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Current Issue: April 2014
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High atop at the crest is a perfect view of the I-10/SR-57/SR-71 connectors in San Dimas. To avoid a larger landslide, as soon as the hillside stabilized, two bulldozers – one at the crest and one below - were put to work removing lose gravel for a preliminary grading of the slope.

A Landslide Brought It Down
by  Maria Raptis
Issue Date: 03/2010

Just minutes after motorists alerted California Highway Patrol to falling rock and boulders, officers arrived on scene and closed a freeway connector. Then, a landslide covered the roadway.

Two District 7 freeway connectors remain closed since the morning commute hours of Thursday, February 18, when a landslide sent rock, boulders and earth onto the freeway system in San Dimas. The slide measured approximately 175 feet high and nearly 250 feet wide. There were no reported injuries.

The CHP was alerted to falling rocks by passing motorists and upon arrival they immediately closed the westbound San Bernardino Freeway (I-10) connector to northbound Orange Freeway (State Route 57). The landslide occurred just 10 minutes after the CHP was on the scene. At that time, the northbound SR-71/57 connector was also closed because of the potential for more sliding, as well as for the safety of the motorists and the public.

The westbound I-10/57 connector and northbound SR- 71 connector to northbound SR-57 will remain closed for several weeks as work crews continue to haul excess soil, rock and debris away from the site and grade the slope for stabilization.

Caltrans geotechnical engineers and work crews arrived on site shortly after CHP and worked throughout “Furlough Friday” and the weekend to assess the damage and initiate a stabilization plan. During his initial field inspection on Thursday morning, Caltrans geologist Gustavo Ortega described the slide as still active, with rock and debris continuing to fall.

That same day, an emergency contract was awarded to Autobahn Construction Inc., of Orange, whose crews worked to stabilize the hillside. Once falling rock and debris ceased, workers removed loose gravel and earth, allowing for a preliminary grading of the slope to avoid a larger landslide. In the first three days following the slide, two bulldozers worked to fill and refill nearly 35 dump trucks hauling away 11,000 cubic yards of dirt and rock.

“A lot of hauling and grading was done in the first few days because we were able to dump debris at a nearby Caltrans site, which saved a lot of travel time between loads,” said Roy Fisher, Deputy District Director of Construction.

The graded section of the landslide was covered with 80,000 square feet of plastic to protect the slope from further erosion due to weekend rain. More rain is expected in early March, which could slow progress.

“Certainly, the pounding rain we received in the last six weeks helped the soil lose its cohesion quality,” said Ortega.

Currently, Caltrans is conducting a massive grading operation, creating a ‘stepped’ terrace on the hillside. The next step will be to place concrete median barriers (K-rail) around the site, which will remain in place until slope stabilization is complete. Once the k-rails are in place, it’s possible that Caltrans could open one connector lane to motorists.

Caltrans immediately notified other stakeholders, including the County of Los Angeles and Southern California Edison, and a partnership was formed to help resolve the task at hand. The County of LA and Edison have interests in the property. The County has oversight of the abutting Frank G. Bonelli Regional Park and Edison is responsible for nearby transmission towers and poles located within the right of way.

“Getting the County and Edison on board right away was very helpful,” said Martin Sandoval, construction resident engineer. “Together, we resolved right of way and land use issues cooperatively, benefitting all agencies, stakeholders and the public.”

The construction project is expected to complete before the end of April, pending any weather-related delays.

 

 

 

In the first three days following the slide, nearly 35 dump trucks hauled away 11,000 cubic yards of dirt and rock. Gustavo Ortega, Caltrans Senior Engineering Geologist, Office of Special Geologic Studies,  reviews photos of the landslide during an on-site planning meeting with staff from Southern California Edison.  Some boulders that fell in the slide measured approximately 6 feet in length. On the day of the slide, an emergency contract was awarded to Autobahn Construction, Inc. of Orange.  Staff surveys the progress of the preliminary grading operation and flags locations according to the stabilization plan.