Workers removed more than 120,000 gallons of residual sludge from the bottom of three storage tanks at the Pueblo plant, a two-month process that culminated in March as part of pre-closure activities.

“These tanks originally stored hydrolysate, a liquid product of chemical-agent neutralization, which was then subsequently processed downstream using biotreatment, in the Immobilized Cell Bioreactors,” said Patrick Sullivan, research scientist and closure liaison, Pueblo Chemical Agent-Destruction Pilot Plant. “The hydrolysate contained some solid particles, mostly iron oxides generated through corrosion of the interior of the munition bodies and subsequent chemical reactions in the agent neutralization process, that settled out through a process known as sedimentation. Removal of this sludge was necessary to continue preparing these tanks for closure.”

Considered a secondary waste, the sludge was removed from the three hydrolysate storage tanks by vacuum and transferred safely to tanker trucks for off-site disposal. More than 50 trucks were required to ship the sludge to a hazardous waste treatment, storage, and disposal facility in Colorado. All hazardous wastes removed from the Pueblo plant are documented with hazardous waste manifests.

Sullivan explained that after the bulk solids are removed from the tanks, additional flushing will be performed according to established maintenance procedures to further decontaminate the tanks. The three hydrolysate tanks are designated for demolition in the plant’s closure plan, which remains under review by state regulators.