The Hanford site houses 177 underground storage tanks that contain 56 million gallons of radioactive and chemical waste produced during World War II and the Cold War as byproducts of plutonium production. These tanks are divided into 149 single-shell tanks (SSTs) and 28 double-shell tanks (DSTs), grouped into 18 farms. They vary in size from 50,000 to 1.25 million gallons.
Originally designed for a 20-year lifespan, the SSTs—constructed with sturdy concrete and carbon steel—have significantly exceeded their operational life and no longer meet regulatory standards. In contrast, construction of the DSTs began in 1968, each featuring an inner tank with a separate steel liner and an outer shell for backup containment.
Monitoring teams carefully track tank waste levels and other data to detect potential leaks in both SSTs and DSTs. Leakage issues have been reported since the 1950s. To minimize these leaks, steps have been taken to transfer liquid waste from SSTs to DSTs and operate the 242-A Evaporator Facility, which evaporates excess water from tank waste. Additionally, monitoring wells are in place to check for substances that may reach the groundwater, and periodic video inspections are conducted inside the tanks.
Known Leakers:
- Tank T-111: Discovered to be leaking approximately 300 gallons/year in 2013
- Tank B-109: Identified as leaking approximately 560 gallons/year in 2021
- Tank T-101: Suspected of leaking approximately 200 gallons/year as of August 2024
Additionally, in 2012 double-shelled tank AY-102 was found to have leaked waste from the inner tank into the annulus, but the waste did not leak beyond the outer tank into the soil. The majority of waste from AY-102 (over 725,000 gallons) was removed by 2017.
In August 2022, the DOE and the Washington State Department of Ecology signed an agreement, known as the Agreed Order, to address two leaking underground waste tanks, including Tanks B-109 and T-111. The settlement aims to evaluate methods to halt the leaks, requiring the DOE to consider two technologies: enhanced salt-well pumping and an in-tank pretreatment system. It will also assess disposal options for the removed liquid waste, which may involve transporting it to a DST or a treatment plant. The Pacific Northwest National Laboratory (PNNL) will conduct a third-party review of these methods.
In addition to monitoring tank waste volumes, the Hanford contractor Washington River Protection Solutions (WRPS) works to “close” SSTs by retrieving as much waste as possible from the tanks and transferring it to DSTs. Retrieval operations are currently underway at Tank AX-101, where approximately 426,000 gallons are set to be extracted. Upon certification of this process, AX-101 will become the 21st SST at the site to be emptied, marking AX Farm as the second tank farm at Hanford where waste retrieval operations have concluded (C Farm being the first).
Ultimately, the long-term plan for much of the tank waste is to solidify it at the Waste Treatment and Immobilization Plant (WTP) in Hanford’s 200 East Area.
