Dust billows from the site of a major gas line rupture in Castaic on Saturday. (KNN.NEWS)
Crews from Southern California Gas Co. are investigating a major pipeline rupture that forced a shutdown of the 5 Freeway in Castaic this past weekend. At least one expert believes heavy rains likely caused significant land movement, which may have triggered the break.
The rupture, described by some residents as sounding like a jet engine, occurred Saturday afternoon and led to a nearly four-hour freeway closure, with nearby residents ordered to shelter in place.
While the utility has not announced an official cause, a spokesperson said Monday that the break appeared linked to substantial land movement in the area. Aerial footage showed giant plumes of dust rising from the damaged pipeline and a collapsed hillside nearby.
Jonathan Stewart, a UCLA Samueli School of Engineering professor, said the images indicate a “pretty clear landslide,” with recent heavy rains likely contributing to soil movement. Stewart is not part of the utility’s investigation.
Southern California recently experienced its wettest Christmas in modern history, with some mountain areas receiving nearly 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,” Stewart explained. “It’s kind of acting in two directions together — both bad — that can increase the likelihood of movements.”
Although Stewart has not visited the site, he noted that photos show a large head scarp, marking the top of a landslide, “indicating substantial movement” that could have ruptured the pipeline. He added that while landslides are common in Southern California during heavy rain, this event is “an example of a deeper seated slide.”
Fewer than five non-residential gas customers are experiencing outages due to the break, according to SoCal Gas. Crews will work over the next few days to separate the damaged pipeline from the system. Stewart said the line may need to be rerouted, either around the unstable land or buried deeper underground.
The smell of rotten eggs spread across large areas 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 the leak posed no immediate threat and that the gas odor 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., covering about 15 square miles, and was lifted roughly four hours later.
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