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From VX and Sarin to Mustard: How a Team Reunited to Help America Destroy Its Most Dangerous Chemical Weapons

For more than 70 years, some of the United States’ most dangerous chemical weapons have been safely, securely stored at the U.S. Army Pueblo Chemical Depot. Mortar shells filled with mustard agent are the last of the Army’s chemical weapons stockpile slated to be destroyed in Colorado  At one time, this amounted to more than 2,600 tons of the deadly chemical agent in mortar rounds and projectiles of an assortment of sizes, complicating the challenging process of rendering them harmless.

Leading the initiative is the U.S. government’s Program Executive Office – Assembled Chemical Weapons Alternatives, known as PEO ACWA. As the name suggests, the program’s origin dates to a decision by Congress in 1997 to seek alternatives to the then-ongoing incineration of America’s obsolete chemical weapons stockpile, as mandated by an international treaty, because initial efforts prompted environmental and community concerns.

Near Pueblo, Colorado, the mustard agent’s safe destruction is being overseen by officials at the Pueblo Chemical Agent-Destruction Pilot Plant. With an aggressive destruction deadline of September 30, 2023, the leaders found themselves in a difficult position. The robotic system they had used to successfully wash mustard agent out of 105mm and 155mm projectiles presented increased worker risks and challenges with maintainability on the far more complex 4.2-inch mortar rounds.

The military turned to the same multi-organizational team that successfully created a safer, more efficient process to destroy VX and sarin rockets at the Blue Grass Chemical Agent-Destruction Pilot Plant near Richmond, Kentucky. Engineers from companies including Amentum, Bechtel and CRG Automation, among others, came together as one team with a focused mission: to develop a solution that reduced worker risk, lowered maintenance requirements and increased efficiency.

“Teamwork and cooperation were the keys to this project,” said Terry Staggs, Amentum project test director and a retired Army Chemical Corps veteran.

The reunited team began their work in September 2021, learning about the different munition and quickly finding the needs in Colorado to be more complicated than those in Kentucky. The team would have to develop a solution under a strict set of guidelines:

  • The system would have to be able to function in a caustic area.
  • Each of the mortar rounds included a welded, immovable baffle assembly that ran through the center of the agent cavity in which the mustard agent had often caked onto over time, complicating the cleaning process.
  • The interior would only be accessible by a ¾-inch opening created by the removal of the mortar’s bursterwell assembly casing.
  • The system would need to fit exactly on the existing Cavity Access Machine (CAM) pads utilizing existing utilities, nothing added.
  • Proposed modifications would be strictly reviewed by state authorities, which could cause delays in the timeline.

“What was already a very difficult and challenging timeline had layers of complexity,” said Amentum Project Manager Ken Ankrom.

In contrast to the previously destroyed 105mm and 155mm projectiles which simply had open agent cavities inside them with no baffle assemblies, the team found the agent distribution patterns to vary significantly throughout the 4.2-inch mortar stockpile. The mustard agent inside each round could be as thin as water or thick as “molasses and sand,” PEO ACWA Technical Adviser Jeff Brubaker said. The new system would need to be able to completely rinse the agent – thick or thin – in the interior as well as the immovable baffle assembly running through the center of the munition.

To hasten the project, the team quickly developed and assembled an x-ray device to examine which mortar shells would be most challenging given the mustard agent’s varying degrees of solidification. The Mortar Non-Destructive Examination System “was probably the fastest single project I’ve ever worked on and delivered,” Ankrom said. “This effort was executed with an extremely compressed schedule.”

With the scope of the problem identified, the team set about developing ways to remove the mustard agent safely and efficiently. The team quickly implemented a way to pull the bursterwell assembly from the mortar, and then began the process of designing a system that would both vacuum extract out the liquified mustard agent while also washing the solidified mustard off the immovable baffle, all the while making sure that none of it leaked and introduced a hazard into the processing area. Complicating the issue further was that some of the mortars had become pressurized over time. Removing the bursterwell would sometimes lead to a bit of frothiness, similar to opening a bottle of champagne.

“This was a series of complexities we had never dealt with before,” said CRG Automation CEO James DeSmet. “We often talk here at CRG about how our engineers like the kind of problems that leave other teams scratching their heads or banging them against the wall. We knew this was an opportunity unlike any other, and, even staring down the aggressive deadline, we knew we could do it.” The custom engineering firm, based in Louisville, Kentucky., employs engineers across several fields from mechanical to process to electrical, but it was one in particular whose skill set proved to be instrumental in developing a successor to the CAM technology, what became the Improved Cavity Access Machine or ICAM.

DeSmet’s team set about designing a system that would first introduce a vacuum tube into the mortar that vacuums liquified mustard agent, including what might immediately swell up from the removal of the bursterwell. As the vacuum reaches a midway point in the mortar, a wash wand with 10 nozzles begins a high-pressure wash using three gallons of water per minute. While this is taking place, the ICAM rotated the mortar 180 degrees, back and forth, to ensure the mustard agent is fully washed out from the interior and baffle surfaces. The system was designed virtually using what’s called computational fluid dynamics (CFD), quickly proving that the concept would work. It was essential given the finished technology involved five subsystems and more than 2,000 parts.

The team also developed a containment manifold to fit around the top of each mortar to capture any agent coming out as the vacuum and wash wand tackle the inside. “That was one of our biggest challenges,” Ankrom said. “It took the entire team sitting down and looking at the machine and not only figuring out how to contain the agent and the wash water but also how to contain them under different mustard conditions.” 

With so many existing systems in Pueblo’s facility, it was essential for the team to accommodate the current setup. “Integrating this machine into the plant was a challenge,” said Pueblo Plant Support Specialist Randy Johnson, noting that the assembly of the ICAM requires workers to wear hazardous suits. “You can only go in for 90 minutes at a time. It’s very, very difficult to install anything with those kinds of restrictions. The whole time we’re designing this, we’re thinking about how people in suits with five layers of gloves have to work on this,” Johnson said. “Small screws and bolts aren’t really an option.”

Johnson praised the development team at CRG Automation, which assembled the ICAMs at the company’s modern machine shop for testing. “They’re a really good group of people – very, very responsive and very, very willing to listen and solve problems.” Not only did the team design the system within the same footprint of the original CAM, the team was also able to reprogram the existing robots that Pueblo’s staff hoped to continue to use.

DeSmet credited the full team for its enthusiasm in tackling all requests, as everyone worked toward achieving the mission of reduced worker risk, lower maintenance requirements and increased efficiency.

With the team’s challenges solved, the tests at CRG’s headquarters exceeded expectations and the ICAM machines quickly shipped to Colorado for assembly with two lines incorporating five each.

Prior to reaching the ICAM, each mortar being destroyed had its fuse and explosive burster charge inside removed during a separate reconfiguration operation. Once introduced into the demilitarization facility the reconfigured mortars are moved by robots to one of the 10 total ICAM stations. Once there, a steel tube extractor device pulls out the bursterwell then the vacuum tube is inserted at the next station to remove the mustard agent. That’s followed by an 80-second high-pressure wash within the mortar’s agent cavity that completely rinses the contents. The plant’s agent collection system then sends the collected mustard agent for further processing by its agent neutralization system. While that takes place, the station that removed the bursterwell punches four vent holes in its bottom and then it is partially reinserted back into the mortar. The munition bodies are then processed through a metal part treatment unit at a temperature exceeding 1,000°F.

“That ensures that any remaining chemical agent is completely destroyed,” Ankrom said.

With the destruction process now underway, the Pueblo staff expects to meet the required timetable for destroying the remaining mustard agent mortars. Listening to the Pueblo staff’s needs – and going a step further to really understand them – made CRG Automation stand out, Ankrom said. “I believe it’s just instilled in CRG that they not only hear the customer, they take it a step further to really understand, and as a result of that, we stayed very synced up.”