Portion of Gas Pipeline Underneath South San Francisco Identified as Among 100 Riskiest

In 2007, Pacific Gas & Electric Co. identified a portion of the pipeline that exploded in San Bruno on Thursday night as one of its 100 riskiest segments of gas line.  But that segment, targeted for replacement in 2013, isn't actually the part that blew.

The segment in question, which PG&E said in a filing to the California Public Utilities Commission has a "relatively high risk and likelihood of failure," is several miles from the site of the explosion.

In fact, it lies underneath South San Francisco.

PG&E wouldn't identify the geographic location of the pipe segment for security reasons, but the filing puts it in a "heavily urbanized area."  This means a lot of people and businesses.

It's hard to say what kind of risk this poses to South City.  There are no federal requirements about when companies must replace pipes, and pipelines are aging.  The pipe that ran under San Bruno and runs under South San Francisco was placed in 1948.

At the same time, accidents like the explosion in San Bruno are rare.  Despite the fact that there is more than 300,000 miles of gas pipeline in the United States, there have been 33 fatalities related to natural gas lines since 1990, according to a report in MarketWatch.

Katie Romans, a spokesperson for PG&E, told me that the segment of pipe under South City was checked for leaks on Friday and there was no breach in the line.  The filing to the California Public Utilities Commission that identified this segment of pipe requested a rate increase that would pay for the $5 million replacement. 

Romans said that while PG&E takes a proactive approach to daily maintenance, she can't say when that segment of pipe will be replaced.