During the early Cold War years, the Y-12 nuclear weapons plant secretly used about 20 million pounds of mercury to process lithium for hydrogen bombs. At least 700,000 pounds of the toxic metal, according to government estimates, was released into the environment.
Bit by bit, project by project, some of that lost mercury is being recovered, treated and disposed of properly. But it’s going to require a long-term effort.
The U.S. Department of Energy has identified mercury as its top environmental priority in Oak Ridge and promised to accelerate cleanup efforts in future years — especially after demolition of buildings at the former K-25 uranium-enrichment plant has been completed.
U.S. Sen. Lamar Alexander says the Oak Ridge legacy of mercury pollution worries him more than radioactive hazards, and he has pledged to pursue the necessary funding.
Alexander last year announced a new $125 million treatment facility to be installed at the headwaters of East Fork Poplar Creek — the unfortunate recipient of about 239,000 pounds of mercury over the past half-century.
The new facility is supposed to filter about 3,000 gallons of water per minute and remove about 65 percent of the mercury in the storm sewer’s main outfall. However, the treatment system isn’t expected to come online until about 2020.
Other projects may have to wait even longer.
Y-12′s old processing buildings still contain residual amounts of mercury, which long ago seeped into cracks or found its way into walls and foundations. Recovery planning is difficult because some buildings are inside the weapons plant’s high-security Protected Area and aren’t easily accessible to cleanup teams without security clearances.
Four buildings — known as Beta-4, Alpha-2, Alpha-4 and Alpha-5, totaling 1.8 million square feet — have to be demolished before cleanup teams can even evaluate the mess that’s underneath them. An estimated 20,000 pounds of mercury still resides in Alpha-4, according to Mike Koentop, executive officer of DOE’s Office of Environmental Management. Mercury estimates for the other three buildings were not immediately available, he said.
Besides removing mercury from the buildings, it’s likely that large volumes of mercury-contaminated soil will have to be treated after the demolitions are done. An estimated 428,000 pounds of mercury is reportedly tied up in Y-12 soils or held in underground rock formations as a result of historic spills and discharges, Koentop said.
A number of mercury-removal projects have shown some success.
The West End Mercury Area project, which cleaned out and repaired the plant’s deteriorated stormwater sewer system, recovered more than 50 pounds of mercury-contaminated sediments.
A Recovery Act-funded project removed five mercury storage tanks, which reportedly posed an ongoing hazard to workers and the environment because of escaping vapors.
The Department of Energy said at least 650 pounds of elemental mercury was removed from the former storage tanks, which had been taken out of service in the 1980s but remained in a scrap yard at Y-12’s west end. The tanks cleanup started in 2012 and was completed last year.
The work was reportedly coordinated between URS-CH2M Oak Ridge, the department’s cleanup manager in Oak Ridge, and B&W Y-12, then the managing contractor at Y-12.
Wayne McKinney of UCOR said two of the tanks were not contaminated and were sent to the sanitary landfill at Y-12. The other three were transported to Materials and Energy Corp., a local firm, for removal of the mercury contents and then cut into pieces, he said.
“More than 650 pounds of mercury was removed and treated from the three tanks,” McKinney said. “The mercury was disposed at the Nevada National Security Site. A formal report documenting completion of the project was submitted to the Environmental Protection Agency and Tennessee Department of Environment and Conservation.”
Additional cleanup actions at the storage site will probably be necessary. Soils were excavated from the site and sent to specialty vendors for analysis. DOE is hoping to identify methods of treating mercury within the soil so that the material can be accepted for disposal at the federal’s agency on-site landfill. Local disposal would significantly lower the cost.
So far, DOE said the study had provided nine treatment technologies of potential use.
The Department of Energy identified at least six other projects, including a 1996-97 effort to excavate contaminated soil from the East Fork floodplain, that had reduced the mercury burden in the environment.
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