State engineering and safety enforcement experts say that the Aliso Canyon natural gas storage facility is safe to operate and can reopen, albeit at a greatly reduced capacity, in order to prevent an energy shortage in southern California.

At the same time, California's governor has directed the state's energy commission to plan for the facility's permanent closure.

The Aliso Canyon natural gas well blowout, first reported on Oct. 23, 2015, released over 100,000 tons of methane—the largest such leak in U.S. history—before the well was sealed on Feb. 11, 2016.

Energy storage was rapidly deployed to help support regional electricity demand.Energy storage was rapidly deployed to help support regional electricity demand.Total emissions during the 112-day event were equal to one-quarter of the annual methane pollution from all other sources in the Los Angeles basin combined.

Southern California Gas Co., which owns the facility, reacted to the decision by the California Public Utilities Commission and Division of Oil, Gas, and Geothermal Resources, saying “Aliso Canyon is an important part of Southern California’s energy system, supporting the reliability of natural gas and electricity services for millions of people. SoCalGas has met—and in many cases, exceeded—the rigorous requirements of the state’s comprehensive safety review."

Plan for Closure

In a letter dated July 19, California Energy Commission Chairman Robert B. Weisenmiller told state utility regulators that Gov. Jerry Brown has asked him to plan for Aliso Canyon's permanent closure.

"The recent gas leak at the Aliso Canyon natural gas storage facility reminds us of the dangers of our dependency on fossil fuels," he wrote.

A recent study says that more than 1 in 5 active U.S. underground natural gas storage (UGS) wells could be at risk of leaks due to obsolete well designs.

The study, from the Harvard T.H. Chan School of Public Health, says that the obsolete wells operate in 19 states across 160 facilities that encompass more than half of the total working gas capacity in the U.S. The oldest wells are in Ohio, Pennsylvania, New York, and West Virginia.

The research team says the potentially vulnerable wells are likely to be similar in design to the well that failed and led to the nearly four-month-long Aliso Canyon gas leak in California in 2015/16.

SoCalGas, which owns and operates the facility, asked to resume natural gas injections in November 2016.

Avoiding Disruptions

Storage capacity will be restricted to approximately 28% of the facility’s maximum capacity, which officials say will be just enough to avoid energy disruptions in the Los Angeles area.

SoCalGas relies on Aliso Canyon to provide gas for core customers—homes and small businesses—as well as non-core customers, including hospitals, local governments, oil refineries, and 17 natural gas-fired power plants with a combined generating capacity of nearly 10,000 megawatts.

As part of a multi-part response to the crisis, the California Public Utilities Commission in May 2016 fast-tracked approval of 104.5 MW of battery-based energy storage systems within the service areas of Southern California Edison (SCE) and San Diego Gas & Electric (SDG&E).

Those utilities, along with the Los Angeles Department of Water and Power—the nation’s largest municipal utility—provide gas and electric service to most of southern California. By the end of February 2017, seven of eight fast-tracked Aliso Canyon–related energy storage projects were online, helping the region’s energy grid regain stability.

In a statement, SoCalGas says it has introduced additional technology and practices in its operations at Aliso Canyon, including:

  • Around-the-clock pressure monitoring of all wells
  • Daily patrols to visually examine every well four times each day
  • Daily scanning of each well, using sensitive infrared thermal imaging cameras that can detect leaks
  • Enhanced training for employees and contractors.

Injection will not resume immediately, the utility says. State agencies have outlined steps that must be completed before injections can resume, including a leak survey of the facility and a flyover to measure methane emissions at the site.


California regulators say that each of the 114 wells in the facility either had to pass a series of tests to potentially be eligible to resume gas injection or be taken out of operation and isolated from the reservoir. This testing protocol included:

• Lowering sensors into the well to measure temperature and verify the integrity of the well

• Lowering an acoustic sensor to confirm no gas was leaking

• Extensive measurements of the well casing walls

• A sonic test to confirm adherence between cement and the external casing of the well

• A multi-arm caliper inspection to verify the casing’s ability to withstand pressure

• A pressure test to confirm the well remains sound when the pressure is 115% its maximum

operating pressure.

Around 60% of the wells have now been taken out of operation and isolated from the facility. All the remaining wells that passed were subject to retrofit and inspection requirements, including:

• Active wells are now equipped with real-time pressure monitors.

• The company must conduct routine aerial monitoring for the presence of any methane.

• Well heads are inspected daily using infrared and other leak-detecting technology.

• All of the wells used for injection and production have new steel tubing and new seals (known as

packers) inside the wellbore.

• The gas pressure in the storage reservoir has been reduced, from 3,600 PSI to 2,926 PSI.

• Another layer of protection ensures that gas flows only through an inner steel pipe. This allows the

outer casing to serve as a secondary safety barrier.

An investigation into the cause of the Aliso Canyon leak continues. SoCalGas has prepared a risk management plan that identifies prevention and mitigation steps for potential hazards, and a supplemental analysis of the seismic risk to the facility is in process.

Additionally, California utility regulators continue to a hold a proceeding that will decide the future of the Aliso Canyon facility.