Crews Clear Palmdale Road Before Storm

Rain, heavy at times, is forecast in the Southland this weekend, causing residents in canyon areas denuded by last month’s wildfires to brace for mudslides and sending road crews scurrying to clear hundreds of tons of debris along the Antelope Valley Freeway.

Scott Entrekin, a meteorologist with the National Weather Service, said there is a 20% chance of scattered showers this morning, increasing to a 70% chance by this afternoon.

Most areas of the Southland, he said, can expect one-third to one-half inch of rain.

Thundershowers in the late afternoon or early evening could bring heavy rains to some regions.

The snow level during the cold storm, which Entrekin said developed over the Gulf of Alaska, is expected to drop to 4,000 feet by afternoon with most of the rain ending late Saturday night and a slight chance of scattered showers Sunday morning.

A department spokesman said that crews will be on standby in fire-ravaged areas such as Topanga and Malibu, where light rains could cause mudslides in the burned hills.

A second storm that was predicted to begin Sunday night and last through Tuesday is not expected to materialize, weather forecasters said.

Even though this will be the second big storm of the season, rainfall totals are well below normal, Entrekin said.

As of Friday, 1.49 inches had fallen at Los Angeles Civic Center since June 1. Normal rainfall is 3.97 inches.

Last week’s rains caused only minor problems along the Pacific Coast Highway, forcing the temporary closure of traffic lanes.

This weekend’s storm also is not expected to have a severe impact.

But experts said mudslides can be triggered by only small amounts of rain in vulnerable areas.

That kind of concern increases when forecasters predict rain, as they are for the weekend.

Since heavy rains deluged the area last winter, millions of pounds of rocks and mud have slid onto the Antelope Valley Freeway where it crosses the San Andreas fault in Palmdale.

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Another wet season could bring more slides.

“We’ve had problems all year,” said Tom Pellerin of the California Department of Transportation. “If we get heavy rains this year, we’re going to have problems again.”

Caltrans is still contending with the damage from the deluges of last winter, said Pellerin, a maintenance supervisor in the Antelope Valley.

His department has removed as much as 2,000 tons of debris from the freeway near the Avenue S exit in the last several months.

And bracing for the expected rain this weekend, Caltrans over the last few days has knocked another 300 to 400 tons of rock and debris onto the northbound lanes of the freeway from the adjacent ridge.

Pellerin said the material removed from the slopes beside the Antelope Valley Freeway was loose and would have eventually cascaded onto the roadway on its own.

Such an event could cause much more serious problems than the disruptions Caltrans created by closing the two northbound lanes for short stretches Thursday and Friday.

“That area’s in the San Andreas fault line, and there’s not enough glue in the dirt to hold everything together when it gets wet,” Pellerin said, offering a layman’s explanation for the deterioration on both sides of the freeway just north of Avenue S.

Caltrans geologist Gustavo Ortega said the fault is the culprit. The movement of the fault diminishes, if not eliminates, the structural integrity.

“It’s a very chaotic situation there because of the San Andreas fault,” he said. “The materials are all crushed. The beds are contorted.”

The area is destined to have erosion problems, Ortega said. Rain and the desert winds simply aggravate the process.

Since 1966, when Caltrans opened the stretch of freeway leading into Palmdale that crosses the fault, Pellerin said there has been a problem with erosion.

This year has been especially troublesome because of the rains.

In the last few months, he said, Caltrans has had the slope on the southbound side re-graded and the northbound slope may be re-cut next spring.

But even that will not solve the problem.

Already the upper tier of the southbound slope is starting to erode slightly.

Fortunately, the falling rock has yet to cause any accidents, Pellerin said.

Caltrans has placed cement barriers along the shoulder on both sides of the freeway to keep the fallen rock from rolling into the traffic lanes.

“There’s nothing you can really do,” Pellerin said. “Just keep the rail there to stop the falling material.”