, to use the Columbia River and its banks for subsistence purposes and to access contaminated seeps and springs and the Hanford town site. Native Americans have reportedly developed rashes consistent with exposure to chromium after being in the vicinity of contaminated seeps. If contaminated soil at Hanford were not cleaned up and the installation were open to unrestricted use in the future, risks to other occasional and frequent users would be potentially high. Fernald Environmental Management Project. Some uranium from Fernald has migrated off property in groundwater to the south of the installation. Residents near the south boundary who use private wells are being provided with bottled water. In addition, uranium levels in surface soils on Fernald property can be hundreds to thousands of times greater than natural background levels; these levels would translate to high risks if people came into continual contact with the soils. For now, access restrictions and use of bottled water appear to be controlling risks, although models indicate that off-property migration of contaminants may pose risks through the consumption of local produce, beef, and milk grown or raised on contaminated agricultural land. Savannah River Site. Most areas at the Savannah River Site having high contaminant concentrations are several miles or more from installation boundaries. The potential for off-site contaminant transport is low due to the large transport distances involved, the high levels of dilution, and the generally low mobility in groundwater and soils of many of the major contaminants. No significant health risks to the general public appear to exist under current conditions. Although the DOE has identified several large plumes of contaminated groundwater at the installation, current and planned remedial actions have been designed to control off-site migration of the plumes at the two known areas where such migration appears possible in the near future. Rocky Flats Environmental Technology Site. Because of its proximity to a major population center (Denver), Rocky Flats operates an aggressive installation-wide monitoring program, and monitoring has shown that there are no current off-site exposure risks to the public from groundwater contamination. However, predictions indicate that contaminated groundwater will migrate off-site in 30 to 300 years if no action is taken to control contamination. Similarly, on-site soils currently pose no risks to the public because of access restrictions. However, if unrestricted access occurs prior to remediation, potential risks would be significant, due to high levels of radionuclides in the soil at portions of the installation. Oak Ridge Reservation. Under current conditions at Oak Ridge, exposure to contaminants in groundwater could occur either via groundwater discharge to the Clinch River or via direct off-site migration of the groundwater, which has occurred in Union Valley. However, according to CERE, radioactive and nonradioactive contaminants in the Clinch River occur at concentrations that "pose a low risk from exposure either

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants in drinking water or in contact through recreational use." Contaminant levels in groundwater plumes that have migrated off-site are below drinking water standards. Risks could occur in the future if groundwater contaminants are allowed to migrate off-site at high concentrations or if restrictions on land use are lifted. Idaho National Engineering and Environmental Laboratory (INEEL). INEEL is isolated, so the potential for public exposure to site contaminants is limited, and strong institutional controls are currently in place to limit access. The primary possible route of public exposure to contamination in the future is via migration of contaminants to the Snake River Plain Aquifer. However, CERE concluded that the risk of such exposure is low because of the long distances between INEEL and the nearest water supply wells and natural processes (such as biodegradation, radioactive decay, and dilution) that decrease contaminant concentrations along potential migration pathways. SOURCE: Summarized from CERE, 1995. BOX 1-3 Ecological Risks of Subsurface Contamination at Select DOE Installations The Consortium for Environmental Risk Evaluation, in its 1995 study, reported the following information about ecological risks due to subsurface contamination at select DOE installations. Hanford Site. According to the limited available ecological risk information, risks due to contaminated soils at Hanford are primarily in the vicinity of major operations at the installation. Ecosystems in these areas were initially disturbed during construction of Hanford's facilities. The primary ecological risks of concern due to groundwater contamination at Hanford are possible effects on salmon spawning areas from the discharge of contaminated groundwater into the Columbia River. Concentrations of contaminants in spawning areas could in theory approach those in groundwater because several areas are near points at which plumes of contamination emanating from former reactors discharge to the Columbia River. For example, concentrations of chromium(VI) in some plumes discharging to the river are more than 25 times the concentration known to damage juvenile salmon. So far, however, the magnitude of this risk has not been determined. Fernald Environmental Management Project. Ecological risk studies conducted after completion of the CERE study did not identify significant ecological risks due to groundwater and soil contamination at Fernald. Onsite, metal contaminants are found in all media, but only uranium and molybdenum have been detected at levels above the benchmark toxicity value for ecological risk as reported in ecological literature. Offsite, only uranium has been detected at above benchmark ecological toxicity values, and the highest levels of uranium are less than twice the benchmark toxicity value. No excess radiation has been detected in plants or animals on-or offsite.

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Savannah River Site. Ecological risks are better characterized at the Savannah River Site than at any other DOE installation, due in part to the designation of the site as a national environmental research park and the presence of the Savannah River Ecology Laboratory. Researchers at the installation have detected no significant risks offsite due to groundwater and soil contamination, though they have indicated that more information is needed to understand the migration of nonradioactive contaminants into the Savannah River Swamp, transport of contaminants offsite with biota, and effects of soils contaminated with solvents. The influence of groundwater seeps on surface water at the installation also has not been well studied. One episode of plants' dying due to exposure to contaminated groundwater from a seep has been reported. Future land use decisions are key in judging the level of ecological risk. The CERE study concluded that "human encroachment of the Savannah River Site is the source of greatest ecological risk to the ecosystem." Rocky Flats Environmental Technology Site. Ecological risk studies at Rocky Flats were quite limited when CERE conducted its study. Based on the limited studies available, CERE was unable to identify significant ecological risks due to groundwater or soil contamination. CERE concluded that the major ecological risk to the site, which is home to seven endangered and threatened species, is industrialization. Oak Ridge Reservation. Although extensive ecological studies have been conducted at Oak Ridge, limited information is available on risks due to groundwater and soil contamination. The existing studies focused on surface water systems, bottomland hardwoods, and "old field" communities (ecosystems that have evolved on previously cleared land). Some accumulation of mercury and polychlorinated biphenyls has been observed at top levels of the terrestrial food chain, perhaps due in part to uptake of contaminants by plants. Idaho National Engineering and Environmental Laboratory. Groundwater transport of contaminants at Idaho is very slow and, CERE concluded, probably does not have a significant impact on ecosystems. The major off-site transport routes for contamination are wind-blown dusts and waterfowl migration, but studies carried out to date have concluded that concentrations are too low for ecological effects to occur as a result of these migration pathways. As at other installations, however, large data gaps and uncertainties make these conclusions tentative. SOURCE: Summarized from CERE, 1995. risk posed by groundwater and soil contamination (see Box 1-3). However, CERE concluded that although contamination of biota, soil, sediment, and water resources is widespread across the weapons complex, ecological effects generally appear to be confined to localized contaminated areas. Ecosystems in these areas may be as much or more affected by the original construction and manufacturing activities that took place at the various installations as by the presence of contamination, CERE suggests. Further, some planned remediation activities

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants may cause additional harm to ecosystems. For example, soil cleanup plans at Fernald call for digging up surface soil across nearly 50 percent of the installation, which will destroy the native ecosystem in excavated areas. At Oak Ridge and elsewhere, plans for capping some waste areas and for in situ vitrification of others will limit the ability of these areas to support plant and animal life. Some DOE installations, because of restrictions placed on public access, have unique ecosystems that have been preserved virtually undamaged; several also support endangered and threatened plant and animal species. For example, seven threatened and endangered species, including the bald eagle and peregrine falcon, have been sighted at Rocky Flats. Some potential remedies for these sites, as well as the possible future lifting of land use restrictions, could jeopardize important habitats. A major limitation of CERE's study is the lack of sufficient understanding of the ecosystems (for example, lack of data showing changes over time) at most DOE installations. Thus, additional studies are needed before definitive conclusions can be reached about ecological risks due to groundwater and soil contamination in the weapons complex. Around the time that CERE completed its study, DOE undertook a pilot-scale project to develop improved methods for quantifying human health risks across the weapons complex (Hamilton, 1994, 1995). The pilot project focused on a few contamination problems at the Savannah River Site, Fernald, and the Nevada Test Site. At Fernald and the Nevada Test Site, investigators calculated potential health risks associated with drinking contaminated groundwater. In both instances, off-site risks were within or below EPA's acceptable range of excess individual lifetime cancer risk (10-4 to 10-6). At Fernald, the highest predicted lifetime risk for an individual consuming well water was 1.3 × 10 -5 for a well placed near the installation boundary. At the Nevada Test Site, the lifetime risk of cancer mortality due to exposure to radionuclides in groundwater for persons living off-site was projected at 7 × 10-7. However, the risk from consuming well water on site was 7 × 10-3, pointing to the importance of maintaining restrictions on site access. DOE'S PROGRESS TO DATE IN CLEANING UP GROUNDWATER AND SOIL CONTAMINATION Estimating DOE's progress in cleaning up contaminated ground-water and soil is difficult because of conflicting terminology. DOE's Office of Environmental Restoration generally tracks groundwater and soil cleanup projects by "operable unit" or "project"—that is,

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants a subset of an installation at which contaminated groundwater and/or soil problems are being cleaned up as one unit. Each installation generally has a number of operable units or projects. However, the Office of Environmental Management reports information on groundwater and soil contamination in terms of "release sites"—that is, the number of individual sites at which contaminants were released. One operable unit may encompass more than one release site. Thus, data on the number of operable units at which cleanup plans are under way cannot be compared directly to data on the total number of individual sites at which contaminant releases have been reported. DOE has estimated that a total of 10,000 sites must be cleaned up at its installations (EPA, 1997). Cleanup plans are being prepared for groundwater contamination at a total of 92 projects (or operable units), according to recent DOE data (Tolbert-Smith, 1998). Remedies have been selected for 27 (29 percent) of these projects (Tolbert-Smith, 1998). Similarly, soil cleanup plans are under way for 221 projects, and remedies have been selected for 163 (74 percent) of these projects (Tolbert-Smith, 1998). It is unclear what percentage of the 10,000 contaminated sites is being addressed by these remedies. Based on reports to the committee and visits to DOE installations, it appears that most of the groundwater and soil remediation work remains to be completed. DOE's recent budget projections have assumed that most groundwater will not be cleaned up, in part because of technical limitations. DOE's 1996 budget assessment, presented in the 1996 Baseline Environmental Management Report (DOE, 1996a), assumed that sources of ground-water contamination would be removed and pump-and-treat technologies would be used where effective, but that otherwise contaminated groundwater would simply be contained on-site and monitored, rather than cleaned. For example, the budget projection assumed that ground-water contamination at Hanford and the Idaho National Engineering and Environmental Laboratory would be managed by a combination of limited pumping and treating followed by monitoring of remaining contamination. The 1998 budget assessment, entitled Accelerating Cleanup: Paths to Closure, assumes that groundwater remediation will be considered complete when the contamination is contained or when a long-term treatment or monitoring system is in place (DOE, 1998). Although DOE's budget projections have discounted the problems of contaminated groundwater, it is still obliged to meet the requirements of federal statutes requiring groundwater cleanup. Further, political pressure to clean up these resources will remain. Recently,

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants DOE has faced considerable pressure from members of Congress to shore up its efforts to protect groundwater from contamination by radioactive wastes leaking from underground storage tanks, for example (GAO, 1998). Thus, DOE cannot avoid its groundwater and soil contamination problems or the limitations in technologies for addressing them. REFERENCES Betts, K. S. 1998. Energy efficiency research gains in Department of Energy's 1999 budget request. Environmental Science & Technology 2(4):167A. CBO (Congressional Budget Office). 1994. The Total Costs of Cleaning up Nonfederal Superfund Sites. Washington, D.C.: U.S. Government Printing Office. CERE (Consortium for Environmental Risk Evaluation). 1995. Health and Ecological Risks at the U.S. Department of Energy's Nuclear Weapons Complex: A Qualitative Evaluation. New Orleans: Tulane University Medical Center. D'Antonio, M. 1993. Atomic Harvest: Hanford and the Lethal Toll of America's Nuclear Arsenal. New York: Crown Publishers, Inc. DOE (Department of Energy). 1992. Chemical Contaminants on DOE Lands and Selection of Contaminated Mixtures for Subsurface Science Research. DOE/ER-0547T. Washington, D.C: DOE, Office of Energy Research. DOE. 1996a. The 1996 Baseline Environmental Management Report. Washington, D.C.: DOE, Office of Environmental Management. DOE. 1996b. Subsurface Contaminants Focus Area Technology Summary. DOE/EM-0296. Washington, D.C.: DOE, Office of Science and Technology. DOE. 1997. Linking Legacies: Connecting the Cold War Nuclear Weapons Processes to Their Environmental Consequences. DOE/EM-0319. Washington, D.C.: DOE. DOE. 1998. Accelerating Cleanup: Paths to Closure. Washington, D.C.: DOE, Office of Environmental Management. EPA (Environmental Protection Agency). 1997. Cleaning up the Nation's Waste Sites: Markets and Technology Trends. EPA 542-R-96-005. Washington, D.C.: EPA, Office of Solid Waste and Emergency Response. EPA. 1998. Treatment Technologies for Site Cleanup: Annual Status Report (Ninth Edition). EPA-542-R98-018. Number 9. Washington, D.C.: EPA, Office of Solid Waste and Emergency Response. GAO (U.S. General Accounting Office). 1997. Department of Energy: Funding and Work-force Reduced, but Spending Remains Stable. GAO/RCED-97-96. Washington, D.C.: GAO. GAO. 1998. Nuclear Waste: Understanding of Waste Migration at Hanford Is Inadequate for Key Decisions. GAO/RCED-98-80. Washington, D.C.: GAO. Hamilton, L. D. 1994. Pilot study risk assessment for selected problems at three U.S. Department of Energy facilities. Environment International 20(5):585–604. Hamilton, L. D. 1995. Lessons learned: Needs for improving human health risk assessment at USDOE sites . Technology Journal of the Franklin Institute 332: 15–33. Harden, B. 1996. Half-lives: Government, poison, lies and the splitting of atomic America. Washington Post Magazine (May 5):12–19; 26–29. INEEL (Idaho National Engineering and Environmental Laboratory). 1997. Decision Analysis for Remediation Technologies (DART) Data Base and User's Manual. INEEL/EXT-97-01052. Idaho Falls: INEEL.

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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants MacDonald, J. A., and M. C. Kavanaugh. 1994. Restoring contaminated groundwater: An achievable goal? Environmental Science and Technology. 28(8):362A–368A. NRC (National Research Council). 1994. Alternatives for Ground Water Cleanup. Washington, D.C.: National Academy Press. NRC. 1997. Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization. Washington, D.C.: National Academy Press. Probst, K. N., and M. H. McGovern. 1998. Long-Term Stewardship and the Nuclear Weapons Complex: The Challenge Ahead. Washington, D.C.: Resources for the Future. Riley, R. G., and J. M. Zachara. 1992. Chemical Contaminants on DOE Lands and Selection of Contaminant Mixtures for Subsurface Science Research. DOE/ER-0547T. Washington, D.C.: Department of Energy, Office of Energy Research . Sandia National Laboratories. 1996. Performance Evaluation of the Technical Capabilities of DOE Sites for Disposal of Mixed Low-Level Waste. SAND96-0721/1 UC-2020. Albuquerque, N.M.: Sandia National Laboratories. Technical Strategies Panel, Hanford Environmental Dose Reconstruction Project. 1994. Summary: Radiation Dose Estimates from Hanford Radioactive Material Releases to the Air and the Columbia River. Atlanta, Ga.: Centers for Disease Control. Tolbert-Smith, L. 1998. Unpublished data on groundwater and soil contamination remedies at DOE installations. Washington, D.C.: U.S. Department of Energy.