The U.S. Department of Energy and Savannah River Remediation on Monday will officially recognize the operational closure of two tanks at the Savannah River Site.

The two tanks, 18 and 19, previously held radioactive liquid waste from nuclear weapons production at SRS.

Participants in Monday’s events include Undersecretary for Nuclear Security Thomas D’Agostino, U.S. Sen. Lindsey Graham, S.C. Department of Health and Environmental Control Commissioner Catherine Templeton, DOE-Savannah River Operations Office Manager Dave Moody and SRR President and project manager Dave Olson.

Tanks 18 and 19 were completed ahead of the December 2012 deadline and are the first to be closed at SRS in 15 years. According to a statement, the closure signifies another substantial environmental risk reduction in South Carolina and the end of the projects meets a requirement of the Federal Facility Agreement, or FFA, between DOE, DHEC and the Environmental Protection Agency.

The last tanks closed at SRS – which were also the first closed in the nation – were in 1997 with Tanks 17 and 20, which are near Tanks 18 and 19. Since then, nine other DOE waste tanks were closed in Idaho in 2009.

Closing the tanks involves removing the waste from the tanks and stabilizing them with formulated grout-like cement. The 2 million-gallon tanks needed enough grout to fill four Olympic-sized swimming pools, according to information from DOE.