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.”