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| Fig. 1: Aliso Canyon well leak. (Source: Wikimedia Commons) |
On October 23rd 2015, the generally quiet community of Porter Ranch, a semi-affluent neighborhood in the San Fernando Valley, tucked against the Santa Susana Mountains north of Los Angeles, continued being quiet. But it smelled different.
The adjacent portion of the mountains are owned by Southern California Gas Company, a subsidiary of Sempra Energy. Here at the Aliso Canyon Gas Storage Facility, they store natural gas (primarily gaseous methane) in 114 underground wells from which they can withdraw gas on command and provide to the residents of Los Angeles. With 86.2 billion cubic feet of storage capacity, the Aliso Canyon facility (see Fig. 1) is the largest natural gas storage in California. [1] Continuing a multi-year trend, natural gas remained the largest source of electricity generation in California in 2022, supply over one-third of the total California power mix. [2]
On that Friday, well SS-25 sprung a leak. It began leaking methane, ethane, benzene, and various other hydrocarbons, as well as standard odorants such as tetra-butyl mercaptan which is non-toxic but assists inspectors when searching for leaks. [3] Taking relatively swift and standard action, the facility attempted to conduct well control attempts, first trying "top kill" techniques which pump heavy fluid into the well to counteract the pressure which was driving the exit of the gases. All seven attempts failed. A "bottom kill" attempt successfully halted the leak on February 11th, 2016 before the well was cemented shut on February 18th, 2016.
Over the nearly four months that the leak was active, natural gas poured into the atmosphere, leading to the displacement of thousands of residents of the San Fernando Valley and ultimately impacting all of California and, to an extent, the whole world. The California Air Resources Board through their own assessment and review of other assessments concluded that, in total, about 100,000 metric tonnes of methane were released directly into the atmosphere. [4] For reference, over an equivalent four month period, the entire California South Coast Air Basin emits just over 100,000 metric tonnes of methane. [5]
In 2015, the price of a thousand cubic feet of methane in the US was rated at a benchmark of about $3. [6] The leak released over 5 × 109 cubic feet of methane. Using these figures, SoCal Gas lost approximately $15 million in potential energy sales. In the grand scheme of the issue, this is nothing. (Sempra Energy ultimately paid out $1.8 billion in damages to the city and its residents.)
Of course, the cost is much more than just a dollar amount. Thousands of residents of the community were displaced in order to avoid the gas. While methane is considered biologically inert, the odorants caused nausea, headaches, and nosebleeds. Benzene is carcinogenic, though measurements taken during the leak suggest that the exposure to benzene was minimal. [7] The true impacts of the leak on the health of the residents is still under study and may take decades to discern. But the health of the atmosphere undoubtedly took a major hit. When considered over a 20 year period, the global warming potential of methane is over 80 times greater than that of carbon dioxide. [8] This potency and the outsized ability of methane to warm the atmosphere is of great concern when considering methane leaks such as Aliso Canyon. For the climate goals of California, this was a major setback.
This disaster has left much of the population of the community and Los Angeles at large calling for the closure of the Aliso Canyon facility. But this requires careful consideration.
First, natural gas provides a the California Independent System Operator with a convenient and reliable source of on-demand power, allowing the California ISO to properly and quickly respond to increase demands for electricity from the grid. Closing the Aliso Canyon facility would put a significant strain on the grid. Second, the grid would require a replacement source for this portion of the electricity, likely from alternative sources such as renewables which struggle to provide the on-demand quality that natural gas does. Third, since natural gas is a comparatively cheap source of energy, the removal of this source of energy could cause a significant increase in energy costs in California, likely hurting lower income residents the most. [9] Even with the leak sealed, methane leakage is a persistent problem in natural gas facilities across the US. [10] However, the closure of the Aliso Canyon Gas Storage Facility would likely have various extreme undesirable impacts.
Questions about resident health, environmental impacts, and whether to close the facility are likely to continue. For me, I will follow the developments carefully. I was there. On Friday, the leak was discovered. On Saturday, my father bought me my first bicycle, a cheap mountain bike, for my 15th birthday. On Sunday, he drove my best friend and me up to the Aliso Canyon where we rode our bikes along the trail that runs for miles through the Santa Susana Mountains, lined on one side with signs declaring "No Tresspassing: Property of SoCalGas." On Monday, news spread of the leak.
© Ky Friedman. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Direct Testimony of Phillip E. Baker: Underground Storage," Southern California Gas Company, November 2014.
[2] "State of California Energy Sector Risk Profile," U.S. Department of Energy, March 2021.
[3] S. Conley et al., "Methane Emissions From the 2015 Aliso Canyon Blowout in Los Angeles, CA," Science 351, 1317 (2016).
[4] "Determination of Total Methane Emissions from the Aliso Canyon Natural Gas Leak Incident," California Air Resources Board, October 2016.
[5] D. Wunch et al., "Quantifying the Loss of Processed Natural Gas Within California's South Coast Air Basin Using Long-Term Measurements of Ethane and Methane," Atmos. Chem. Phys. 16, 14091 (2016).
[6] "Annual Energy Outlook 2016," U.S. Energy Information Administration, DOE/EIA-0383(2016), August 2016.
[7] "Aliso Canyon Gas Leak: Results of Air Monitoring and Assessments of Health," Los Angeles County Department of Public Health, February 2016.
[8] G. Myhre et al., "Anthropogenic and Natural Radiative Forcing,"in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed. by T. F. Stocker et al. (Cambridge University Press, 2013).
[9] "Energy Conservation Program for Consumer Products: Representative Average Unit Costs of Energy," 88 Fed. Reg. 58,575 (August 28, 2023).
[10] R.A. Alvarez et al., "Assessment of Methane Emissions From the U.S. Oil and Gas Supply Chain," Science 361, 186 (2018).
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