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For 15 years, chemical weapons were destroyed at the former Deseret Chemical Depot. Thursday, work began to destroy something else: buildings.

The demolition is expected to take nine months and will bookend the former facility's role in complying with the international Chemical Weapons Convention.

The property last year was transferred to the control of the nearby Tooele Army Depot and given the new designation as that depot's South Area. Amy Blauser, a spokeswoman for South Area, said two modular buildings were scheduled for demolition Thursday.

One was a building that housed foreign inspectors who ensured U.S. compliance with the convention treaty. The other building was used to support those inspectors.

"Ultimately, we'll knock down everything associated with destroying the chemical weapons," Blauser said.

The last mustard gas-agent filled munition was destroyed at the depot in 2010 and the last bulk mustard gas was destroyed a year later. Chemical weapons destruction formally completed Jan. 21, 2012. But that doesn't mean South Area, or Utah, is free of chemical weapons.

An unknown number of munitions — some which still hold the remnants of deadly chemical agents — remain at South Area.

Thomas Ball, the staff engineer and Utah Division of Solid and Hazardous Waste, who oversees the Army's cleanup of the remaining waste, said the Army will probably spend several more years removing burnt or buried munitions, some of which contain chemical weapons that were not subject to the treaty.

"They haven't assessed the entire depot, but [the Army has] assessed the majority of it," Ball said, "and they have a plan in place and for those areas where they don't have a plan in place those plans are in development."

But the end of chemical destruction has been heralded by the U.S. Army. Besides mustard gas, the facility destroyed the nerve agents sarin, Tabun, VX, and a variety of blister agents. The chemicals were in everything from ton containers to rockets, mortars and land mines. The chemicals and ordinances were stored in concrete and earthen igloos beginning in World War II.

The United States signed the convention treaty in 1993. Destruction of the stockpiles began three years later.

Along with its incinerator in Utah, the Army is destroying chemical weapons incinerators in Alabama, Arkansas and Oregon. Total cost for the four demolition projects is expected to be $1.3 billion. The contractor for the Utah demolition is Envirocon.

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