With two out of three specific munitions destruction campaigns completed and a new proposal to expedite the destruction of all remaining munitions, the Pueblo Chemical Agent Destruction Pilot Plant (PCAPP) is on track to meet the 2023 for the elimination of stockpiles of chemical weapons.

When the United States ratified the Chemical Weapons Convention in 1997, it accepted the treaty’s mandate to completely and verifiably eliminate its chemical weapons stockpile and related facilities by April 2007, with the possibility a five-year extension until 2012.

But the 2007 and 2012 deadlines turned out to be serious underestimates of the time and effort needed to safely demilitarize the nine declared US chemical weapons stockpiles. The United States has requested and obtained two additional time extensions from the international chemical weapons watchdog, the Organization for the Prohibition of Chemical Weapons (OPCW).

Today, the United States is working to complete the destruction of the last remnants of its once massive Cold War-era chemical weapons stockpile by September 30, 2023.

Since beginning operations in 2016, the Pueblo Chemical Weapons Destruction Facility has safely destroyed more than 2,300 US tons of blister agent mustard in 105mm and 155mm projectiles. The site’s third and final campaign focuses on clearing a stockpile of approximately 97,000 4.2-inch mortar shells, also containing the blister mustard agent.1

Unlike the 105mm and 155mm campaigns, in which the projectiles were robotically dismantled in the main plant and the mustard agent underwent neutralization and bioprocessing, the final campaign was to use chamber technology. static detonation to eliminate 4.2 inch mortar rounds.

Assembled Chemical Weapons Alternatives, the government agency that oversees destruction operations at the Colorado site, explained in a 2016 press release that the processing of 4.2-inch mortar rounds in static detonation chambers, rather than in the main plant, was necessary in order to improve worker safety. and ensure that the United States completes stockpile destruction by 2023.

Static detonation chambers eliminate the need to disassemble the ammunition as well as the need to drain the agent from the projectile. Instead, the entire munition is loaded into a feed box and is transported by conveyor belt into a heated containment vessel, after which the agent and projectile are destroyed by thermal decompression. The entire process allows for minimal processing by humans, reducing the safety risks to personnel.

Detonation chambers are also capable of operating 24/7. Chemical munitions are stored in earth-covered service magazines near the three sites to allow operations to continue at night, on weekends and during holidays.

Construction and testing of three static detonation chamber sites at the Pueblo Chemical Destruction Facility is complete and 5,610 4.2-inch mortar rounds (or 5.77% of the total number of mortar rounds on the site) have been eliminated so far.

Since July 24, Site 2 of the static detonation chamber has been operating at a post-test burn rate of 75% of 5 mortar shells per hour. Site 1 and Site 3 operate at a 50% post-test burn rate of 3 mortar rounds per hour, but only one of the two sites can operate at a time.

According to Ken Mackey, the facility’s hazardous waste permit unit manager, all three sites will eventually operate at 6 rounds per hour per site. In the meantime, plant employees were able to fire projectiles into operating static detonation chamber sites for approximately 20 hours per day – also known as a site’s “up time” – at post-burn rates. current tests. At the current rate, the three sites process approximately 100 mortar rounds per day.

If the three static detonation chambers operate at their maximum rate of 6 rounds per hour and maintain a 20-hour availability, the three sites will be able to process 360 mortar rounds per day. Considering the 5,610 mortar shells already destroyed, there are approximately 92,000 mortar shells remaining to be disposed of from the Colorado Chemical Depot. At a rate of 360 mortar rounds per day, Pueblo could complete stockpile destruction in about 8–9 months—a campaign completion date well before the treaty deadline.2

(Credit: Colorado Citizens Advisory Commission on Chemical Demilitarization Meeting (July 27, 2022), Youtube/PEO ACWA)

This schedule, however, could only be maintained if there were no delays caused by technical problems, work accidents, equipment maintenance or other potential disruptions.

However, at an April 27 public meeting of the Citizens’ Advisory Commission on Chemical Demilitarization in Colorado, Walton Levi, project manager of the PCAPP site, announced a new plan to deal with some of the 4.2 mortar shells. inches in the main plant in addition to static detonation. Chambers – a positive change that will alleviate some of the uncertainty around meeting the deadline.

“We can run 4.2s in the main plant: it gives us greater certainty that we will meet the treaty deadline,” Levi said at the meeting.

The main plant used an automated process to drain the 155mm and 105mm projectiles and process the chemical agent stored within – a process for which 4.2-inch mortar shells have previously proven “unsuitable “.

Levi’s announcement seems to mark a shift in that old assessment. According to Levi, work is already underway to plan a modified piece of machinery called the Enhanced Cavity Access Machine (ICAM) that would allow 4.2-inch mortar shells to be processed safely and efficiently in the main factory.

“The main difference is that the 155 and 105 use gravity to drain the ammo after it has been washed. These [4.2-inch mortar rounds] will be reversed, so we will use a negative pressure or vacuum system to accomplish the same feat,” Levi said.

He explained that due to the success of the 105 mm projectile campaign, which ended on July 20, the PCAPP has a window of 7 to 8 months to operate a demilitarization of the 4.2 inch mortar. in the main factory which was not planned before.

The design process for the Enhanced Cavity Access Machines is nearing completion, and the transition from the 105mm Cavity Access Machines to the 4.2-inch Enhanced Cavity Access Machines is expected to take place in late August through September. and October. Readiness assessment demonstrations of the newly expanded main plant are scheduled to begin in early November.

Mallory Stewart, Assistant Secretary of State for Arms Control, Verification, and Compliance, recently visited the Colorado facility to congratulate everyone who helped bring the 105mm campaign to a successful conclusion and to highlight the importance of meeting the treaty deadline.

“Continuing to ensure steady progress toward meeting the deadline for the complete destruction of all U.S. chemical weapons by September 2023 is obviously an important commitment for all of us, but we know how helpful it has been to have the guidance, expertise and advisory capacity of this group to keep us on the right path to success,” she said. “The implications of missing this deadline would be extremely critical and difficult to manage diplomatically for we.”

The US chemical weapons destruction program began in 1990 on Johnston Atoll in the Pacific Ocean, and seven of nine declared US chemical weapons stockpiles have been safely destroyed in the past 32 years. The remaining two stockpiles in Pueblo, Colorado and Blue Grass, Kentucky accounted for about 10% of the 31,500 US tons of deadly chemical agents declared by the United States to the Organization for the Prohibition of Chemical Weapons (OPCW). The United States has now destroyed about 98% of that tonnage, with the final 2% remaining at Pueblo and Blue Grass. The other seven nations that have declared stockpiles to the OPCW have completed their destruction activities.


1. Although PEO ACWA does not release the total count of a specific round until a campaign is complete, graphs documenting the progress of 4.2-inch mortar shell disposal have been publicly displayed at monthly meetings of the Colorado Citizens Advisory Commission on Chemical Demilitarization. In June the graph showed that 4,194 or 4.32% of the total number of 4.2 inch mortars had been destroyed, and 4.32% of 97,083 or 4,194. In July the graph showed that 5 610 or 5.77% of the 4.2-inch mortars had been destroyed, and 5.77% of 97,227 or 5,610. The figure of 97,000 mortar rounds also matches a 1997 DoD stockpile inventory, which indicates that there were a total of 97,106 4.2-inch mortar rounds at the Pueblo Chemical Depot. (See also: The Cold War-era Chemical Weapons Stockpile in the United States).

2. The estimate of approximately 255 days, or approximately 8-9 months, assumes that the three SDCs will maintain a rate of 6 rounds processed per hour and operate at least 20 hours per day, 7 days per week.