IDAHO FALLS, Idaho – In the early 1990s, DOE, the Environmental Protection Agency (EPA) and state of Idaho signed a record of decision to clean up a pit within a waste repository at the DOE Idaho National Laboratory Site using a chemical extraction process, which later proved unsuccessful.

The three government entities agreed to a new approach for Pit 9 that would fold the project into a broader buried waste environmental investigation at the landfill. In the meantime, they agreed to use the pit, which had last received waste in 1969, to obtain data on the condition of the buried waste containers and determine the feasibility of retrieving the waste.

A small building was erected over a portion of Pit 9 and a pie-shaped enclosure was built within the building to house and operate a remote-controlled excavator. Initially, probes were inserted into the waste zone that allowed engineers to insert detection equipment and cameras.

Later, the excavator dug up the equivalent of 900 drums of soil and waste material for analysis. At that point, a state of Idaho project manager noticed that the waste could be identified. Organic sludges could be identified by their rust or gray color. Graphite molds used in the manufacture of plutonium pits, and plutonium-contaminated filters also could be seen.

With this new data, the DOE, EPA and state agreed to use a process under the Comprehensive Environmental Response, Compensation and Liability Act to remediate a much larger portion of the 97-acre landfill, named the Subsurface Disposal Area. This new project would become the basis for all future remediation at the landfill.