Saltstone Disposal Unit (SDU) 7 is the second of seven mega-volume disposal units planned at SRS. Savannah River Remediation (SRR), the SRS liquid waste contractor, is building on the successful design and lessons learned from construction of SDU 6, which was completed last year 16 months ahead of schedule and $25 million under budget.
SDUs are permanent disposal units for low-activity waste grout produced from solidification of decontaminated non-hazardous salt waste. EM approved the concept of replicating the mega-volume design for all remaining SDUs at SRS, a storage design that has been proven effective in the commercial sector.
To prepare the SDU 7 foundation, a local small business subcontractor is using heavy machinery to dig approximately 20 feet below grade. More than 170,000 cubic yards of soil will be moved for placement of concrete mud mats, which will serve as the foundation for the concrete structural base slab and protect the leakage detection system, which is comprised of a specially engineered geosynthetic clay liner and a high-density plastic liner, similar to commercial landfill applications.
Excavation is projected to continue through the summer and the concrete mud mats and leakage detection system will be in place by the end of the year to support construction of the mega-volume disposal unit beginning in January 2019. SDU 7 will stand about four stories tall and extend beyond the size of a football field when complete. It will take about three years for SDU 7 to be operational.
The seven larger units will result in more than $500 million in cost savings over the life of the low-level saltstone waste storage program because less infrastructure and materials are required to design and build the larger SDUs. The mega-volume SDUs are more than 10 times larger than the smaller units on site and will accommodate the larger stream of decontaminated salt solution from the Salt Waste Processing Facility when operational.
Continuous improvement and innovation are key principles for EM, and the new-style SDU is a prime example of applying these principles to the mission, DOE-Savannah River Manager Mike Budney said.
“The use of larger disposal units, like SDU 7, proves DOE’s and SRS’s commitment to continue to be good stewards of taxpayers’ money in that we always pursue the latest, most cost-efficient technologies to assist us in safely performing our mission of dispositioning the Cold War-era liquid waste,” Budney said.
The SDUs at SRS are built to protect people and the environment for generations to come, SRR President and Project Manager Tom Foster said.
“SDU 7 and its sister units allow us to manage the grout for the long-term, providing a safe destination for the low-level waste and reducing the risk to the surrounding communities and environment,” Foster said.