Seismic Fragility of Natural Gas Transmission Pipelines and Wells Prepared for: California Energy Commission Copyright: G&E Engineering Systems Inc. 2020 G&E Engineering Systems Inc. July 15 2020 | R130.01.01 Revision 3 DISCLAIMER An earlier version of this report was prepared as the result of work sponsored by the California Energy Commission. It does not necessarily represent the views of the CEC, its employees, or the State of California. The CEC, the State of California, its employees, contractors, and subcontractors make no warrant, express or implied, and assume no legal liability for the information in this report; nor does any party represent that the uses of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the California Energy Commission, nor has the California Energy Commission passed upon the accuracy or adequacy of the information in this report. G&E Engineering Systems Inc. and the author make no warranty or guaranty of any sort that the information in this report is suitable for your use. If you download or use this report, you agree to indemnify G&E and the author entirely. You are totally on your own if you use this information!! Do not download or use this document unless you agree with these limitations. ACKNOWLEDGEMENTS The author of this report would like to acknowledge the support and contributions from many people and organizations. The technical findings in this report would not have been possible without the efforts to study the performance of critical lifeline infrastructure by Mr. Le Val Lund (Los Angeles Department of Water and Power), Mr. Anshel Schiff (Precision Measurements), Mr. Alex Tang (L&T Consulting), Mr. Curtis Edwards (Poutney Consultants), Mr. Bruce Maison (East Bay Municipal Utilities District), Prof. Tom O'Rourke (Cornell University) and Prof. Mike O'Rourke (Rensselaer Polytechnic Institute). A special acknowledgement to Prof. Kazuo Konagai (U. Tokyo) and Prof. Barry Davidson (U. Auckland) for their support over many years in the study of lifeline system performance in Japan and New Zealand. The leadership of many PG&E people over the years has been instrumental to the understanding of the earthquake performance of critical gas and electric system infrastructure. PG&E's Geosciences, Gas Transmission and Gas Distribution teams have made contributions to the understanding of earthquake performance of gas pipelines, under the leadership of Mr. Jeff Bachhuber, Mr. Nozar Jahangir, Mr. Bill Horstman, Mr. Bronson Ingemansson and many others. Mr. Eric Fujisaki, Mr. Ed Matsuda and Mr. Brian Low have served as vice chairman, officers and members of the IEEE 693 committee; IEEE 693 is the industry-wide seismic guideline for high voltage power equipment, and is widely used by many utilities throughout the USA, Canada and the world. Their support for developing and implementing the SERA risk model for PG&E's gas and electric systems is gratefully acknowledged. The seismic design of natural gas pipelines was documented in the 1984 seminal report, "Guidelines for the Seismic Design of Gas and Liquid Fuel Lifeline Systems", by Doug Nyman (Ed.). This report was the product of research and design efforts that supported the construction of the 800-mile long Trans Alaska Oil Pipeline from the north shore to Valdez. This report was written by members the Technical Council of Lifeline Earthquake Engineering (TCLEE). Over the years from the 1970s through 2014, the members of TCLEE developed and published more than 50 reports and guidelines on the seismic evaluation of lifeline infrastructure, including natural gas systems. Dr. Robert Kennedy (Structural Mechanics Consulting) developed many of the methods still used to quantify uncertainty and randomness in seismic hazards and performance of components; before his recent passing, Dr. Kennedy was honored with the Le Val Lund medal for his lifetime contributions to earthquake design of lifelines. Mr. Pete McDonough (Questar) was the chairman of TCLEE's Natural Gas and Liquid Fuels committee, Mr. Ron Eguchi, has been a leader in lifeline risk loss estimation efforts, and Mr. Doug Honegger has made many important contributions to current codes and standards for gas pipelines. Our current state of knowledge reflects the tireless efforts of the many engineers who were members of TCLEE. John Eidinger, July 2020 i PREFACE This report describes seismic fragility models for natural gas transmission pipelines and wells. There are three classes of natural gas pipelines: high pressure transmission pipelines, medium pressure distribution pipelines and medium to low pressure service laterals. This report presents the empirical evidence of how each of these types of pipelines have performance in past earthquakes in California, as well as selected earthquakes in Japan, New Zealand and Alaska. The report compares the empirical evidence with the stress / strain quantitative limits in modern gas pipeline design codes and standards. Two approaches are provided as to how to estimate the potential for damage of gas transmission pipes: a "repair rate per length" approach and a "strength of mechanics - finite element - strain limit" approach. The "repair rate per length" approach is best applicable to large lengths (preferably 100 miles or more) of gas transmission pipes including all their appurtenances. The "finite element" approach is best suited to examine a specific pipe that is exposed to specific seismic hazards and is the approach recommended for design and evaluation of important gas transmission pipes at specific locations. The empirical record shows a variety of leaks in past earthquakes for gas transmission systems. For steel pipes with good quality welds and no corrosion, the majority of the leaks are to appurtenances and due to ground shaking. For steel pipes with potentially weak welds, with corrosion or other defects, there have been many major breaks and leaks to the main barrel of the pipe, due to both ground shaking and permanent ground deformations. This report examines the records of gas pipe performance in 37 earthquakes (including foreshocks, aftershocks and sequences). These include 29 in California from 1906 to 2019, 5 in Japan from 1964 to 2018, 1 in New Zealand in 2010-2011, 1 in Alaska in 2018, 1 in Utah in 2020. Key trends include: • In northern California, there has been a handful of leaks to gas transmission pipes. All are believed to have been in the "minor" category, requiring repair but without life safety implications or ignition / fire. There have been many leaks in gas distribution pipes and service laterals. • In southern California, there have been dozens of failed gas transmission pipes; most of which were to pipes with potentially weak welds, corrosion or other defects. The vast majority of the failed pipes were installed pre-1930. One failed pipe released significant gas that led to a fire ignition that burned a few adjacent residential structures. There have been many leaks in gas distribution pipes and service laterals. • For earthquakes that occurred in 1995 or later in Japan, New Zealand, Anchorage and Sal Lake City, as documented in this report, there have been no failures to gas transmission pipes, while there has been a range of damage to gas distribution system pipes. Older gas transmission pipes, with defects, had a high failure rate in the 1964 Niigata, Japan earthquake. This report documents that the vast majority of all gas leaks identified post-earthquake have been in the gas distribution system. The CEC project excludes evaluations of gas distribution systems, including service laterals and customer-owned "in-structure" pipes and gas appliances. However, from a gas utility ii planning perspective, the post-earthquake repair efforts need to address all the damage and response issues, including repairs for transmission pipes, gas distribution mains, service laterals, as well as inspections of customer-owned gas pipes / appliances and corresponding re-light efforts. The empirical evidence indicates that the ratio of leaks in a modern gas system in a M 6 to M 7 earthquake might be: transmission (0 - 3%); distribution mains (3% - 30%); service laterals and meter sets (60% - 90%). In- house inspections and pilot light "relight" efforts can exceed the effort to repair all the transmission and distribution pipes and service laterals. G&E's SERA software can be used to help quantify the seismic performance of the entire gas system. Most leaks in the transmission system, if the pipes all have good quality welds and have no corrosion, are likely to be minor leaks in appurtenances (including regulating stations, branch pipes, blow offs). For the main barrel of well-built steel transmission pipes, leaks are rarely, if ever, expected due to ground shaking; but leaks and major breaks can occur if the pipe is exposed to significant permanent ground deformations due to liquefaction, landslide or surface faulting. The fragility models for "repair rate per length" forecast the number of repairs due to shaking, liquefaction, landslide and fault offset hazards. These fragility models are to be used with a geographically-described inventory of the main barrel of the transmission pipe, and imply a corresponding inventory of attached branch pipes and appurtenances associated with a gas transmission system. The strength-of-materials / finite element approach shows that a well-built gas transmission pipe, with butt-welded girth joints, and without any branches or appurtenances, should essentially never fail due to ground shaking, but could exceed strain limits if exposed to excessive permanent ground deformations. An example is provided in this report that showed an actual pipe that failed when it was subjected to fault offset: the steel ripped open (failure of the pressure boundary), and the computed strains in the pipe were several times higher than the allowable strain limits. Fragility formulations for natural gas wells are outlined. The models reflect the observations from a limited number of gas wells have been exposed to strong earthquakes in California.