Colorado Department of Transportation officials and avalanche experts say highly unusual storms caused avalanches across the state Tuesday, stretching the department’s resources and leading to extended closures.

Two major avalanches severed the Interstate 70 mountain corridor for much of the day Tuesday. The first, a natural avalanche at about 3 a.m., hit Vail Pass, forcing a full closure. Then at 11 a.m. CDOT purposely triggered an avalanche just west of Eisenhower Tunnel as part of its mitigation work.

Three semis were caught in the natural avalanche on Vail Pass, brought down by the density of the snow, though no injuries resulted. Berthoud Pass also had some slides triggered for mitigation and was reopened by 6 p.m. Tuesday.

Colorado 133 over McClure Pass was closed late Monday afternoon due to the high avalanche danger and not opened until Tuesday afternoon with chain laws in effect for commercial vehicles. With the exception of a pair of lengthy closures on I-70 in Glenwood Canyon last weekend and one on Colorado 13 north of Rifle on Monday, highways in Garfield County have so far been relatively unaffected.

U.S. 6 over Loveland Pass is projected to open on Wednesday after some morning mitigation work. Colorado 65 on the Grand Mesa reopened late Tuesday following mitigation.

While the state’s avalanche mitigation plan doesn’t prioritize areas with ski resorts above those that don’t, many major resorts benefit from being on the I-70 corridor, which is a priority route, Mike Lewis, CDOT deputy executive director, said during a Tuesday afternoon conference call with reporters.

This has been a really unusual event, which has to do with the amount of snow and its water content, said Ethan Greene of the Colorado Avalanche Information Center.

The state has seen heavy precipitation over that last 10 days and significant, heavy snow came in fast over the last 24 to 48 hours, he said.

The high amount of water, from snow and freezing rain, means a huge amount of weight on the snowpack, said Greene.

Monitoring these areas, CDOT crews have been conducting mitigation work by intentionally triggering avalanches above the state’s mountain highways.

Greene said these planned slides do not make an area more likely to produce a natural avalanche later. And though mitigation crews try to structure the slides in a way that they won’t reach the roadway, the recent heavy precipitation has caused many of the triggered slides to cover roads and force lengthy closures.

“It’s the breadth of this storm and how many locations that are in avalanche danger that is pretty atypical,” said Lewis. “This is sort of everywhere, so it definitely stretches our resources. The state’s northern mountains have seen epic snow with high moisture content.”

That density and moisture content of the snow also makes it more difficult to clean up.

Crews can’t use just snowblowers because of all the rocks and debris that came down with the avalanche, he said.

For commercial, recreational or other types of traffic, “We want to keep the roads open as much as we can,” but public safety takes priority, he said.

Lewis had a few pieces of advice for drivers: Be observant, follow your media, CoTrip.org and CDOT for information, plan ahead for trips, drive defensively and make sure you have the proper tires.

People who aren’t paying attention are winding up in wrecks that cause further problems by holding up traffic and plows, he said.

A fuel tanker overturned on the icy I-70 between Dotsero and Gypsum Monday morning caused a day-long closure in that section of the interstate. Numerous other accidents on I-70 led to closures across the mountain corridor throughout Monday.

In Glenwood Canyon and other prone areas, CDOT is also wary of potential rockfalls, a risk heightened by repeated freeze-thaw cycles, said Tracy Trulove, CDOT Region 3 communications manager.

“I would say it’s always on our radar,” said Trulove. “Anytime we get heavy moisture it’s always on our minds.”

And the weather forecast shows that pattern of temperatures hovering above and below freezing to continue.

In the backcountry, the Colorado Avalanche Information Center has nine of its 10 avalanche areas in the state designated as high avalanche danger.

In the meantime, the forecast shows more snow coming through Friday, so more mitigation work will be required, said CDOT officials.