The Pueblo plant workforce safely destroyed the final 4.2-inch mortar rounds filled with HT mustard agent on March 30, leaving 4.2-inch HD mortar rounds as the last munition category requiring elimination at the U.S. Army Pueblo Chemical Depot in Colorado.

“This is yet another milestone for the workforce, the community, and the state to celebrate,” said Walton Levi, site project manager, Pueblo Chemical Agent-Destruction Pilot Plant, or PCAPP.  “It is another indicator that the finish line is drawing near.”

On Dec. 1, 2022, Pueblo crews began destroying 4.2-inch mortar rounds in the main plant, using Improved Cavity Access Machines. Now, more than 95% of the original 2,613 tons of mustard agent has been eliminated. The last of the more than 20,000 HT mortar rounds was processed through the Projectile/Mortar Disassembly system on March 21. Final destruction through the Munitions Washout System and Munitions Treatment Units occurred on March 30.

Next up for elimination will be approximately 37,000 4.2-inch mortar rounds filled with HD mustard, which must receive state approval before destruction processing can begin in the main plant. Testing is underway in the plant to provide information on destruction of these munitions to the state.

“The statistical analyses of the weights and carbon dioxide readings all look great,” said Patrick Sullivan, research scientist, PCAPP. “The 200-second washout has been sufficient to remove all agent and debris, and we made minor adjustments to vacuum out the remaining water.”

The Program Executive Office, Assembled Chemical Weapons Alternatives is targeting completion of the destruction of the remaining U.S. chemical weapons stockpile by the Chemical Weapons Convention treaty commitment of Sept. 30, 2023. U.S. Public Law mandates stockpile destruction by Dec. 31, 2023.