The Porter Ranch gas leak lawsuit ended in a $1.8 billion settlement announced in September 2021, resolving personal injury and property damage claims brought by more than 35,000 residents against Southern California Gas Company and its parent, Sempra Energy, over the 2015–2016 Aliso Canyon blowout. A separate $40 million property class settlement, government enforcement agreements, and a criminal plea pushed SoCalGas’s total payouts past $2 billion.1
What Residents Were Suing Over
On October 23, 2015, SoCalGas crews discovered an uncontrolled leak at well SS-25 at the Aliso Canyon underground storage facility above Porter Ranch. The well, drilled in 1953 and converted for gas storage in 1973, was not sealed until February 11, 2016, 112 days later. Over that period roughly 109,000 metric tons of methane escaped, at a peak rate of about 58,000 kilograms per hour. It stands as the largest documented anthropogenic point-source methane release in United States history and, at its worst, accounted for around 20 percent of California’s statewide methane emissions.
The plume drifted over Porter Ranch, Chatsworth, Granada Hills, and Northridge, carrying methane along with trace amounts of benzene, hydrogen sulfide, radon, and oil residue. Residents reported headaches, nausea, severe nosebleeds, dizziness, and eye and throat irritation. Local schools recorded about 50 children per day going to nurses for nosebleeds. SoCalGas relocated 2,824 families totaling more than 11,000 people, and two schools were moved to other campuses in January 2016.
An independent root cause analysis by Blade Energy Partners, released in May 2019, traced the failure to corrosion of the aging well casing. The report found that 40 percent of reviewed wells at Aliso Canyon had experienced past casing failures, averaging two failures per well, and that SoCalGas had been aware of casing problems since at least the 1970s without investigating the risk of a catastrophic event. A 1988 company plan to inspect 20 of its oldest wells assigned SS-25 low priority; the well was never inspected.
How the Cases Were Consolidated
More than 100 separate suits were filed on behalf of residents and businesses. On March 4, 2016, Judge Emilie Elias granted a petition to coordinate them into a single proceeding, JCCP No. 4861, in Los Angeles Superior Court. Judge John Shepard Wiley Jr. was appointed as the coordination trial judge and managed the case through six years of discovery and pretrial rulings.
The $1.8 Billion Settlement
The settlement was announced on September 28, 2021, by a group of nine plaintiffs’ firms: Panish Shea & Boyle, the PARRIS Law Firm, Baron & Budd, Weitz & Luxenberg, Boucher LLP, Cotchett Pitre & McCarthy, Kirtland Packard, Kiesel Law, and Morgan & Morgan. The agreement covered more than 35,000 individual plaintiffs and included both personal injury and property damage claims. It required approximately 97 percent participation from the roughly 36,000 plaintiffs and was subject to court approval of its distribution plan.
BrownGreer PLC administered the claims. Payouts were calculated on a points-based system. Each claimant received base points tied to how close they lived or worked to the leak site. Those base points were then adjusted for age, pre-existing health conditions, medical treatment received, whether the claimant relocated, economic losses, and any property remediation. Two independent arbitrators reviewed the individual situation of each of the 35,000-plus claimants to set final allocations, with exceptional circumstances handled separately.
SoCalGas and Sempra denied any wrongdoing in the settlement and continued to maintain that the leak posed no long-term health risks. SoCalGas said settlement costs would not be passed on to ratepayers.
The $40 Million Property Class Settlement
A separate class settlement of $40 million, also administered by BrownGreer, covered property owners in a class estimated at no fewer than 23,000 properties. It resolved property-based claims not folded into the individual personal injury allocations.
Discovery Sanctions Against SoCalGas
The coordinated proceeding produced one of the largest discovery sanctions in California history. Judge Wiley issued a series of rulings on privilege, including an October 2018 order finding that SoCalGas had largely failed to prove that communications with its environmental consultant AECOM qualified for attorney-client privilege. After the judge specified which categories of documents could legitimately be withheld, SoCalGas and its outside counsel, Morgan Lewis & Bockius LLP, continued making broad privilege claims over materials outside those categories.
SoCalGas, Sempra Energy, and Morgan Lewis were sanctioned more than $5.7 million for wrongfully withholding over 150,000 documents. The court characterized the conduct as “willful, intentional and in bad faith.”
Judge Wiley also compelled the Los Angeles Department of Public Health, in January 2020, to produce health survey data including respondent names and addresses, finding that the public interest in understanding the leak’s health effects outweighed the respondents’ limited privacy concerns.
Government Settlements and Criminal Plea
Beyond the private class litigation, SoCalGas resolved several enforcement actions:
- A $119.5 million multi-agency settlement with the California Attorney General, the California Air Resources Board, the Los Angeles City Attorney, and Los Angeles County, finalized by consent decree on February 25, 2019. The money was allocated across greenhouse gas mitigation ($26.5 million, funding methane digesters at 12 San Joaquin Valley dairies), supplemental environmental projects ($45.4 million, covering a long-term health study, school air filtration, electric school buses, air monitoring in Porter Ranch, a mobile asthma clinic program, and lead paint abatement), $21 million in civil penalties, and $19 million in investigative and response cost reimbursement. The decree also required eight years of fence-line methane monitoring with real-time reporting, an internal safety committee, and an independent safety ombudsman.
- A California Public Utilities Commission settlement adopted in August 2023 that included a $71 million penalty and recognized $485.5 million in costs SoCalGas shareholders must absorb, with a prohibition on recovering those costs from ratepayers through at least 2028. SoCalGas had previously paid $34.1 million for greenhouse gas mitigation under CPUC direction.
- A 2016 criminal resolution with the Los Angeles County District Attorney, who charged SoCalGas with four misdemeanor counts. The company pleaded no contest to one count of failing to immediately report the leak. Total cost, estimated between $4 million and $4.3 million, included fines, penalty assessments, investigation reimbursement, an infrared methane monitoring system, and six full-time employees to operate leak detection equipment around the clock for at least three years.
- A 2022 agreement with the Center for Environmental Health requiring additional methane and benzene monitors near the facility.
Combined with the private settlements, SoCalGas and Sempra paid more than $2 billion in total.
Other Lawsuits Outside the Class
In October 2018, dozens of firefighters who responded to the leak sued, claiming exposure to methane, benzene, and other chemicals caused nosebleeds, severe headaches, nausea, and dizziness. In June 2019, Kenneth Bruno, a CPUC program manager deployed to monitor the capping of SS-25, sued Sempra and SoCalGas in Los Angeles Superior Court, alleging benzene exposure caused him to develop hairy cell leukemia, a rare blood cancer linked to benzene. Bruno said he was never instructed to wear protective gear or decontaminate before going home. Both the firefighter cases and Bruno’s suit were settled for undisclosed amounts.
Where Aliso Canyon Stands Now
The facility resumed limited operations in July 2017 at a reduced capacity of 68.6 billion cubic feet, down from 86 billion cubic feet before the leak, with maximum operating pressure capped at 2,926 psi. In December 2024, Governor Gavin Newsom backed a decision by state officials to keep it open and proceed with expansion, citing regional dependence on natural gas for energy reliability. The CPUC approved additional capacity in 2025, though its own biennial assessment recommended a 10-billion-cubic-foot reduction, a question the commission is expected to revisit later in 2026.
Community groups including the Aliso Moms Alliance continue to press for a shutdown, and a coalition of university scientists has urged the governor to close the site permanently. State officials have said the facility can close only once natural gas demand drops enough to preserve energy reliability without it.