The parties to the Tri-Party Agreement on environmental remediation of the Hanford Site in Washington state have verified that the challenging cleanup of the 618-10 Burial Ground has been completed. That meets the deadline under the agreement for completion of the project by the end of this fiscal year, according to the Department of Energy.
The Energy Department is one of the parties to the agreement. The others are Hanford’s two regulators: the U.S. Environmental Protection Agency, which led oversight of the burial ground project, and the Washington state Department of Ecology.
The 618-10 and 618-11 burial grounds were left for last in cleanup of the Columbia River Corridor at Hanford because they were expected to be the most challenging projects. Both were used for disposal of waste generated at the Hanford 300 Area, primarily from research that generated radioactive waste and development of reactor fuels. Cleanup of the 618-11 Burial Ground has yet to start, although some site characterization has been done.
Removal of contaminated material from the 7.5- acre 618-10 Burial Ground was completed in late 2017. Including preparations, the project took eight years.
In March, workers completed backfilling the waste site with clean soil. Equipment was demobilized in June. The final step will be revegetating the area with native plants in late fall of this year to take advantage of winter precipitation.
The 618-10 Burial Ground, used for waste disposal from 1954 to 1963, held 94 vertically buried pipes reaching more than 20 feet below ground. Trucks from the 300 Area would back up to the pipes to drop loads of cans and buckets of waste with radioactive and hazardous chemical contamination. Less radioactive waste was buried in trenches at the site. Nearby was the 316-4 Crib, where two bottomless tanks resting below ground on gravel were used to dispose of liquid contaminated with uranium. The crib was cleaned up as part of the 618-10 Burial Ground project.
Workers for Washington Closure Hanford started the project, with CH2M Hill Plateau Remediation Co. taking over when Washington Closure’s river corridor cleanup contract expired at the end of fiscal 2016. In total, workers removed more than 512,000 tons of contaminated soil and waste debris, hauling it to the Environmental Restoration Disposal Facility in central Hanford.
The 618-10 Burial Ground was about 4 miles northwest of the 300 Area and only a few hundred yards from Hanford’s main highway on a stretch of road open to the public. The 618-11 Burial Ground is about 7 miles from the 300 Area and adjacent to the Columbia Generating Station, the Pacific Northwest’s only commercial nuclear power plant, which is on leased land at Hanford.
The Energy Department has a Tri-Party Agreement deadline to complete cleanup of the 8.6-acre 618-11 Burial Ground by the end of fiscal 2021. However, plans have been complicated by its location, with concerns that any problem, such as an inadvertent spread of contaminants, could interfere with ongoing operation of the nuclear power plant. The 618-11 Burial Ground encompasses three 900-foot-long trenches, 50 vertically buried pipes, and four caissons, or underground boxes with angled chutes. It was used for waste disposal from 1962 to 1967.
