Work has started after years of preparation to remove radioactive waste dropped down pipes buried vertically at Hanford’s 618-10 Burial Ground.
The first contaminated debris came up last week to be deposited in steel boxes to be mixed with grout for disposal.
There’s good news on two fronts on the project. Work is ahead of schedule, and so far, none of the waste in the pipes — called vertical pipe units — looks like it will need to be set aside to be shipped to a national repository.
The 618-10 Burial Ground is one of just two burial grounds at Hanford to use vertical pipe units for waste disposal. They were left for last, with work on the 618-11 Burial Ground yet to start. They were anticipated to be the most complex and challenging excavations in the area along the Columbia River.
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From 1954-63, large cask trucks, heavily shielded to provide protection from radiation, carried highly radioactive laboratory waste to the 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.
Work started in 2009 to map the 618-10 Burial Ground to locate each buried pipe and estimate levels of radioactivity.
Steel overcasings are placed around the vertical pipe units. Augers chew up everything inside the overcasings and then the contents are scooped out.
Contractor Washington Closure Hanford has since driven overcasings that are 28 feet long and 4 feet in diameter vertically into the ground around the pipes, isolating them.
In September, workers started using an auger to chew through the vertical pipe units, mixing up the waste they hold, pieces of the pipe and the band of soil between the walls of the vertical pipe units and the overcasings.
To date, 38 of the vertical pipe units have been augered, with work running well ahead of schedule.
“This is great,” said Mark French, the Department of Energy river corridor division director.
Washington Closure had conservatively planned to auger 28 vertical pipes by the end of its contract, he said.
At the current pace, Washington Closure could complete all 80 vertical pipe units that are made from 14-inch-diameter corrugated piping or from five 55-gallon drums, tops and bottoms cut off and welded together, he said.
It would leave the remaining 14 vertical pipe units, all made of thick-walled steel, for CH2M Hill Plateau Remediation Co. The pipes came as a surprise not revealed in historical records and have been planned to be left for last.
Washington Closure’s contract expires at the end of September and with much of the cleanup of Hanford along the Columbia River completed, a new river corridor contract will not be put out for bids. Instead, CH2M Hill will take over some remaining work in river corridor projects like the 618-10 Burial Ground.
None of the 38 vertical pipe units augered so far have waste that must be sent to a national repository, which would increase the cost of the cleanup project.
With augering well under way by the start of spring, Washington Closure moved on to the next step for one of the vertical pipe units, scooping out the mixture of soil, radioactive waste and pieces of vertical pipe unit contained in the overcasing.
A clamshell shovel was lowered into the overcasing to bring up the the mixture and deposit it in a nearby steel box. The clamshell can circle 360 degrees and is equipped with a light and camera to guide the operator, said Mark Buckmaster, Washington Closure project manager for the vertical pipe units.
Waste placed in the steel box is mixed with grout. The waste in each vertical pipe unit is expected to fill nearly four boxes.
Waste from most, if not all, of the vertical pipe units is expected to be taken to the Environmental Restoration Disposal Facility, a lined landfill in central Hanford for low-level radioactive and hazardous chemical waste.
So far, none of the vertical pipe units that have been augered have had high enough levels of plutonium or certain other isotopes to require the waste to be disposed of at the Waste Isolation Pilot Project, a national repository in New Mexico.
One, at most, of the remaining vertical pipe units still to be augered may have waste that would be required to be sent to the national repository, French said.
Sending waste there requires more characterization, certification and repackaging, which adds time and expense to the project.
1,700 approximate number of drums with radioactive waste dug up from 618-10 trenches
The 7.5-acre 618-10 Burial Ground also has 12 trenches where waste was buried directly in the ground.
Most of the waste has been retrieved there.
However, part of the trenches are so close to some vertical pipe units that they cannot be dug up until the vertical pipe unit cleanup is completed. In addition, there may still be some waste buried deeper than expected in one area of the trenches.
Most waste has been found buried 20 to 25 feet deep in the trenches, with waste up to 35 feet deep in some places, said Dave Martin, Washington Closure project manager for trench remediation.
More than 1,700 drums of waste, plus other debris, have been dug up from the trenches, with about 1,500 of the drums processed.
Some drums held uranium shavings in oil. They have been sent to PermaFix Northwest for treatment. Others, which are lined in concrete to shield radioactive debris, have been crushed in boxes of grout.
Most of the trench waste will be disposed of at the central Hanford landfill, although six drums have been set aside that may be required to be sent to the Waste Isolation Pilot Plant.