Big Oak Flat Road into Yosemite Valley reopens after cliffside rockfall

Big Oak Flat Road, the continuation of Highway 120 in Yosemite National Park, reopened Thursday night after National Park Service trail and road crews finished clearing debris from a rockfall that had kept part of it shut down since Tuesday evening.

The rockfall happened about 6:40 p.m. Tuesday during recent wet weather just east of the lowermost tunnel on Big Oak Flat Road, cutting off Highway 120 traffic from reaching Yosemite Valley and alarming some business owners on the Highway 120 corridor in Tuolumne County.

“The rockfall was triggered by heavy rain, which then turned to snow overnight, complicating assessment of both the rockfall and the road condition,” Greg Stock, the park geologist in Yosemite, said in an email Thursday.

The rockfall appears to have originated from a point about 525 feet above Big Oak Flat Road, where a block detached from a cliff band, rolled down a small unnamed drainage, free-fell over a cliff and hit the base of the cliff, fragmenting into boulders that then tumbled onto the road just east of the lowermost, easternmost tunnel, Stock said.

The total volume of the boulders that fell was about 33 cubic yards, equivalent to about 75 tons, Stock said.

Trail crews and road crews blasted some boulders to break them into smaller pieces. The road was reopened by 5:45 p.m. Thursday with no restrictions, National Park Service spokesman Scott Gediman stated Thursday evening in an email.

“Our trail crews and roads crews did great work, and quickly,” Gediman said.

Before Big Oak Flat Road was reopened, the only open roads to the valley were Highway 140, El Portal Road in the park, and Highway 41, which is Wawona Road in the park.