Engineers with PG&E are figuring out how best to remove and replace a two-foot-long section of gas pipeline in Woodside that burst after failing a pressure test on Sunday. It's a section of Line 132: the ill-fated conduit that exploded under a neighborhood in San Bruno in September 2010, leveling homes and killing eight people.
The section that burst yesterday spewed water, not natural gas. PG&E'was hydrostatic testing the lines, and crews had increased the water pressure to 550 pounds per square inch (psi) when the pipe broke, spilling mud onto Interstate 280 and blocking traffic. That's much higher than the pipe's typical operating pressure of roughly 300 psi.
"Our plan is to get it up to a little over 800 psi when this hydro test is complete," said PG&E spokesman David Eisenhauer.
As for any link between this pipe and the San Bruno pipe, Eisenhauer says the two are "completely different." The one in San Bruno was wider and had welds between two sections, unlike the narrower, seamless Woodside pipe.
Crews hope to get a new section in place this week and re-test it this weekend. That could be tough to do without affecting residents or traffic, since the pipe sits inside a hill next to the freeway with homes on the other side. The busted section will be taken away for further testing. Early theories are that the failure may be due to some kind of mechanical damage, like being hit by a backhoe.
As for any public concerns over Line 132 - or any other high-value PG&E lines - Eisenhauer said this failed pressure test is actually a good thing. Better to have it fail now when it's filled with water, he says, than have it fail later when it's filled with gas.
"This is exactly what we want to have happen when we're doing a hydro test, because that lets us know that we're doing it right and we're finding the weaknesses that we need to find," Eisenhauer said.