Caltrans crews clearing the section of Tioga Pass east of Yosemite National Park in recent weeks encountered snow 8 to 15 feet high along the road. In some places, snowdrifts, where deep banks have been heaped up by the wind, reach up to 50 feet.

Clearing the mountain passes over the Sierra is always laborious, but this year it's an especially tough job after a winter marked by record-breaking snowfall.

Caltrans spokesperson Skip Allum says crews started work in April to meet the goal of having the four main passes that close in winter — Monitor on Highway 89, Sonora on Highway 108, Tioga on Highway 120 and Ebbetts on Highway 4 — cleared and open to motorists by the Memorial Day weekend.

Monitor is the only pass that crews have finished clearing, and this year it opened May 8 at 1 p.m., which is later than usual.

"With the records I was able to check going back to 2004, this is the first time in 13 years that it hasn't been open in April," Allum says. "That speaks to the amount of snow that fell this year and the amount of problems we discovered that needed to be fixed to get the roads safe."

Plowing the snow is the first step in opening a mountain pass, then officials have to address the problems that become apparent once the road is clear.

"You don't know what you're going to uncover and discover," Allum says. "You might find damaged culverts, roads that have cracked, trees that have fallen, striping that needs replacing."

While Caltrans clears the eastern side of Tioga, Yosemite National Park handles the section running through the park, and at this point spokesperson Jamie Richards can't guarantee when the pass will be fully open.

"It varies every year depending on snow and weather conditions," Richards says. "Typically we try for somewhere near Memorial Day weekend. We've opened as late as early July. This year it's too early to tell when we'll be able to open the road."

She added: "Yosemite road crews are working Monday through Friday and might be going to seven days a week soon."

Caltrans crews are working on Ebbetts Pass and Allum says the road will open as far as the east side of Lake Alpine by the end of the week. Work has also started on Sonora Pass and the road was open as far as Kennedy Meadows as of Thursday. It's unknown when these passes will be fully open.