The gas pipeline that exploded in a San Francisco suburb two weeks ago puts needed focus on the issue of expanding cities, suburbs and exurbs, and the old infrastructure those communities are being built upon. The obvious risk is that old infrastructure if not repaired or replaced can fail. The Valley of the Sun has seen tremendous growth over the years and the same risk of serious injury or death for the Phoenix metropolitan area is just as poignant. 

The pipeline owned by Pacific Gas & Electric was a transmission line built in 1956. The San Bruno neighborhood where the line was built was sparse then, but now the pipeline's neighborhood falls into an industry category called a "high consequence area." The United States has more than 2 million miles of pipeline including 300,000 miles of transmission lines. High consequence areas account for 21,000 miles of pipeline, and the term does not refer to safety concerns.

Since there are only 100 federal inspectors, the regulatory system for industry is largely left to the utility companies. However, there is a lack of incentive for self-inspections because of cost. Since 1990, federal officials have cited 2,840 pipeline accidents where more than one-third have caused deaths and significant injuries. Only in 2002 did Congress finally require that utilities perform inspections, but there is not a requirement that companies report whether the problem is fixed and how the repair was achieved.

Sixty percent of gas transmission lines in the United States are 40 years or older. The usual lifespan of a steel pipeline is around 50 years old and a section of the line connected to the San Bruno pipe was built in 1948. Some areas of the country have lead pipes, which are more prone to corrosion than steel. An area in Pennsylvania last year still had wooden gas pipes.

The cost to replace long lengths of pipelines can be more than $30 million. In recent years Pacific Gas & Electric has spent over $100 million to rebuild its gas system.
Old infrastructure in now densely built areas exemplifies a nationwide problem. Hopefully, millions more will be spent to prevent another disaster.

Source: Associated Press, "Aging Gas Pipes at Risk of Explosion Nationwide," Garance Burke and Jason Dearen, 9/14/10