Lighting sparked multiple wildfires Tuesday night on the Umatilla Chemical Depot and burned thousands of acres.
The fires were on the northern portion of the 19,729-acre depot, a depot news release said, as well as on adjacent property. The first blaze started around 6:20 p.m., and depot emergency workers immediately responded.
Fire departments from Boardman, Irrigon and Hermiston also joined the battle under a mutual assistance agreement with the depot.
One emergency worker suffered a knee injury while getting out of a vehicle, and the depot's clinic treated him. That was the only injury the depot reported. Depot workers also moved vehicles and other equipment out of the fire's path.
Crews contained the fires by 11:30 p.m., and firefighters worked on hot spots overnight.
Preliminary estimates are that fires burned several thousand of the depot's 19,729 acres, a news release said.
The depot's chemical weapons stockpile was not involved in the fire, the press release said. Chemical weapons at the depot are in reinforced concrete, earth-covered "igloos" designed to resist fire or other threats.
The depot's processing facility has destroyed all nerve agent at the site; the only remaining munitions are bulk containers of mustard blister agent that do not have explosive components.