PG&E on Friday finished removing a section of pipe from Line 132 that the California Public Utilities Commission requested this week as part of its investigation into the Sept. 9, 2010, pipeline explosion.
The CPUC ordered Pacific Gas & Electric Co. to excavate the pipe to see if it could provide any more clues why Line 132 ruptured near Glenview Drive and Earl Avenue, leaving eight people dead and 38 homes destroyed in the Crestmoor neighborhood.
Investigators still haven't determined the cause of the explosion. However, officials believe that the weld that ruptured on the line was a type known as DSAW, or double submerged arc welded, where, according to the San Francisco Chronicle, the welds were completed from both the inside and the outside of the pipe with the two welds merging at the center, creating a longitudinal seam.
PG&E initially said that the pipe that ruptured was seamless, but the National Transportation Safety Board, which is investigating the cause of the blast, found that the and had a number of defective welds.
PG&E has since taken that segment of Line 132, which was orginally installed in 1956, . That segment was connected to a section of pipe north of the explosion site that was abandoned in 1948. The CPUC ordered PG&E to remove an 8-foot section of pipe to see if it had any similarities to the pipe segment that ruptured.
"Once it became clear that the NTSB was not going to pursue testing of this pipe, we took over moving this forward," said CPUC spokeswoman Terrie Prosper. "We have been working with PG&E for the past several weeks to arrange for the excavations and to identify an appropriate independent testing facility where the removed pipe can be transported to for testing."
Prosper said the CPUC will be evaluating the metallurgical charactistics of the excavated pipe, which could be helpful in determining how PG&E's pressure-testing could be better prioritized or whether pipes need to be replaced.
Since May, PG&E has been to determine the reliability of numerous pipeline segments throughout its service area. PG&E hasn't been able to find proper records for those segments and was ordered to test pipes that had characteristics similar to Line 132.
PG&E also will be running a camera through the abandoned 1948 pipe, said PG&E spokeswoman Brittany Chord.