ABERDEEN PROVING GROUND, Md. -- Officials confirmed processing of the first mustard agent-filled munitions Sept. 7 in the facility built to destroy the chemical weapons stockpile stored at the U.S. Army Pueblo Chemical Depot.

"Our team in Pueblo has successfully begun processing the first mustard-agent munitions, marking the start of the pilot phase of operations," said Program Executive Officer Conrad F. Whyne, Assembled Chemical Weapons Alternatives, headquartered here.

"Our operations require the skills of a dedicated workforce, community support and many organizations working together," Whyne said. "This teamwork will continue until we destroy the stockpile."

"This is a momentous day for all of us involved in the U.S. chemical demilitarization program," said Colonel Thomas A. Duncan II, depot commander. "After years of design, construction and systemization, the Pueblo plant, its operators and the depot workforce have proven their readiness. As we move forward, we continue to keep the workforce, the community and the environment safe."

The 85-acre Pueblo Chemical Agent-Destruction Pilot Plant, also known as PCAPP, will employ neutralization followed by biotreatment to safely destroy more than 2,600 tons of mustard agent in artillery projectiles and mortar rounds stored at the Pueblo depot since the late 1950s, said Greg Mohrman, site project manager.

"The start-up of this facility reflects the diligence and determination of multiple local, state and federal agencies, all dedicated to ensuring safe, secure and environmentally sound operations," Mohrman said.

The Program Executive Office, Assembled Chemical Weapons Alternatives, known as PEO ACWA, is responsible for destroying the remaining U.S. chemical weapons stockpiles in Colorado and Kentucky. The PEO oversees the contract for design, construction, operation and closure of the Pueblo facility with Bechtel National, Inc. and subcontractors AECOM, Parsons and Battelle Memorial Institute, known collectively as the Bechtel Pueblo Team.

The pilot phase of operations at the plant will include ramp-up, testing, demonstration and an integrated facility demonstration to validate final operating conditions, said Scott Susman, an ACWA engineer.

"The pilot phase ramp up approach also allows the operators get slow and deliberate practice in performing their duties with actual chemical munitions after having been practicing over the last several months with simulated munitions," Susman said.

PCAPP is forecast to complete its destruction mission by 2020, at which time the chemical destruction facilities will be decontaminated, decommissioned and dismantled in compliance with public law.

Problematic chemical munitions not easily processed by the main plant's automated equipment will be eliminated using an Explosive Destruction System. In its initial 10-month campaign which ended in February, the Army system destroyed 560 artillery projectiles, mortar rounds and sealed steel bottles containing agent samples. Mohrman said the unit will remain on site ready to destroy any future reject munitions found during each of the main plant's three planned destruction campaigns.

The Pueblo stockpile, together with that at Blue Grass Army Depot in Kentucky, accounts for the last 10 percent of what was originally a national stockpile of more than 30,000 tons of chemical weapons. The U.S. Army Chemical Materials Activity destroyed the initial 90 percent, which was stored at nine sites across the U.S. and on Johnston Atoll in the Pacific. The Kentucky site is currently scheduled to begin destroying munitions in late 2017.