The blast at the Nosler Inc. plant in Bend caused the sprinkler system to run for 90 minutes, contaminating the water, the Bulletin newspaper reported (http://bit.ly/15eu24O).
"It was mainly lead-related, as you might imagine from a bullet manufacturer," said Cliff Walkey, a hydrogeologist for the Department of Environmental Quality.
The company scrubbed drains and hauled tainted soil to the landfill, so no lead got into the Deschutes River or groundwater, the department reported in a memo this month.
Much of the contamination was in underground shooting areas the company uses to test its bullets by firing them through 50- and 100-yard tubes.
The factory was back to full operation about a year after the explosion, which leveled a corner of its building. The cleanup was finished last fall.
"We just want to do the right thing and be good community members," Nosler spokesman Zach Waterman wrote in an email. "We fully cooperated with DEQ, and together we achieved a positive result."
The explosion on June 2, 2010, shook windows and sent debris over several blocks. A 20-foot concrete wall crashed onto a parked car. But none of the about 100 employees in or near the factory were injured.
"It was really a miracle no one was killed," Walkey said.
Rather than risk trying to get to a shut-off valve near the collapsed section of the factory, a public works crew shut off the flow from outside, said Larry Medina of the Bend Fire Department. Water gushed through the mangled portion of the factory for about 90 minutes, he said.
Investigators know a fire involving smokeless gunpowder in one of the test rooms led to the explosion, but they weren't able to pinpoint what caused the fire, he said.
Information from: The Bulletin, http://www.bendbulletin.com