Masking zone requirements at the Pueblo plant were reduced over time and ultimately eliminated in June.
“All mandatory masking zones have now been removed based on safety data and risk assessment conclusions,” said Marty Vigil, project specialist, Bechtel Pueblo Team. “However, we will not consider the plant officially ‘mask-free’ until the final round of specific monitoring is completed for all main plant Agent Filtration Area units later in July.”
At the height of chemical weapons destruction operations, about 75% of the Pueblo Chemical Agent-Destruction Pilot Plant (PCAPP) footprint was designated as a mandatory masking zone due to the potential for agent exposure, Vigil said. All personnel were assigned chemical-agent protective masks and trained in their use to ensure readiness and protection in designated zones, some for working in the toxic areas and all for escape purposes should an unlikely chemical event occur.
This requirement was gradually phased out beginning in September 2023 as munitions destruction ended and closure activities like decontamination and cleaning began. Three major updates were made to the masking zones, culminating in elimination of the masking zone for the main plant in June 2025. At the Static Detonation Chamber complex, masking reductions began with SDC Unit 1 in January, followed by Unit 2 in February and Unit 3 in April.
Masking zone reductions are based on multiple safety and monitoring criteria. The primary requirement is that the area in question must be confirmed to be below specific limits designated by state regulators. Unventilated Monitoring Testing (UMT) plays a critical role by verifying that all areas have been accessed and sampled, ensuring there are no lingering agent sources or explosive materials that could result in future airborne releases.
A series of successful UMT campaigns and occluded space area reviews confirmed the removal or neutralization of any remaining contamination sources at PCAPP.
The state also approved the Reuse Readiness Report for Static Detonation Chamber, or SDC, Unit 3 June 17, which allowed disassembly of that final unit to begin. (Earlier, in May, the state approved the SDC closure plan update, which spelled out the process for reuse of the three units, and the report for SDC Unit 2, allowing for its transport and eventual reuse.)
SDC Unit 1 has already been disassembled and transported. All three SDC units are expected to be transferred to other U.S. Army sites by mid-summer.
The process is underway for selection of a subcontractor for PCAPP demolition, which is on track to begin in early 2026. Selected, non-contaminated buildings and equipment may be retained by PuebloPlex, the local reuse authority.
