PG&E ordered to reduce gas pressure limits

February 3, 2011

The California Public Utilities Commission (PUC) has ordered PG&E to reduce pressure on four natural gas transmission lines, saying the utility ran the safety lines well above legal safety levels. [SF Chronicle]

Two of the pipes are located in the South Bay, under heavily populated areas, and must be reduced by at least 20 percent to meet the PUC mandate.

Regulators discovered the illegal pressure levels as part of the investigation into the gas-pipeline explosion Sept. 9 in San Bruno that killed eight people and destroyed 38 homes.

PG&E admitted late Wednesday that in addition to running the four lines on occasion at far above legal limits, it had intentionally increased the pressure on a dozen transmission lines temporarily and, in eight instances, exceeded maximum levels by just “a few pounds.”

The PUC issued its pressure-reduction order for the four transmission system lines Wednesday in a letter to PG&E President Chris Johns, and the utility said it would comply.

The four transmission lines include:

The lines are:

— A 3 1/2-mile stretch from Milpitas to San Jose and a separate half-mile span in Milpitas. Pressure on both lines exceeded maximum levels on the same three dates in 2008, 2009 and 2010. In last year’s incident, the pressure was 50 percent above the legal limit.

— An 8 1/2-mile section between the Santa Cruz County communities of Watsonville and Aptos Hills, which was run at more than 30 percent above the legal limit on June 12, 2009.

— A 17 3/4-mile stretch from Manteca to Modesto, which was run more than 50 percent above its cap on Dec. 15, 2008.