NTSB Interim Report On San Bruno Gas Explosion

They have ruled out corrosion or third party damage.

"PG&E survey sheets and charts for the rupture location indicate that the pipeline was constructed of 30-in.-diameter seamless steel pipe (API5L Grade X42) with a 0.375-in. thick wall. Evidence obtained so far, however, indicates the pipeline in the area of the rupture was constructed, at least in part, with seam-welded pipe, says the NTSB."

Some of the welded pipe was welded from inside and out, but some was only welded from the outside side. Such pipe cannot handle the same pressure as seamless pipe.

Somebody cheated during construction.

I do not know how many clients Erin Brokovich has lined up but her job just got a lot easier.

Paul in PA