Inside Seven
Current Issue: September 2014
When threats of rain  neared several times in February and March, crews covered the earth with 80,000 square feet of plastic tarps to prevent further erosion to the graded slopes.  The transmission tower and poles located within the Caltrans right of way (center of photo) are the responsibility of Southern California Edison, a stakeholder.  Edison's and the County of Los Angeles' early involvement contributed to the success of this emergency project.

Landslide Repairs from Tip-to-Toe Leave a San Dimas hillside in Tip-Top Shape
by  Maria Raptis
Issue Date: 04/2010

Caltrans re-opened two freeway transition roads on Thursday, March 25, that had been closed for more than a month because of a landslide.

When a hillside collapsed during the morning commute hours on Feb. 18, it covered two connector roads: one from the westbound San Bernardino Freeway (I-10) to northbound Orange Freeway (SR-57) and another from the northbound SR-71 to northbound SR-57 in San Dimas. That same day, a $3.25 million emergency contract was awarded to Autobahn Construction Inc., of Santa Ana, whose crews worked to stabilize and repair the hillside.

Once rock and debris ceased to fall, workers removed loose gravel and earth from the top of the hillside, called the tip. Starting from the top, bulldozer operators graded the slope to avoid a larger landslide at the toe, or bottom of the hill.

Engineers call it “earthwork,” because a lot of earth is moved. In the first three days following the slide, two bulldozers filled nearly 35 dump trucks, which hauled 11,000 cubic yards of dirt and rock away from the landslide area. By the time the connectors opened, 120,000 cubic yards of dirt had been hauled away.

An adjacent slope – just east of the landslide – was also repaired as it showed signs of erosion. Both slopes were graded from the top to the toe of the slope.

With a hillside in tip-top shape, from head to toe, and after five weeks of full roadway closures, the two connectors were re-opened on March 25 in time for the morning commute. The hillside was stabilized, new drainage ditches were built and other improvements were made to diminish the threat of future sliding.

So, what happened to all the dirt?

“One of the reasons that this project was able to move so quickly was that Caltrans already had a dump site near this location,” said Martin Sandoval, construction resident engineer. ”Keeping the connectors closed allowed the trucks to move freely and frequently between the landslide and the landfill site.”

“Caltrans reused the dirt as backfill at another nearby project site,” said Roy Fisher, Deputy District Director of Construction. “This saved time and money.”

During the final weeks repair crews continued to remove dirt and debris from the roadway and drain inlets and culverts, maintained erosion control, replaced damaged lighting and reflectors, repaved the damaged roadway and shoulders, and restriped the connector roads. K-rail, or concrete barriers, will remain at the toe of slope to prevent any loose rock from entering roadway.

“Caltrans thanks the motoring public for their patience and understanding during this emergency project,” said Fisher. “Their ability and willingness to use alternate routes easily as part of their commute, allowed Caltrans to efficiently, swiftly and safely deliver this project.”

With the connectors closed, the contractor, Autobahn Construction, Inc., was able to work throughout the night.  This was an advantage in meeting construction schedules during an unpredictable rainy season.  From tip-to-toe, a view of the graded slope from top to bottom. Earthwork on the night shift.  Keeping the connectors closed allowed loaders and dump trucks to move freely and frequently between the landslide and the landfill site.  An aerial view of the hillside shows trucks lined up on the connector to load and haul dirt to a nearby dumpsite.  In the final stage, the hillside was seeded with landscape material that will hopefully, with a few more showers, grow a greener hillside.