Two fixes on table for Highway 140 rock slide

Shed or tunnel proposed by Caltran

jsmith@mercedsunstar.comFebruary 12, 2013 

— If you've sat in your car waiting for up to 15 minutes at the one-lane bridge on Highway 140 heading into Yosemite National Park, you've been affected by the Ferguson rock slide.

The 70,000 tons of rock that fell on the road about 12 miles outside the park prompted emergency construction of the detour and have been slowing traffic for more than six years.

State transportation officials say they're close to coming up with a plan to ditch the detour and fix the situation.

Officials with the California Department of Transportation visited Mariposa on Tuesday to lay out for county officials what they say are two viable options for allowing a smooth flow of traffic to return to the highway.

"It's taking a longer time than usual projects, but this project is very complex," said Grace Mangsayo, Caltrans engineer and project manager.

According to a draft environmental document to be submitted for public review this spring, officials will choose between creating a "rock shed" and tunneling through the side of the mountain that borders the road.

Building the shed would include clearing debris on the road and creating a structure to shield vehicles from future rock slides.

The tunnel option would mean bypassing the impacted section of the road by drilling through the mountain.

This project is "enormously important," said Mariposa County Supervisor Lee Stetson. "The slide has long been a major problem for both the tourist trade and local folks. It absolutely needs to be restored to a major highway."

The state released in 2010 its first attempt at a draft plan outlining several project alternatives. However, federal and state environmental concerns sent engineers back to the drawing board.

"The previous alternatives were not always well thought out," added Stetson, who represents the affected area. "The ones that remain now are the ones we should pursue, and we are."

The project has been complicated because of environmental protections on the adjacent Merced River, Mangsayo said.

"The discussions had become very complex when looking at the wild and scenic river," she said. "It takes a congressional act to allow us to impact that river."

Federal and state agencies have signaled support for the current alternatives, according to Caltrans officials.

The Legislature passed a bill last summer allowing the project alternatives to be considered without fear of violating laws for protected species, especially for the limestone salamander.

"We don't anticipate having mortality on any limestone salamander, but now we have the authorization that if something does happen, the project's not going to be shut down," said Margaret Lawrence, a regional Caltrans official working on the project.

The rock shed alternative would cost about $52 million and take about two years to construct, according to Caltrans officials. The tunnel project would cost about $120 million and take about three years to complete.

Officials said they anticipate selecting a project alternative by fall, and construction should start by summer of 2015.

Reporter Joshua Emerson Smith can be reached at (209) 385-2486 or

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