The Umatilla Chemical Depot began processing mustard agent today after it received the go-ahead from the Oregon Department of Environmental Quality Wednesday evening.
This is the disposal facility's last chemical weapons destruction campaign.
Unlike the other agents, the mustard is not technically a munition, but stored in bulk containers called ton containers. Most of the mustard agent was made between 1945 and 1946 as part of the Rocky Mountain arsenal.
The depot will process more than 2,500 ton containers of mustard agent. It expects the campaign to take one to two years to complete.
Though the mustard agent starts out colorless, after 40 years of storage it's turned to a yellow or brown substance. Some in the containers has turned to sludge, referred to as a heel. Those heels contain metals such as mercury, which require instillation of sulfur-impregnated carbon filters.
The ton containers are in underground bunkers on the depot, more commonly known as igloos. Before they're processed, workers bring in warming units for seven days to bring the temperature up to 85 degrees. Then they seal two ton containers at a time in large, barrel-shaped units called enhanced on-site containers to take them from the igloo to the plant.
At the plant workers unpack the containers and put them into a device called a "glovebox," which allows them to vent gas inside the containers, while workers stand safely outside reaching in through gloves installed in the box, hence the name.
From there the ton containers go to the munitions processing bay where machines punch holes in the containers, drain them and clean them out. Workers use special equipment to spray warm, high pressure water to break up the larger heels.
Drained mustard agent is destroyed in the liquid incinerator at 2,700 degrees and the empty ton containers and their heels are sent to the metal parts furnace, where they're destroyed at 1,600 degrees.
The depot finished its last campaign in November. Since then the plant has been in a changeover process, where workers retrofitted plant equipment, added to pollution abatement (like the sulfur-impregnated filters) and trained in preparation for processing mustard agent.