Several hundred workers at the Advanced Mixed Waste Treatment Project, a facility that will be done with its waste treatment work in about a month, gathered Thursday to hear thanks from their bosses and local and state officials.

“The workers have always been key to success at the AMWTP,” said Fred Hughes, president of Fluor Idaho, the contractor that manages waste cleanup at the U.S. Department of Energy site west of Idaho Falls.

The AMWTP is one of the facilities at the desert site west of Idaho Falls that, since 2003, has been processing radioactive waste the DOE sent to Idaho from the Rocky Flats nuclear weapons plant in Colorado. It is expected to be done processing the remaining debris waste there in mid-November. Some sludge waste that is at AMWTP now will be treated at the Accelerated Retrieval Project facilities instead.

While there had been talk of keeping AMWTP open to treat some nuclear waste that is in Hanford, Wash., now, the DOE decided against this almost a year ago, meaning AMWTP will be shuttered and dismantled when its current mission is done.

The Radioactive Waste Management Complex would still be shipping waste to the Waste Isolation Pilot Plant in Carlsbad, N.M., until 2028, said Waste Management Director Bryan Breffle. It is averaging about six shipments a week now. As for AMWTP, after it is done processing waste in November, it will start the closure process set forth in the federal Resource Conservation and Recovery Act, which regulates the disposal of hazardous waste. Breffle expects to take about six years, after which the buildings can be demolished.

While there is plenty of work yet to be done, Breffle said entering the final stages of work at AMWTP is a major milestone.

“You’ll see a lot of faces that haven’t been here in a while, and we’re one big happy family,” he said.

Gov. Brad Little, who was the co-chairman of the state’s Leadership in Nuclear Energy commission when he was lieutenant governor, said the lessons learned doing waste cleanup in Idaho will help with similar projects elsewhere.

“You made Idaho cleaner and safer and those advancements ... will be built upon around the world,” he said.

The 1995 settlement agreement between Idaho, the DOE and the U.S. Navy that set requirements for the federal government to remove waste from the state emerged out of a contentious period. Former Gov. Cecil Andrus blocked new waste shipments into the state and sued DOE. Andrus’ successor Gov. Phil Batt finalized the agreement. Little told the cleanup workers that their efforts have helped to allay fears about the site and make Idaho National Laboratory’s numerous other projects possible.

“You make everyone in Idaho proud about what’s taking place here,” he said.

Idaho Falls Mayor Rebecca Casper called Fluor’s contract employees “super citizens” who have donated a lot of their time and money to charitable and educational programs. She said she will be sorry to see some of them go on to jobs elsewhere but is glad that Fluor has been able to avoid involuntary layoffs so far and that some will be staying in the area in other jobs.

“We so appreciate this workforce,” she said.

Breffle said 465 people are working in the entire Radioactive Waste Management Complex now. The number has been going down since DOE announced AMWTP would be closing, although so far Fluor has avoided involuntary layoffs through a mix of retirements, people leaving voluntarily and transferring people to other jobs. Breffle said it’s possible he may need more people for some tasks even after waste processing at AMWTP is done.

“I need all these people to finish the mission we have and then commence the cleanup,” he said.

Among the remaining waste at the site are 900,000 gallons of liquid radioactive waste that is slated to be treated at the Integrated Waste Treatment Unit facility. Treatment of this has been delayed for years due to technical problems, leading DOE to miss deadlines in the settlement agreement and prompting Attorney General Lawrence Wasden to block shipments of spent nuclear fuel for research at INL.

Fluor spokesman Erik Simpson said more testing is being done at IWTU now and waste processing work will start after a final test run sometime in 2020.

Reporter Nathan Brown can be reached at 208-542-6757. Follow him on Twitter: @NateBrownNews.