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 vegetation across about 120 acres.
“It’s nice to see the area match the surrounding terrain and get back to what it used to look like,” said Mike Kruzic, the site’s revegetation project manager for cleanup contractor CH2M Hill Plateau Remediation Co.
The burial ground was used from 1954 to 1963 for disposal waste from the 300 Area just north of the city of Richland on the southern edge of the plutonium production complex. Waste that 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 originated in laboratories in the 300 Area that tested and researched plutonium production methods.
The burial ground encompassed 94 vertically buried waste-disposal pipes extending up to 20 feet deep into the ground. It also held 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.
River corridor contractor Washington Closure Hanford started the cleanup work in 2011, preparing a plan for remediation of the vertically buried pipes. “There were a number of people who thought this project, the remediation, couldn’t be done safely,” Kruzic said. CH2M finished the job after the Washington Closure contract expired in September 2016 with most Columbia River corridor cleanup completed.
The vertically buried pipes were filled with sealed cans, ranging from the size of juice cans to paint buckets, holding radioactive or other hazardous wastes. Most of the pipes were made of corrugated piping or five 55-gallon drums welded into a pipe. Cleanup workers drove overcasings into the ground around the buried pipes and then used an auger to destroy the pipes. Soil, the waste, and pieces of pipe within the overcasing were mixed together by the auger. The mixture then was scooped out of the overcasing and encased in concrete-like grout.
Fourteen of the pipes were made of heavy-gauge steel piping, which the auger could not chew through. Workers dug up enough soil to leave the top 4 to 5 feet of each of those pipes exposed. Then a box with a hole in the bottom was lowered around each pipe and grout was added to the box. A hydraulic shear on an excavator was used to chop up the steel pipe, with the soupy grout confining the contamination to within the box. The grout and waste mixture was loaded out into casting boxes to harden.
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 from waste removal, 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.
A similar dump site several miles to the north near the Columbia River at Hanford has yet to be cleaned up. The 618-11 Burial Ground was used to dispose of 300 Area research waste from 1962 to 1967. It has three trenches, 54 vertically buried pipes, and five caissons, or large underground boxes that had waste dumped into them.
The burial ground is adjacent to Energy Northwest’s Columbia Generating Station, a nuclear power plant on leased land at Hanford. The Energy Department has had discussions with Energy Northwest and the Nuclear Regulatory Commission about when cleanup could be done without possible interference to nuclear plant operations. The remediation project has not been scheduled.
