Seismic/Geologic Risks as Factors in Prioritizing Gas Pipeline System Replacement

by James A. Clark, Pacific Gas and Electric Co, San Francisco, United States,
Chih-Hung Lee, Pacific Gas and Electric Co, San Francisco, United States,
William U. Savage, Pacific Gas and Electric Co, San Francisco, United States,

Document Type: Proceeding Paper

Part of: Lifeline Earthquake Engineering


During the past decade, Pacific Gas and Electric Company (PG&E) has intensified efforts to evaluate earthquake hazards and their potential effects on gas and electric power systems, with the goals of implementing reductions of earthquake vulnerability and increasing post-earthquake reliability. The October 17, 1989, Loma Prieta earthquake caused extensive damage in PG&E's service territory, and brought increased focus and emphasis to earthquake reviews and mitigations. The company's activities have taken advantage of recent earthquake lifeline engineering research and modeling advancements in the understanding and mitigation of earthquake hazards. The earthquake lifeline engineering approach applied to the gas pipeline system involves (1) identifying potential locations of high-probability, large-magnitude scenario earthquakes; (2) developing seismic zonation maps for surface fault rupture, liquefaction potential, and slope-failure potential; (3) evaluating the condition of the existing gas pipeline system and the consequences of the scenario earthquakes in order to assess and implement mitigations. This paper describes an example of application of this approach to modify the PG&E Gas Pipeline Replacement Program (GPRP), which is a long-term replacement of aging and leak-prone installed pipelines. An additional pipeline prioritization factor is defined and applied to accelerate the replacement of GPRP pipeline segments in areas subject to earthquake effects that are likely to increase gas leak potential.

Subject Headings: Gas pipelines | Electric power | Seismic tests | Seismic effects | Pipe leakage | Electrical systems | Earthquake engineering | Mapping

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