Established in 1943, the Hanford Site produced the plutonium used in developing the world’s first nuclear device. At the time, little attention was given to the resulting by-products—massive amounts of radioactive and chemically hazardous waste. From 1944 through 1988, about 525 million gallons of radioactive tank waste was generated by Hanford’s plutonium- processing plants. The federal government initially managed this waste by building underground tanks to store it until it could be treated and permanently disposed of; intentionally discharging it into the ground; and reducing its volume through various waste concentration methods, such as evaporating off the liquids. From the 1940s through the mid-1960s, 149 storage tanks were built at Hanford. Originally designed to last 10 to 20 years until a permanent disposal solution could be found, each of these tanks consisted of an outer concrete wall lined with one layer of carbon steel. Clustered into 12 tank farms and buried some 6 to 11 feet beneath the surface, most of these single-shell tanks measure roughly 75 feet in diameter, range from 30 to 49 feet high, and have a capacity between 530,000 gallons and 1 million gallons of waste. Together, the single-shell tanks contain almost 30 million gallons of waste; about 27 million gallons are in solid or semisolid form, and about 3 million gallons are liquid. As early as 1948, concerns arose about the use and viability of these tanks over the long term. By 1961, leakage of waste from one single-shell tank into the underlying soil was confirmed. Later, by the mid-1990s, 67 of the single-shell tanks had leaked or were presumed to have leaked about 1 million gallons of waste into the soil. To address concerns with the design of the single-shell tanks, a new tank design with two carbon-steel shells was adopted in the late 1960s. From 1968 through 1986, 28 of these double-shell tanks, each with storage capacities of 1 million gallons or more (see fig. 2), were built and sited in 6 more tank farms at Hanford; together, these double-shell tanks contain about 27 million gallons of waste. In the late 1980s, DOE stopped producing nuclear materials and shifted its mission to treating and disposing of the decades of accumulated nuclear waste. At Hanford, DOE’s planned cleanup process entails retrieving waste from the tanks; mixing this waste with molten glass through a process known as vitrification; and pouring the waste into steel canisters, where it will cool and solidify. As part of this process, DOE has been constructing the Hanford Waste Treatment and Immobilization Plant, a large complex including waste-processing facilities; an analytical laboratory; and more than 20 smaller, supporting facilities to treat and package the waste. The waste treatment plant is designed to separate tank waste into high- and low-radioactivity portions, often referred to as high-level and low-activity waste, respectively. The high-level fraction (which amounts to less than 10 percent of the total waste volume) is to be stabilized at the Hanford Site and then sent to a geologic repository for permanent disposal. DOE plans to stabilize the low-radioactivity fraction (more than 90 percent of the total waste volume) and dispose of it permanently in an on-site facility. Over the years, the waste contained in these tanks has settled; today it exists in four main forms or layers: Vapor: Gases produced from chemical reactions and radioactive decay occupy tank space above the waste. Liquid: Fluids (supernatant) may float above a layer of settled solids or under a floating layer of crust; fluids may also seep into pore spaces or cavities of settled solids, crust, or sludge. Saltcake: Water-soluble compounds, such as sodium salts, can crystallize or solidify out of wastes to form a moist saltlike or crusty material. Sludge: Denser, water-insoluble or solid components generally settle to the bottom of a tank to form a thick layer having the consistency of peanut butter. To carry out its missions, DOE relies almost entirely on private firms under contract with the department. Accordingly, DOE manages Hanford’s tanks and tank waste through two main contracts: a tank farm operations contract with CH2M Hill Hanford Group Inc., which employs about 1,100 workers, to store the waste safely and prepare it for retrieval from the tanks and a construction contract with Bechtel National Inc., which employs approximately 3,500 workers, to design, construct, and commission the waste treatment plant. DOE oversees these contractors through its Office of River Protection, which was established in 1998 as required by Congress. As of May 2008, the office had a staff of 108 DOE employees and a fiscal year 2008 budget of about $1 billion. Neither DOE nor its contractors have comprehensive information about the overall integrity or contents of Hanford’s underground waste tanks; as a result, they cannot predict the tanks’ long-term viability with any degree of certainty. Although recent studies indicate that the newer, double-shell tanks are generally sound, the integrity of many single-shell tanks has been compromised in the past, and the condition of the rest is difficult to ascertain. Further, although DOE has identified the major waste constituents in the tanks, the specific proportions of the constituents contained in individual tanks remain uncertain, as does their combined effect, if any, on the tanks’ integrity. The only certainty is that the tanks are aging, and at DOE’s present rate of progress, all will have exceeded their design life—many significantly—by the time the tanks are finally emptied and closed. The primary design difference between Hanford’s single- and double-shell underground waste storage tanks—a second carbon-steel lining, or shell, within the outer concrete housing to provide secondary containment of the waste (see fig. 3)—has improved DOE’s ability to monitor and assess the tanks’ integrity and contents. The two shells in the double-shell tanks are separated by about 3 feet of space, which enables workers to use remote leak detection sensors and remotely operated cameras to “see” between the inner and outer shells, thereby making it possible to find signs of corrosion or leaks before waste breaches the outer shell and leaches outside the tank structure. Using remote cameras, ultrasonic equipment, and structural analyses, DOE examines about three to five tanks each year and to date has found no evidence of leakage from the double-shell tanks or of degradation that could lead to leakage during approximately the next 10 years. In contrast, the condition of single-shell tanks is much harder to ascertain. Although DOE knows that about half the single-shell tanks are confirmed or presumed to have leaked, indicating some kind of liner failure, it has limited means to assess the leak integrity of the remaining single-shell tanks. DOE uses three primary methods to monitor waste and determine if leaks have occurred, although each of these methods has limitations. First, DOE periodically compares waste levels in each tank with prior waste records to detect major fluctuations in waste level, which may have been caused by leaks. This method has limitations because in many tanks, especially those with single shells, thick layers of waste can obscure the liquid sandwiched between them. To monitor liquid levels, DOE has placed liquid observation devices that extend below the layers of waste in about half of the single-shell tanks. Nevertheless, it is difficult, and in some cases nearly impossible, to determine if the waste level in a tank has changed. In tanks with liquid trapped between layers of waste, even if the overall waste level does not appear to have changed, liquid waste could still have leaked out. Second, DOE can monitor the waste in a tank using a remotely operated camera lowered into the tank’s interior. The camera can be used only in the space above the waste, however, because the waste obscures the rest of the tank from the camera’s view (see fig. 4). Although this method is useful for monitoring certain conditions, it is not effective for detecting tank leaks, which do not produce a visible change or a visible loss of liquid, because only a breach of the steel lining covered by or adjacent to the waste would cause a leak. Third, to help address these in-tank monitoring limitations, DOE has built numerous wells around the tanks, which contain monitoring equipment for detecting leaks. Even so, because many of the single-shell tanks have already leaked waste into the soil, detecting further leaks can be difficult, depending on the location of the leak relative to the monitoring well and the waste’s radioactivity. DOE tank waste management and Ecology officials told us that unless significant quantities of waste—4,000 gallons or more—leaked near one of the wells, they would be unlikely to detect it. DOE tank management officials acknowledge that the integrity of the single-shell tanks is a continuing uncertainty—with potentially significant effects on DOE’s tank management strategy—and have taken steps, such as limited examination of the tanks’ external structure and in-tank observations and analysis, to learn more about the condition of the single- shell tanks. In 2002, DOE attempted to assess the condition of the single- shell tanks to ensure that the tanks would not experience a catastrophic structural failure before tank waste cleanup activities were completed. Using photographs, video cameras, and leak-monitoring results, DOE studied the structural characteristics of the reinforced concrete exterior; the condition of the tanks’ concrete tops, or domes; and the visible portion of the tank shells’ interior. The waste in the tanks, and the tanks’ location several feet below ground level, however, prevented DOE from studying the concrete exterior of most of the tanks or the bottom and concrete foundation of any of the tanks. Despite these limitations and the fact that many tanks had already leaked, the study concluded that the single-shell tanks’ overall structural integrity was sound and that the tanks were structurally adequate for continuing to store the waste. The department lacks conclusive information about the emptied tanks’ condition, which might offer insights into the condition of other single- shell tanks that have yet to be emptied. DOE has used surveillance cameras to make limited observations of the seven single-shell tanks that have been emptied; DOE has not, however, thoroughly examined any of the seven emptied tanks. From the surveillance camera views, DOE tank management officials told us that the inner shells in these tanks, including the four tanks that leaked waste in the 1980s, show signs of corrosion, but despite long-term immersion in waste, the tanks’ sides and bottoms generally appeared in good condition. Still, these officials acknowledged that such surveillance work cannot reveal a complete picture of the tanks’ integrity because small corrosion leaks are very difficult, if not impossible, to detect with a surveillance camera; these preliminary observations are thus inconclusive at best. Further, although DOE completed waste retrieval from the first tank in 2003, it has yet to perform a comprehensive study of this tank’s interior. DOE officials told us that they were in early stages of planning to further study the single-shell tanks. According to the manager of Hanford’s River Protection office, this study is expected to take several years to complete. DOE plans to spend about $800,000 in fiscal year 2008 to plan how to proceed with the study and has projected expenditures of about $2.5 million for fiscal year 2009 to begin it. DOE believes that it has an adequate understanding of the tank waste’s general composition but acknowledges it has limited information on the specific proportions of constituents in each tank. Routine sampling and analysis over more than 2 decades show that the tanks contain millions of gallons of highly radioactive or long-lived radioactive materials; tons of hazardous chemicals; and a variety of miscellaneous materials, such as discarded equipment. About 46 different radioactive elements—by-products of chemically separating plutonium from uranium during weapons production— represent the majority of the radioactivity currently residing in the tanks. Some of these elements lose most of their radioactivity in relatively short periods of time, while others remain radioactive for millions of years. The rate of radioactive decay is measured in half-lives, that is, the time required for half the atoms in a radioactive substance to disintegrate, or decay, and release their radiation. The half-lives of major radioactive tank constituents differ widely. The vast majority (98 percent) of the tank waste’s radioactivity comes from two elements, strontium-90 and cesium- 137, which have half-lives of about 29 and 30 years, respectively. The remaining radioactive elements, which account for about 2 percent of the waste’s total radioactivity, have much longer half-lives. For example, the half-life of technetium-99 is 213,000 years, and that of iodine-129 is 15.7 million years. Although some of the tanks once contained radioactive materials “hot” enough that the tanks self-boiled—that is, the temperature resulting from the radioactive decay reached 280 to 320 degrees Fahrenheit and stayed high for a decade or more—the waste’s overall radioactivity is decaying over time (see fig. 5), thus lowering the risk of exposure to radioactivity for humans and the environment. As we reported in 2003 on the basis of radioactive levels measured as of August 2002, within 100 years, more than 90 percent of the radioactivity in the tanks will have dissipated, and within 300 years, 99.8 percent will disappear. The tanks also contain large volumes of hazardous chemical waste, including various metal hydroxides, oxides, and carbonates. Similar to the radioactive by-products of plutonium production, some of these chemicals—including acids, caustic sodas, solvents, and toxic heavy metals such as chromium—came from chemically reprocessing spent nuclear fuel to extract weapons-grade plutonium. A 1997 tank waste characterization study stated that “Hanford waste tanks are, in effect, slow chemical reactors in which an unknown but large number of chemical and radiochemical reactions are running simultaneously.” Altogether, DOE added about 240,000 tons of chemicals to the tanks from the 1940s to the mid-1980s. A majority of the chemicals (caustics, such as sodium hydroxide) were added to neutralize toxic reprocessing acids in the waste; other chemicals, such as solvents, ferrocyanide, and several organic compounds, were added during various waste extraction operations to help recover selected radioactive elements (uranium, cesium, and strontium) for reuse. These hazardous chemicals are dangerous to human health, and they can remain dangerous for thousands of years. Finally, the tanks contain a variety of miscellaneous material, such as discarded equipment, cement to soak up liquids, casks of experimental fuel elements, and plastic bottles containing plutonium and uranium. These items were placed in the tanks during operations or in some cases, intentionally discarded. Although these items may not add significantly to the danger of materials already in the tanks, they may further complicate waste retrieval activities. Beyond the general characterization of tank wastes, DOE lacks knowledge of the specific proportions of constituents in each tank. The radioactive elements, chemicals, and miscellaneous materials have been extensively mixed and commingled over the years. Wastes were mixed as they initially went into the tanks and were transferred extensively between tanks. Such waste transfers compounded existing uncertainties about waste composition because of the department’s poor record keeping, which, as we reported in 1991 and again in 1996, was incomplete and often inaccurate. Despite DOE’s sampling efforts, the viscous and layered consistency of the waste has challenged measurement of physical and chemical properties. For example, given the multitude of waste constituents in a tank, taking 1- to 3-inch-wide samples that extend from the surface of the waste to the bottom of a tank that is 75 feet wide may not always produce representative results. DOE contractors acknowledged that they do not know the specific proportions of wastes in any given tank, and they continue to characterize tank wastes to mitigate corrosion; understand future waste delivery, treatment, and disposal needs; and support future waste retrieval and closure activities. Still, understanding the types and quantity of waste constituents in each tank and the effect, if any, this waste has on the tanks’ integrity may be critical to predict how long they can be safely used. Recognizing this concern, DOE plans to further study the long-term integrity of the single-shell tanks and, in an effort to extend tank life span, has tried to control the acidity of the waste in the double-shell tanks to minimize its corrosive effects. While uncertainties about the tanks’ structural integrity and contents persist, the aging of the tanks goes without question. By 1987, all the single-shell tanks had already lasted beyond their estimated design life of 10 to 20 years. Some of these tanks may be more than 80 years old by the time they are emptied and the tank farms are closed (see app. II). Although none of the double-shell tanks have yet exceeded their estimated design life of 25 to 50 years, all will have done so by the time waste treatment is complete and the last of them has been emptied and closed (see app. III). While a tank’s design life is not a firm deadline beyond which a tank is no longer usable, site engineers considered design life a reasonable estimate of how long a tank could be expected to contain the radioactive and hazardous wastes and did not regard the tanks as a permanent solution to DOE’s weapons production legacy. In the 1940s and 1950s, site contractors viewed tank failures as inevitable and assumed that as the tanks failed, new tanks would be constructed to store the waste until a more permanent disposal solution could be developed. DOE and its contractor acknowledge that aging equipment is subject to more frequent failure. The likelihood of a major failure of a tank increases with time. The conclusions of a 2007 Ecology study on the single-shell tanks seem to agree with this position. From an evaluation of the tanks’ leak history, this study concluded that the probability of a single-shell tank’s leaking may double about every 10 years. The study estimated that about half (41 tanks) of the single-shell tanks designated as sound could leak waste into the ground by the time they are emptied. Regardless of whether the tanks have exceeded their design life, their long-term viability remains unknown. Given the uncertainties over the bottom portions and foundations of the single-shell tanks uncovered by DOE’s 2002 study, and that 67 tanks have leaked or are presumed to have already leaked and additional tanks are likely to leak in the future, these tanks’ viability is both questionable and unpredictable. Furthermore, according to independent experts, DOE has never controlled the chemical composition of the wastes in the single-shell tanks to reduce corrosion of the tanks’ steel liners, as required for the double-shell tanks. It also remains unclear to what extent the single-shell tank study being planned will evaluate the expected viability of these tanks throughout the remainder of the treatment process. As for the double-shell tanks, DOE has taken steps to try to assess whether they will remain usable until they are emptied. An independent panel of experts, including engineers, chemists, and corrosion experts from DOE sites, academia, and industry analyzed actual corrosion rates of the inner carbon-steel linings of the 28 double-shell tanks. Using these corrosion rates, the experts projected when future leaks in the tanks were likely to occur. They concluded that in a worst-case scenario—as when the waste is highly corrosive—assuming corrosion rates continue as observed, as many as 7 double-shell tanks may develop leaks in their inner steel shells between 2037 and 2043. Another study conducted by an independent professional engineer for DOE’s contractor used laboratory corrosion rate data, rather than rates from in- tank corrosion monitoring. Assuming that tank shell corrosion rates would not necessarily remain constant, this study concluded that the inner steel shell of all the double-shell tanks would be capable of containing the waste without developing corrosion leaks until about 2083. Given these conflicting conclusions, DOE tank management officials continue to study the condition of the double-shell tanks and believe that they will remain sound during an extended waste storage schedule. DOE’s strategy for managing Hanford’s tanks involves transferring waste from the single- to the double-shell tanks and using the latter to store the waste until it can be treated and the tanks closed. With Hanford’s waste treatment plant still under construction, DOE is carrying out this strategy under lengthening and seemingly disparate time frames. DOE’s strategy and schedule also appear to rely on overly optimistic assumptions, in particular, that the aging tanks will remain viable throughout the treatment process and that sufficient double-shell tank space will be available to hold waste retrieved from the single-shell tanks. DOE has been gradually emptying the liquid waste from the single-shell tanks into the double-shell tanks. Beginning in the 1970s, DOE transferred as much liquid as possible from the single-shell tanks, a process called interim stabilization, to minimize or prevent further leaks of waste from these aging tanks to the soil below. By May 2005, DOE had completed the interim stabilization of all single-shell tanks. Because of the layered nature of tank waste, however, DOE was unable to remove all the liquid. As of February 2008 (the latest date for which data were available for this report), DOE reported that about 3 million gallons of liquid waste remains in these tanks, most of it unpumpable. Of this remaining liquid waste, about one-third, or 1 million gallons, resides in tanks known or presumed to have already leaked. In 1998, DOE began emptying the single-shell tanks of their remaining waste, mostly saltcake and sludge, and transferring it to double-shell tanks, where it will be temporarily stored until the waste treatment plant becomes operational. To loosen and retrieve the waste from tanks, DOE has used a variety of technologies, including sprays of acid or water to help break up the waste and a vacuumlike system to suck up and remove waste through openings, called risers, in the top of the tank (see fig. 3). Under the Tri-Party Agreement, DOE has agreed to remove as much waste from the tanks as technically possible and the volume of waste remaining may generally not exceed specified volumes. According to a DOE official, these volume limits were set to ensure that at least 99 percent of the waste was removed from the single-shell tanks. As all the tanks are emptied of as much waste as practical, DOE expects to first close the single-shell and then the double-shell tanks, along with ancillary piping and other instruments. To date, the department has not yet reached agreement with its regulators on final closure of the tanks. Regulatory alternatives for closing the tanks are either “clean closure,” a regulatory concept under which the tanks themselves, ancillary equipment, and contaminated soil would be exhumed, treated, and disposed of as radioactive waste, or “closure as a landfill,” in which DOE would leave a small amount of waste in the each tank; fill each with grout, a cementlike material; and monitor tank conditions in perpetuity. As of May 2008, DOE was preparing an environmental impact statement that evaluates alternatives for closing the tanks, including how much waste can be left in the tanks at closing. DOE does not expect to issue the final statement before late 2009, with a decision about tank closure to follow later. Within DOE’s general strategy for addressing the aging tanks, time frames for completing specific actions, such as emptying the tanks and closing them, remain in flux. Under the existing Tri-Party Agreement, DOE agreed to empty all 149 single-shell tanks by September 2018 and to close them by 2024. These milestones were tied to waste treatment operations, which were scheduled to be complete by December 31, 2028. As of May 2008, however, the startup of Hanford’s waste treatment plant had been delayed by at least 8 years, and it was unclear when waste treatment operations would be complete. Moreover, DOE has made limited progress in actually emptying the tanks, and at its present rate of progress, it will not achieve the milestones it agreed to. In contrast to its Tri-Party Agreement commitments, DOE’s own internal project baseline schedule (approved in mid-2007) for emptying and closing the tanks reflects time frames almost 2 decades later. For example, according to this baseline, emptying the single-shell tanks will be completed 19 years later than agreed to in the Tri-Party Agreement. DOE officials told us that this baseline schedule reflects a 5-year delay in the start of waste treatment operations and a lengthened waste treatment period. Since the baseline schedule was developed, however, DOE has acknowledged that the start of waste treatment operations will be delayed at least 8 years (from 2011 to 2019), not 5, most likely making DOE’s approved baseline schedule for emptying the tanks unachievable. In February 2008, DOE prepared an internal single-shell tank waste retrieval analysis that reflects this 8-year delay. Under this new scenario, DOE postpones emptying all single-shell tanks from 2018 to at least 2047, a delay of 29 years from the agreed-to Tri-Party Agreement date, with tank closure to follow. Although DOE officials said this analysis was not a schedule to which the agency was working, they acknowledged that the time frames in the analysis more accurately reflect what the agency believes it can achieve given the waste treatment plant delay. DOE has been negotiating with Ecology and EPA since May 2007 to extend the Tri-Party Agreement milestones, including dates for emptying and closing the tanks. DOE acknowledged that it could not meet the current Tri-Party Agreement and instead proposed to regulators that it empty the single-shell tanks by 2040—a delay of 22 years. Given the delays in starting waste treatment plant operations and DOE’s February 2008 single-shell tank waste retrieval analysis, however, it is unclear whether the proposed changes to the Tri-Party Agreement dates are realistic. In carrying out its tank management strategy under successively lengthening time frames, DOE is relying on some key assumptions that may be overly optimistic. The aging tanks will remain viable until they can be emptied and closed. At the foundation of DOE’s strategy lies the department’s assumption that the tanks will remain viable throughout what has become a protracted waste treatment process. At the time they were built, the single-shell tanks were intended to be in service for 10 to 20 years, but under DOE’s current plan, some of these tanks will be more than 80 years old by the time they are emptied. Concerns have been raised over the years about the risk of tank failure, most recently in an internal analysis assessing management risks associated with tank farm activities, where the responsible contractor said that the likelihood of a major tank failure or failure of ancillary systems increases over time. Double-shell tank space will be sufficient to receive all the waste retrieved from single-shell tanks until waste treatment operations can begin. DOE also assumes that the 28 double-shell tanks will have enough space to hold waste transferred from single-shell tanks until the waste treatment plant begins operating. The double-shell tanks have an estimated capacity of slightly over 32 million gallons and, as of February 2008, contained nearly 27 million gallons of waste. To fit the expected volume of single-shell tank waste, plus liquids added in emptying these tanks, DOE plans to evaporate off as much liquid as possible, concentrating it for storage in the double-shell tanks. But DOE’s evaporator facility is 31 years old, and an internal DOE 2006 document identified evaporator reliability as a critical challenge to meeting project goals. Unplanned evaporator maintenance could in the worst case result in delays of a year or more. In addition, any failure of a double-shell tank would further reduce available space. Although DOE officials told us they believe that sufficient double-shell tank space will remain available, the 2006 DOE document noted that management of double-shell tank space remains critical to successful completion of the entire waste treatment operation. Emptying single-shell tanks will proceed two to three times faster than it has to date. DOE’s tank management strategy assumes that the department can progress with waste retrieval from the single-shell tanks at a rate that contrasts with experience so far. In its February 2008 single- shell retrieval analysis, DOE shows completion of single-shell tank retrieval in 2047 if a total of 33 tanks are emptied through 2019—a waste retrieval pace averaging more than 3 tanks per year. Since 1998, however, DOE has emptied only 7 tanks and is in the process of emptying 3 more—a rate of about 1 tank per year. Further, 4 of the 7 emptied tanks are among the smallest, at 55,000 gallons of capacity, and contain relatively small amounts of residual waste. The other 3 tanks range in capacity from 530,000 to 758,000 gallons, and each took almost a year or more to empty. Moreover, a 2007 tank spill illustrates that a relatively small spill can halt retrieval activities, further complicating schedules. On July 27, 2007, during retrieval of radioactive mixed waste from a 758,000-gallon single- shell tank, a pump failed, spilling 85 gallons of highly radioactive waste to the ground. At least two workers were exposed to chemical vapors, and later several workers reported health effects they believed to be related to the spill. Retrieval operations for all single-shell tanks were suspended after the accident, and DOE did not resume operations until June 2008, a delay of 11 months. In addition, the accident added at least $8 million to the retrieval cost for that tank. Hanford project management officials acknowledged that such an ambitious retrieval schedule might not be achievable. DOE’s site manager for the Office of River Protection told us that she believed DOE could achieve a retrieval rate of about 1.7 tanks per year until 2019. In its fiscal year 2009 budget submitted to Congress, however, DOE indicated that it could achieve retrieval of waste from only 1 tank. Without a comprehensive analysis that quantifies the risks of tank waste and the proposed strategies to address them, DOE lacks critical information to weigh the benefits of pursuing its present strategy against costs that continue to climb. DOE has undertaken some studies that assess general tank waste risks, but these studies lack detailed, tank-farm- specific information, not only about the tanks’ long-term viability but also about incremental changes in risks associated with remediation actions. As a result, DOE, Congress, and the public cannot be assured that DOE’s present strategy appropriately balances risk reduction with cost. DOE has taken the position that using a risk-based approach to managing its tank waste is a top priority. In addressing the progress of cleaning up Hanford’s underground tanks in its fiscal year 2009 congressional budget request, DOE stated that it is pursuing a risk-based approach that focuses first on the greatest contributors to risk. In April 2008, the Assistant Secretary for Environmental Management reemphasized that the department would follow a risk-based approach and announced that DOE would give top priority to retrieving and treating the radioactive waste in the tanks. In addition, DOE’s own project management order and implementing guidance calls for the department to consider programmatic risk before proceeding with a project. In actual practice, DOE’s main tank risk studies have looked at the long-term health and environmental risks of the waste in the tanks, but none of the studies has explicitly investigated such risks in association with using the tanks for an extended period of time: DOE’s 1996 environmental impact statement documented and analyzed potential environmental consequences related to 10 proposed alternative approaches to cleanup of the tank waste at the Hanford Site. The environmental impact statement evaluated the short- and long-term effects of these alternatives on site workers, the public, and the environment; it also compared the costs and technical and regulatory feasibility associated with each alternative, although the study did not make clear how DOE compared these factors to arrive at its preferred alternative for cleanup. The study did not purport to analyze the tanks’ condition or long-term viability or the risks posed by leaving the waste in the tanks for several more decades. Rather, DOE assumed that no further waste leaks would occur and that both single- and double-shell tanks would maintain their structural integrity for the next 100 years. A DOE 2006 performance assessment of the single-shell tanks estimated the potential health and environmental effects that may remain after the single-shell tanks are emptied under DOE’s current strategy. This study assumed that 99 percent of the waste would be removed from the tanks and treated and that the tanks themselves would be left in the ground after retrieval. The study concluded that after 99 percent of the waste had been retrieved from the tanks and the tanks were filled with grout, the groundwater beneath the tanks would never exceed drinking water standards, even 4,000 to 6,000 years from now. The study did not assess the short-term risks to Hanford Site workers, the public, or the environment, but it did evaluate long-term risks as far as 10,000 years into the future. In addition, like the 1996 environmental impact statement, this study did not attempt to analyze the tanks’ condition or long-term viability. DOE is preparing an environmental impact statement evaluating a number of potential strategies for permanently closing the tanks after the waste has been retrieved. According to DOE, this study will include an analysis of (1) the costs and risks posed by waste left in tanks under a number of different closure configurations; (2) the contamination associated with other waste sites at Hanford; and (3) risks under various treatment, disposal, and closure scenarios to workers, the public, and the environment. According to DOE officials, this study is not intended to assess the tanks’ present condition or their ability to continue safely storing waste until retrieval. Although we have discussed the progress of this study with DOE officials, drafts of the study were not available at the time of our review. We could not therefore determine whether or to what extent this new study will detail the “risk-based” approach that we believe is needed for making key decisions about waste retrieval and final closure of the tanks. Both EPA and Ecology officials stated that this study will contribute to the risk information available on tank wastes but will not represent a comprehensive study of those risks. They acknowledged that even after this study is completed, more data will likely be needed to make long-term decisions about the risks of using the tanks over an extended period. Meanwhile, DOE is proceeding under its current tank management strategy and renegotiating new milestones with its regulators, even though the department does not expect to issue the final environmental impact statement before late 2009, with a decision about tank closure to follow later. According to DOE and its tank farm contractor’s own estimates, the cost of retrieving Hanford’s tank waste and maintaining and closing the tanks is escalating. DOE estimated in 2003 that waste retrieval and closure costs from fiscal year 2007 onward—in addition to the $236 million already spent to empty the first seven tanks—would be $4.3 billion. By 2006, this estimate had grown to $7.6 billion. As DOE empties tanks, it has found that its estimates for retrieving the waste have significantly understated actual costs. For example, in 2003, DOE estimated that retrieving waste from all the single-shell tanks would cost approximately $1.1 billion, or an average of about $7.6 million per tank. The actual costs of removing waste from the first seven tanks have totaled about $236 million, or about $34 million per tank. Because four of the emptied tanks were Hanford’s smallest tanks, actual costs for the more-numerous larger tanks could be much higher. Moreover, as DOE continues to extend its time frames for tank waste retrieval, the time and costs for monitoring and maintaining the tanks also continue to expand. DOE and its contractor have also found that the costs of retrieving the last portion of waste from a tank can be costly. Yet in the absence of specific risk analyses, the accompanying reduction in risk, if any, is unclear. Specifically, DOE estimates that the cost of retrieving the final 15 percent of waste can equal or exceed the cost of removing the initial 85 percent (the cost per gallon can be as much as three times higher); in contrast, DOE has little information about any concomitant risk reduction. Our review did find one case where DOE and its tank farm contractor weighed the relative risks, benefits, and costs of retrieving the last portion of waste from a tank. After retrieving all but just over 1 percent (or about 400 cubic feet) of the waste in tank C-106, DOE analyzed the costs and risks associated with retrieving the rest of the waste. This analysis concluded that the risk to workers from removing the waste, combined with the associated high cost, outweighed a relatively minimal reduction in risk to the public and future users of the site. The analysis determined that the cost of removing each additional cubic foot, or about 8 gallons, of waste ranged from $35,000 to $84,000—in other words, from 7 to 16 times the average cost per cubic foot to retrieve the first nearly 99 percent of the waste. Until DOE completes an analysis of risks to human health and the environment due to the waste in the tanks throughout the retrieval and closure process, DOE cannot demonstrate the risk reductions that will be achieved by its increasingly costly tank management strategy. Without quantifying these risks and comparing the data to the costs associated with various tank management approaches, DOE cannot be sure that it has developed a strategy that appropriately addresses the risks posed by the tank waste to workers, who are most vulnerable to direct exposure during retrieval operations; the public, who live near the site or will use the site in future years; and the environment. Hanford’s manager of the Office of River Protection told us that having this kind of risk information would be valuable in negotiating tank closure guidelines and standards with federal and state environmental agencies and in controlling costs. To date, however, such information has not been available. DOE has spent billions of dollars over the last 2 decades managing Hanford’s underground tanks and the radioactive and hazardous wastes they contain; nevertheless, progress in emptying the tanks has been limited. In addition, many critical uncertainties—such as whether the tanks can safely be used until all have been emptied and closed—remain. In the absence of comprehensive information, DOE is relying on several key assumptions to carry out its tank management strategy, some of which seem overly optimistic in light of DOE’s past experiences. We recognize that, with technical complexities, intensifying fiscal pressures, and multiple stakeholders with competing visions of success, DOE faces unique challenges in carrying out its responsibility to protect people and the environment during its tank remediation efforts. Nevertheless, we believe that fulfilling this responsibility requires a strategy grounded in fundamental information about the tanks and the risks they pose as they are emptied and closed. DOE’s knowledge about tank integrity, tank viability over time, and tank risk is still incomplete. Consequently, DOE cannot appropriately weigh the relative risks of its strategy to workers, the public, and the environment against the climbing costs or weigh the risks and costs of its present strategy against other possible options for managing the tanks and their waste. Moreover, in the absence of this needed information, DOE may continue to face difficulties in developing achievable and reliable remediation milestones. To ensure that DOE has the fundamental information needed to make appropriate and cost-effective decisions about how to manage Hanford’s tank waste, we recommend that the Secretary of Energy take the following three actions: Give priority to carrying out the department’s assessment, in early planning stages as of 2008, of the structural integrity of Hanford’s single- shell tanks—an effort we fully support—and ensure that this assessment includes examining the following key attributes: corrosion of the tanks’ inner steel shells; the condition of concrete domes and outer shells, especially where waste has leaked; the integrity of long-obscured parts of the tanks for tanks that have been emptied; and the long-term viability of the tanks in light of their increasing age and DOE’s extended schedule for waste retrieval, waste treatment, and tank closure. On a routine basis—such as every 3 to 5 years—specifically quantify the risks posed by the tank waste to workers, the public, and the environment and the risks posed by DOE’s tank management strategy in light of the tanks’ questionable viability. Work with Ecology and EPA to (1) reassess its tank management strategy, incorporating quantified risk information, and (2) develop and agree to realistic schedule and cost milestones. We provided a draft of this report to the Secretary of Energy for review and comment. In a written response, DOE’s Principal Deputy Assistant Secretary for Environmental Management, acting for the Assistant Secretary for Environmental Management, stated the department does not agree that it lacks the necessary information to make informed decisions regarding tank integrity, waste retrieval, and treatment but views the report’s recommendations as consistent with the department’s present and planned activities in tank integrity, risk management, and regulatory negotiations. DOE also provided technical comments, which we incorporated throughout the report as appropriate. DOE’s comments are reproduced in appendix IV. Regarding our report’s conclusions, DOE stated its belief that it has adequate knowledge to make decisions about tank waste storage, retrieval, and treatment, although it acknowledged that as the mission progresses, additional tank integrity monitoring, waste characterization, and development of retrieval technology will be required. In its response, DOE cited work by the Defense Nuclear Facilities Safety Board and the National Academy of Sciences as support that it has adequate knowledge of the tanks and their contents. DOE stated that, working with its regulators and the Safety Board, it had conducted extensive characterization of tank contents, resolved safety issues, and implemented the Safety Board’s recommendation. This 1993 recommendation focused on the safety of selected Hanford tanks, specifically those containing potentially flammable and explosive chemicals. The Safety Board did not address the continued use, condition, or viability of Hanford’s waste tanks during a treatment schedule that may be extended by decades. DOE also stated that in a 2006 report, the National Academy of Sciences concluded that the department’s knowledge of tank waste characteristics was adequate for waste retrieval activities. The National Academy of Sciences, however, made this statement within the context of “waste processing and the design of processing facilities.” Its report acknowledged that the tanks still needed to be “sampled for specific data needs,” which at Hanford are driven by waste compatibility, chemistry control to mitigate corrosion, and other factors. Similar to the Safety Board’s recommendation, this report did not address the extent to which single-shell waste tanks—about half of which are confirmed or presumed to have leaked—will remain viable under the lengthening cleanup time frames. Our report recognizes that DOE has made some progress in gaining data about the condition of the tanks, in particular the double-shell tanks, and general tank contents. Despite its monitoring efforts, however, the department still has limited information about the actual condition of the single-shell tanks. For example, DOE has performed limited examinations of the condition of the tanks’ inner steel shells beneath the waste and the buried concrete exteriors and foundations—information that is critical for assessing the long-term viability of these tanks. Moreover, DOE is in early planning stages of a multiyear study to assess single-shell tank integrity, which represents the department’s own acknowledgment of the need for more information. At this early stage, it is unclear if or when this study will provide DOE with more comprehensive information. Without timely execution of this study, neither DOE nor its regulators can benefit from the information the study would provide as they negotiate a new schedule for retrieving the tank waste and closing the tanks. Thus, in our view, DOE’s current knowledge is not adequate, for the single-shell tanks in particular, to assess the appropriateness of the department’s tank management strategy—which involves continuing to store waste in aging tanks until they can be emptied and closed—especially in light of lengthening cleanup time frames. Regarding our report’s recommendations, DOE stated that it views them as consistent with its present and planned activities; nevertheless, we are not convinced. We continue to believe that the department must give priority to its assessment of single-shell tank integrity, quantify the risks posed by the tank waste and the tank management strategy, and work with Ecology and EPA to reassess its strategy and develop realistic milestones. Without these specific steps, DOE can not ensure that its tank management strategy is appropriate in light of escalating costs. We are sending copies of this report to other interested congressional committees and to the Secretary of Energy. We will also make copies available to others upon request. In addition, the report will be available at no charge on the GAO Web site at http://www.gao.gov. If you or your staffs have any questions regarding this report, please contact me at (202) 512-3841 or aloisee@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. Key contributors are listed in appendix V. To determine the current condition, contents, and long-term viability of Hanford’s underground tanks, we gathered and reviewed numerous reports and studies addressing the tanks’ physical status, expected design life, age, and integrity. To understand the tanks’ physical condition, we reviewed historical as well as current documents that describe the condition of the tanks’ carbon-steel shells, concrete domes and exteriors, and ancillary piping and equipment. We reviewed studies, including tank waste sampling and analysis data, to document the major radioactive constituents, chemically hazardous materials, and other miscellaneous material found in the tanks. To address the tanks’ long-term viability, we reviewed historical documents, studies by independent experts, and Department of Energy (DOE) reviews to determine the tanks’ actual age and estimated life span and their predicted leak and corrosion rates over time. We interviewed DOE and contractor officials, Washington State Department of Ecology (Ecology), and Environmental Protection Agency (EPA) officials to obtain their views on these topics and to obtain additional information. To assist in evaluating the technical aspects of the tanks, their contents, and viability, we obtained assistance from a technical consultant, Dr. George W. Hinman, Professor Emeritus of Applied Energy Studies at Washington State University, who has extensive nuclear energy experience in industry, government, and academia. To determine DOE’s strategy for managing the tanks and the waste they contain, we reviewed DOE’s most recent tank waste retrieval documents, detailing how the department plans to manage the tanks and their contents. We reviewed regulatory requirements and milestones governing the tank waste cleanup. To document DOE’s approach for removing waste and closing the tanks, we reviewed DOE’s approved project baseline schedule and cost for the department’s tank management strategy and discussed this schedule and other schedule proposals with DOE officials at Hanford. We also reviewed DOE and its tank farm contractor’s reports assessing management risks associated with tank farm activities to identify potential problems facing Hanford’s aging tanks and the possible effects of these problems on DOE’s strategy for dealing with the tank waste. To understand these problems and to obtain information on the tank waste cleanup milestones that were in negotiation as of May 2008, we interviewed representatives from Ecology and EPA. To understand the complexity of removing waste from the tanks, we visited several tank farms on the Hanford Site and observed workers removing waste from a tank. We also gathered and reviewed documents describing the status of various waste retrieval technologies that DOE has used and plans to use and discussed these technologies with DOE and contractor officials. To determine the extent to which DOE has assessed whether the reduction in risk that may result from its current tank management strategy warrants the growing costs of that strategy, we examined budget and financial documents, environmental impact studies, and assessments of risks. We reviewed financial documents to obtain the most current information on the estimated life-cycle cost of retrieving wastes and closing the tanks. We reviewed environmental studies and risk assessments to determine the extent to which cleanup costs and risks to workers, public health, and the environment associated with the tank waste have been quantified. As we reviewed these documents, we frequently interviewed key DOE and contractor officials to discuss, clarify, and confirm our interpretation of the information. We relied on dollar figures and tank strategy assumptions provided by DOE and its contractors but took various steps—such as reviewing cost estimating documents and strategy assumptions, reviewing budget documents, and obtaining clarifications from the officials who prepared them—to ensure that the data were sufficiently reliable for purposes of this report. We discussed our findings with, and obtained the views of, DOE and contractor officials responsible for the tank farms and with representatives of Ecology and EPA agencies, as well as with outside experts. We conducted this performance audit from July 2007 through June 2008 in accordance with generally accepted government auditing standards. Those standards require that we plan and perform the audit to obtain sufficient, appropriate evidence to provide a reasonable basis for our findings and conclusions based on our audit objectives. We believe that the evidence obtained provides a reasonable basis for our findings and conclusions based on our audit objectives. (gallons) (years) Anticipated age when emptied of waste (years) Total waste (gallons) (gallons) (years) Anticipated age when emptied of waste (years) (gallons) Total waste (gallons) (gallons) (years) Anticipated age when emptied of waste (years) Total waste (gallons) (gallons) (years) Anticipated age when emptied of waste (years) (gallons) Total waste (gallons) (gallons) (years) Anticipated age when emptied of waste (years) Appendix III: Capacity, Age, and Retrieval Schedule for Hanford’s Double-Shell Tanks as of February 2008 (gallons) (years) Anticipated age when emptied of waste (years) In addition to the individual named above, Janet E. Frisch, Assistant Director; Robert Alarapon; Ellen W. Chu; Doreen Eng; George W. Hinman; Richard Johnson; Karen Keegan; Nancy Kintner-Meyer; Jeff Larson; Mehrzad Nadji; Omari Norman; Thomas Perry; and John Smale made key contributions to this report. Hanford Waste Treatment Plant: Department of Energy Needs to Strengthen Controls over Contractor Payments and Project Assets. GAO-07-888. Washington, D.C.: July 20, 2007. Nuclear Waste: DOE Should Reassess Whether the Bulk Vitrification Demonstration Project at Its Hanford Site Is Still Needed to Treat Radioactive Waste. GAO-07-762. Washington, D.C.: June 12, 2007. Hanford Waste Treatment Plant: Contractor and DOE Management Problems Have Led to Higher Costs, Construction Delays, and Safety Concerns. GAO-06-602T. Washington, D.C.: April 6, 2006. Nuclear Waste: Absence of Key Management Reforms on Hanford’s Cleanup Project Adds to Challenges of Achieving Cost and Schedule Goals. GAO-04-611. Washington, D.C.: June 9, 2004. Nuclear Waste: Challenges to Achieving Potential Savings in DOE’s High-Level Waste Cleanup Program. GAO-03-593. Washington, D.C.: June 17, 2003. Nuclear Waste: Department of Energy’s Hanford Tank Waste Project— Schedule, Cost, and Management Issues. GAO/RCED-99-13. Washington, D.C.: October 8, 1998. Nuclear Waste: Management and Technical Problems Continue to Delay Characterizing Hanford’s Tank Waste. GAO/RCED-96-56. Washington, D.C.: January 26, 1996. Nuclear Waste: Further Improvement Needed in the Hanford Tank Farm Maintenance Program. GAO/RCED-95-29. Washington, D.C.: November 8, 1994. Nuclear Waste: Hanford Tank Waste Program Needs Cost, Schedule, and Management Changes. GAO/RCED-93-99. Washington, D.C.: March 8, 1993. Nuclear Waste: Hanford Single-Shell Tank Leaks Greater Than Estimated. GAO/RCED-91-177. Washington, D.C.: August 5, 1991. Nuclear Waste: Problems and Delays with Characterizing Hanford’s Single-Shell Tank Waste. GAO/RCED-91-118. Washington, D.C.: April 23, 1991. Nuclear Energy: Consequences of Explosion of Hanford’s Single-Shell Tanks Are Understated. GAO/RCED-91-34. Washington, D.C.: October 10, 1990. Nuclear Waste: DOE’s Program to Prepare High-Level Radioactive Waste for Final Disposal. GAO/RCED-90-46FS. Washington, D.C.: November 9, 1989. Nuclear Waste: DOE’s Management of Single-Shell Tanks at Hanford, Washington. GAO/RCED-89-157. Washington, D.C.: July 18, 1989. Progress and Problems in Programs for Managing High-Level Radioactive Wastes, Atomic Energy Commission. Washington, D.C.: January 29, 1971. Observations Concerning the Management of High-Level Radioactive Waste Material. Washington, D.C.: May 29, 1968.

Summary: The Department of Energy (DOE) manages more than 56 million gallons of radioactive and hazardous waste stored in 149 single-shell and 28 double-shell underground tanks at its Hanford Site in Washington State. Many of these aging tanks have already leaked waste into the soil. Meanwhile, DOE's planned process for emptying the tanks and treating the waste--mixing it with molten glass and solidifying it in canisters for storage--has experienced delays, lengthening the time the tanks will store waste and intensifying concerns about the tanks' viability during a long cleanup process. This report addresses (1) the condition, contents, and long-term viability of Hanford's underground tanks; (2) DOE's strategy for managing the tanks; and (3) the extent to which DOE has weighed the risks and benefits of its tank management strategy against the growing costs of that strategy. GAO analyzed numerous studies and reports on the tanks and interviewed DOE officials and other experts on relevant issues. DOE lacks comprehensive information about the condition, contents, and long-term viability of Hanford's waste tanks. Although recent work indicates that the newer, double-shell tanks are generally sound structurally, the condition of the older, single-shell tanks is less certain. All the tanks contain a complex mix of radioactive elements and chemicals, making the proportions of constituents in any tank uncertain and emptying the tanks technically challenging. DOE officials acknowledged the lack of information about the condition of the single-shell tanks and are in early stages of a study to assess these tanks' structural integrity. The uncertainties over tank condition, especially as the time frames for emptying tanks are extended and the tanks age, raise serious questions about the tanks' long-term viability. DOE's tank management strategy involves continuing to use Hanford's aging tanks to store waste until they can be emptied, the waste treated, and the tanks closed. As work proceeds, however, DOE's time frames for completion are lengthening by decades, and the agency appears to be operating under more than one schedule. For example, DOE's internal milestone for emptying single-shell tanks is 19 years later than the date agreed to with its regulators. Although DOE and its regulators have been discussing new tank waste management milestones, as of May 2008, no decisions had been reached. Moreover, DOE's tank management strategy relies on assumptions that may be overly optimistic, such as assuming that emptying single-shell tanks will proceed significantly faster than it has to date. DOE lacks comprehensive risk information needed to weigh the benefits of pursuing its tank waste removal and closure strategy against growing costs. In particular, DOE has not assessed the risks posed by continuing to store waste in the aging tanks until the waste is removed and cannot demonstrate that benefits are commensurate with the costs of its tank management strategy. DOE is nevertheless moving forward with negotiating new tank waste milestones with its regulators.