Avalanches that hammered Colorado highways with up to 30 feet of snow prompted closures Tuesday of thoroughfares as far-flung as U.S. 550 and Interstate 70.
Travelers on Interstate 70 west of Denver were stalled most of the day, as the interstate closed about 9 a.m. for avalanche blasting between Herman Gulch and Silverthorne. The Colorado Department of Transportation crews’ bombing sent snow barreling off slopes and onto the highway.
That stretch of I-70 didn’t fully reopen until about 6:30 p.m.
The interstate also was closed for hours in Ten Mile Canyon between Copper Mountain and Frisco.
U.S. 40 over Berthoud Pass was closed for avalanche mitigation too, and U.S. 6 between Arapahoe Basin and mile marker 225 closed for rock fall danger.
With the myriad closures, travelers heading east and west detoured 182 miles via Colorado 91, U.S. 24 and U.S. 285.
“We do have a pretty big toolbox, but today, with the kind of historic nature of the recent storm event and the avalanche cycle ... today, we brought a helicopter in from Montrose and did helicopter bombing missions at several locations in the I-70 corridor,” said Jaime Yount, CDOT’s avalanche program manager.
A helicopter bombing mission triggered a huge avalanche on U.S. 40 near Berthoud Pass, which hadn’t been affected by that avalanche since 1957, Yount said. The copter bombing in Ten Mile Canyon triggered avalanches that poured onto the highway.
“So it’s been a very active day, and I would define it as almost a historic avalanche cycle with significant impact in places that we don’t typically see it,” Yount said.
A natural avalanche on Red Mountain Pass, where U.S. 550 is known as the Million Dollar Highway, prompted closure of that highway between Ouray and Silverton since Monday. Officials don’t know when it might reopen.
Plows were clearing snow slabs 10 to 30 feet deep Tuesday morning on the pass, which has more than 100 named avalanche paths above it and is known for its dangerous, guardrail-free curves.
CDOT also closed Wolf Creek, Coal Bank/Molas and Lizard Head mountain passes Monday, but they all reopened.
Avalanche danger has been considerable since Saturday throughout most of Colorado, with 83 slides reported statewide and 29 avalanches along the Front Range, the Colorado Avalanche Information Center reported.
A backcountry skier was killed near Lizard Head Pass on Sunday, buried by about 3 feet of snow that slid at least 400 feet.
The man, who was skiing near the Matterhorn Nordic trail system north of Trout Lake, was found Monday by San Miguel County Search and Rescue and the Telluride Ski Patrol.
His was the sixth avalanche death this season in Colorado.
Thirty other people have been caught in slides, and 11 have been submerged in snow.