Ten years ago this week, (Oct. 23, 2015) the largest U.S. methane leak was discovered at Aliso Canyon in northwestern Los Angeles County. It focused attention on the state’s aging gas wells.
The well that leaked was one of 115 connected to a subsurface storage reservoir in the Aliso Canyon gas field. The field has been used for natural gas storage since 1973 and is the second-largest facility of its kind in the U.S., capable of holding up to 86 billion cubic feet.
8,000: Approximate number of home evacuations
112: Days between reporting of gas leak and stoppage
109,000 metric tons: Estimated amount of methane leaked. Considered an environmental disaster due to toxic nature of gas.
The fallout
Notable events following the leakFeb. 8, 2016: Southern California Gas Co. agrees to pay $8.5 million to settle a lawsuit filed by air quality regulators in 2016.February: A Porter Ranch physician says a pattern of health symptoms has emerged among the almost 50 patients he has followed since the leak began. He hopes other doctors in the area, as well as outside researchers, will collaborate with him on a long-term study.
July: James Mansdorfer, who was formerly responsible for managing SoCalGas’ storage wells and reservoirs, tells state regulators he was concerned that movement on the Santa Susana fault would “almost surely sever the casing” and tubing of every gas well at Aliso Canyon, resulting in a major leak.
July 29: A state appeals court lifts a temporary hold on injections of gas into the facility, overriding the concerns of Los Angeles County and clearing the way for SoCalGas to continue adding to storage.
July 31: SoCalGas resumes gas injections. The company completes all safety measures to do so.
August: Nearby residents say they are bracing for the worst after SoCalGas announces it had “started the process to resume limited injection operations” after approval from state gas and utility regulators and days of legal wrangling with Los Angeles County.
2021: More than 35,000 plaintiffs receive compensation for personal injuries and property damage from the Aliso Canyon leak. The $1.8 billion settlement is reached with SoCalGas and its parent company, Sempra Energy, after a six-year legal battle. In the wake of the incident, the federal government establishes an Interagency Task Force on Natural Gas Storage Safety.
Natural gas in California
Californians’ issues with gas prices aren’t just at the pump. Californians use natural gas to heat their homes, cook food, charge electric vehicles at night and make electricity. The cold spells this winter brought up demand for natural gas heating, which 70% of California homes require. Capacity limitations in a pipeline flowing from Texas to the west put additional constraints on supply because the state imports about 90%-95% of its natural gas.The map to the right shows the interstate pipelines for natural gas. Southern California’s supply comes from as far away as Texas and Louisiana. Gas can flow through the pipeline at about 20-30 mph.How much gas do we use?California invests in renewable energy. The state produces the third-most (in 2022) megawatt hours of renewable energy behind Texas and Washington. But it is a glutton for the gas line as well. In 2023, U.S. total consumption of natural gas was about 30.66 trillion cubic feet. The five states that consumed the most natural gas in 2021 and 2023 by amount and percentage share of total U.S. natural gas consumption were:20211. Texas: 4.67 tcf — 15.2%2. California: 2.09 tcf — 6.8%3. Pennsylvania: 1.81 tcf — 5.9%4. Louisiana: 1.75 tcf — 5.7%5. Florida: 1.54 tcf — 5.0%
20231. Texas: 5.13 tcf — 15.7%2. California: 2.09 tcf — 6.4%3. Louisiana: 2.09 tcf — 6.1%4. Pennsylvania: 1.87 tcf — 5.7%5. Florida: 1.64 tcf — 5%
Interstate and intrastate natural gas pipelines in the West
The U.S. natural gas pipeline network is a highly integrated network that moves natural gas throughout the continental United States.The natural gas pipeline grid comprises:More than 210 natural gas pipeline systems.305,000 miles of interstate and intrastate transmission pipelines.400 underground natural gas storage facilitiesMore than 11,000 delivery points, 5,000 receipt points, and 1,400 interconnection points that provide for the transfer of natural gas throughout the United States.
93%: Percentage of natural gas imported to California in 2021.
In-state electric generation by fuel type gigawatt hours
In 2024, natural gas had the highest percentage of producing the state’s electricity.
You can see the state’s energy estimates here.The information in the chart below is from the California Energy Commission. It is compiled from power plant data reporting and is based on metering at each power plant site and, therefore, does not account for the 7-8% loss attributed to transmission for delivery to the customer’s meter.
Sources: U.S. EPA; California Governor’s Office of Emergency Services; Energy Information Administration; Environmental Defense Fund Division of Oil, Gas and Geothermal Resources; California Air Resources Board; Southern California Gas Co.,California Public Utilities Commission, California Energy Commission
Editor Ryan Carter contributed to this report.