Blast raises questions on gas line safety

“It was pretty devastating,’’ Fire Chief Dennis Haag said. “It looks like a moonscape in some areas.’’

At least 50 people were hurt, with three suffering critical burns in the explosion Thursday evening that left a giant crater and laid waste to dozens of 1960s-era homes in the hills overlooking San Francisco Bay.

The utility that operates the 30-inch diameter line said it was trying to find out what caused the steel gas pipe to rupture and ignite.

Some residents said they smelled gas in the neighborhood during the past several weeks. The utility said it was checking its records for complaints, but added that none of its crews were at work on the line Thursday.

Compared with the tens of thousands of miles of gas pipelines nationwide, accidents are relatively rare, but usually deadly.

In 2008, there were 44 significant accidents involving gas transmission or distribution pipelines, killing 365 people and injuring 1,553.

Transmission lines like the one that burst in San Bruno deliver natural gas from its source to distribution lines, which then carry it into neighborhoods before branching off into homes.

During the past two decades, there have been more than 5,600 significant pipeline accidents nationwide — including more than 1,000 in which someone was killed or required hospitalization, according to the Pipeline and Hazardous Materials Safety Administration.

Experts say the nation’s 296,000 miles of onshore natural-gas lines routinely suffer 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, Wash.

Most of the older pipelines lack anticorrosion coatings that are prevalent in the industry today, said Carl Reimer, executive director of the trust, which was set up after a 1999 explosion that killed three people in Bellingham.

“The industry always says that if you take care of pipelines, they’ll last forever,’’ Reimer said. “But what we see over and over again is companies are not doing that, and corrosion and other factors are causing failures.’’