About 11 gallons of GB nerve agent leaked from a 160-gallon container at the Army's Deseret Chemical Depot, some of it escaping its storage bunker.
The agent was detected by a monitor about 600 feet from the bunker at 3:23 p.m. Wednesday.There were no injuries and no agent was detected off base, said Myron Lee, spokesman for the Tooele County Emergency Management Office.
But the leak prompted several depot workers to don protective masks and evacuate the depot's 1,000-acre storage area, where 208 bunkers house 31,495 tons, or about 40 percent, of the nation's chemical-weapons arsenal.
The aging weapons leak routinely, but usually the leaks are confined within the bunkers.
Decontamination crews turned the container over to stop the leak and capped the opening.
Wednesday's spill was the largest since a container of mustard gas, a blistering agent, spilled onto the ground on Sept. 9, 1993.
Adjacent to the chemical-weapons storage yard is a chemical-weapons incinerator, which is destroying the stockpile.