# Pueblo Chemical Agent-Destruction Pilot Plant

The Pueblo Chemical Agent-Destruction Pilot Plant (PCAPP) is a chemical weapons destruction facility built to destroy the chemical weapons stockpile formerly stored at the U.S. Army Pueblo Chemical Depot (PCD), now known as the U.S. Army Chemical Materials Activity-West, in southeastern Colorado. The stockpile originally contained 2,613 U.S. tons of mustard agent in 155 mm projectiles, 105 mm projectiles, and 4.2-inch mortar rounds. The weapons had been stored at the 23,000-acre (93-km²) depot since the 1950s.
On June 16, 2023, the main plant at PCAPP destroyed its last munition, a 4.2-inch mortar round. On June 22, 2023, the last munition in the stockpile of chemical weapons in Colorado, an overpacked 155 mm projectile containing mustard agent, was destroyed using a Static Detonation Chamber. The last munition in the declared U.S. stockpile was destroyed in July 2023 in Kentucky.
PCAPP used neutralization followed by biotreatment to destroy the majority of the stockpile, and Static Detonation Chamber technology to augment the main plant.
Destruction of this stockpile was a requirement of the Chemical Weapons Convention, an international treaty to which the United States is a party. The Organisation for the Prohibition of Chemical Weapons (OPCW) is the implementing body of the Chemical Weapons Convention and monitored the progress of the nation's declared destruction programs. The Program Executive Office, Assembled Chemical Weapons Alternatives (PEO ACWA) oversaw the destruction of the chemical weapons stockpile in Colorado and now is managing destruction of agent-contaminated secondary waste in Kentucky and closure-related activities in Colorado and Kentucky.
PEO ACWA was responsible for the safe and environmentally compliant destruction of the U.S. chemical weapons stockpile in Colorado and Kentucky and is now responsible for closing the plants in both states.
The Bechtel Pueblo Team (BPT; consisting of Bechtel National, Inc.; Amentum; Battelle Memorial Institute; and GP Strategies) designed, constructed, pilot-tested, operated, and is closing PCAPP.

## Planning of activities

Destruction began in 2016 and concluded June 22, 2023. The plant will conduct closure activities (shutdown, dismantling, and restoration of site) for three to four years past conclusion of destruction operations.
In 2010, the Pueblo Chemical Depot, in conjunction with the ACWA program, completed an environmental assessment (EA) to meet the requirements of the National Environmental Policy Act, or NEPA, and Title 32 Code of Federal Regulations Part 651 regarding the construction and operation of the U.S. Army's Explosive Destruction System (EDS) and/or other explosive destruction technologies (EDT), at the U.S. Army Pueblo Chemical Depot in Colorado. The EA was withdrawn and a new EA was completed in 2012. The new EA focused on the use of EDT for destroying overpacked and reject munitions. In April 2013, Program Executive Officer Conrad F. Whyne announced his selection of EDS to augment the Pueblo Chemical Agent-Destruction Pilot Plant for the safe destruction of chemical munitions unsuited for processing by the main plant's automated equipment. In Spring 2018, the decision was made to end EDS and utilize three Static Detonation Chamber units to augment the main plant.

## History of chemical demilitarization in Colorado

| Decade | Milestones |
| 1950s | Pueblo Ordnance Depot (later redesignated as the U.S. Army Pueblo Chemical Depot) begins storage of chemical weapons containing mustard agent. |
| 1980s | Public Law 99-145 designates the U.S. Army responsible for the destruction of the U.S. chemical weapons stockpile. |
| 1990s | The United States Congress establishes the ACWA program under the Department of Defense to identify and demonstrate alternatives to incineration. Congress ratifies the Chemical Weapons Convention treaty, which directs all member nations to destroy their chemical weapons and production facilities. |
| 2000s | Department of Defense selects neutralization followed by biotreatment as the destruction method for the Colorado stockpile. The Bechtel Pueblo Team is awarded a contract to design, build and operate PCAPP. PCAPP Groundbreaking is held. Design work and preliminary construction is suspended pending evaluation of cost reduction measures. PCAPP redesign is approved by the Department of Defense and construction work resumes. The Secretary of Defense affirms to Congress that there are no options by which the U.S. can destroy 100 percent of its chemical stockpile by the extended Chemical Weapons Convention treaty deadline of April 29, 2012. The Department of Defense accepts the final design for the Pueblo Chemical Agent-Destruction Pilot Plant. Above-ground vertical construction begins with erection of the Multipurpose Building. Public Laws 110-116 and 110-181 are enacted, mandating destruction of the chemical stockpile by April 2012 or in no case later than Dec. 31, 2017. PCAPP receives the U.S. Department of Labor Occupational Safety and Health Administration Voluntary Protection Program Star Status certification in recognition of safety excellence. PCAPP construction is more than halfway complete, with interior and exterior work ongoing in multiple buildings, including the Agent Processing Building, Control and Support Building, Enhanced Reconfiguration Building, Biotreatment Electrical Building, Entry Control Facility, Immobilized Cell Bioreactor and Off-gas Foundation Pads, and Munitions and Energetic Service Magazines. |
| 2010s | Construction continues with interior and exterior work ongoing in multiple buildings, including the Agent Processing Building, Control and Support Building, Enhanced Reconfiguration Building, Biotreatment Electrical Building, Multipurpose Building, Filter Press Building, PCAPP Medical Clinic, Entry Control Facility, Laboratory Facility, Immobilized Cell Bioreactor, Brine Reduction System, Off Gas Foundation Pads, and Munitions and Energetics Service Magazines. The systemization phase begins at the PCAPP. Construction teams turn over the first subsystems to the start-up groups for systemization testing and commissioning to begin to prepare the facilities for chemical weapons destruction operations. To meet the requirements of the NEPA and Title 32 Code of Federal Regulations Part 651, ACWA, in conjunction with the U.S. Army Pueblo Chemical Depot, completes an environmental assessment regarding the possible use of explosive destruction technologies in Pueblo. Following a public comment period and extensive review by Department of Defense leadership, the environment assessment is withdrawn. As part of systematizing the facility, Assembled Chemical Weapons Alternatives Test Equipment, or ATE, arrives for practice and training use. PCAPP is formally notified by the U.S. Department of Labor's Occupational Safety and Health Administration (OSHA) that the PCAPP project was re-certified as a Star Worksite under OSHA's Voluntary Protection Program. In April 2012, Pueblo Chemical Depot and ACWA completed an environmental assessment to meet the requirements of the NEPA, and Title 32 Code of Federal Regulations Part 651, to address any potential impacts of the installation and operation of explosive destruction technology at the depot. The environmental assessment concluded that the installation and operation of an explosive destruction technology will have no significant environmental impacts. A draft Finding of No Significant Impact was prepared and provided for public comment for a 60-day period. It was concluded that no additional analysis was necessary for the proposed action under NEPA. On Dec. 12, 2012, PCAPP declares construction complete and moves into the systemization phase of the project. On April 18, 2013, Program Executive Officer Conrad F. Whyne announces his selection of the U.S. Army's Explosive Destruction System (EDS) to augment PCAPP. The decision followed a lengthy review of several explosive destruction technologies designed for the safe destruction of chemical munitions unsuited for processing by the main plant's automated equipment. Construction began and was completed on the PCAPP EDS site, located at the U.S. Army Pueblo Chemical Depot in 2014. The first of two EDS units arrived on site, aligning with the completion of specially-designed environmental enclosures that will house the EDS units for added protection. Provisional Operations, a two-month period in which operations and maintenance staff practice training with simulated munitions and agent, began at the PCAPP in 2014. This extensive training is conducted on a large-scale to ensure employees are better prepared for plant operations. Chemical stockpile destruction in Colorado was initiated on March 18, 2015, by the EDS, located on the U.S. Army Pueblo Chemical Depot near the PCAPP. This event marked the first step towards eliminating the final 10 percent of the U.S. chemical weapons stockpile. In 2015, the Bechtel Pueblo Team earns recertification of Star Status in the OSHA's Voluntary Protection Program. On Feb. 11, 2016, the EDS successfully completed its first destruction campaign, eliminating 265 105 mm projectiles, 196 155 mm projectiles, 88 4.2-inch mortar rounds and 11 Department of Transportation bottles for a total of 560 munitions. Systemization was completed and operations began on Sept. 7, 2016. On Sept. 7, 2016, operations began at the PCAPP. The plant began destroying the stockpile of chemical weapons at the U.S. Army Pueblo Chemical Depot in Colorado. The plant is utilizing neutralization followed by biotreatment as the technology to destroy munitions containing more than 2,600 tons of mustard agent. Additionally, the Army's EDS, is on stand-by to augment the main plant to destroy problematic chemical munitions that cannot be easily processed using its automated equipment. PCAPP operations were paused on Nov. 20, 2016, due to an industrial hazardous waste spill of approximately 450 gallons of hydrolysate. The spill was associated with a seal failure of one of the agitators located on the side of a hydrolysate storage tank. On Nov. 23, an unrelated, second issue was discovered; rainwater had leaked through the liner of the secondary containment system surrounding the Brine Concentrator Feed Tanks. These tanks hold the effluent produced in the Immobilized Cell Bioreactors and are essential to the operation of the biotreatment process. PCAPP operations resumed on Jan. 12, 2017. Under the purview of the Colorado Department of Public Health and Environment, the agitators were removed from one of the hydrolysate storage tanks, and the openings were sealed with blind flanges. Additionally, the liners, from the floor and part way up the walls of the secondary containment system around Brine Concentrator Feed Tanks were removed. On April 27, 2017, the Biotreatment Area at the Pueblo plant began processing hydrolysate, which is the product of the neutralization of mustard agent. From July to September 2017, PCAPP temporarily shipped wastewater off site for treatment and disposal at the Veolia Environmental Services Hazardous Waste Incinerator, in Port Arthur, Texas. The wastewater, known as hydrolysate, is the product of the neutralization of chemical agent at the plant. A total of 52 truckloads safely transported 236,473 gallons to Veolia for disposal. In September 2017, PCAPP marked its first full year of the pilot testing phase in which the plant destroyed 253 U.S. tons of mustard agent and 42,897 155 mm projectiles. On Sept. 8, 2017, agent-destruction operations were paused at PCAPP due to higher than anticipated amounts of solids being washed out of munitions and clogging agent neutralization systems. On Feb. 15, 2018, PCAPP ordnance technicians reached a plant milestone when the last of more than 28,000 105 mm projectiles went through Baseline Reconfiguration. On April 12, 2018, PCAPP ordnance technicians started the Baseline Reconfiguration process for the 4.2-inch mortar rounds. At the end of this campaign, more than 97,000 of these rounds will have undergone this process. On June 12, 2018, agent-destruction operations resumed after required modification to the Agent Neutralization Reactors were completed. On Nov. 13, 2018, PCAPP moved one step closer to full operations when the staff initiated Integrated Facility Demonstrations. Within the first 24 hours, the plant experienced its highest throughput, the rate at which munitions are processed, to date. IFDs successfully concluded on May 3, 2019. On April 1, 2019, PCAPP announced the achievement of a significant milestone - the elimination of a quarter (25%) of the mustard agent stockpiled in chemical weapons in the Pueblo Chemical Depot. In May 2019, PCAPP successfully completed the third and final round of background sampling for pilot testing. In July 2019, PCAPP exceeded destruction of half the 155 mm projectiles in the Pueblo Chemical Depot stockpile. |
| 2020s | In February 2020, PCAPP exceeded destruction of half of the agent stored at the Pueblo Chemical Depot stockpile. In June 2020, assembly of the plant's three Static Detonation Chamber units was completed. On June 23, 2020, PCAPP ordnance technicians completed the Baseline Reconfiguration process for the 4.2-inch mortar rounds. During the summer of 2020, PCAPP set monthly munitions processing records. In June, 14,126 munitions were processed, 15,440 were processed in July, and 19,033 munitions were destroyed in August. In September 2020, the first munitions campaign at PCAPP was completed with nearly 300,000 155 mm projectiles stored at the Pueblo Chemical Depot destroyed. On Dec. 11, 2020, PCAPP began its second destruction campaign with the 105 mm projectiles. As of April 2021, PCAPP had destroyed 390,000 projectiles, accounting for half (50%) of the original U.S. chemical weapons stockpile stored in Colorado. On June 30, 2021, PCAPP destroyed 75% of the mustard agent stockpiled in chemical weapons at the Pueblo Chemical Depot. As of Aug. 13, 2021, more than 2,000 U.S. tons of mustard agent was destroyed at PCAPP. On Sept. 15, 2021, PCAPP reached the destruction milestone with more than half (50%) of the 105 mm projectiles stored at the Pueblo Chemical Depot destroyed. As of Sept. 27, 2021, a half-million projectiles containing mustard agent were destroyed at PCAPP On Feb. 19, 2022, the Pueblo Static Detonation Chamber complex began agent-destruction operations, destroying 4.2-inch mortar rounds. SDC operations marked the beginning of the third and final chemical weapons destruction campaign at PCAPP. On July 20, 2022, the second munitions campaign at PCAPP was completed with more than 383,000 105 mm projectiles destroyed. On July 27, 2022, PCAPP recognized the End of the 105mm Projectile Campaign marking the end of the second destruction campaign in the main plant. Community members joined government officials and project staff to recognize the chemical weapons destruction milestone. On Aug. 28, 2022, Ryan Williams became the new Pueblo plant Principal Deputy. In September 2022, the closure contract for the Pueblo plant was awarded to Bechtel National Inc. In September 2022, enhanced equipment added to the main plant enabled previously rejected projectiles to be re-introduced into the main plant's automated robotic destruction system. On Dec. 1, 2022, PCAPP began destroying 4.2-inch mortar rounds in the main plant using Improved Cavity Access Machines. On March 29, 2024, PCAPP moved into its final stage, closure, following approval of its main plant closure plan by the Colorado Department of Public Health and Environment On March 31, 2023, PCAPP completed destruction of more than 20,000 4.2-inch mortar rounds filled with HT mustard agent. On April 8, 2023, PCAPP began destroying 4.2-inch mortar rounds filled with HD mustard agent in the main plant. On May 24, 2023, PCAPP began destroying overpacked 4.2-inch mortar rounds in the Static Detonation Chamber units. On May 25, 2023, PCAPP received the final delivery of mortar rounds from the U.S. Army Pueblo Chemical Depot. Delivery of all munitions is complete. On June 16, 2023, the last munition, a 4.2-inch mortar round, was destroyed in the PCAPP main plant. On June 22, 2023, the last munition in the chemical weapons stockpile stored at the Pueblo Chemical Depot, an overpacked 155 mm projectile, was destroyed in the plant's Static Detonation Chamber complex. On March 29, 2024, PCAPP moved into its final stage, closure, following approval of its main plant closure plan by the Colorado Department of Public Health and Environment. On September 12, 2024, the U.S. Army Pueblo Chemical Depot was deactivated, becoming the U.S. Army Chemical Materials Activity-West (CMA-West). CMA-West is providing closure support to PCAPP. |

## Technology

The Department of Defense conducted studies to evaluate potential impacts of the elimination of these weapons using incineration and non-incineration methods. Four technologies were considered:
* incineration
* chemical neutralization followed by supercritical water oxidation
* chemical neutralization followed by supercritical water oxidation and gas-phase chemical reduction
* electrochemical oxidation
Neutralization followed by biotreatment was selected for the destruction of the Colorado stockpile.
The technology comprised the following steps:
* Robotic equipment removed energetics (explosives) from the weapon, including the fuze and the burster. The energetics were disposed of at a permitted facility off-site.
* The inside of the weapon was remotely accessed and mustard agent was washed out with high-pressure water.
* The mustard agent was mixed with hot water. The resulting mixture was neutralized with a caustic solution. The byproduct was called hydrolysate. The hydrolysate was treated biologically.
* The water was recovered for reuse in the destruction process and the excess activated sludge was secured in containers for disposal at an off-site permitted facility.
* Metal parts were heated to 1,000 °F (538 °C) for 15 minutes for thermal decontamination and were then recycled.

### Explosive Destruction Technology (EDT)

After an assessment of problem munitions showed that their destruction would be difficult using neutralization and biotreatment, ACWA decided to explore use of Explosive Destruction Technology (aka Explosive Demolition Technology, Explosive Detonation Technology, EDT) for these projectiles.
EDT uses heat and pressure from explosion or just heat to destroy the munitions; it is not considered incineration and does not require disassembly of the weapons. There are three general types of technologies that can destroy chemical weapons:
* Detonation technology – destroys the majority of the agent and explosive in the munition by detonating donor explosives wrapped around the munition. The resulting off-gases are processed through secondary treatment to ensure agent destruction. Examples of detonation technology include the Transportable Detonation Chamber (TDC), and the DAVINCH (Detonation of Ammunition in a Vacuum-Integrated Chamber).
* Neutralization technology – uses small explosive shaped charges to open the munition and consume the explosive in the burster and fuze. The agent is destroyed by subsequent neutralization. The U.S. Army's Explosive Destruction System (EDS), is an example.
* Thermal destruction – uses the heat of the electrically heated containment vessel to deflagrate the munition and destroy the agent and energetics. The resulting gases are treated in an off-gas treatment system. The Static Detonation Chamber, or SDC, is an example of thermal destruction technology.
In April 2013, Program Executive Officer Conrad F. Whyne announced his selection of the U.S. Army's EDS to augment the PCAPP for the safe destruction of chemical munitions unsuited for processing by the main plant's automated equipment.
The PCAPP EDS started destruction on March 18, 2015, with the elimination of Department of Transportation (DOT) bottles which contained chemical agent drained from selected munitions over the years to assess the condition of the stockpile. On April 8, the first munitions were successfully processed. In June, operators at the PCAPP EDS took things up a notch with the introduction of 4.2-inch mortars into the destruction process. The first three mortars were joined by three 105 mm projectiles. All were safely detonated in the vessel on June 18. On July 16, the first 155 mm projectiles from Pueblo's stockpile were safely destroyed in the PCAPP EDS. The PCAPP EDS completed its first campaign in February 2016, destroying 549 munitions that leaked or were sampled in the past and 11 bottles containing mustard agent. The second and final campaign ran from June 25 to Dec. 5, 2018.

### Static Detonation Chamber (SDC)

In spring 2018, PCAPP announced a proposal to procure three Static Detonation Chambers (SDC).
Due to performance issues identified during the first year of pilot testing, and in order to complete destruction of the stockpile by 2023, this technology was chosen to augment the main plant under a proposal by the ACWA program. To meet the requirements of the National Environmental Policy Act and federal regulations, an Environmental Assessment was conducted. A Finding of No Significant Impact resulted from the assessment.
Preparations at the SDC site began in June 2019. The first Static Detonation Chamber components arrived at the depot on Aug. 6, 2019, in a convoy of more than a dozen flatbed trucks. Assembly began Oct. 31, 2019. Protective, tension fabric coverings were erected around each unit, with construction beginning in September 2019. They were completed in June 2020.
On Feb. 19, 2022, chemical-agent destruction began at the Pueblo SDC complex with the processing of a portion of the 4.2-inch mortar rounds. SDC operations marked the beginning of the third and final chemical weapons destruction campaign at PCAPP.
On June 22, 2023, the last munition in the chemical weapons stockpile stored at the Pueblo Chemical Depot, an overpacked 155 mm projectile, was destroyed in the plant's Static Detonation Chamber complex.
The SDC closure plan was approved by state regulators Nov. 5, 2024, allowing workers to begin execution of the plan to transfer the units to other government agencies.

## Closure

State environmental regulators approved the PCAPP closure plan March 29, 2024, and the plant is in the closure phase, expected to take three years. Closure is the final phase of the project, coming after chemical weapons destruction operations have been completed. Closure encompasses planning, preparation and disposal of agent-contaminated and non-contaminated secondary waste; facility and equipment decontamination; and decommissioning and demolition of facilities in accordance with public law and U.S. Army direction. In addition, personal property is dispositioned, real property is returned to the U.S. Army Chemical Materials Activity-West, formerly known as the U.S. Army Pueblo Chemical Depot, as environmental permits are closed and the contract is closed.

## Public Outreach

The Pueblo Chemical Stockpile Outreach Office permanently closed to the public in 2023, but staff continues to be available at pueblooutreach@iem.com.
The Pueblo Chemical Stockpile Outreach Office was established in 1997 to serve as the community's primary information resource on chemical weapons destruction in Colorado. The staff responds to inquiries, provides information materials, coordinates guest speakers for a variety of different civic groups and organizations and interfaces with the governor-appointed Colorado Chemical Demilitarization Citizens' Advisory Commission.
The project's environmental permitting information is available for review during regular business hours at:
· Robert Hoag Rawlings Public Library, 100 E. Abriendo Ave., Pueblo, CO 81004
· McHarg Community Center, 405 Second Lane, Avondale, CO 81022
· Boone Community Center, 421 E. First St., Boone, CO 81025
Additional information is also available on the following websites:
* https://cdphe.colorado.gov/hm/HMWMD-public-notices
* https://www.peoacwa.army.mil/pcapp/environmental-activities-at-pcapp/