Frequently Asked Questions: Leaking underground tanks at Hanford
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1) How many tanks are leaking and when did they start?
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 a settlement agreement which gave DOE more than 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.
USDOE has a reliable leak detection system for the tanks and continues to maintain that system. It has the ability to detect tank leaks that could pose a threat to the environment. AY-102 has not leaked to the environment based on what we know today.
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.
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:
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.
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.
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?
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 email@example.com or 509-372-7950.
DST: Double-shell tank
SST: Single-shell tank
USDOE: United States Department of Energy (Hanford Site owner)
AY-102 PUMPING ORDER
Single-Shell Tank Evaluations, USDOE Hanford website (external link)
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)
Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.htm