PERFORMANCE OF THE TRANS-ALASKA PIPELINE IN THE NOVEMBER 3, 2002 DENALI FAULT EARTHQUAKE William J. Hall1, Douglas J. Nyman2, Elden R. Johnson3, and J. David Norton4Abstract The magnitude 7.9 earthquake that occurred in south-central Alaska on November 3, 2002 ruptured a 336-km long segment of the Denali Fault. The epicenter was located about 88 km west of the Trans-Alaska Pipeline, and the rupture propagated to the east across the pipeline right-of-way. The above-ground segments of the pipeline were subjected to violent near-fault ground shaking approachingor exceeding design criteria, and liquefaction was observed at a number of locations along the pipeline, including a remote gate valve location. The performance of the pipeline was in line with original project design requirements, and there was no oil leakage. The paper presents a high-level overview of the seismic design of the Trans-Alaska Pipeline, performance of the pipeline system during themagnitude 7.9 event, and a brief commentary on post-event emergency response. Introduction The Atlantic Richfield Company discovered oil at Prudhoe Bay, on the Alaskan North Slope, in 1968. Construction of the Trans-Alaska Pipeline System (TAPS) was proposed in early 1969, but controversies over Alaska native land claims and environmental issues delayed pipeline construction until 1974 (Roscow,1977). On June 20, 1977, after three years of construction by 70,000 men and women and an investment of eight billion dollars, oil began flowing through the pipeline. Since then, this pipeline system has safely transported over 14 billion barrels of oil from Alaska's North Slope to the Port of Valdez. Currently the pipeline transports approximately 17 percent of the crude oil produced in the UnitedStates. In 2003, the pipeline owners received state and federal right-of-way approval for another 30 years of operation. The pipeline is operated by Alyeska Pipeline Service Co (Alyeska) for its owners. Over its 1,287-km (800-mile) route from Prudhoe Bay to a marine tanker terminal at the port of Valdez, the 1,219-mm (48-inch) diameter Trans-Alaska Pipeline passes through areas with highpotential for significant seismic activity. To safeguard the fragile arctic environment, major seismic design requirements were imposed on the TAPS, namely that the entire pipeline system should be capable of withstanding all reasonably anticipated effects of earthquakes without impairing the structural integrity of the oil pipeline or the associated pressure containing system components.
1 2Professor Emeritus of Civil Engineering, University of Illinois, Urbana, IL, H.M. ASCE. Consulting Engineer, D.J. Nyman & Associates, Houston, TX, F. ASCE. 3 Engineering Advisor, Alyeska Pipeline Service Co., Fairbanks, AK, M. ASCE. 4 Principal, J.D. Norton and Associates, Anchorage, AK, M. ASCE.
With the exception of nuclear power plants, the attentiongiven to the seismic design of TAPS rivals that for any other critical facility in the United States. For many aspects of TAPS design, just as in the case of nuclear power plants, no seismic criteria, standards or codes existed at the time of design. Alyeska's adoption of seismic criteria for pipeline design was the first major action of this kind in the pipeline industry. Even so, during that timeperiod, TAPS design and construction was benefited immensely by the research and development under way for seismic design of nuclear power plant facilities. Consequently, the design of TAPS was stateof-the-art for its time and has remained remarkably consistent with current practice in earthquake engineering. The attention given to seismic design paid off on November 3, 2002, with the occurrence...