All winter long, the Colorado Department of Transportation wages war against Colorado's mountain passes, where crews trigger avalanches and plow roads to keep the mountain highways open. But on Independence Pass, a treacherous but crucial route between Buena Vista and Aspen, Mother Nature wins.

Winding and breathtakingly narrow, the pass straddles Lake and Pitkin counties as it climbs above 12,000 feet over the Continental Divide. It is one of a handful of high elevation roads around the state that close in the winter, but with more than 100 avalanche paths along the route, Independence Pass can be one of the trickiest to open for the summer season.

Mother Nature's hold on the pass comes to an end by mid-May, when CDOT and a group of avalanche forecasters prepare to open the road for Memorial Day weekend. For southern Coloradans, once open, the pass will become the quickest route to the Aspen area, sparing drivers an hourslong detour. But opening the pass is no easy feat - it takes at least a day of avalanche control as helicopters drop bombs on ridges. After a recent heavy snow, CDOT was later than usual on Thursday to start its annual bombing of the pass. Crews pummeled the steep mountainsides with more than two dozen bombs, hoping to trigger snow slides before traffic hits the road for the first time next week.

For CDOT crew members like Jack Stieber, opening the pass is a salvo to summer. Like a Memorial Day barbecue with the neighbors, bomb day on the pass signals the end of Stieber's long winter crisscrossing the mountains doing avalanche control. After a decade on the job, Stieber knows the most impressive part of the show is not the 30-pound bombs dropped by helicopter.

He and his crew wait eagerly to see the avalanches that cascade down the mountains.

"Mother Nature's in charge," he said.

In spite of Mother Nature's ultimate dominance, Stieber and his crews get a kick out of tricking her. They make the bombs themselves, loading each with 25 pounds of highly explosive chemicals and a 5-pound detonator. Then, they place each bomb in a burlap bag and wrap it in rolls of duct tape. With a long fuse and "neck" for grabbing, the bombs resemble a load of massive frozen fowl - the crews call them "turkey bombs." On the ground, crews load the bombs eight at a time onto a helicopter; once they're up high, they chuck the bombs out onto ridges and cornices below. The bombs can take minutes to detonate, and once they do, they explode in a plume of smoke.

On Thursday, the helicopter crew targeted an east-southeast facing ridge above the first climbing switchback on the road, a precipitous area that requires extensive bombing every year. CDOT's Jerry Gammill watched a bomb drop from several thousand feet below, and timed it from the moment it hit the slope.

"Should be anytime now," Gammill said to other members of the crew watching with necks craned. "It's been 2 minutes, 30 seconds since they've been working."

After complete stillness, the bomb went off in a puff of black smoke. Seconds later a boom shook the mountains, echoing for miles.

"There you go!" Gammill cried.

The crew bombed for hours. Sometimes a bomb left little more than a black gouge on the mountain; other times it triggered an avalanche that roared several thousand feet to the highway below.

Even when not artificially set, avalanches are a common phenomena on Independence Pass, where for years slides and streams have carved paths into the mountains. On Thursday, the slides flowed effortlessly down familiar channels; they twisted like rivers and cascaded like waterfalls.

"They've been here a lot longer than us, right?" said Colin Mitchell, a Carbondale-based avalanche forecaster for the Colorado Avalanche and Information Center. "They've left their marks on the mountain."

Nonetheless, Thursday was not a banner day for avalanches on the pass.

Although snowpack in the region has been close to or above average this year, warmer-than-average spring temperatures melted much of the snow that typically comes down with the bombs, said Rebecca Hodgetts, a Leadville-based avalanche forecaster for CAIC. Recent weather meant that the snow was also less inclined to slide, Hodgetts added. Only a handful of the 16 bombs dropped on the pass' east side triggered slides, perhaps the most meager show avalanche forecasters have seen in the past 15 years of bombing, said Scott Toepher, a forecaster based in Breckenridge.

There have been years when avalanches barreled down the mountains and sent crews scrambling to get out of the way as the slides threatened to cross the highway twice.

Those are the kinds of slides that everyone likes to see. For CAIC, they mean less snow to potentially come down on drivers in June. For Stieber, a good slide means more than a job well-done - it's an impressive thing to behold.

"If one makes the road, it'll roar," he said. "It's a beautiful sound. At least, it is for us, anyway."

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Contact Ryan Maye Handy: 636-0198

Twitter @ryanmhandy

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