Getting Answers: Climate And Fire Impacts On Rockslide Frequency
SACRAMENTO (CBS13) - Within 48 hours, three rockslides at Echo Summit along Highway 50. The first blocked the road for nearly a day while CalTrans crews worked to carry pieces of rock out of the roadway and stabilize the side of the mountain.
The largest boulder in the first rock fall compared to the size of a cabin. Due to the boulder's size, Caltrans decided to rig it with explosives and break it up.
Even as snow started to fall early in the morning, crews were drilling into the boulder to get it ready to be detonated.
Within two hours of the roadway reopening, two more smaller slides were reported in the same area. No one was hurt, but one of the rocks damaged a vehicle in the area.
CBS13 asked experts: what caused these three rockfalls to happen within days of each other?
A CalTrans spokesperson said CalTrans geologists haven't pinpointed one cause.
"Our geologists say it could be a whole number of different factors, it could be water that gets in there, tree roots, it's really hard to say it's just kind of mother nature," said Gilbert Mohtes-Chen, a CalTrans spokesperson.
The U.S. Geological Survey reports that a rockslide can be triggered by a number of factors. Differentiating weather cycles, freeze and thaw cycle, excavation due to road bulding, earthquake or other intense vibration, wetting and drying, are among the factors.
The area struck by three rock falls was also scorched last year by the Caldor Fire and the ground above the rock has not regrown. That means, any rain water or snowmelt doesn't sink into the ground but instead flows down the side of the mountain. Rocks that area already weakened, like cracked from inconsistent temperatures, may freeze and thaw and the rock itself expands and contracts causing more instability.
CalTrans maintenance crews are monitoring the Echo Summit area through Monday until work can begin to stabilize the side of the mountain. That work will cause Highway 50 to be one way traffic controlled, and drivers should expect one lane. If larger blasts are required, traffic may be temporarily held over the next week. A timeline for the project completion hasn't been determined.
