The safe treatment and disposal of secondary wastes from the destruction of chemical weapons was a key element in successfully destroying the chemical weapons stockpile at the U.S. Army Pueblo Chemical Depot, now known as the U.S. Army Chemical Materials Activity-West. The Program Executive Office, Assembled Chemical Weapons Alternatives (PEO ACWA) was responsible for completing the destruction of the Pueblo chemical weapons stockpile by the Chemical Weapons Convention treaty commitment of Sept. 30, 2023. The last munition in the stockpile of chemical weapons in Colorado was destroyed June 22, 2023. PEO ACWA is now focused on the safe and environmentally protective closure of the plant.
The Pueblo Chemical Agent-Destruction Pilot Plant (PCAPP) produced secondary wastes during plant agent-destruction operations and continues to do so during closure. These wastes include personal protective equipment, cleaning materials, equipment parts, dunnage and packing materials.
Secondary Waste Management
Together with federal, state and local environmental regulators, the PCAPP team identified secondary wastes and established procedures for processing them in compliance with all applicable laws. Lessons learned from other chemical weapons destruction facilities were also applied.
Materials that might be contaminated are monitored for residual agent. Contaminated materials are treated on site through the appropriate decontamination or waste-handling system, or shipped off site to an approved treatment, storage, and disposal facility (TSDF) for treatment and disposal in accordance with state and federal regulations. Worker safety and environmental protection were not compromised by the off-site shipment and treatment of secondary wastes from plant agent-destruction operations. This treatment or disposal of the wastes was safely accomplished at PCAPP and other chemical weapons destruction sites with acceptance of both the generating and receiving communities for shipped waste.
TSDFs selected to receive these wastes demonstrated excellent safety and environmental protection records, were subject to strict regulatory oversight, possessed adequate equipment and processes and established active public involvement programs with their surrounding communities. Transport contractors were properly licensed hazardous material carriers with strong safety and performance records. Based on the nature of a waste, coordination was made with emergency response agencies along the transportation routes.
Secondary Waste at PCAPP
PCAPP coordinates all secondary waste treatment and/or disposal with the Colorado Department of Public Health and Environment and other agencies as appropriate. Approaches to the disposal of different types of secondary waste material are described in the chart on the next page. They include the Supplemental Decontamination Unit (SDU), used to decontaminate secondary and closure waste materials and reusable equipment or components. Decontamination was achieved by heating the items up to 240 degrees Fahrenheit for the time required to drive off residual agent. The potentially contaminated air from within the SDU was transferred into the off-gas treatment system for processing.
In addition, an autoclave was used to decontaminate secondary and closure waste materials and reusable equipment or components. Decontamination was achieved by heating the items up to 267 degrees Fahrenheit with steam and then applying a vacuum to cool the contents. The potentially contaminated vapors from the autoclave were transferred into the off-gas treatment system. Potentially contaminated liquids from the unit were collected and processed in the agent collection and neutralization system.
A Static Detonation Chamber (SDC) unit, an electrically heated containment vessel located at the Anniston Army Depot in Alabama, augmented PCAPP by destroying non-agent contaminated explosive components from the Pueblo stockpile.
Secondary Waste Management Approaches at PCAPPP
| Waste | Source | Management Method |
| Carbon from filter banks | Operations and closure activities | TSDF |
| Concrete | Maintenance and closure activities | TSDF (if agent contamination concentration is below release criteria) |
| Energetics (propellants and explosives) | Operations activities | On-site treatment (agent contaminated) and Anniston SDC (clean energetics) |
| Decontaminated munitions bodies, processed through the Munitions Treatment Unit | Operations activities | Recycler (105mm and 155 mm projectiles) and TSDF (4.2-inch mortars) |
| Metallic debris | Operations, maintenance and closure activities | Recycler or TSDF (If agent contamination concentration is below release criteria) |
| Non-metallic debris | Operations, maintenance and closure activities | TSDF (if agent contamination concentration is below release criteria) |
| Brine Reduction System solids (salt cake) | Operations | TSDF |
| Munitions Treatment Unit residue | Operations | TSDF |
| Rubber/rubber-coated items | Operations, maintenance and closure activities | SDU or autoclave (agent contaminated) or TSDF (if agent contamination concentration is below release criteria) |
| Spent decontamination solution | Operations, maintenance and closure activities | On-site processing and recovery of water |
| Expired shelf-life chemicals | Laboratory activities | Off-site disposal |
| Tank, sump and strainer sludge | Maintenance and closure activities | TSDF (non-agent contamination and is considered a sanitary, industrial or hazardous waste) or trash and non-hazardous debris disposal. Agent-contaminated residuals are dewatered, with liquids sent through the hydrolyzers and solids sent to a TSDF. |
| Used oils | Maintenance and closure activities | Designated vendors |
| Universal waste (lightbulbs, batteries) | Operations and closure activities | Designated vendors |