DENVER (AP) — Blowing up defective chemical weapons inside a closed chamber in Colorado would cause no significant environmental impacts, the Army said Monday.

The finding, which was expected, brings the Army one step closer to destroying an estimated 780,000 shells containing 2,600 tons of mustard agent stored at the Pueblo Chemical Depot in southern Colorado.

The U.S. is destroying all its chemical weapons under a treaty. A plant under construction at the Pueblo facility would use robotic technology to dismantle most of the shells and then use water and bacteria to neutralize the mustard agent.

Shells that are leaking or that the robotic system could not dismantle would be blown up in the closed chamber. The Army now estimates that fewer than 13,000 shells would need to be destroyed that way, although previous estimates ran as high as 40,000.

The chamber would also be used to destroy explosive components of the dismantled shells.

Monday's finding marked the latest milestone in the long and often convoluted path toward eliminating the Pueblo depot's vast stockpile of mustard agent, which can maim or even kill. Mustard causes blisters on skin, scars on the eyes and inflammation in airways. It can also cause cancer.

The Army said this year it could take until 2019 to eliminate the entire Pueblo stockpile and until 2023 to get rid of chemical weapons stored at the Blue Grass Army Depot near Richmond, Ky.

The Army has already destroyed chemical weapons stored in Utah, Alabama, Arkansas, Indiana, Maryland, Oregon and a Pacific atoll.

The Army once proposed using explosives to destroy as many as 125,000 shells stored at Pueblo, both defective and intact, to speed up the process and show other nations the U.S. was intent on eliminating the weapons despite missing a 2012 deadline in the treaty. That plan was abandoned because of stiff opposition in Colorado.

The Army also said that by the time it obtained all the necessary approvals for the explosives technology, it would be too late to speed up the process.

Bechtel Corp., the contractor building the robotic plant at the Pueblo depot, can now ask for bids for building the explosives chamber and related facilities, said Miguel Monteverde, a spokesman for the Army agency in charge of the process.

Four systems are under consideration. Monteverde could not immediately say if Bechtel would have a deadline for the explosives chamber to be up and running. No cost estimate was immediately available.

Irene Kornelly, chairwoman of a congressionally mandated citizen advisory panel for the Pueblo depot, said she expected the Army to conclude the technology would have no major effects on the environment.

"We had to figure out some way to get rid of the munitions down there that were difficult to handle," she said.


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