PG&E didn't document the fact that Line 132 had welded seams. So really, what's the big deal? Aside from proving that PG&E is sloppy on its paperwork, what difference does make?
Back in 1998, the Department of Transportation sent out to all utilities, including PG&E, a Safety Alert (see below). The Alert explained that pipes with welded seams (known as "ERW" pipes) are dangerous. Special precautions need to be taken to make sure they don't explode. For example, the pipes should be periodically tested to make sure they are sound.
Because PG&E's paperwork said that the pipe was not ERW pipe, PG&E took none of the recommended safety precautions.
One of the problems with ERW pipe is that the welds are subject to a type of corrosion that is hard to detect. According to the Alert:
ERW seams have been involved in 145 service failures . . .since 1970, and . . .all but 2 occurred on pipe manufactured prior to 1970. . .selective seam corrosion appears to be a contributing cause of failure in a significant number of these incidents. . .
If the welded seam pipe was installed before 1970 (as was Line 132) the Alert called upon the utility to not just review the pipe's history, but to fill it with water and pressure test it to make sure it is sound.
All operators who have pre-1970 ERW pipe in their systems should carefully review their leak, failure, and test history as well as their corrosion control records. . .operators should consider hydrostatically testing to ensure the integrity of the pipeline.
It appears that PG&E neither conducted nor even considered hydrostatically testing Line 132, despite the fact that Line 132 was suspect pre-1970 ERW pipe.
Did PG&E fail to properly document the type of pipe running through San Bruno due to a mere oversight? Or did PG&E deliberately fail to document the pipe so that it wouldn't have to conduct the expensive and time consuming hydrostatic tests?