TRI-PARTY AGREEMENT: THE BEGINNING OF ENVIRONMENTAL OVERSIGHT AT HANFORD In 1989, the U.S. Department of Energy, U.S. Environmental
Protection Agency, and Washington State Department of Ecology signed the landmark Hanford Federal Facility Agreement and Consent Order, or Tri-Party Agreement. This legally binding document sets up a schedule for cleanup, including milestones, or deadlines, for key steps in the process. Ecology’s Richland Field Office regulates the
mixed chemical and radioactive waste at Hanford with a focus on protecting the Columbia River and restoring the groundwater that flows into it. In 2000, President Clinton designated the Hanford Reach a National Monument. The Columbia River is the fourth-largest river (by volume) in the U.S., and the Reach, which flows through Hanford, is the only remaining free-flowing stretch besides its headwaters in British Columbia, making it extremely important spawning ground for salmon and steelhead and crucial to tribes practicing subsistence living. The river is the lifeblood of eastern Washington’s agriculture and provides drinking water for many Washington and Oregon communities located along it. Currently, approximately 72 square miles of
Hanford groundwater are contaminated above safe drinking water standards. While no one drinks this water, it is mobile and interchanges with river water, but at such low levels that it’s undetectable in the Columbia’s massive volume.
Groundwater cleanup is carried out through a variety of
methods. · Pump and treat: Contaminated water is pumped out
of the ground; treated for carbon tetrachloride, chromium, trichloroethene, nitrates and radioactive iodine-129, technetium-99 and tritium; and pumped back into the aquifer.
· Apatite sequestration: A slurry of water and fish bones, which contain apatite, a naturally occurring mineral, is injected into the soil. As contaminated groundwater passes through it,
apatite bonds with radioactive strontium-90, keeping it from reaching the Columbia River.
· Phytoremediation: Vegetation is planted along shorelines to suck up any contamination making its way to the river. The contaminated plants are then dug up and taken to the large, lined landfill (Environmental Restoration Disposal Facility) located in Hanford’s 200 Area.
· Biostimulation: Molasses thinned with vegetable oil is pumped into the ground, causing microorganisms to accelerate their life cycle with the introduction of a new food source. As these organisms eat, breed, and die, they use three molecules of oxygen, transforming dangerous chromium-6 (hexavalent) into safe chromium-3 (trivalent). The most toxic threat to groundwater is the
approximately 56 million gallons of high-level waste remaining in underground tanks. The plan is to vitrify, or “glassify,” it in the $12.3 billion Waste Treatment and Immobilization Plant (also known at the “vit plant”) currently under construction. The pretreatment facility will separate waste into two streams: low-activity (less radioactive) and high-level. Then the waste will be piped to the low-activity and high-level waste vitrification facilities. The waste will be mixed with molten glass, heated to 2,100 °F, and poured into stainless-steel containers for cooling and storage. After the outsides of the containers are decontaminated, the solidified waste can be more safely stored in a remote location while the radioactivity decreases over hundreds to thousands of years.
The cleanup schedule in the Tri-Party Agreement includes milestones lasting until 2052 for closing the underground double-shell tanks after retrieving the waste from them and treating it at the vit plant. But that’s not the end. The cores of Hanford’s nine production reactors have been or will be “cocooned”, or encased in concrete to keep water, wind, and biota out while the radioactivity decays away. Although milestones don’t yet exist for this, it’s planned to reopen the cocooned reactors between 2054 and 2070 to finish cleanup. Because some contamination will remain even after all the milestones are completed, long-term stewardship will be an issue “in perpetuity” or until radioactivity decays away after ten “half-lives.” The radioactive “half-life” of plutonium-239 is 24,000 years, so that’s a quarter of a million years!
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CLEARING 2011
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