We’re picking up our discussion from last week about the San Bruno pipeline accident that leveled a neighborhood in September 2010. The gas explosion killed eight people, as well, and the National Transportation Safety Board’s findings indicate the same conditions that led to that explosion could exist elsewhere in the country, including Oregon.

The NTSB said the accident was an “operational accident.” It was caused by systemic failures at the utility, Pacific Gas & Electric, and at federal and state regulatory agencies.

For example, PG&E had trouble locating years and years of safety records for some of its pipeline. Regulatory inspections should have discovered this long before the NTSB got there. But they did not.

PG&E did produce some records, but the NTSB found them to be less than reliable. In one glaring instance, the records indicated that the pipe was seamless and of uniform thickness. In fact, the pipe was seamed and of variable thickness.

The pipe’s construction determines how much pressure it can take. PG&E calculated that 400 pounds per square inch would be appropriate for the San Bruno line. The pressure reached 396 psi and, one hour later, burst.

Had the utility known the pipe was welded, it may have conducted more regular and rigorous inspections of the condition of the pipeline. It would have noticed that one weld — the weld that would eventually rupture — went just halfway through the pipe, and that other welds were also substandard.

We’ll finish this up in our next post.

Source: Post & Courier, “NTSB faults PG&E, regulators in gas explosion,” Joan Lowy and Matthew Brown, Aug. 31, 2011