Aliso Canyon, One Year Later

Just over one year ago, natural gas began leaking from the Aliso Canyon underground storage facility in Los Angeles—one of the more than 400 such facilities in the U.S. The leak went on for nearly four months, resulting in what is now considered the largest leak of methane to the atmosphere from an underground storage facility in U.S. history.

The details that surfaced in the wake of the leak about the Aliso Canyon facility and its regulation painted a stark picture of a perilously broken system. In response, a federal Interagency Task Force on Natural Gas Storage Safety was formed and tasked by Congress to analyze the Aliso Canyon event and make recommendations to reduce the chance that something similar would occur in the future. The Task Force’s report was recently released and contains important strategies and suggestions to improve the safety of the nation’s underground gas storage infrastructure. Overall, the report indicates that we have a long way to go to ensure that something like Aliso Canyon won’t happen again.

By any measure, Aliso Canyon was an environmental catastrophe. A report by the California Air Resources Board (CARB), released just days before the one-year anniversary, puts the final leakage estimate at 109,000 metric tons of methane—a powerful greenhouse gas that can cause more than 80 times as much warming as carbon dioxide over the short term. The methane that escaped is equivalent to the CO2 emissions from more than 1 million homes’ energy use for one year. The residents of the nearby Porter Ranch neighborhood also experienced health impacts as a result of the leak, and serious disruption to their daily lives. Thousands were temporarily relocated for the duration of the leak and beyond.

In the years prior to the leak, even the operator of the facility, Southern California Gas, warned of the potential for a sudden, major failure. The surprise is not that the massive Aliso Canyon leak occurred, but that a similar disaster hadn’t occurred sooner.

The aging infrastructure and lax regulatory oversight that led to the Aliso Canyon leak were in no way unique, and after the disaster, state and federal officials decided these issues could no longer be ignored. California took the lead on stopping the leak, determining its root cause, and assessing its environmental and public health impacts. Multiple federal agencies provided support and technical assistance and later the Interagency Task Force was formed. The key findings and recommendations of their recent report are summarized here.

As the report notes, regulatory authority for gas storage facilities varies depending on whether the facility is interstate (i.e. those that link multiple states) or intrastate (i.e. those that are contained wholly within one state and receive gas only from within that state). Interstate facilities are regulated by the Federal Energy Regulatory Commission (FERC); intrastate facilities are regulated by individual states, often through multiple regulatory bodies. There are 415 underground gas storage facilities in the U.S. and about half of them are interstate and half are intrastate.

At the federal level, the Pipeline and Hazardous Materials Safety Administration (PHMSA) has broad authority to regulate underground gas storage facilities, but so far PHMSA has chosen not to exercise its regulatory authority over the subsurface portions of these facilities. In other words, there are currently no federal standards for operating underground gas storage facilities. It is unclear why PHMSA has never written such rules.

In 2016, as part of the PIPES Act, Congress directed PHMSA to issue minimum federal standards for interstate and intrastate underground gas storage facilities served by pipeline, within two years of passage of the bill. The PIPES Act also provides that states can adopt additional or more stringent safety regulations as long as they are compatible with the federal minimum standards. PHMSA has stated that it is planning a phased rollout, with the first phase coming by the end of this year.

At the state level, the Task Force selected and reviewed the gas storage regulations of 19 states, representing 90% of all active natural gas storage wells. They found that:

  • Only 11 of those states have regulations of some type that specifically address surface or subsurface infrastructure of gas storage facilities. Of those 11, only four have regulations addressing underground natural gas storage in all three reservoir types used for gas storage in the U.S. (depleted fields, aquifers, and salt caverns).
  • Only three states—California, Kansas, and Pennsylvania—have regulations that address three critical aspects of well integrity: construction, maintenance, and plugging and abandonment. (It is important to note, however, that California’s rules are still in the pre-rulemaking phase and are not yet final. Gas storage wells in California are currently operating under emergency rules put in place after the Aliso Canyon leak, and which do not comprehensively address all three topics related to well integrity identified in the report).  
  • Only six additional states have regulations addressing one or two of these well integrity aspects. The remaining states have no regulations addressing gas storage well integrity whatsoever.

The Task Force found that about 80% of natural gas storage wells with known completion years were drilled before 1980. As such, they concluded that “the vast majority of the natural gas storage wells presently in use predate current materials and technology standards and have experienced physical and mechanical stresses from injection and withdrawal of natural gas across multiple decades.” In addition, oil production wells that have been converted to gas storage wells, like the Standard Sesnon 25 that failed at Aliso Canyon, may not be designed to withstand the greater pressures of gas storage operations.

In sum, both the states and the federal government are failing to adequately regulate the nation’s 415 underground gas storage facilities. The consequences of this failure—whether a major catastrophe like Aliso Canyon or the more routine leaks of methane that happen much more frequently—are not trivial.

An analysis by the Interagency Task Force estimated the frequency of a major incident at one of the gas storage facilities in the U.S. to be every four months to three years, for an average of 1.4 incidents per year. While the federal government and states like California are taking steps to address these regulatory shortcomings, the outcomes of these processes and the stringency of the regulations they will produce are far from certain. PHMSA and the states must move rapidly to implement the recommendations of the Task Force and put in place enforceable stopgap measures in the interim to reduce the threats to public health and safety and the environment from underground natural gas storage facilities. 

About the Authors

Briana Mordick

Senior Scientist, Land & Wildlife and Climate programs

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