From the San Jose Mercury News:
A federal report issued Friday said the natural gas pipe that ruptured in San Bruno on Sept. 9, killing eight people and destroying 38 homes, had numerous flawed welds, and some experts said the pipe did not meet the welding standards in place when it was installed in 1956.
Based on the data in the National Transportation Safety Board report, "I think we have a pretty good understanding of why the pipeline burst where it did and the pressure required to burst the pipeline," said Bob Bea, a professor of engineering at UC Berkeley with extensive pipeline experience.
"The critical flaws in the pipeline are associated with the lack of penetration of the welding," he noted. "The welding should have penetrated through the entire thickness of the pipeline. In the fracture area it penetrated only about 50 percent of the steel thickness."
Bea added that "the incomplete weld penetrations are not permitted by the pipeline code in force at the time of the construction -- nor by the present code."
PG&E spokesman Katie Romans declined to comment on the welding issue, saying only, "we have received and are currently reviewing the NTSB's report." Full article