On Sept 9, 2010, a 30 inch diameter natural gas transmission pipeline (Line 132) ruptured in the residential area of San Bruno, California, about 10 miles south of San Francisco. The tragic accident killed eight people and injured 58 more; affected 108 houses, 38 of which were destroyed and 17 of which were severely to moderately damaged. The event has driven an intense focus on pipeline safety with PG&E being at the forefront of this focus. The event has caused profound impacts to the entire PG&E gas organization. While the immediate impact of the event started in the San Bruno area and on the San Francisco Peninsula, over time the impacts became far reaching to every portion of PG&E's gas transmission system. The San Bruno event and pipeline safety is being addressed through a comprehensive and systematic gas pipeline safety program. This paper will focus on the profound impacts that the San Bruno event and PG&E's pipeline safety program has had on the Gas System Planning function at PG&E. The paper will discuss unprecedented increases in the need for system hydraulic analyses due to a wide range of safety related activities.


PG&E's gas transmission system consists of approximately 6750 miles serving 4.3 million gas customers a total of about 1 Tcf annually.


The initial impacts to gas system planning analyses were centered on the Peninsula Local Transmission system which is shown in the figure 2 below. The system contains 3 transmission lines ranging from 20"-36" (mostly 24") diameter (Lines 101, 109, and 132) that are supplied at the southern end by Milpitas Terminal. Gas flows from the south near San Jose and terminates in San Francisco at the north.

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