Officials demonstrate scientific process at Idaho Falls event that will be used in upcoming INL project
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IDAHO FALLS — More than a dozen vendors were on hand at the Idaho Falls Zoo Saturday to celebrate Earth Day.
Inclement weather prevented the event from happening last week, so it was rescheduled for this weekend.
One of the vendors on display was the Idaho Environmental Coalition, which manages nuclear waste cleanup operations at the Idaho National Laboratory. The IEC performed an experiment where people could see how many tablespoons of water it takes to seep through different kinds of dirt and land in a jar at the bottom.
Charles Sullivan, a project engineer for the IEC, tells EastIdahoNews.com the purpose of the experiment was to educate people about a process called evapotranspiration.
“Evapotranspiration is the evaporation of water from the soil. A plant’s roots soak up water from the soil, which exits the leaves and (goes) into the air,” Sullivan says. “It’s a mechanism to dry out the soil in the desert.”
This is the basic concept behind a project at the INL’s Radioactive Waste Management Complex in Arco, where engineers with the IEC are designing a soil and gravel cap to cover a 97-acre subsurface disposal area.
In March 2022, the U.S. Department of Energy and the Idaho Cleanup Project celebrated the completion of a 17-year exhumation project that involved the cleanup of transuranic and other hazardous waste. A lot of the waste was rubber gloves, personal protective equipment, test tubes and other items that had been contaminated through the processing of radioactive materials over the years. It was buried in nine designated locations throughout the Butte County site.
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The bulk of the waste dated back to the 1950s and 60s when America was at the height of the Cold War. It was collected in 49,000 drums between 2005 and 2022 and shipped to the Waste Isolation Pilot Plant in New Mexico.
Sullivan explains the next step in this process is to demolish the buildings covering the waste burial sites and build a natural soil cover over the area to protect the environment.
“The reason we’re building a cap is to prevent any of the hazardous (debris) that was buried from getting wet and … carrying any contaminants towards the (Snake River) aquifer,” says Sullivan.
The aquifer is anywhere from 200 feet to 1,000 feet below the surface.
The surface barrier, which will be put over the entire 97-acre area, will mimic the natural desert landscape and rely on the process of evapotranspiration.
It will include a one-foot thick topsoil layer of fine grained soil and rock to help prevent erosion. There will also be a four-foot thick storage layer of “mostly silt, with some sand and clay,” according to information on display at the IEC’s booth. The total thickness of the SDA surface barrier will be five feet.
The design specifications of the barrier are based upon annual precipitation trends for the Idaho Falls area.
“The typical precipitation for the Idaho Falls area is about 22 centimeters/year, but the wettest year on record (56 cm) was used as an extreme stress event for modeling design performance,” an IEC diagram for the project says.
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Demolition of the buildings on-site and construction of the soil cap is slated for completion in 2028.
