HERMISTON -- The last container that once held chemical weapon agent at the Umatilla Chemical Depot has been incinerated.
The final ton container that held liquid mustard blister agent came out of the metal parts furnace at 9:17 a.m. Tuesday, ending the depot's mission to store surplus chemical weapons.
The 20,000-acre depot just south of the Washington and Oregon border once stored 12 percent of the nation's stockpile of chemical weapons, including nerve and mustard agent.
"Our employees are proud to complete the mission of destroying the chemical agent safely and ahead of schedule," said Steve Warren, project general manager for URS Corp., which holds the Army contract for the project.
The Chemical Weapons Convention international treaty required the depot's entire inventory of chemical agent to be destroyed by April 29, 2012.
Although Army officials called incineration of the last ton container the end of nearly 50 years of chemical agent storage, the incineration plant still must incinerate some of the last chemical weapon agent recently drained from that and other containers.
That could be done this week. Then any remaining agent will be flushed out of lines and burned.
But "for all intents and purposes, this is the end of processing," said Hal McCune, protocol manager for the Umatilla Chemical Agent Disposal Facility, on Tuesday.
What is now the depot was created to store conventional munitions in 1,001 earth-covered "igloos" just before the United States entered World War II. In 1962, it began to be used also to store chemical weapons.
The last conventional munitions were shipped off the depot in the mid-90s, and in 2004, the depot began to incinerate chemical weapons on site.
It started with deadly GB and VX nerve gas, much of it in weapons such as rockets, bombs, projectiles and mines.
The last of the nerve gas was destroyed in 2008 and the incineration plant was converted to destroy the remaining agent, mustard blister agent, starting in 2009.
In total, 3,717 tons of chemical weapons agent were destroyed. The final ton container of mustard agent destroyed Tuesday was the last of 220,604 munitions and containers that held the agent.
"Today, the employees of the (incineration plant) made their mark on history by completing agent destruction operations," said Gary Anderson, project manager, in a statement. "More than 1,000 dedicated Army and contractor employees have made Oregon safer for its citizens."
Next, work will turn to cleaning up and tearing down the incineration plant, using the metal parts furnace to destroy any contaminated equipment, tools, piping and protective clothing, until it too is demolished.
The Army has adopted a locally developed plan that calls for the depot to eventually be divided into areas for the Oregon National Guard, a wildlife refuge, agriculture and industrial use.
The goal of the industrial use is to replace some of the jobs that will be lost during the next few years as remaining environmental cleanup and demolition is finished at the depot.