Roland Collard, foreman of a civilian construction crew that unearthed chemicals at Dugway Proving Ground two years ago, has filed a $500,000 negligence suit against the federal government.

He is the third member of the construction crew to file suit in U.S. District Court in recent weeks.The first of two incidents happened on June 16, 1986, and the other was a few days later. Collard and his crew from a Murray-based independent contracting company were excavating a parking lot for a new munitions building at Dugway.

The suit says canisters unearthed by the workers began releasing vapors, exposing workmen. But Dugway officials told Collard the substances were nontoxic, and it was safe for him to return, the suit says. Officials said this was a non-dangerous simulant.

Work resumed and "additional chemical canisters were exposed . . . again exposing plaintiff to toxic and life-threatening chemical substances," the suit says.

Shortly after the second incident, Collard told the Deseret News that the front-end loader dug up discolored earth, rags, sealing rings.

"The smell was really bad. I mean it was unreal," Collard said. Workers suffered headaches, and Collard's suit says he has spleen and liver damage.

An engineer with the Utah Bureau of Solid and Hazardous Waste said some chemical warfare mustard agent was detected at the excavation suit, when tests were made.