Natural-gas-transmission pipelines like the one that exploded Thursday in San Bruno are like highways for energy; anywhere there are people, natural gas follows to heat homes, power stoves and run factories.
SAN BRUNO, Calif. — Natural-gas-transmission pipelines like the one that exploded Thursday in San Bruno are like highways for energy; anywhere there are people, natural gas follows to heat homes, power stoves and run factories.
While energy companies know where the lines are, residents are not routinely told. In San Bruno, some residents said they didn’t realize a gas-transmission main ran through the neighborhood.
“If I had known that a gas pipeline was there I never would have moved there,” said Maria Barr, 69, who had lived near the blast site for 34 years.
Security concerns are part of the reason that exact line details are not widely publicized, experts said, although general location information is publicly available.
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“They are critical infrastructure,” said professor Jean-Pierre Bardet, chair of the University of Southern California’s civil- and environmental-engineering department. “If you point them out to anybody, they could have malevolent intentions.”
But, he said, such security concerns set up a “a very interesting conflict” with the desires of residents in places such as San Bruno to be informed about potential hazards near their homes.
High-strength steel pipes, often as wide as a large truck tire, transport natural gas at up to 1,400 pounds per square inch, a pressure roughly equivalent to the weight of five passenger cars. Some run just three feet underground in dense urban and industrial areas, such as Central Los Angeles.
In general, gas lines are much less susceptible to failure than, for example, aging water pipes.
But when something does go wrong, the damage can be far greater than flooded streets and homes.
Over the years, pipeline breaks have killed dozens of people and resulted in millions of dollars in damage to property. On Dec. 24, 2008, a gas leak in a small pipe also operated by Pacific Gas & Electric caused an explosion that killed one person and injured five in Rancho Cordova, near Sacramento.
“This is a troubling event, and it is a great mystery,” USC engineering professor James Moore said of the San Bruno disaster. “The system is designed to avoid exactly this kind of failure. I regard the need to answer the question ‘how did this happen’ as rather urgent.”
In the past 20 years, federal officials tallied 2,840 significant gas-pipeline accidents nationwide, including 992 in which someone was killed or required hospitalization, according to the Pipeline and Hazardous Materials Safety Administration.
Those accidents killed 323 people and injured 1,372.
Experts say the nation’s 296,000 miles of onshore natural-gas lines routinely experience breakdowns and failures.
More than 60 percent of the lines are 40 years old or older and almost half were installed in the 1950s and 1960s, according to a recent analysis by the Pipeline Safety Trust, a nonprofit advocacy group based in Bellingham.
Most of the older pipelines lack anti-corrosion coatings that are prevalent in the industry today, said Carl Weimer, executive director of the trust, which was set up after a 1999 explosion that killed two boys and an 18-year-old man in Bellingham.
“The industry always says that if you take care of pipelines, they’ll last forever,” Weimer said.
“But what we see over and over again is companies are not doing that and corrosion and other factors are causing failures.”
And once a high-pressure pipeline fails, he added, anything can trigger a deadly blast. A cigarette or rocks smashing as high-pressure gas shoots by. Even someone answering a cellphone can cause a spark because it is battery-powered, Weimer said.
California is the second-largest natural-gas-consuming state, after Texas. Eighty-seven percent of the gas comes in through five pipelines from Canada, the Rocky Mountain states and the southwest.
The state’s average daily consumption is about 6,300 million cubic feet.
A big danger when it comes to gas pipelines is posed by earthquakes.
Many modern homes have an earthquake shut-off valve, which automatically cuts gas service when it detects seismic activity.
But they would not have prevented a disaster such as the San Bruno explosion because the leak was not in a home but in a nearby transmission line.
Material from The Associated Press is included in this report.