Saltstone Disposal Unit 9 is the latest mega-size disposal unit completed at the Savannah River Site, bringing the U.S. Department of Energy Office of Environmental Management and liquid waste contractor Savannah River Mission Completion a step closer to achieving the mission.

AIKEN, S.C. - The U.S. Department of Energy Office of Environmental Management (EM) has authorized the newest mega-size disposal unit to begin operating at the Savannah River Site (SRS), completing a 2024 priority for the cleanup program.

The authorization marks the last step before the Saltstone Disposal Unit (SDU) 9 can begin to receive decontaminated material for disposal. The unit was completed over $60 million under budget and seven months ahead of schedule.

Achieving significant construction milestones, such as SDU 9, is an EM priority and part of the cleanup program's 10-year Strategic Vision, according to Jim Folk, DOE-Savannah River assistant manager for waste disposition.

"These units play a critical role in EM's commitment to undertaking one of the largest environmental cleanup efforts in the country," Folk said. "The mega-size saltstone disposal units are vital in our ability to safely dispose of legacy liquid waste and underscore DOE's commitment to complete the SRS Liquid Waste Program."

It wasn't the first time the liquid waste team at SRS fulfilled an EM annual priority by completing construction of a mega-size disposal unit. They met the challenge last year with SDU 8 and in 2021 with SDU 7.

EM's liquid waste contractor at SRS, Savannah River Mission Completion (SRMC), manages the construction and operation of the SDUs. Subcontractors Quality Plus Services, US FUSION & Specialty Construction, and DN Tanks completed the site preparation, interior and exterior liner systems, and unit construction.

The SDUs are the end of the salt waste processing path. The Salt Waste Processing Facility (SWPF) produces decontaminated material that is sent to the Saltstone Production Facility, where it is mixed with dry materials to make a cement-like grout. The grout is pumped into the SDUs, where it solidifies into a monolithic, non-hazardous form.

Radioactive liquid waste is generated at SRS as byproducts from processing nuclear materials for national defense, research, medical programs and for NASA missions. The waste - totaling 33 million gallons - is stored at SRS in two groupings of underground waste tanks known as tank farms.

SDU 9 is the fourth mega-size unit built at SRS and can hold up to 33 million gallons of saltstone. These larger SDUs are designed to support the increased material production from SWPF. The new SDUs result in more than $500 million in cost savings over the life of the SRS Liquid Waste Program because they require less infrastructure and materials than the previously planned 80 smaller SDUs.

SRMC is also in various stages of constructing the final SDUs needed at SRS - 10, 11 and 12. SDU 10 is under construction while sites have been prepared for SDUs 11 and 12 with mud mat construction beginning for SDU 11 this year.

The SDU 9 construction project was another well executed undertaking by the team, according to SRMC President and Program Manager Dave Olson.

"To safely and successfully complete a construction project of this magnitude required incredible focus, collaboration and talent by the entire team," Olson said. "I am proud of the SRMC team's accomplishment that brings us one step closer to completing our mission through this essential project."

-Contributor: Dara Glass