The agency issued the permit Friday to Omega Morgan and warned motorists to expect delays on southern and eastern Idaho highways as the 382-foot-long load heads for Montana on its way to tar sands in Canada.
Omega Morgan spokeswoman Holly Zander said the load was expected to leave Oregon and enter Idaho Saturday night near the Homedale area on State Highway 19. Snow forced them to drop plans to move Friday night.
Protesters delayed the load's progress across Oregon, and 16 people from Oregon, Washington, Alaska and California were arrested Monday night in John Day on charges of disorderly conduct.
Zander said the company, based in Hillsboro, Ore., is anticipating protesters in Idaho.
"I'm sure that there will be," she said. "They have been pretty vocal about their plans. I'm sure we will be facing that in Idaho as well. I haven't heard any specific plans."
She said the company hires security to travel with the 450-ton load and that local law enforcement officials are notified ahead of time about when the load is expected to travel through specific areas.
Protesters have said they're concerned that burning tar sands for energy contributes to climate change.
The permit allows the load to travel between 10 p.m. and 6 a.m. in Idaho. Authorities said the load won't move Christmas Eve or Christmas Day, but will start traveling again at 10 p.m. on Thursday.
The load, Zander said, will take about six or seven travel days in Idaho. But she said that could change depending on weather. The load won't travel if visibility is less than 500 feet.
The route includes a short distance on Interstate 84 near Mountain Home, and eventually crosses into Montana at Lost Trail Pass on U.S. Highway 93.
The giant heat exchanger for a piece of water purification equipment was manufactured in Portland, barged up the Columbia River, and is traveling on a huge truck through eastern Oregon, Idaho, and Montana into Alberta, Canada.
Last month a judge blocked megaloads shipments through northern Idaho on scenic U.S. Highway 12 from Lewiston to Missoula, Mont. But the Morgan Omega shipment isn't taking that route.