One of the last stockpiles of chemical weapons remaining in the United States is being methodically destroyed in southern Colorado, bit by bit.

The Pueblo Chemical Agent Destruction Pilot Plant, which occupies about 85 acres on the grounds of the U.S. Army’s Pueblo Chemical Depot, is one of two sites in the nation — the other being the Blue Grass Chemical Agent-Destruction Pilot Plant in Kentucky — where the country’s remaining chemical stockpile is slowly being disassembled and eliminated.

The PCAPP is a government-run, contractor-operated facility built with Department of Defense funds and operated by the Assembled Chemical Weapons Alternatives program based out of Aberdeen, Md.

Tom Schultz, the public affairs specialist for PCAPP, said the goal of the project is so simple it can be summed up in one word: safety.

“Safety to the community that surrounds the stockpile where the weapons are stored here in Pueblo; safety to the workforce; and safety for the future,” he said. “Because we simply do not need these chemical weapons. We don’t even have the weapons systems to launch them anymore. They are obsolete. So to keep them around as they continue to deteriorate would simply be insane.”

The mission to destroy the country’s chemical stockpile began as a result of the nation’s participation in the Chemical Weapons Convention — an arms treaty outlawing the production, stockpiling and use of chemical weapons that went into effect in 1997. The treaty sought to elminate the category of chemical weaponry entirely, and all of its signatories agreed to destroy their stockpiles.

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When the U.S. began destroying its chemical arsenal, the country had approximately 31,000 tons of chemical agent to destroy. As of 2012, 90 percent had been successfully eliminated.

After more than a decade of planning and construction, the PCAPP was completed in 2012. The first munitions were destroyed at the plant on March 18, 2015. Since then, approximately 2,600 tons of blistering mustard agent stored at the Pueblo Chemical Depot has been reduced by more than 40 percent. The rest, found in Pueblo and Blue Grass, is on track to be destroyed by 2023.

The project officially began in 2002, when the Bechtel Pueblo Team won the contract to design, build, test, operate and — once the munitions destruction is complete — close the PCAPP.

The majority of the munitions destroyed thus far have been eliminated through a process called neutralization followed by biotreatment: a robotic process in which hot water is used to neutralize the chemical agent and effectively destroy the mustard molecules. Microbes subsequently consume the organic materials in the resulting hydrolysate.

The current campaign at PCAPP has been destroying 155-millimeter projectiles, which have the depot’s highest concentration of mustard agent, at about 12 pounds of agent per munition. The next scheduled campaign will destroy 105-millimeter projectiles, but eliminating 4.2-inch mortar rounds at the facility looks to be more difficult, as they have undergone significant corrosion.

To destroy the approximately 97,000 mortar rounds safely, the PCAPP will use three static detonation chambers that are now under construction.

They’re expected to be completed by late next year, at a cost of around $30 million, a sum not included in the $4.5 billion estimated cost for the project.

Barring any setbacks, Schultz said the PCAPP is on track to hit its Congressionally-mandated destruction deadline of December 2023, which would mark not only the end of the PCAPP, but also the end of the Pueblo Chemical Depot. The depot has been featured on the DoD’s Base Realignment and Closure commissions list since the late 1980s.

“Obviously when we destroy the rest of the stockpile, our mission is done, as will [be] the depot’s mission of maintaining the security of the stockpile,” Schultz said.

At that point, the depot and PCAPP will fall under the management of PuebloPlex, the local redevelopment authority formed by the state Legislature in 1994.