Another segment of the California natural-gas pipeline that exploded in September 2010 has ruptured and unleashed a mudslide onto a highway—the third incident in less than two weeks involving the troubled line.
A pinhole leak was found last week in a third segment of the line in the Palo Alto area, near Stanford University. And testing in a fourth segment ripped a six-foot-long gash in a pipe Oct. 24 near Bakersfield.
Scrape and Gouge Found
Pacific Gas & Electric’s Line 132—which recently was found to have leaked 26 times before it flattened a neighborhood in San Bruno in 2010—burst Sunday (Nov. 6) afternoon during pressure testing about 250 feet from Interstate 280 in Woodside, authorities said.
|A National Transportation Safety Board investigator cleans a fractured segment of pipeline that ruptured Sept. 9, 2010. Recent testing has uncovered more trouble along the line.|
The rupture blew a 7-by-7-foot square crater in the hillside, dumping mud and rocks on the highway and shutting down parts of it for four hours.
PG&E spokesman Brian Swanson described the segment as a seamless 24-inch pipe.
On Monday (Nov. 7), the utility said it had found “a large scrape and a gouge” in the Woodside line. There was no indication when or how the damage had occurred. PG&E blamed the problem on an unknown “third party,” probably using a backhoe.
News photos and video show the damage.
‘We’ll Learn from This’
The ruptures occurred and the leak was discovered as the various segments of the natural-gas pipeline were undergoing hydrostatic spike testing, designed to uncover weaknesses and holes.
“We’ll learn from this experience,” Swanson said. “It’s definitely a concern that this hydrostatic pressure test impacted 280. We’ll do an analysis to determine how we can minimize disruptions like this in the future.”
The utility is still looking for the location of the Palo Alto area leak, and spokesmen said the task could take several days. Nevertheless, they said the leak was about 1 millimeter wide.
The San Francisco Chronicle, citing PG&E records, reports that both the Woodside and Palo Alto segments are more than 50 years old and include “at least 22 feet of pipe salvaged from a decommissioned part of the line and reinstalled in 1957.”
“The company has said such reuse was common industry practice into the 1960s and that lines with refurbished, salvaged pipe are safe,” the Chronicle reported.
PG&E began pressure testing the line only after the San Bruno explosion killed eight people and destroying 38 homes.
The National Transportation Safety Board concluded in August that PG&E was responsible for the disaster, citing use of substandard pipe, an inadequate pipeline integrity management program, and regulatory exemptions on pressure testing for older pipelines. Earlier, NTSB also noted coatings irregularities along the ruptured line.
PG&E originally said that the San Bruno line was seamless, until a federal investigation revealed that it, in fact, contained numerous welds, including a longitudinal weld that proved to be the origin of the deadly blast.
Prior to that disaster, PG&E had conducted only simpler, less expensive corrosion detection tests. Utility records recently analyzed by the Chronicle, however, show that Line 132 had had dozens of unexplained leaks since 1951.
By law, such lines require high-pressure-water testing, not just corrosion inspection.
In addition, federal regulations prohibit the use of corrosion-only methods on any gas transmission line with a history of longitudinal seam weld failure.
Experts say high-pressure water testing conducted earlier would have detected the seam flaws that led to the San Bruno explosion.
Now, the utility is trying to complete hydrostatic testing on 150 miles of transmission pipe by the end of the year.