Office of Environmental Management

Idaho Site Finishes Landfill Cap Design as Waste Removal Nears Completion

September 3, 2019

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IDAHO FALLS, IdahoEM and cleanup contractor Fluor Idaho have completed the design for the cover to a 97-acre Cold War landfill as workers move closer to removing all targeted transuranic waste there.

The U.S. Environmental Protection Agency (EPA) and state of Idaho recently approved the design for the Subsurface Disposal Area cover, which will protect the underlying Snake River Plain Aquifer.

Workers are about eight months ahead of schedule in the waste removal project, with 88 percent of the targeted waste removed and 0.68 acres of the landfill remaining to exhume.

Since 2005, crews have removed more than 9,000 cubic meters of targeted radioactive and hazardous waste from a combined area of more than 5 acres of the landfill in compliance with a 2008 record of decision between the DOE, EPA, and state of Idaho. The landfill received waste in unlined pits and trenches from the former Rocky Flats Plant near Denver from 1954 until 1970.

A current view of the Subsurface Disposal Area, at top
A current view of the Subsurface Disposal Area, at top, compares to a rendering of what the site would look like upon completion of the cleanup project. EM recently received approval for the design of the cap for the 97-acre Cold War landfill.
A current view of the Subsurface Disposal Area, at top, compares to a rendering of what the site would look like upon completion of the cleanup project. EM recently received approval for the design of the cap for the 97-acre Cold War landfill.

A cover that prevents the migration of rain and snowmelt through the landfill’s remaining debris and contaminated soil is key to the record of decision and crucial for long-term protection of the aquifer located 585 feet below ground. The cover also was designed to withstand a 1,000-year flood event with a canal system that channels excess water away from the landfill.

A cover consisting of native soils and gravel was chosen due to the desert climate and low rainfall conditions in eastern Idaho. Two ancient dry lake beds near the landfill will provide a portion of the more than 3.5 million cubic yards of material — the equivalent of 250,000 commercial dump truckloads — needed to build the cover.

Construction of the cover will begin after completion of waste exhumation and demolition of the buildings where exhumation takes place. The cover is scheduled for completion in three years.

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