The Department of Energy last week completed cleanup of the 618-10 Burial Ground, one of the most hazardous radioactive waste dumps in the Columbia River Corridor at the Hanford Site in Washington state. The last step involved replanting about 120 acres.
The burial ground was used from 1954 to 1963 for waste from the 300 Area just north of the city of Richland on the southern edge of Hanford. Waste that Hanford officials deemed too hazardous for disposal close to Richland was hauled to the burial ground about 6 miles north of the city along the main Hanford highway. Much of the waste was from laboratories in the 300 Area that were used for testing and researching plutonium production methods.
The burial ground included 94 vertically buried waste-disposal pipes extending into the ground up to 20 feet deep. It also had 12 waste trenches that were excavated to about 30 feet deep. Roughly 2,200 drums and other miscellaneous waste, including a 20,000-pound equipment decontamination chamber, were dug up.
A total of 528,000 tons of waste and contaminated soil were removed between 2011 and late 2017. The waste was transported for disposal at the Environmental Restoration Disposal Facility in central Hanford. The cleanup also included the nearby 316-4 liquid waste disposal crib, where liquid contaminated with uranium had been dumped. Workers there removed contaminated soil down to about 68 feet deep.
The massive hole, piles of staged soil, and infrastructure for 618-10 and related cleanup projects added to the 120 acres that needed to be revegetated. The total revegetation project cost $1.4 million, according to DOE.
Subcontractor Environmental Assessment Services collected seeds from about 40 species of shrubs, forbes, and legumes across the Hanford Site for planting. Native grass seed was purchased from Washington state growers. Shrubs, including big sagebrush and antelope bitterbrush, were started in nurseries and then 76,000 seedlings were hand planted. Planting began in November, timed to take advantage of the winter rainfall of Hanford’s arid climate.