More than 600,000 residents of Boulder and Larimer counties should expect to wait until next year or longer for construction crews to finish repairing their flooded and damaged highways.

The Colorado Department of Transportation’s immediate goal is winter survival in towns built along roads curling beside canyon rivers and creeks.

Last week’s deluge left little time this year to rebuild 18 state and federal highways partly closed by flooding. Asphalt and concrete become hard to pour below about 40 to 50 degrees, and snow often reaches the northern foothills in October.

With winter coming, “our goal is to get to where people can go from A to Z” on a patchwork of roads, said Tim Harris, the department’s chief engineer.

In some places, highway use “might be limited to residents only,” he said. In others, the department might use prebuilt military bridges to span gaps.

“What can we do as a response just to get it open?” he asked. “Can we live with a gravel road? Can we do just one lane where you’d want two or three?”

Harris listed six canyon highways in Boulder and Larimer counties as highest priorities: U.S. 34 and 36, and Colorado 7, 14, 72 and 119. But “out east, we certainly can’t ignore those either,” he said.

Many families along those highways took helicopters to safety. Some were warned that if they didn’t, help might not come again until springtime.

Mike Grady, an insurance claims specialist, lost all utilities last week at his home about 10 miles west of Boulder. A volunteer firefighter came by Friday, warning that if he wanted to get out by helicopter, this was his last chance.

Finally, he and his girlfriend hiked three miles up the canyon to a passable road, where they caught a ride to Boulder.

Basically, “we needed to get back to work,” he said.

The long list of Colorado highways closed by flooding ranges from Sterling on the Eastern Plains to Walden west of the Continental Divide.

As a result, the permanent repair projects “could even extend beyond 2014,” said Mindy Crane, a transportation department spokeswoman.

To date, the department cannot say how many repairs lie ahead.

“We just haven’t had a real good look at some of those canyon areas yet,” Harris said. Assessment crews went out Sunday, “and they got chased out by rain and rising water.”

The department is hiring emergency contractors to speed repairs. It’s also getting consulting help from three Vermont transportation officials whose highway system was cut in two by Hurricane Irene in 2011.

The epicenter of flood damage lies along a triangle of highways — U.S. 34 and 36 and Colorado 7 — linking Boulder, Loveland and Lyons to Estes Park and Rocky Mountain National Park. Those roads carry an average of 24,000 to 39,000 cars per day. All are extensively damaged with closed stretches, leaving people in mountain towns no easy way out.

David Olinger: 303-954-1498, dolinger@denverpost.com or twitter.com/dolingerdp