All Gas Companies are Affected by the San Bruno Pipeline Rupture

by Bob Shively, Enerdynamics President and Lead Instructor

Safety and emergency response are critical to pipeline and distribution operations.  In general, the industry has a very strong safety record.  But every so often accidents do occur, and the consequences can be dramatic.

One recent example of such an accident occurred Sept. 9, 2010, in San Bruno, Calif., when a portion of the 30-inch diameter underground natural gas transmission system owned by Pacific Gas and Electric Company (PG&E) suddenly ruptured.

According to a California Public Utilities Commission (CPUC) report on the incident: “An explosion ensued, fueled by blowing natural gas. The explosion and fire resulted in the loss of eight lives and the total destruction of 38 homes. Seventy homes sustained damage and eighteen homes adjacent to the destroyed dwellings were left uninhabitable.”[1]

An investigation by the National Transportation Safety Board (NTSB)[2] identified several factors contributing to the incident:

  • The original pipe that was installed in 1956 contained a substandard and poorly welded pipe section with a seam weld flaw that caused a crack in the pipe
  • Despite the flaw, the pipeline functioned normally from the time of its installation until the incident
  • The crack was not discovered during standard pipeline testing because the nature of the pipeline prevented use of smart pigs; the line was not tested using hydraulic methods because such testing was not required under grandfathered provisions in CPUC and U.S. Department of Transportation regulations
  • The pipe was progressively weakened over time due to crack growth until the pipe ruptured at a pressure below the Maximum Allowable Operating Pressure (MAOP)
  • Concurrent electric work at a nearby gas terminal resulted in limitation in the pipeline SCADA system, which made it difficult for operators to respond promptly to the incident
  • A lack of automatic or remote-controlled shut-off valves contributed to a 95-minute delay in crews’ ability to manually shut off the pipeline

Mitigating Risk
Unfortunately, with 2.2 million miles[3] of natural gas pipelines in the U.S., much of which was installed many years ago, it is likely that numerous other flawed pipes exist buried underground – literally accidents waiting to happen.  The lead regulator for pipeline safety is the Office of Pipeline Safety (OPS) within the U.S. Department of Transportation. State agencies often also take a role in regulation, either implementing state safety legislation or working as agents for the OPS. As a part of OPS regulation, transmission and distribution pipelines must implement a Pipeline Integrity Management program. These programs provide for identification of pipe located in high-consequence areas – those with high risk of human injury or property damage if an accident occurs. Pipe in high-consequence areas must then be assessed to determine pipe condition, threats, and consequences should an incident occur. Pipelines then must develop specific mitigation plans to deal with identified threats[4].

In the PG&E situation, all of the above were followed according to regulation; however the facts relating to the pipe’s condition were unknown. This resulted in a mitigation strategy that proved inadequate.

A Safer Future?
So what can be done to avoid incidents like San Bruno in the future?  The answer really comes down to weighing safety versus costs.  Indeed, safety could greatly be enhanced by replacing all pipelines older than a certain age, but it’s highly doubtful consumers would be willing to pay the ensuing higher costs of natural gas. Instead, lawmakers and regulators must decide how to best balance consumers’ desire for low gas rates with improved safety measures such as more thorough yet more costly inspections and the installation of automatic valves.

In January 2012, President Obama signed into law a new pipeline safety bill based on recommendations from OPS (see  This bill includes:

  • doubling of potential fines for safety violations to $2 million per incidence
  • an increase in the number of federal inspectors
  • mandatory automatic or remote-controlled shut-off valves for new or replaced pipelines; (it did not require retrofitting these values onto existing pipelines)
  • Up to $110 million/year in grants for state pipeline safety programs

However, the effect of the bill was muted a bit by an added provision stating that outside of high-consequence areas, the pipeline safety regulator cannot issue regulations establishing leak-detection requirements or expanding integrity management requirements until a study and rulemaking process is completed, which will take at least two years.

Meanwhile, California signed into law a bill that requires California pipeline owners to install automatic shut-off valves in vulnerable areas and to pressure test pipelines. And, in August 2011, OPS opened a new rule making to investigate whether rules for integrity management programs should be changed.  Industry comments are due this month.

It is safe to say that the San Bruno incident, coupled with other recent pipeline incidents, has caught the attention of legislatures, regulators, and pipeline companies. Already more stringent pipeline testing and installation of safety devices has begun as companies try to get ahead of the anticipated new regulation.

Will our pipeline system ever be 100 percent safe? No. That’s just not realistic. But careful evaluation of integrity issues and reasonable system upgrades can and should reduce the number of future incidents.

References and Resources 

[1] Report of the Independent Review Panel San Bruno Explosion Prepared For California Public Utilities Commission Revised Copy June 24, 2011, p.1

[2] NTSB Pipeline Accident Report, NTSB/PAR-11/01 PB2011-916501 available at

[3] American Gas Association: retrieved December 8, 2011

[4] A good visualization of the Pipeline Integrity Management process can be viewed here:

About Enerdynamics

Enerdynamics was formed in 1995 to meet the growing demand for timely, dynamic and effective business training in the gas and electric industries. Our comprehensive education programs are focused on teaching you and your employees the business of energy. And because we have a firm grasp of what's happening in our industry on both a national and international scale, we can help you make sense of a world that often makes no sense at all.
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2 Responses to All Gas Companies are Affected by the San Bruno Pipeline Rupture

  1. Pingback: Can Technology Improve Natural Gas Pipeline Safety? « Zap! Crackle! Pop!

  2. Enerdynamics says:

    Glad you enjoyed this post and our blog in general! If you have any topics you’d like to see covered in future posts, please send us your ideas.

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