A gondola support tower leans over after it partially collapsed in Whistler, British Columbia north of Vancouver December 16, 2008. Several people were injured and trapped inside the the gondolas.ANDY CLARK
The B.C. Safety Authority has ordered that drain holes be added to all ski-hill towers in the province after investigating a 2008 gondola crash in Whistler.
The safety authority issued the order a week before releasing the results of the investigation on Tuesday.
Twelve people were injured when a support tower for Whistler Blackcomb's Excalibur Gondola collapsed on Dec. 16, 2008. Water had seeped into the tower and, as it froze, a column of ice formed in the lower section of the tower. The pressure of the expanding ice caused the top of the structure to collapse, the report said.
Now all ski-hill towers must have drainage holes before November of this year.
This is the second safety order to come out of the Whistler crash. An October, 2009, order required all towers associated with Doppelmayr - the company that designed the Excalibur Gondola - to have drainage. All the affected ski resorts, including Whistler, have complied, said lead investigator Jason Gill.
"We feel that all ski lifts are safe in British Columbia," Mr. Gill said. "We feel that we've put strategies in place to mitigate this kind of occurrence."
Lifts at Whistler were checked for water after the crash, with one tower needing an immediate drain hole. Drainage was added to all towers in the spring of 2009, said Doug Forseth, Whistler Blackcomb's senior vice-president of operations.
"Failing to take away any lessons from this would be a tragedy," he said. "The procedure going forward is to check [drainage]each year in the fall."
Doppelmayr sent out a safety bulletin notifying Whistler Blackcomb of possible water accumulation in 2006, Mr. Forseth said.
The notification prompted Whistler Blackcomb to start a resonance-testing procedure in 2007. The test, which involves knocking a hammer on the outside of the steel tower, did not uncover the water accumulation, the report said.
Resonance tests are a common practice, but their effectiveness can be hampered by human subjectivity and incomplete knowledge about the interior construction of the tower, Mr. Gill said.
"The hammer test was not always effective at detecting water, so to provide drainage is the best method to make sure we are not accumulating water within these structures," he said.
Mr. Forseth said Whistler Blackcomb will still do resonance tests to double-check that the drain holes are effective.
The safety authority will also present the findings to the Canadian Standards Association to determine whether they warrant code changes.