SAN FRANCISCO — A section of natural gas pipeline that exploded south of San Francisco does not appear on Pacific Gas & Electric Co.'s list of its 100 riskiest pipeline segments, the utility company said Monday.
PG&E President Chris Johns said the pipeline segment that ruptured and exploded beneath a San Bruno neighborhood Sept. 9, killing at least four people and destroying dozens of homes, did not warrant inclusion on the list.
"We were not aware of anything in this particular area that would have met the criteria to put it on that list," Johns said.
The utility company's 6,700 miles of transmission pipeline in northern and central California includes 20,000 segments, ranging in length from 2 feet to a mile long.
The "Top 100" list was assembled from data gathered in late 2009. It's a list PG&E compiles every year based on monitoring, maintenance or construction work occurring near the line that could risk a rupture from digging.
California utility regulators on Monday warned that people should not fear the pipelines on the list, and that they are not considered at-risk or dangerous.
"The list is a tool used by PG&E to prioritize maintenance, repair or monitoring of its gas pipelines," said Paul Clanon, executive director of the California Public Utilities Commission.
"The CPUC will review the list to ensure that PG&E is monitoring their system effectively."
Whether or not the segment that exploded should have been on the list remains to be seen, Johns said.
It is unclear at this point what caused the blast, so Johns said PG&E would not know if its inspectors missed something until the National Transportation Safety Board released its investigative findings.
"We don't know yet what the cause was. So, that will inform us as to how we need to look at these various pipeline segments and whether the process we're using is a good process or not," Johns said.
A document PG&E submitted to regulators in September 2009 for gas rate proceedings showed the company had ranked as high-risk a section of pipeline 2 1/2 miles north of the blast site.
The company said that listing was based on 2006 data, and that a newer review of the segment by engineers found its protective coating and overall condition to be safe, which is why it was dropped from the new list.
PG&E's Top 100 pipeline segments: http://tinyurl.com/top100pipes