Anchorage sports dome collapses under snow

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The Dome CEO Bryan Underwood, left, and board chairman Mike Martin walk past insulation on Sunday, Jan. 22, 2017, from the roof collapse that occurred just before midnight on Saturday. (Bill Roth / Alaska Dispatch News)

The massive inflatable roof of Anchorage's indoor sports venue The Dome collapsed just before midnight on Saturday under the weight of heavy snow, canceling athletic events for thousands of users and leaving the future of the heavily used facility in question.

No one was hurt in the collapse of the structure off Raspberry Road, which is roughly 600 feet long and 300 feet wide. The building had been evacuated eight hours before the collapse.

On Sunday, the nonprofit that runs the facility said The Dome would be repaired and reopened.

"Our plans are to reinflate The Dome," said Mike Martin, The Dome board chairman. "The infrastructure within The Dome appears undamaged."

He gave no timeline.

On Sunday, The Dome — usually a gleaming white structure 85 feet high at its tallest point — was completely collapsed. Chunks of insulation could be seen scattered around the wreckage, and vending machines, bleachers and turf playing fields were exposed to the still-falling snow. The huge fabric covering that inflates over the field like a balloon was crumpled like a piece of paper, ripped in places.

The Dome, which opened in 2007, has long been touted as the largest air-supported sports structure in the world. It was previously managed by ChangePoint church and went through bankruptcy in 2012, after which it became an independently run nonprofit. It has become a crucial venue for youth and adult athletics in Anchorage, especially during the long winter season.

Used by thousands of Anchorage children and adults for everything from soccer leagues to running to early-season baseball and softball workouts, it is also the daily practice facility for some of the city's most elite athletes as the home track for UAA track and cross-country teams. The Anchorage School District track and field meets are held there before the season becomes warm enough to move outside. On any given day, more than a thousand people might come and go from the facility, Martin said.

"It's a huge impact to Alaska athletics," Martin said.

[Under The Dome: Indoor facility a 'game-changer' for Alaska athletes]

As of Sunday, it was unclear what the many organizations that use The Dome would do in its absence.

Trouble on the roof

The final collapse happened suddenly.

But managers said throughout the day Saturday, The Dome was showing signs of stress, the result of a major snowstorm that dropped 12.5 inches of snow on the area starting Friday evening, according to the National Weather Service.

The Dome, kept inflated by air pumped in to maintain pressure, is covered with a fabric made out of two layers of extra-thick white polyvinyl chloride tent material with 5 inches of insulation sandwiched between, all held in place by steel cables, according to Martin. The outside of The Dome is coated with a super-slippery product that is supposed to make snow and ice slide off.

Staff has always tried to keep snow from accumulating on the structure, Martin said.

"Our process since day one is when it snows we remove it. We don't want a lot of excess weight on the fabric."

This week had already produced some unusual weather: Snowfall followed by extreme cold midweek, which prompted managers to turn up the heat inside.

[Heavy snowfall in Anchorage leads to whiteout conditions, road closures]

Then came what Martin called the "extreme snow loads" of Saturday. The roof started to visibly droop, as seen in a time-lapse video posted on KTVA Channel 11 News.

"It was an unbelievable accumulation of snow. It just kept pushing down," said Dino Sutherland, the facility manager.

There were eight people on the roof removing snow, Sutherland said. But then it continued to bow.

Around 4 p.m., management decided to evacuate the roughly 200 people inside the facility.

The weight continued to press down in the middle of The Dome.

"The snow all came in the middle, lengthwise. Underneath the snow there was water," Sutherland said. "And that water begat more water. So it just kept going."

By the time of the final collapse just before midnight, the roof was only about 10 feet off the ground in the middle, and maybe 30 feet on the sides, said Sutherland — in the shape of a peanut.

When it finally gave way, a few members of the management team and Martin were standing in the hard roofed lobby.

It sounded like the snow was sliding off, Martin said.

"I thought it sounded like a good load of snow shifting. I thought OK, the issue is resolving itself — The Dome is shifting itself."

What happened — and why?

On Sunday, managers were talking to its insurance company and the manufacturers of the fabric to get an idea of what it would take to repair the structure. And they are trying to figure out what, exactly, happened and how it could have been avoided.

It is not clear whether turning up the heat inside The Dome contributed to the pooling of meltwater that contributed to the collapse, or if so, how much, Martin said.

The major snowfall of Saturday was not unprecedented, but it was also not fully expected.

If they'd known how much snow would fall in such a short time, "maybe we would have attacked (the snow removal) a little differently," Martin said.

Michael Friess, the coach of the UAA track and field and cross-country squads, walked around the wreckage of his teams' practice facility Sunday morning. His teams would use university resources for their practices, he said. But even a temporary loss of The Dome will affect many in the city.

"It is extraordinarily valuable to us," he said. "But we aren't the only ones."