Hanford workers saved what was anticipated to be the toughest jobs at one of the most hazardous burial grounds at the nuclear reservation until last.
“It’s going very well,” said Mike Jennings, director of the 618-10 Burial Ground cleanup project for contractor CH2M Hill Plateau Remediation Co.
That may be an understatement.
About two months into cleanup of heavy-gauge steel pipes buried vertically in the ground and filled with radioactive waste, the project is close to halfway completed.
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From 1954-63, some of the most hazardous waste created by research using radioactive materials at the Hanford 300 Area just north of Richland was hauled to the 618-10 Burial Ground for disposal.
Trenches were dug to bury waste packaged in 2,201 drums and other miscellaneous waste, including a 20,000-pound chamber once used to decontaminate equipment.
But the 618-10 Burial Ground also included 94 pipes buried vertically in the ground.
12 trenches filled with waste
80 vertically buried light-weight pipes filled with waste
14 vertically buried heavy steel pipes filled with waste
Large cask trucks, heavily shielded to provide protection from radiation, carried highly radioactive waste to the burial ground about six miles north of Richland along the main highway to the Hanford Wye Barricade.
Some of the waste came out of hot cells, where workers handled materials that were so radioactive that crews stood outside to manipulate tools inside the cells and watched their work through thick leaded-glass windows.
The trucks would back up to the pipes buried in the ground and drop down cans and closed buckets of waste.
Former contractor Washington Closure Hanford came up with a plan to drive overcasings around the pipes, then use an auger to chew through the pipes. The soil within the overcasing, bits of pipe and the radioactive waste would be mixed together, scooped out and incorporated in grout for disposal.
The method worked well on 80 of the vertically buried pipes. They were made of either 14-inch-diameter corrugated piping or five 55-gallon steel drums, with bottoms removed from all but one and then welded together end-to-end to make a pipe to hold the waste.
“It went better than anyone imagined it would,” said Mark French, Department of Energy project director for Hanford along the Columbia River.
The bit would just rotate in the ground.
Mike Jennings, CH2M director of the 618-10 Burial Ground project
But in a surprise not shown in historical records, 14 of the 94 pipes were made of heavy-gauge steel.
Hanford officials knew from mockup testing that an auger would not chew through those pipes.
“The bit would just rotate in the ground,” Jennings said.
The pipes are not only made of heavy steel, but are as narrow as 12 inches across and likely about 20 feet long.
CH2M took over work to finish the 618-10 Burial Ground cleanup when Washington Closure’s contract expired.
Washington Closure finished augering the first 80 vertically buried pipes and left CH2M with a plan for the remaining 14, which CH2M has followed with some additional safety controls. The new contractor on the project also is using experienced crews, with most 618-10 Burial Ground workers transferring from Washington Closure to CH2M to continue the work there.
Workers dug up the soil around each of the 14 pipes until the top 4 to 5 feet of the pipe was exposed.
Then an open box with a hole in the bottom was fitted over each steel pipe. A soupy grout mixture was poured into the box and a hydraulic shear on the end of an excavator was lowered into the grout to munch up the steel pipe.
We are approaching 50 percent completion with no unplanned events.
Mike Jennings, CH2M director of the 618-10 Burial Ground project
“We encase waste in a grout mixture before we start chopping it up to protect the environment and the workforce from radiation and contamination and chemical hazards,” said Tammy Hobbes, CH2M vice president for the 618-10 Burial Ground project and the Environmental Restoration Disposal Facility, or ERDF.
The mixture from the box, which includes the waste inside the pipe, is then transferred to a box where it will harden. The block of grouted waste can then be taken to ERDF, a lined landfill in central Hanford.
CH2M plans to repeat the process for each four- to five-foot section of the pipes, going deeper on each round of the 14 pipes. Workers are now well along on the second elevation.
“We are approaching 50 percent completion with no unplanned events,” Jennings said.
Getting to this point in the cleanup of the 7.5-acre burial ground has taken nearly eight years. Work started in 2009 with ground-penetrating radar and other technology to get an idea of what might be buried there.
Cleanup work started six years ago with excavation of the trenches. CH2M completed the final excavation of the trenches last week, finishing some areas that were too close to the first 80 vertically buried pipes to work on until now. All that is left in the trenches is some residual debris that will be scraped off the floor of the excavation.
Work has yet to start to clean up Hanford’s burial ground that is similar to 618-10. The 618-11 Burial Ground, which is close to the Energy Northwest’s nuclear power plant on leased Hanford ground, also holds Cold War research waste.
Workers also continue to dig up the overcasings left from the demolition of the first 80 vertically buried pipes.
Two nearby waste sites have been added to the project — both of them too close to 618-10 to address until much of the cleanup work at the large burial ground was finished.
One is minor — a small site where testing was done related to tracking soil contamination using a tracer material.
But the second was used to dispose of liquid wastes by dumping them into the ground. The liquid was contaminated with uranium and fossil fuels.
CH2M is digging up contaminated soil there down to 87 feet deep. Although the column of contamination is just 20 by 20 feet as measured at the ground’s surface, digging that deep will require a hole that measures about 300 by 400 feet at the ground’s surface and a 900-foot ramp to get equipment and trucks to the bottom of the hole.
All work to remove hazardous material from the 618-10 Burial Ground and the two nearby sites is scheduled to be completed by the end of September, with some wrap-up work such as backfilling left for 2018.
With the project completed, the risk of more contaminants there reaching groundwater and moving toward the Columbia River will be eliminated, Hobbes said.