The investigation by the National Transportation Safety Board into the September 9 San Bruno gas line explosion has so far yielded no definitive answers about the cause of the blast or the culpability of PG&E, however investigators have been unearthing pipe in the vicinity which isn't the "seamless" steel pipe PG&E claimed was down there. Via the Wall Street Journal, we learn that PG&E has both seamed and seamless pipe in the area, according to their records of what was installed back in the 1950s. In the meantime, as we now know, houses were built on top of it all, and now investigators are finding pipes that were seamed and welded lengthwise, which may or may not have been a key factor in the disaster.

The NTSB is now "in the process of researching pipe-welding standards and practices in effect at the time the pipeline was installed in 1956," and PG&E is meanwhile doing an "exhaustive search" to figure out what else they might not know about what kind of pipes they've got running underground.

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