A PG&E natural gas pipeline that exploded during pressure testing on Sunday afternoon (Nov. 6), causing a mudslide across Interstate Highway 280 in Woodside, was likely damaged by a backhoe, a utility spokesman said Monday (Nov. 7).
PG&E crews this morning were determining how to extract and replace the damaged section of Line 132, which ruptured during hydrostatic testing on a knoll above Highway 280 near Farm Hill Boulevard at about 3:20 p.m., PG&E spokesman David Eisenhauer said.
A preliminary investigation indicated that the section of pipe that ruptured had been damaged by a backhoe sometime after the line was installed in 1947. PG&E is looking into when that damage might have occurred and what agency might have been responsible, Eisenhauer said.
The explosion left a 5-foot-by-5-foot crater in the hillside, and water from inside the pipeline caused a mudslide that reached northbound Highway 280 and blocked two lanes for about four hours, California Highway Patrol Officer Art Montiel said. No one was injured.
The test was being conducted as part of an ongoing safety evaluation of natural gas transmission lines in "high consequence" or highly populated areas, Eisenhauer said.
"That's exactly why we do these type of safety tests, to find weaknesses in the pipeline," Eisenhauer said.
PG&E crews have conducted pressure tests on more than 120 miles of pipeline since April. Eisenhauer said no homes or buildings were damaged by Sunday's rupture and that the utility employs different testing strategies on pipelines that run directly through neighborhoods, such as placing cameras or "pigs" that run inside the pipes to detect corrosion or faulty seams.
Last week, PG&E found a 1-millimeter leak in Line 132 in Palo Alto, and last month a line ruptured in Bakersfield during hydrostatic testing. A faulty seam on Line 132 ruptured in San Bruno on Sept. 9, 2010, causing an explosion that killed eight people and damaged 38 homes.