The Department of Energy and its regulators have issued a decision adopting a final cleanup plan for the Hanford 300 Area just north of Richland, the first of six final plans that will cover 220 square miles along the Columbia River.
Much of the plan follows usual Hanford nuclear reservation procedures for digging up contaminated soil and waste sites, treating the waste as needed and then disposing of most of it in a central Hanford landfill for low-level radioactive waste.
But it also addresses the uranium groundwater plume beneath the 300 Area, which allows contaminated water to seep into the Columbia River.
The Hanford Advisory Board had asked that a pilot project be conducted to address the uranium-contaminated groundwater before a final plan was adopted. But DOE and the Environmental Protection Agency said the cleanup plan adopted in the final decision appears to be the best way to address contamination.
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The Comprehensive Environmental Response, Compensation and Liability Act, which required the final decision, also requires a review every five years. The groundwater plan will be reviewed then and changes made if it is not working as planned, said Geoff Tyree, DOE spokesman.
The final decision "paves the way for several major policy issues such as future land use," said Dennis Faulk, EPA Hanford project manager.
Under the Hanford Comprehensive Land Use Plan, the part of the 300 Area traditionally used as an industrial complex is planned for future industrial use, with the rest to be used for conservation and preservation.
But EPA has not wanted future uses to be precluded for most of the traditionally open land at the 300 Area, and the final decision covers cleanup to standards similar to those for residential use, Faulk said.
DOE said it plans cleanup to standards needed for unrestricted surface use of the land.
Cleanup of the 40 square miles of the 300 Area has been under way since the 1990s and most of it is expected to be completed by fall 2015. Work was done under interim cleanup decisions.
However, the interim decisions did not cover the work planned now to address uranium contamination, and the final decision will help get the cleanup system funded and in place by the Tri-Party Agreement target date of the end of 2015, Faulk said.
The 300 Area was used for fabricating uranium into fuel pieces for the Hanford reactors that produced plutonium for the nation's nuclear weapons program. It also was used for research, including testing processes for chemically removing plutonium from irradiated uranium fuel.
Process trenches used to dispose of contaminated liquid into the soil were removed in the 1990s, and levels of uranium in the groundwater dropped. Hanford officials assumed then that if uranium-contaminated soil was excavated down to about 15 feet -- which has been done -- the groundwater contamination gradually would dissipate.
But it later became clear that more lightly contaminated soil near the groundwater was continually recontaminating the water. As the river would rise and fall, the level of groundwater also would change, allowing the groundwater to periodically soak the contaminated soil.
The final cleanup decision calls for adding a binding solution to the soil to reduce the movement of contamination to the groundwater while contamination in the groundwater dissipates over time.
Phosphate would be added, which combines with uranium in a carbonate form to make autunite, a uranium phosphate mineral that does not readily dissolve when hit by water. That sequesters it, or keeps it in the soil instead of the water.
The Hanford Advisory Board has recommended a field test to determine the effectiveness of the method. Then DOE would be better prepared to make a final decision on whether it's the best method for cleaning up the uranium, and cleanup could be done in a more timely and cost-effective manner, the board said in July.
But Mike Thompson, a DOE hydrologist, said then that DOE has studied the issue of uranium-contaminated groundwater for more than two decades and no better method is on the horizon.
The sequestration would not have to be 100 percent effective to give the groundwater some protection and allow enough uranium to dissipate to reach regulatory standards in a matter of decades, he said.
About 330 pounds of uranium per year is released to the Columbia River from the Hanford 300 Area, according to DOE. But three irrigation outlets on the Franklin County side of the river release 3,500 pounds of uranium a year into the river from fertilizer and uranium that's naturally in the ground. In addition, the Yakima River adds about 8,800 pounds a year.
Digging up all the 300 Area contaminated soil is not an option, DOE said. It would cost more than $1 billion and the soil would fill an area measuring 1,000 feet by 1,000 feet in the 70-foot-deep lined landfill in central Hanford.
The digging also could backfire and increase contamination in the groundwater, according to DOE. Water is used to control dust and prevent airborne contamination during excavation, but the water would filter through the soil and push more uranium into the groundwater.