A fifth, 30-million-gallon salt waste disposal unit has been cleared for operations at the Department of Energy’s Savannah River Site, reflecting the increase in waste treatment operations the site has seen in recent years.
DOE announced Tuesday that Saltstone Disposal Unit (SDU) 10 can begin receiving decontaminated salt waste. Construction of the unit was completed in June 2024, about 10 months ahead of schedule, and passed its leak test in December 2025, meaning it can store up to 33 million gallons of treated salt waste.
Thomas Burns Jr., the president and program manager of BWXT-led liquid waste contractor Savannah River Mission Completion (SRMC), praised the development. “I am truly proud of what the SRMC team accomplished with SDU 10,” he said in the news release. “This milestone moves us even closer to completing our mission and demonstrates the critical importance of this project.”
The news release did not specify how much the SDU 10 cost, though it serves as the first leg of a 3-unit (SDU 10-12) project expected to cost $496 million. For comparison, SDU 6, the 30-million mega unit at the 310-square-mile Savannah River Site, cost about $118 million by the time construction was complete in July 2017.
SDU 7 cost $159 million, coming in about $32 million under budget, according to DOE. And Units 8 & 9 were part of a combined project that cost $218 million, about $60 million under budget. Prior to construction of the mega units, SRS was storing remediated salt waste in much smaller units, including Vaults 1 and 4, and SDUs 2, 3 and 5, with each one only capable of holding 2.9 million gallons.
The units are the final destination for the site’s salt waste, which makes up 90 percent of the 36 million gallons of waste stored in aging, underground tanks at SRS. The salt waste is sent to the Salt Waste Processing Facility (SWPF), where it is mixed with a concrete-like grout, creating a saltstone product that is stored in the units.
The other 10 percent of liquid waste is sludge waste, which is treated at the Defense Waste Processing Facility (DWPF), then stored temporarily on site until the federal government identifies a permanent repository.