Failure of three systems forced Dec. 23 evacuation

The state agency in charge of chairlift safety has determined that the Aspen Skiing Co. properly dealt with the Dec. 23 shutdown of the Tiehack Express chairlift at Buttermilk, which required the evacuation of 76 passengers.

 

“After review, the board determined that the ski area appropriately handled the incident addressing prevention and ongoing consumer safety, and that additional action by the board was not warranted at this time,” says a statement emailed on Tuesday from the Colorado Passenger Tramway Safety Board. The board is a department of the state’s Division of Regulatory Agencies.

 

According to a form that SkiCo, as the operator of the lift, was required to fill out and submit to the Passenger Tramway Safety Board, the lift stopped working at 10:59 a.m. on the day before Christmas Eve because “the emergency stop circuit Channel 2 diagnostic fault would not reset.”

 

In non-engineer-speak, that means there was a failure of one of the dozens of circuits and switches that are involved in a piece of machinery as complex as a detachable high-speed quad, according to Rich Burkley, SkiCo’s vice president of mountain operations.

 

Crews then sought to bypass the failure, still using the electrical system, but that did not work. The third safety net — a backup diesel generator to power the lift — also failed, despite its being tested successfully that morning, Burkley said.

 

According to the information form about the incident SkiCo filed with the state, which was requested by the Aspen Daily News, “The mechanics did not find the official fault and went to emergency mode to bypass and clear the lift. The bypass switch did not get fully engaged, [which did not allow] the auxiliary start to run the lift.”

 

Burkley said the series of three failures in a row, necessitating an evacuation that involved lowering all passengers to the ground via ropes, was a “perfect storm” and extremely rare. It represented the first time the SkiCo had to evacuate a chairlift since the early 1990s, he said.

 

“I have such faith in the lift maintenance team,” Burkley said. “In my experience, they always fix it.”

 

The problem this time, he said, was that crews were unable to identify the root cause of the problem — the faulty switch — so they moved on to other aspects of the chairlift’s system. As a result of the incident, notifications will be or are being installed on lifts that alert an operator when a circuit has failed to engage.

 

“When you know exactly what’s wrong, it’s easy,” Burkley said. “But there are so many possibilities. Plus there’s time.”

 

He added that once all passengers were off the lift, crews were able to find the cause of the failure, and the lift ran later that afternoon. It was not officially fixed, with the faulty circuit replaced, until the next day.

 

Roughly an hour after the lift went down, and after the failure of the backup generator, ski patrol began evacuating passengers one by one from the lift. While there are a few ways to evacuate a lift, in this case, crews on the ground threw a line over the overhead cable, to which a chair-like rope device was attached. Passengers then placed themselves in the chair, shimmied off the lift and were lowered down by patrollers on the ground. The lift evacuation team, which regularly drills on such scenarios, is comprised of patrollers from all four SkiCo resorts.

 

No injuries were associated with the incident, although the last passengers to be evacuated did not get off the lift until 2:15 p.m., over three hours later. Temperatures at the time were in the low 20s with light winds and partly sunny skies. Everyone one on the lift got a voucher for a free lift ticket.

 

According to SkiCo’s report to the state, the faulty switch that caused the incident was replaced.

 

Burkley said the incident has been thoroughly debriefed internally. One takeaway for the future is to assemble the evacuation team sooner, and make the call to begin clearing the lift no later than 45 minutes after it goes down, he said.  

 

“Overall, it was a fairly positive experience from a learning perspective,” Burkley said.

 

 The state tramway board requires verbal notice of any electrical or mechanical lift malfunction within 24 hours of an incident. In the Tiehack case, SkiCo officials notified the state at 1 p.m. on the day of the incident.

 

The written submission follows, which the state reviews to determine if any further action is needed. In this case, the state has found that no follow-up is needed at this time. The form is shared with other chairlift operators, who look to see if there are any lessons for their equipment that can be taken from the incident.

 

The state conducts lift inspections — both planned and unannounced — at least twice per year, according to the tramway safety board.

The SkiCo tests its backup generators weekly.

curtis@aspendailynews.com