The first came in 1988 when Alyeska first opened its flanks to young, rebellious snowboarders, who now dominate Alaska's biggest ski hill during the snow season.
The second arrived on Sunday when Nittelstad watched packs of downhill mountain bikers wend their way down Silvertip Traverse, one of the singletrack trails that he helped design and build over the last three years with countless swings of his pickax on the 3,939-foot mountain.
"Sometimes it seems like anything in Alaska is 10 to 15 years behind the trend," Nittelstad said as he stood near the resort's upper tram terminal and watched downhill bikers negotiate jumps, creek crossings and enough surprises to force even experienced riders to tumble on occasion. "It gets here, but they have to have patience with it."
Bikers' patience was rewarded Sunday when more than 200 of them showed up, eager to pay $30 to ride the tram up the mountain and coast 3 1/2 miles back down on an achingly gorgeous bluebird afternoon.
"It's incredibly nice," said Greg Miller of Anchorage after his first 20-minute ride to the bottom. "It was all good."
"I've been trying to beg, steal and borrow my bike up here for years," added the goateed Brian Riggle of Girdwood. "I've got a lot of friends around who are downhill bikers. We're getting a bargain. It's cheap, honestly."
Riggle was of two minds. He loved riding up the mountain and cruising down. Likewise, he was impressed by the turnout.
"Half of me wants 200 people to show up," he said, "and the other half of me hopes I'm the only one here."
Suffice to say, Riggle suffered no pangs of loneliness. At 12:30 p.m., about 70 people with bikes queued up at the Lower Tram Terminal in a bike-and-rider line that stretched down the tram stairs and about 40 feet outside. The bottleneck meant waits of up to an hour.
That was only one indication of the interest. Just after 11 a.m., an hour before the first biker descended, Alyeska sold its 200th and final ticket. Some 40 other names made a waiting list.
"It is the beginning of a new era at Alyeska," beamed Di Hiibner, the resort's general manager. "We are very excited with the turnout. It definitely shows us the demand and support ... Folks were smiling all day."
Resort managers weren't frowning, either.
Even with seven months of skiing and boarding in Southcentral, ski areas have five other months to fill. At big Outside resorts such as Whistler in British Columbia, mountain biking helps keep lifts running and visitors arriving.
Alyeska, for its part, is adding downhill biking on top of an aggressive trail-building campaign that began after John Byrne bought Alyeska in 2007. A new trail cut into the scenic North Face Trail opened to hikers last August, and the Winner Creek Extension Trail, completed three months ago, was among several expansions this season.
"I am absolutely thrilled," said Brian Burnett, the mountain services manager at Alyeska. "It's a successful model that every alpine slope in North America uses. It brings a summer activity to an under-utilized infrastructure."
Of course, mountain biking is limited by Alyeska's weather, and few days are as sun-soaked as Sunday. This year, the 526 inches of snow that fell at mid-mountain didn't melt until the end of July.
Next summer, Hiibner said, the resort expects to offer downhill mountain biking every weekend once the trails firm up.
Experienced downhill bikers bore some resemblance to the NFL athletes playing on fields across the nation at the same time Sunday afternoon. Many wore body armor, anticipating the inevitable falls, with kneepads, elbow pads, a full-face helmet and full finger gloves.
"This is hair-ball riding," warned one of the guides, Ryan Davis. "It'll scare you -- though none of the jumps are really bad.
"It's definitely a rowdy trail. Some people will be bombing down this mountain."
The fastest were back at the bottom in less than nine minutes.
Riggle noted that over the years he'd dislocated his shoulder, broken bones and banged up his hip riding downhill.
"You're gonna get hurt," he said. "It's just a matter of when, where and how bad."
To introduce the trail to riders -- and limit mishaps -- Alyeska paired small groups of riders with a guide on the first trip downhill. After that, riders had free access to open trails -- including particularly steep ones above the Upper Tram Terminal that required an uphill push before the downhill rush.
The afternoon's injury toll was limited to bruises, cuts and one dislocated shoulder, according to the resort. A converted litter equipped with a wheel was only used to provide courtesy rides for bikers with broken gear.
"People that turned out tended to be experienced riders who could handle the trails," said Amy Quesenberry, the resort's mountain marketing manager. "It was great to know that our trail crews are building appropriate trails that are not too difficult."
With weekend-long openings next summer, expect the long tram lines to diminish. Some 15-20 bikers at a time can squeeze onto the tram, with the bikes stacked front to back wheel on each end.
Experienced downhillers like Riggle owned bikes specifically designed for downhill riding, an investment that can run several thousand dollars. Most sit lower, feature full-suspension and lean back farther than other mountain bikes.
"But all you really need is a helmet and a pulse," joked Burnett.
The resort even rented helmets.
"It was a big day," Burnett said. "When you looked out at the riders, it was that look you see on an epic day of skiing -- bright eyes and big smiles, with a little drool coming down the side of their mouth."
Reach reporter Mike Campbell at mcampbell@adn.com or 257-4329.
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