For the past year, nearly half of the continental U.S. has faced drought conditions, including Colorado, highlighting concerns about the sustainable usage of our water resources.  

At the Pueblo Chemical Agent-Destruction Pilot Plant (PCAPP) in Colorado, the U.S. Department of Defense has been mindful of preserving the region’s natural resources while safely destroying the chemical weapons stockpile at the U.S. Army Pueblo Chemical Depot (PCD). It’s a project of international significance as the U.S. seeks to eradicate its remaining two stockpiles of chemical weapons. 

It takes a great deal of water to destroy, or neutralize, the mustard agent in the munitions, but the plant’s design ensures as little waste as possible. At PCAPP, the chemical agent is destroyed by a hydrolysis process that involves mixing hot water with the agent, resulting in a solution called “hydrolysate” that is then broken down further by a biological treatment process so that the water can be recovered, recycled, and reused at the plant rather than wasted.  

Recycling 75% of water

The plant, operating since 2016, recycles approximately 75% of the water it uses, and it recently added onsite facilities that are currently being tested with the same water usage target in mind. The newly built Static Detonation Chamber (SDC) units, developed to deal with munitions that cannot successfully be neutralized at the main plant, were designed with a closed-loop off-gas treatment system (OTS) to recycle its water. 

The OTS uses a chiller (refrigerated heat exchanger) that condenses water before recycling it to a spray dryer. With the closed-loop system, the SDC units can minimize the use of fresh site water and the need to ship excess water from the system after its use.   

Water usage estimates  

Although the SDCs at PCAPP are not yet active—they are in their final testing stage and awaiting state permitting—water usage was estimated based on the operating Blue Grass Chemical Agent-Destruction Pilot Plant SDC in Kentucky, which has been online since summer 2019.  

While the plant at Blue Grass uses one SDC, the Pueblo plant plans to operate three SDCs. The operational water usage at the Colorado plant’s three SDCs is estimated to be 3.5 million gallons per year, nearly all of which will be recycled through the system to minimize impacts on the region’s water resources. 

The main plant requires about 25 million gallons per year, and with its recycling capabilities of 75%, the plant has saved approximately 100 million gallons of water, equivalent to over 150 Olympic-sized swimming pools, since 2016. 

Water is pulled from 11 onsite wells, which connect to a groundwater reservoir with a capacity of approximately 177 million gallons per year. Plant operation has had little-to-no impact on water levels of the site’s groundwater reservoir. The plant has been designed to protect groundwater. The Colorado Department of Public Health and Environment has been overseeing operation of the plant to confirm that water treatment, conservation, and the groundwater protection goals are all met. 

Bechtel, which leads a team that includes Amentum and Battelle, has been working on PCAPP since the contract was awarded in 2002 by the Pentagon’s Program Executive Office for Assembled Chemical Weapons Alternatives. The plant has destroyed close to 80% of the 2,600 tons of mustard agent to help the U.S. fulfill its obligations under the 1997 Chemical Weapons Convention Treaty. Congress has mandated a deadline for all munitions to be destroyed by 2023.