A 2-foot-wide section of pipe burst Sunday during a high-pressure water test along the same Pacific Gas & Electric pipeline in Northern California that had a deadly explosion last year, sending mud, debris and a pipe cover into Interstate 280 and shutting down parts of the freeway for several hours, authorities said.
The pipe, which sits about 250 feet on a hill above the freeway in Woodside near San Mateo, burst at about 3:20 p.m. and saturated the hillside, PG&E Vice President for Gas Engineering and Operations Kirk Johnson said.
The pipe would normally carry natural gas at a pressure of 300 pounds with a maximum of 400 pounds, Johnson said. Workers were sending water through it at a pressure of 550 pounds.
Johnson said that while the problem was not encouraging he was glad it was discovered during a test.
"We want to make sure any possible weakness in the pipeline is found this way," Johnson said. "In terms of the test itself this is exactly what we are looking for," he said.
The northbound lanes of I-280 were shut down and slowly reopened as utility crews cleaned up the mess. All lanes were open again about four hours later.
The burst pipe was about 20 miles south of the section of pipeline in San Bruno that exploded in September 2010, killing eight people, injuring dozens more and destroying 38 homes on Sept. 9, 2010.
Federal investigators in a report issued in September blamed the blast on a "litany of failures" by PG&E and weak oversight by regulators.
National Transportation Safety Board chairwoman Deborah Hersman said the explosion the explosion the most significant pipeline accident in the last decade, both for its destructiveness, and for the safety lapses it revealed.
Johnson acknowledged that the line _ number 132 _ was the same, but downplayed the connection, saying it was of a different size and type and a good distance away.
"It's completely different pipe," he said.
Since the explosion the utility has been conducting hydrostatic tests like Sunday's on 150 miles of its pipeline.
"The whole point of a test like this is to make sure these pipelines can operate at a pressure well in excess of what they're designed for," Johnson said.
On Thursday PG&E crews doing a hydrostatic test found a small leak on the same line 132 in Palo Alto.
Gas service was not affected by the burst because it had already been routed around the pipe for the test.
Johnson said the burst section of pipe would be replaced this week with hopes of performing similar tests next weekend.