As Southern California Gas Co. crews investigate a major pipeline rupture that triggered a shutdown of the 5 Freeway in Castaic this weekend, at least one expert said that heavy rains were likely to blame for causing massive land movement in the area.
The pipeline break, which some residents said sounded like the roar of a jet engine, occurred Saturday afternoon and forced a nearly four-hour closure of the freeway, as area residents were ordered to shelter in place.
Although the utility has yet to announce an official cause of the accident, a spokesperson said Monday it appeared the break was due to significant land movement in the area caused the break. Aerial news footage of the rupture showed giant plumes of dust rising from the broken pipeline, as well as a collapsed hillside nearby.
Jonathan Stewart, a professor at UCLA’s Samueli School of Engineering said that the images revealed a “pretty clear landslide” and that recent heavy rains could be to blame for the movement of the soil. Stewart is not part of the utility’s investigation.
Southern California just experienced its wettest Christmas in modern history — with some mountain areas receiving close to 18 inches of rain.
Heavy and sustained rainfall over multiple days increases the driving force within the Earth that produces landslides, while also reducing the strength of the soil, he said.
“It’s kind of acting in two directions together — both bad — that can increase the likelihood of movements,” Stewart said.
Stewart hasn’t visited the site, but said a large head scarp, which marks the top of a landslide, is visible in photos of the area, “indicating substantial movement” that could have ruptured the pipeline.
Landslides are common in Southern California during heavy rainfall, he said, but noted that this land movement is “an example of a deeper seated slide.”
Fewer than five non-residential gas customers are experiencing outages as a result of the break, according to SoCal Gas.
Crews with the company will work to separate the damaged pipeline from the pipeline system over the next few days, the spokesperson wrote in an email. The gas line will likely have to be rerouted, either around the land movement or deeper in the ground, Stewart said.
The smell of rotten eggs crept across large swaths of the Santa Clarita and San Fernando valleys on Saturday, as fire and hazmat crews worked to stop the leak.
The L.A. County Fire Department confirmed Saturday the leak posed no immediate threat to the city, adding that the odor from the gas was not harmful.
The California Highway Patrol closed all lanes of the 5 Freeway near Castaic from roughly 5 to 9 p.m.
A shelter-in-place order was issued at 5:40 p.m Saturday, spanning roughly 15 square miles of Castaic, and was eventually lifted around four hours later.
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