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Nuclear Waste Program

Frequently Asked Questions: Leaking underground tanks at Hanford

Ecology knows the public and the news media want and deserve answers about leaking tanks at Hanford, so we have created this page to answer some of the most common questions. Please submit other questions you would like to see answered by emailing or
calling 509-372-7950.

Questions and Answers:

Please click a question from the list to view the answer.

  1. How many tanks are leaking and when did they start?
  2. What is the threat to public health?
  3. What are the options for dealing with leaking tanks?
  4. How are the tanks monitored?
  5. Wasn't all the liquid pumped out of the SSTs years ago?
    If so, why are these tanks leaking again?
  6. What has been done to slow tank leaks?
  7. What has been done to keep water from intruding into the tanks
    and prevent contaminants from moving toward groundwater?
  8. How hard is it to get the waste out of tanks? 
  9. If the waste is pumped out of the tanks, where will it go? Don't you need additional storage space? If so, how much time and money is it going to take to build new tanks?
  10. Is there any good news about Hanford tanks?

  11. 1) How many tanks are leaking and when did they start?

    Single-shell tanks B-203 and B-204 under construction. (Click image to enlarge.)

    One double-shell tank (DST) AY-102, was first reported to be leaking in October 2012. Waste is leaking into the space between the waste tank, or the inner shell of the double-shell tank, and the secondary containment shell. This space, called the annulus, was designed to contain leaks.

    A Settlement Agreement in 2014 determined the timeframe to start and complete tank retrieval. DOE did not want to retrieve the tank before 2019. Ecology and DOE reached the settlement agreement which gave DOE a over a year to plan and construct systems for retrieval and a year to retrieve the tank (by March 4, 2017). Part of the planning required development of monitoring and contingency plans that specify the monitoring requirements and what conditions they believed might arise that would require implementation of contingency plans. The scenarios were identified and included in the plan along with the actions they would take. One of the anticipated scenarios was an increasing leak into the annulus. The contingency plan specified the actions to take. Implementation of those actions is underway.

    One single-shell tank (SST) T-111, was first reported in February 2013.

    Note that 67 tanks leaked at least one million gallons in the past.

    2) What is the threat to public health?

    No immediate or near-term health risks are associated with Hanford’s tank leaks.

    • The tanks are underground, five to eight miles from the Columbia River, in an isolated area far from any homes or farms. 
    • There is no route for the leaked waste to travel from Hanford to agricultural areas, so there is no risk of food crop contamination.
    • Hanford’s groundwater is about 200 to 300 feet below the tanks, so the new leaks will take decades to reach it.
    • The groundwater pump-and-treat facilities in the center of Hanford are keeping the majority of pre-existing groundwater contamination from moving toward the Columbia River.  

    However, the fact that there is no immediate threat to health does not minimize the state's concerns, because any leaks add to future groundwater problems. These leaks underscore the importance of retrieving and treating tank waste as quickly as possible to mitigate the chance of further releases to the environment.

    3) What are the options for dealing with leaking tanks?

    The single-shell tanks (SSTs) are all unfit for use and decades past their design life. It would be impossible to repair and upgrade the SSTs to meet current regulatory standards. Some options for addressing leaks include:

    • Increasing monitoring and sampling.

    • Developing new retrieval technologies.

    • Constructing surface barriers over SST farms. In 2008, an interim barrier was constructed over part of T Tank Farm, where three of the leaking SSTs are located, to protect against precipitation entering tanks and to keep that precipitation from pushing contaminants closer to the groundwater. Construction of additional barriers is a possible solution to slow the spread of leaked tank waste.

    • Building new tanks. We had assumed that the double-shell tanks (DSTs) were still sound and could accept waste from SSTs. However, the leak from the inner shell of AY-102 has led us to re-evaluate that assumption. To move the waste out of that DST and the SSTs, USDOE may have to build new DSTs. Washington, Oregon, and the Hanford Advisory Board have urged USDOE to start the process to build new DSTs at Hanford. However, obtaining funding and designing and constructing new tanks would likely take at least 10 years.

    • Removing liquid waste from DST AY-102 with a portable evaporator.

    • Disposing some of the waste at the Waste Isolation Pilot Plant in New Mexico. Because the Waste Treatment Plant designed to treat Hanford’s tank waste will not start up for at least six more years, USDOE is exploring other options to treat and dispose of this waste. It may be possible to classify the waste in five of the six leaking SSTs as transuranic waste (meaning literally “after uranium,” this waste contains alpha-particle-emitting radioactive isotopes with atomic numbers higher than 92, uranium's atomic number). If this was done, then the waste would be retrieved from the tanks, dried, packaged, and shipped to WIPP for disposal. But this process would, optimistically, take at least two to five years.

    4) How are the tanks monitored?

    Monitoring of the tank waste is difficult in part due to the high radiation and harsh chemical environment inside most tanks.  Access to the insides of the tanks is limited.  

    All of the tanks have monitoring instruments inside them. This is a requirement of the Tri-Party Agreement. However, analyzing the monitoring data is a complex process, and it can be difficult to detect very small changes in waste levels in tanks that do not have much liquid or solid waste.  

    The existing in-tank monitoring equipment is imperfect, but no better systems have been identified. U.S. Department of Energy (USDOE) can currently only monitor the surface level at one location in each tank. Most tanks have annual monitoring requirements. If they have an Enraf® gauge, they are monitored continuously. One data point is gathered each day.

    For tanks with liquid observation wells, a neutron probe is used quarterly to gather data. It was a look at long term trends of that data something USDOE had never done before — that led to the conclusion there must be new leaks.

    External tank monitoring can be used to detect releases to the environment but is much more expensive to implement and also has limitations on its usefulness. It is being done, but Ecology is looking for ways to improve the monitoring process. (See Single-Shell Tank System Leak Detection and Monitoring Functions and Requirements, RPP-9937, Rev. 3, for more information.)

    5) Wasn't all the liquid pumped out of the SSTs years ago? If so, why are these tanks leaking again?

    Hanford’s single-shell tanks were interim stabilized between 1978 and 2010. Ecology sued the  U.S. Department of Energy (USDOE) to finish interim stabilization in 1999 through a Consent Decree. The interim stabilization process removed as much pumpable, or free, liquid as was “practicable.”  Practicable means pumping was continued until the rate was very low — less than 0.05 gallons per minute.  

    Solid waste, called saltcake, that remains after liquid waste is pumped out. (Click to enlarge.)

    However, liquids drain very slowly through the saltcake and sludge, and there was only one pumping location per tank.  Over time, additional liquids can drain to the pumping location, so liquids still in the tanks can only be pumped after they migrate to the pumping location.  

    Tanks are buried under 7 to 10 feet of soil to shield workers from radiation. This safeguard also limits access to the waste in the tanks. The pipes extending from the ground, called risers, are the only entry port to remove waste for safer storage and treatment unless modifications are made.

    Some tanks met interim stabilization requirements because they didn’t have that much waste in the first place. Six tanks were administratively interim stabilized after pumping equipment failed and was too expensive to replace. 

    In addition, precipitation has entered some tanks and increased the liquid volume, a process known as intrusion.

    After reviewing monitoring data, USDOE now knows that some of the tanks have continued to show decreases in waste levels. Ecology would like USDOE to use better monitoring equipment and to prove that existing equipment is in good working condition.

    6) What has been done to slow tank leaks?

    All free liquids were pumped from the single-shell tanks to newer double-shell tanks from the 1970s to the 1990s, leaving solid saltcake and slurry (mixture of liquid and solid waste) in the tanks. However, liquids drain very slowly through the saltcake and sludge, and there is only one pumping location per tank.  Over time, additional liquids drain to the pumping location, so liquids still in the tanks can only be pumped after they move to the pumping location.

    7) What has been done to keep water from intruding into the tanks and prevent contaminants from moving toward groundwater?

    Most raw water pipelines to the single-shell tank (SST) farms were cut and capped between 2001 and 2002. Leaky water distribution lines next to tank farms were also pressure tested. If these lines were not needed or failed the test, they were either remediated or removed from service to further limit the amount of water moving through the soil, a driving force in contaminant migration.

    Water intrusion into SSTs has been reduced, but monitoring data continues to indicate intrusion in some tanks. The sources of intrusion are being investigated and stopped where possible. Engineering controls were installed to prevent rain or snowmelt from forming puddles or ponds over, or in the vicinity of, the tanks. Surface covers were installed over some tank farms, and berms were built on the ground surface to direct water away from the tank farms.

    8) How hard is it to get the waste out of tanks?

    Cutaway diagram showing the inside of a single-shell tank and its external access points.(Click to enlarge.) Removing waste from Hanford's tanks is difficult for many reasons:

    • Access to the tank waste is very limited.  The tops of the tanks are 7 to 10 feet underground, and openings into the tanks are limited. Double-shell tanks (DSTs) have more access points than single-shell tanks (SSTs). Regardless, all work is done remotely using video cameras and robotic equipment.

    • The waste is usually very radioactive and contains many chemicals, creating an environment that limits the types of equipment that can be used. For instance, electronic equipment can be burned out by radiation.

    • Workers must rely on only one or two cameras in each tank to view waste and retrieval equipment.

    • The waste in the tanks is not homogeneous and can have varied properties at different locations in the tank. The solid waste is generally broken up using high pressure spray (existing liquid waste is constantly recirculated so more waste isn't created). The liquid is also used to transport waste from SSTs to DSTs.

    • Retrieval technologies continue to evolve, but retrieval rates are still limited.

    • Waste can only be moved to a tank with the appropriate space and chemistry.

    Cutaway diagram showing the inside of a double-shell tank and its external access points. (Click to enlarge.)In addition to the above challenges, pumps and other equipment break, the weather can become too hot for workers to be safe in protective gear or too cold for equipment to work properly. When equipment operates smoothly and weather conditions are safe for workers, tank retrieval work continues around the clock.

    9) If the waste is pumped out of the tanks, where will it go? Don't you need additional storage space? If so, how much time and money is it going to take to build new tanks?

    A shortage of space in Hanford’s double-shell tanks is a concern, especially because one of them is leaking. Ecology is not convinced that current storage is adequate to meet legal and regulatory requirements for tank retrievals and Waste Treatment Plant operations.  

    The state and the federal governments must have a thorough and candid discussion about the need for additional storage tanks. The U.S. Department of Energy (USDOE) estimates that it could take a minimum of 7 to 10 years and cost around $100 million per tank to build new tanks. But we can’t wait that long. We will be working with USDOE to consider options for accelerating that process.

    10) Is there any good news about Hanford tanks?

    The U.S. Department of Energy (USDOE) has a responsibility to prevent waste from leaking into the environment, and to promptly address any tanks that are found to be leaking. We know that many of these single-shell tanks have leaked in the past and that future leaks are highly likely if the federal government does not act to get this waste retrieved and treated in a timely manner.

    In addition, active retrieval is ongoing, and a variety of technologies are being used in C Tank Farm, also known as Waste Management Area C (WMAC). The 2010 Consent Decree between Washington State and USDOE sets September 2014 as the deadline to complete waste retrieval from all 16 C Farm tanks, but USDOE has said that deadline is in jeopardy.

    For more information about leaking underground storage tanks at Hanford, please contact Ecology at or 509-372-7950.


DST: Double-shell tank

SST: Single-shell tank

USDOE: United States Department of Energy (Hanford Site owner)


Retrieval set to begin March 2016


Single-Shell Tank Evaluations, USDOE Hanford website (external link)

Ecology's Tank Waste Storage, Operations, and Closure Project

Washington regulations for tank systems: WAC 173-303-640(7)

Double-Shell Tank Emergency Pumping Guide in Ecology's Hanford Dangerous Waste Permit

Tank Farms, USDOE Hanford website (external link)