One of the more unusual methods used to dispose of high-hazard radioactive waste just north of Richland at the Hanford nuclear reservation is history.
The last of the pipes buried vertically in the ground and filled with radioactive waste at Hanford’s 618-10 Burial Ground near Richland have been dug up.
It’s a project that Hanford nuclear reservation officials and regulators had talked about with a certain level of dread for nearly two decades.
But once a plan was developed, the 94 vertically buried, waste-filled pipes were cleaned up with one major surprise along the way but without a significant problem.
“It was awesome,” said Tammy Hobbes, CH2M Hill Plateau Remediation Co. vice president for the burial ground and the lined landfill where waste from the project was sent.
“It was one of those jobs that had been in the planning for a lot of years and you could tell by the way it was executed,” she said.
It’s a complex area, with trenches where waste also was buried directly in the ground and two adjacent soil waste sites, with work getting close to completion on all of it.
At the largest of the two adjacent waste sites, Hanford workers have finished excavating soil down to groundwater to remove contamination left from dumping radioactively contaminated liquid into the ground. About 13,000 truckloads of soil were dug up.
Heavily shielded cask trucks would haul radioactive waste to the 618-10 Burial Ground, back up to pipes buried vertically in the ground and drop their cargo down.
The 618-10 Burial Ground was used to dispose of highly radioactive research and fuel development waste from the 300 Area just north of Richland. Processes to be used elsewhere at Hanford to produce plutonium for the nation’s nuclear weapons program were tested first in the 300 Area.
From 1954-63, large cask trucks, heavily shielded to provide protection from radiation, carried highly radioactive laboratory waste to the 618-10 Burial Ground about six miles north of Richland along the main highway to the Hanford Wye Barricade.
There the trucks would back up to the pipes and drop their cargo down.
Washington Closure Hanford, which held the now-expired contract to do most of the cleanup along the Columbia River at Hanford, came up with the plan for the burial ground and started the work, with CH2M taking over last fall.
Most of the vertically buried pipes were made of 14-inch-corrugated piping or from five 55-gallon drums, tops and bottoms cut off and then welded together. But in perhaps the biggest surprise of the burial ground not revealed in historical records, 14 of the pipes were made of thick-walled steel.
Washington Closure pounded an overcasing into the ground around 80 of the pipes made of lighter weight metal and then used an auger to chew through the waste and the walls of the vertical pipe, mixing the waste with a ring of the surrounding soil.
CH2M finished scooping out the waste from the overcasings in February, mixing it with grout and sending it for disposal to the Environmental Restoration Disposal Facility, a lined landfill in central Hanford.
Our goal is to try to finish the excavation by the end of September.
Bryan Foley, DOE project manager
A couple of weeks ago, CH2M also finished removing the waste from the last 14 pipes of heavy steel that an auger could not chew through.
Workers at the burial ground dug up the soil around all 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.
Once the grout in the box hardened, the box was lifted into a second container and also hauled to the central Hanford landfill for disposal.
The process was repeated four times, going deeper each time into the ground around each pipe. A fifth level was needed for four of the pipes, which were discovered to be a little longer than the typical 20 feet.
The method provided almost total protection from contamination spread and blocked radiation spread, Hobbes said.
At the same time workers were digging down 67 feet to groundwater at an adjacent site where uranium-contaminated liquid waste from the 300 Area Chemical Separations Laboratory was dumped into two open-bottom tanks buried in the ground. The hole was accessed by a 900-foot ramp built to allow equipment and trucks to get to the bottom of the hole.
The open-bottom tanks had already been removed, but workers also found unexpected debris in the hole and higher levels of contamination than expected, Hobbes said.
Sampling will be done next to ensure contamination has been adequately removed before work can start to back fill the hole and replant vegetation.
This by far is the busiest waste site I’ve been on in my career.
Tammy Hobbes, CH2M vice president
This summer CH2M workers also will tackle the second and smaller nearby waste site. There, radioactive material was used as a tracer in research to determine how precipitation and irrigation might affect the spread of contamination in the soil.
Now the focus at the 618-10 Burial Ground is a mass excavation to remove the remainder of the contaminated soil there.
Workers are digging up the overcasings driven around the 80 vertically buried pipes and the contaminated soil around all of the waste pipes that have been removed, said Bryan Foley, Department of Energy project director for the work.
“Our goal is to try to finish the excavation by the end of September,” he said.
Hanford workers in March finished digging up 2,201 contaminated drums and other debris buried in the trenches.
With multiple projects underway at different areas, in a single day 300 containers of waste or soil could be moved on the site.
“This by far is the busiest waste site I’ve been on in my career,” Hobbes said.