HERMISTON -- The blue flag of the Umatilla Chemical Depot has flown for the last time.

"End of an Era -- 1941 to 2012" said the sign over the main entrance to the depot Tuesday as workers, former workers, family members and community leaders drove onto the depot.

They gathered for an Operations Lights Out ceremony marking deactivation of the site after 71 years of use by the Army, initially as a munitions and general supply storehouse and then the storage and eventual destruction of about 12 percent of the nation's stockpile of chemical weapons.

"Today the Umatilla Chemical Depot will be officially deactivated and case its color for the final time," said Hal McCune, spokesman for contractor URS and master of ceremonies. "When the colors depart the field this morning, it signifies that the Umatilla Chemical Depot's mission is complete."

Lt. Col. Kris Perkins and Don Barclay, acting director of the Army Chemical Materials Agency, held the flag tight while it was rolled up and cased in a cloth sleeve as several hundred people watched.

The last mission of the depot, destroying 220,604 munitions and containers holding 3,717 tons of nerve and blister chemical weapons agents, was completed Oct. 25.

"We got the job done right -- safely, compliantly and well ahead of schedule," said Perkins, who relinquished command Tuesday. "We made history here."

Aug. 1 the depot will be officially on inactive status and the landlord will be Joint Base Lewis McChord in Western Washington, at least briefly.

The Oregon National Guard has a contract to serve as caretaker now, and in about six months, about 7,400 acres, including the firing range, are expected to be transferred to it to use for training.

Other portions of the depot's 20,000 acres are expected to be used in time as a wildlife refuge, for farming and for industrial use.

The day was significant for the tribes, who have worked with other governments to get rid of risk, said Armand Minthorn of the Confederated Tribes of the Umatilla Indian Reservation.

"By eliminating risk we've taken away the threat to the environment," he said.

Work remains to be done at the depot, including continued dismantling of the Umatilla Chemical Agent Disposal Facility incineration plant that destroyed chemical weapon agents.

Contractor URS had about 830 workers at the plant when incineration was completed, and all but about 100 are expected to remain through this year. But next year about 550 jobs will be cut and most remaining employees will leave through 2014.

The number of workers for the Army at the depot has declined from more than 300 in 2011 to about 135 now, with work for most of them ending Aug. 11. A few people will remain to oversee depot caretakers and the dismantling of the incineration plant.

Tuesday was bittersweet, said Dave Anteau of Irrigon, who retired from the depot as an HVAC mechanic.

"We knew it was coming, but no one wanted to believe it," he said.

"It's good and sad," said Ron Patterson of Hermiston, who worked with him until retirement. "It has 33 years of my life."

The Army picked the northeast Oregon sage land for a new arsenal, originally called the Umatilla Army Ordnance Depot, in 1940, and $35 million and 7,000 workers transformed the prairie site into a complex of warehouses, munitions magazines, shops and office buildings connected by paved roads and railroad tracks in time to receive its first shipment on Oct. 27, 1941, McCune said.

The Pearl Harbor attack six weeks later put workers on round-the-clock shifts to ship, receive, store and care for munitions, he said.

In 1944, tragedy shook the depot in its only munitions fatality. Six workers, some of whose relatives attended the Tuesday ceremony, were killed when a storage igloo exploded the night shift of March 21.

The depot would supply ammunition for war efforts in Korea, Vietnam, Grenada, Panama and Operation Desert Storm, McCune said.

In 1962 it also began receiving and storing chemical ammunition and in 2004 began destroying the chemical weapons in accordance with the United States obligations to the international Chemical Weapons Convention Treaty.

"The men and women of Team Umatilla have left a legacy of hope and inspiration to the current generation and our future generations," Barclay said.

The casing of the flag is not an occasion of sadness or regrets, he said. "We did a good thing here," he said.

When area residents ask about the future of the depot, Perkins said he tells them "the future of Umatilla looks as bright as its past and is in good hands. The depot will continue to be a significant and proud part of this area's future."

Those who have worked at the depot -- and the families who have been part of its history for three and four generations -- have passed on to future generations a better, safer nation, he said.

"You have made history here and should be proud of your accomplishment," he said.

Then, ending the work of the 35 commanders that have led the depot through the decades, he said the words that few commanders get to utter:

"Mission complete."

-- Annette Cary: 582-1533; acary@tricityherald.com