Workers fill the last deactivated ICBM silos with dirt in the missile field operated by Malmstrom Air Force Base. (Air Force)
The last of the deactivated intercontinental ballistic missile silos operated by Malmstrom Air Force Base were eliminated Tuesday.
The silos were previously activated by the 564th Missile Squadron, which was deactivated in 2008.
Under New START, a nuclear arms-reduction treaty with Russia, those empty silos counted as nondeployed missile launchers. New START, which was ratified in 2011, limits the U.S. and Russia to 800 nondeployed launchers.
To meet that, the U.S. was required to eliminate 103 deactivated ICBM silos, including the 50 at Malmstrom, by February 2018.
The final 10 silos that were eliminated have entered a 60-day observation period to allow Russia to verify their elimination.
Lt. Gen. Stephen Wilson was visiting Malmstrom this week with his wife and watched as the last silo was eliminated Tuesday.
The last silo to be eliminated was Launch Facility T-49, located about 25 miles west of Conrad, according to Malmstrom. Contractors used heavy machinery to bury the siteís 110-ton launcher closure door and fill the launch tube with dirt, rendering it unusable as a missile launch site, according to Malmstrom.
The initial phase of elimination began in January.
The U.S. Army Corps of Engineers and the Air Force Civil Engineering Center selected Bryan Construction Inc. of Colorado Springs, Colo., as the demolition contractor.
The silos were eliminated by filling them with earth and gravel. Gravel fill is a more effective and environmentally friendly method of elimination thatís also faster and more economical than those used under the original START treaty. The work doesnít pose any threat to public safety or the environment, according to Malmstrom officials.
The second phase began July 21 when concrete caps were poured over the first 40 launchers that had completed the first phase, according to Rick Bialczak, 341st treaty compliance office chief.
The completion of all Phase II work will take several months, according to Malmstrom. The sites will remain in caretaker status by the 341st Civil Engineer Squadron until the final disposition of the properties is determined.
New START also limits deployed launchers to 700 across ICBM fields, submarines and bomber aircraft.
The Pentagon announced in April it would retain all 450 ICBM silos operated by the Air Force, including the 150 at Malmstrom.
The Air Force will remove missiles from 50 silos, but keep them in a warm status, meaning they can be rearmed at any time.
According to defense officials, the expectation is that the empty silos will be distributed among the three missile wings and will rotate depending on maintenance and operational needs.