Julianne McCaffrey took this aerial photo Thursday of the rock slide that has closed the Sea to Sky Highway near Porteau Cove, B.C. (Submitted by Julianne McCaffrey)

The Sea to Sky Highway, the primary route between Vancouver and 2010 Olympic sites in Whistler, could re-open late Sunday, B.C.'s chief geotechnical engineer says.

A rock slide Tuesday night left up to 10,000 cubic metres of rock and debris on a section of Highway 99 between Lions Bay and Furry Creek south, with initial estimates suggesting it would be shut down until Monday or longer.

But Mike Oliver said Friday that drilling and blasting to clear unstable material on the remaining rock face has been going well.

He said there would be another blast Friday afternoon to bring down loose and unstable rock, and if it goes well highway crews would work around the clock to clear the debris into adjacent Howe Sound immediately.

Engineers said they are confident the road will be repaired and usable by Monday but late Sunday is now a possibility.

However, the slide likely caused severe damage to the roadway beneath, which will need to be re-paved, a job that Oliver said might not take place for days or weeks.

Alternate route in poor shape

The only alternate route is a seven- or eight-hour drive up through the Interior that includes the Duffy Lake Road, which is badly in need of repair, Lillooet Mayor Christ'l Roshard said Thursday.

She said the stretch of the Duffy Lake Road, the only route in and out of Squamish, Whistler and Pemberton, hasn't been upgraded since it was paved 17 years ago.

"The road surface itself is very poor … it has been patched many times," she said, adding her "car takes quite a beating" when she drives the route once or twice a month.

Roshard has been lobbying the provincial government to repair the road since B.C. won the right to host the 2010 Olympics, and she's hoping this week's closure of the Sea to Sky Highway will convince the government that it's time to upgrade the road.

While the main route remains closed, a Vancouver-based helicopter service is operating a temporary shuttle service to Squamish and Whistler.

Jay Minter, director of marketing for Helijet, said nine flights will be offered daily until the rock slide is cleared on the Sea To Sky highway.

The cost of the flight has been reduced to $80 one-way from $300 earlier in the week after the company was able to secure a larger, 12-seat aircraft, Minter said, adding the new price is a goodwill gesture meant just to cover costs.

With files from the Canadian Press