Underground spring culprit of massive crack that shut down Highway 120 into Yosemite Valley

An underground seasonal spring that began flowing again after being dormant for years was the cause of a 200-foot long fissure resembling an earthquake fault that closed U.S. Highway 120 into Yosemite Valley in February.

This portion of the road, in the park called Big Oak Flat Road, began cracking in late February. National Park Service crews patched the crack “but it did not hold and it continued to widen and spread and we began conversations with the National Highway Administration,” said Yosemite National Park spokeswoman Jamie Richards.

Crews had to tear out 200 feet of asphalt and dig 40 feet below the surface of the original road, creating nine tiers to avoid further erosion.

They are creating drainage control by layering rocks, Geotech Fabric and soil. “Geotech Fabric a water permeable fabric that rocks and sand will not go through but water will,” Richards said.

Crews have installed two of these drains and need to continue digging to figure out how many more need to be installed before the road can be rebuilt. It’s too early in the process to estimate a reopen date for the road, Richards said.

Meanwhile, Yosemite Valley can be accessed by Highway 140 from Mariposa and Merced and Highway 41 from Fresno and Oakhurst. However, Highway 41 is in the midst of its own repairs — as of Friday, traffic remained one-way outside of Yosemite.

This story was originally published March 25, 2017 at 8:19 AM with the headline "Underground spring culprit of massive crack that shut down Highway 120 into Yosemite Valley."