Nuclear Waste: DOE Lacks Critical Information Needed to Assess Its Tank Management Strategy at Hanford
Published: 2008-06-30T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: 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.
section_title: What GAO Found
paragraphs: 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.

section_title: Letter
paragraphs: The Department of Energy (DOE) is responsible for one of the world’s  largest environmental cleanup programs—the treatment and disposal of  wastes created by the production of materials for nuclear weapons. From  1943 to 1989, DOE and its predecessor agencies produced nuclear  materials at the Hanford Site, which lies along the Columbia River in  southeastern Washington State. The site occupies 586 square miles upriver  from the cities of Richland, Pasco, and Kennewick, whose combined  population exceeds 200,000 people. Four decades of nuclear weapons  production have left a legacy of chemical, hazardous, and radioactive  waste, making Hanford one of the most contaminated places on Earth.  During production, some of the waste was deposited directly into the soil;  some was encased in drums or other containers and buried; and some was  stored in 177 large, underground tanks. All told, these tanks, clustered  together in 18 locations called tank farms, store more than 56 million  gallons of waste—enough to cover an entire football field to a depth of  over 150 feet, or the height of a 15-story building (see fig. 1).
Since plutonium production ended at Hanford in the late 1980s, DOE has  established an approach for stabilizing, treating, and disposing of the site’s  tank waste. Its planned cleanup process involves removing, or retrieving,  waste from the tanks; treating the waste on site; and ultimately disposing  of the lower-radioactive waste on site and sending the highly radioactive  waste to a geologic repository for disposal. As cleanup has unfolded,  however, the schedule has slipped, and the costs have mounted. According  to DOE’s latest estimate, treatment of the waste is not expected to begin  until late 2019 and could continue until 2050 or longer. Meanwhile, 67 of  Hanford’s tanks are confirmed or presumed to have already leaked about   1 million gallons of waste into the ground, and as a result, experts,  including representatives from the National Academy of Sciences, have  expressed concern about the integrity and usability of the tanks during  what is likely to be a long treatment process.
Cleanup, treatment, and disposal of waste produced at DOE facilities are  governed by a number of federal laws and implemented under the  leadership of the Assistant Secretary for Environmental Management.  DOE is to conduct its cleanup activities in accordance with a number of  federal and state environmental laws, primarily the Comprehensive  Environmental Response, Compensation, and Liability Act of 1980  (CERCLA), as amended, and the Resource Conservation and Recovery Act  of 1976 (RCRA), as amended. In addition, most of the cleanup activities at  Hanford, including emptying of the underground tanks, are carried out  under the Hanford Federal Facility Agreement and Consent Order among  DOE, Washington State’s Department of Ecology (Ecology), and the  federal Environmental Protection Agency (EPA). Commonly called the Tri- Party Agreement, this accord was signed in May 1989 and has been  amended a number of times since then. The agreement lays out legally  binding milestones for completing the major steps of Hanford’s waste  treatment and cleanup process. A variety of local and regional  stakeholders, including county and local governmental agencies, citizen  and advisory groups, and Native American tribes, also have long-standing  interests in Hanford cleanup issues. Like nearly all of DOE’s missions,  work at Hanford is performed by private firms under contract to DOE.
In this context, 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 the waste they contain; 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.
To address these objectives, we gathered and reviewed information on the  tanks and their contents, and we interviewed DOE and contractor officials  and outside experts. Specifically, we reviewed available documentation on  the condition of the tanks, including their expected life span (which  engineers call design life), age, structural integrity, and contents. We  reviewed DOE’s strategy for managing and monitoring the tanks’ contents,  as well as regulatory requirements and milestones governing tanks. In  addition, we reviewed a 2007 DOE tank waste management plan to identify  potential problems facing Hanford’s aging tanks and the possible effects of  such problems on DOE’s strategy for dealing effectively with the tanks. We  examined risk studies and technical reviews to identify the challenges  DOE faces in managing Hanford’s underground tanks. We also determined  the extent to which costs and risks to workers, public health, and the  environment that are associated with DOE’s tank management strategy  have been quantified. We discussed our findings with, and obtained the  views of, DOE and contractor officials responsible for the tank farms and  with representatives of federal and state environmental agencies, as well  as with outside experts. Appendix I describes our scope and methodology  in more detail. 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.
subsections: section_title: Background
paragraphs: 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.
section_title: Uncertainties Raise Questions about Tanks’ Long-Term Viability
paragraphs: 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.
subsections: section_title: Integrity of Double-Shell Tanks Is Considered Sound, but Condition of Single-Shell Tanks Is Difficult to Ascertain
paragraphs: 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.
section_title: DOE Knows the General Composition of Hanford’s Tank Waste but Not the Specific Constituents in Each Tank
paragraphs: 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.
section_title: Many Tanks Have Exceeded Their Expected Life Spans, Raising Questions about Continued Viability
paragraphs: 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.
section_title: DOE’s Tank Management Strategy Involves Continued Use of the Aging Tanks, Perhaps for Decades
paragraphs: 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.
subsections: section_title: DOE’s Tank Management Strategy Calls for Using the Aging Tanks Until They Can Be Emptied and Closed
paragraphs: 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.
section_title: DOE Appears to Be Operating under More Than One Schedule
paragraphs: 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.
section_title: DOE’s Lengthening Time Frames Incorporate Assumptions That Seem Overly Optimistic
paragraphs: 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.
section_title: DOE Cannot Weigh the Benefits of Pursuing Its Tank Management Strategy against Growing Costs Because It Lacks Critical Information
paragraphs: 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.
subsections: section_title: DOE’s Past and Present Risk Studies Have Not Explicitly Considered Health and Environmental Risks Associated with Extended Use of the Tanks
paragraphs: 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.
section_title: DOE Has Not Demonstrated That Its Tank Management Strategy Is Appropriate in Light of Rising Costs
paragraphs: 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.
section_title: Conclusions
paragraphs: 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.
section_title: Recommendations for Executive Action
paragraphs: 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.
section_title: Agency Comments and Our Evaluation
paragraphs: 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.
section_title: Appendix I: Scope and Methodology
paragraphs: 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.
section_title: Appendix II: Capacity, Age, and Retrieval Schedule for Hanford’s Single-Shell Tanks as of February 2008
subsections: section_title: Total waste (gallons)
paragraphs: (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)
section_title: Appendix III: Capacity, Age, and Retrieval Schedule for Hanford’s Double-Shell Tanks as of February 2008
paragraphs: 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)
section_title: Appendix IV: Comments from the Department of Energy
section_title: Appendix V: GAO Contact and Staff Acknowledgments
subsections: section_title: Staff Acknowledgments
paragraphs: 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.
section_title: Related GAO Products
paragraphs: 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.