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Mud and rocks must be removed from Highway 178 through the Kern River Canyon. Caltrans released this photo Tuesday.

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A cascade of boulders, rocks and mud covers parts of Highway 178 through the Kern River Canyon. Caltrans released this photo Aug. 20, 2013.

After two days of nonstop work clearing debris from two rock and mud slides, Caltrans officials said they would reopen one lane of Highway 178 through Kern River Canyon, possibly as soon as Thursday night, but definitely in time for the Friday morning commute. But on Friday morning, it still wasn't open.

"Everybody is confident that we will have one lane of traffic open by the morning. We don't know what time. We may open tonight," said Caltrans spokesman Jose Camarena.

Camarena advised commuters to call 800-427-7623 or visit the Caltrans website (www.dot.ca.gov) before using the highway.

He said that areas along the highway shoulder and the hillside have been filled in where heavy rains Sunday and Monday exposed culverts and washed away chunks of the roadway, but crews will continue working through the weekend to finish repairs and reopen the second lane.

Under single-lane conditions, Caltrans flaggers will stop 10 to 15 motorists at a time, at either end of the canyon, and an escort vehicle will lead vehicles through, first in one direction, then the other.

A Caltrans geologist evaluated the roadway and surrounding area for signs that the rain-soaked ground might slump, or "waste," or fall away.

Area geologists said these are not uncommon problems in the Kern River Valley.

"Rock will come down a hill under the influence of gravity, but it's more than likely triggered by water," said Jack Pierce, an associate professor of geology at Bakersfield College. "The grains in the rock particles become loose, the way they would if you were watering your backyard. It's a constant battle, not only in the 178 area, but also the Malibu area."

Gregg Wilkerson, a geologist in the Bureau of Land Management's Bakersfield field office, described the 178 as "under-engineered and over-utilized."

"It's in a steep canyon; it's a wonder that they keep it open as much as they do," Wilkerson said. "The engineers are capable of doing a certain amount, but Mother Nature is more powerful than all the bulldozers put together."