Hanford officials are about to try something new in Hanford waste disposal.
Instead of digging another 70-foot-deep cell to hold more waste at the massive landfill in central Hanford, they plan to try piling it higher.
The plan has almost no cost but will allow about as much waste to be disposed of as could be held in one of the landfill’s double cells, called supercells, said Dave Einan, an Environmental Protection Agency engineer. EPA, a Hanford regulator, has signed off on the plan.
The Environmental Restoration Disposal Facility has been built in stages, with more 70-foot-deep disposal cells added as needed and filled cells temporarily covered.
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“We are just about to the point of filling those cells to a point where we need to add capacity to continue the cleanup work,” said Stacy Charboneau, Department of Energy manager of the Richland Operations Office.
The landfill is at the heart of Hanford cleanup, with low level radioactive or hazardous chemical waste hauled to the massive, lined landfill away from the Columbia River for disposal.
Now its cells, which have about 18 million tons of capacity, have only about a half-million tons of capacity left.
Building a new supercell will cost $30 million and still will be required in the next few years.
But by piling waste layered with soil higher, one less supercell should need to be constructed, freeing up $30 million to spend for cleanup work and delaying construction of the next one. A supercell, measuring 500 feet wide and 1,000 feet long, can hold up to 3.6 million tons of material.
“It was an innovative idea, a good idea by Washington Closure Hanford,” said Mark French, the DOE project director responsible for cleanup along the Columbia River and the landfill. Washington Closure operates the landfill and has hauled in much of the waste it holds as it has torn down buildings and dug up burial grounds and contaminated soil near the river.
70 feet planned above-ground height of capped landfill at its center
The row of cells at the landfill already are planned to be about 50 feet above grade at the center with a slight downward slope from there to allow water to run off rather than pooling over the landfill once it is closed, permanently capped and planted with vegetation.
The plan to expand upward will add an additional layer of waste material about 20 feet high, bringing the capped height at the center to about 70 feet high. Much of the mound over the landfill will have a 2 percent grade with a 12 percent grade for the side slopes.
At a distance, the landfill’s new profile is expected to blend in with the Hanford landscape.
“Because of the scale of ERDF, you are not going to notice a huge difference,” French said.
Temorary cap over part of the landfill will have to be breached or removed.
DOE already is expected to have some waste disposal areas with a profile above grade. Plans call for cleaning out the site’s massive processing facilities and then collapsing their walls inward. The demolition debris would be covered with an earthen barrier rather than hauling the debris to a landfill for below ground disposal.
A temporary cover made of high-density polyethylene covered with soil already has been placed over part of the landfill that has been filled. Plans are being made to either cut holes in it, possibly by driving over it with a bulldozer, or to remove it entirely.
Removing or breaching the cap would allow any water, such as rainfall that falls on the landfill and could become contaminated, to be collected in a system above the liner at the bottom of the landfill. Studies provided to EPA have shown that the existing landfill liner and leachate collection system have sufficient strength for the additional waste.
DOE is expected to still work toward having another supercell ready for use in about 2019. The landfill now has the equivalent of six supercells.