No Passing Lane on Tioga
Media and public officials get a look at the snowy road to Yosemite
On Wednesday, April 19, Caltrans District 9 staff opened the gates to Tioga Pass Road, also known as State Route 120, to local media and public officials. The group of Mono County staff, along with California Highway Patrol staff and Supervisors Bob Gardner and John Peters, met at the lower gate closure and was briefed by Mountain Superintendent Cliff Weier before donning hard hats and orange vests.
Weier explained that Caltrans District 9 crews are working between 7 a.m. and 12 p.m. daily to remove snow and fallen rocks from the State Highway. At midday, water that froze overnight in crevices between large boulders begins to flow freely, causing rock fall and wet slab avalanches that threaten workers’ safety.
The work is certainly dangerous. In 1995, a National Park Service Employee was killed while removing snow from a large snowdrift on Olmstead Point. According to Weier, one of the most dangerous parts of the process is when crews first cut into the large snowdrifts that cover the road. “In some places, we are seeing drifts that are 50 to 75 feet high,” said Weier. “In areas like the green bridge, we expect to see drifts as big as 150 feet.” When crews cut into a bank of that size, they risk undercutting the slope and triggering an avalanche. The 1995 accident involved a loader-triggered avalanche.
To mitigate the risks associated with rock fall and avalanches, Caltrans District 9 has an Avalanche and Blasting Crew. This four-person team assesses slope stability and scopes out places that could be dangerous before the rest of the road crew gets to them. When large boulders fall into the road, they blow them up. When road crews approach an area where a large snowbank is attached to a snow flow that has a large cornice at its top, they shoot it and trigger the avalanche before the crews arrive.
