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Natural-gas lines under scrutiny

In wake of San Bruno explosion that killed four people, details surface about local pipelines

Posted: September 15, 2010 9:32 p.m.
Updated: September 16, 2010 4:30 a.m.

Could the Santa Clarita Valley fall victim to a massive natural gas explosion like the one that killed four people in San Bruno last week?

That’s what The Signal asked investigators still trying to figure out what happened in the disaster near San Francisco.

The answer, as it happens, is uncertain. While natural gas pipes do run beneath the Santa Clarita Valley, experts still weren’t sure what caused the blast in San Bruno.

Peter Knudson, spokesman for the National Transportation Safety Board’s probe of the blast, said Wednesday that all possible causes for the blast remain “on the table.”

Agency investigators, he said, have asked for many documents, including seismic records monitoring soil stability at the time of the blast.

San Bruno, like Santa Clarita Valley and many other California communities, experiences pronounced seismic activity that shakes the ground holding natural-gas pipelines.

“We’re looking at everything, and we have not ruled anything out,” Knudson said. “We’re looking at corrosion, metal fatigue, defects in the pipe, any sort of damage. ... and we’re getting the seismic records of the area.”

Three sections of pipe have been sent to the agency’s metallurgy lab in Washington, he explained, including a 28-foot section of the steel pipe that was blown 100 feet in the air, and 10-foot sections of pipe cut away from each end of the damaged pipeline.

“We’re also going through an enormous amount of documents supplied by the (Pacific Gas and Electric Co.),” he said. “Also, we put out an e-mail asking for anybody with information — whether they smelled gas or observed something — to contact us. So far we’ve received about 90 e-mails.”

Fatal blast
One week ago, a gas-transmission line in San Bruno exploded into an inferno that killed four people and destroyed nearly 40 homes.

Since then, legislators have been calling for an overhaul of pipelines in the state.

On Wednesday, U.S. Senators Dianne Feinstein and Barbara Boxer (both D-Calif.) announced their intention to introduce legislation to strengthen oversight of the nation’s pipelines and substantially increase the penalties for violations of federal pipeline-safety regulations.

On Sunday, the head of the California Public Utilities Commission ordered PG&E to inspect more than 5,700 miles of natural-gas pipelines and to pay particular attention to high-pressure pipelines that run underground through heavily-populated areas, such as Santa Clarita Valley.

SCV’s pipeline
Residents here receive their natural gas via three steel high-pressure pipelines running through Santa Clarita, two of which are 30 inches in diameter, and the third is 42 inches in diameter.

Denise King, spokeswoman for the Southern California Gas Company, said “vigorous, robust and aggressive” inspections of Santa Clarita’s pipelines are carried out quarterly.

She was asked: Can what happened in San Bruno happen in Santa Clarita Valley?

“Since the investigation there is ongoing, we don’t have the information to answer that,” she said. “Until we know what caused the explosion, we won’t know what lessons have to be learned.”

Inspectors examine the integrity of local pipelines inside and out, she said.

They use technology commonly called a “smart pig” probe, she said, which measures pipe thickness for possible corrosion. A protective material is used to coat the outside of the pipes to prevent corrosion.

Making sure gas pipelines stay intact during and after an earthquake remains a key safety concern for city officials.

Seismic activity
The safety chapter in a 2008 draft of Santa Clarita’s general plan names close to a dozen major fault lines around the Santa Clarita Valley, each of which has the potential of prompting a major earthquake of 6.0 or higher on the Richter Scale.

And that’s not including the San Andreas Fault, which runs 745 miles from the Gulf of California north to the Cape of Mendocino. Its fault zone is located north of Santa Clarita and extends through Palmdale to San Bernardino. In 1857, a magnitude 8.0 earthquake occurred along a 255-mile stretch of the fault, between San Bernardino and Cholame.

City planners note in their master plan that along the fault’s Mojave segment, closest to Santa Clarita, the interval period between major ruptures is estimated to be 140 years.

According to their math, Santa Clarita is due for a major rupture along the San Andreas fault.

The strongest recent seismic event here was the Northridge Earthquake, which hit Jan. 17, 1994, with a magnitude of 6.7 on the Richter scale and an epicenter 13 miles southwest of the Santa Clarita Valley in Northridge.

Although 57 people died in the Northridge earthquake and 9,253 people were injured, no deaths were recorded here.

And, although no natural gas explosions were recorded here, the Northridge quake did damage natural gas service, city planners note in their plan.

Damage to natural gas pipelines, including damage to the three major high-pressure transmission lines, are among the vital public services the City Emergency Plan identifies as at risk in a “catastrophic earthquake.”


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