Thousands fled their homes after a massive gas leak sprung at the Southern California Gas Co.’s Aliso Canyon natural gas storage facility, ultimately spewing more than 100,000 metric tons of climate-altering methane into the atmosphere.

Two years later, a bruised northern San Fernando Valley community is still demanding answers, a comprehensive health study remains in limbo and a bevy of lawsuits has yet to be resolved.

Here’s a reminder of what has happened — and what’s next — in the Aliso Canyon gas leak saga.

ROOT CAUSE STILL UNKNOWN

Two years after the nation’s worst natural gas leak was detected in Los Angeles County, the precise cause of a catastrophic well failure at the Aliso Canyon natural gas storage facility has yet to be determined.

Three investigations or “root cause analyses” are in the works to determine what led to the massive, nearly four-month leak above Porter Ranch. The analyses, which must be conducted safely and thoroughly, are expected to be completed in the spring of 2018, according to state regulators.

“Evidence collection, preservation, cataloging, evaluation and analysis is a meticulous and time-consuming process,” said Don Drysdale, a spokesman for the California Department of Conservation, in an email. “Investigators must recover material related to the well failure not only at the surface but also hundreds of feet underground.”

The Frisco, Texas-based Blade Energy Partners is focusing on the technical root cause analysis. Meanwhile, the California Public Utilities Commission and the Department of Conservation’s Division of Oil, Gas and Geothermal Resources (DOGGR) are basing their probes on these respective agencies’ authority over the offending well and facilities, Drysdale said.

The leak was “likely caused” by a breach in the in the well’s production casing wall, according to a document from state oil and gas regulators. Some of the possible causes include faulty installation, a manufacturing defect, excessive wear from well work and corrosion.

COUNTY HEALTH STUDY IN LIMBO

The Los Angeles County Department of Public Health has yet to start a longterm health study because of funding disputes.

County public health officials estimate $35 million to $40 million is needed for what they call a comprehensive study. Earlier this year, the Southern California Gas Co. agreed to an $8.5 million settlement with air quality regulators, with $1 million of those funds to go toward a health study. But Los Angeles County officials said that wasn’t enough. They also said SoCalGas’ version of a health study fell short of what was needed.

“Public Health believes the long-term health study would benefit the community by ensuring that residents who have been exposed to this extraordinary event can have confidence that health effects are being studied with the scientific rigor required to provide answers,” health officials said recently.

Complaints of headaches and other symptoms continue to be called into the county’s public health department. About 2,000 calls have come in from 1,170 households during and after the active gas leak through Sept. 7, health officials said.

“The high prevalence of nosebleeds are noteworthy, and the continuation of symptoms after the well was sealed, are inconsistent with expectations,” according to the public health department’s office of Environmental Health. “This prompted indoor environmental investigation that demonstrated homes needed be cleaned to prevent exposure to residual oil and gas material inside homes. This cleaning was never done, and now a long-term health study is needed to further study this question.”

INDEPENDENT HEALTH STUDY RELEASED

Meanwhile, results from an independent clinical study conducted by a local physician showed showed a pattern of symptoms from patients he followed and tested just after the leak was capped in February 2016 and then months later, up until this year.

Styrene, a derivative of benzene, which is a known carcinogen, was found at higher than average levels when compared to people who lived outside the Porter Ranch area.

While Dr. Jeffrey Nordella could not say with certainty why this was the case, he said his troubling findings bolster the need for a comprehensive health study.

Also, about 47 percent of the households sampled experience nosebleeds within 3-miles of the leaking well, public health officials said. After the well was sealed, almost 31 percent of the households sampled experienced nosebleeds.

SEISMIC STUDY IN THE WORKS

A former Southern California Gas Co. manager has sounded the alarm over potential “catastrophic” consequences in the event of a major earthquake in the area of Aliso Canyon.

While SoCalGas does not agree with that assessment, it has assembled a team of independent experts to conduct an extensive seismic risk analysis for the underground storage field above Porter Ranch.

The study is required by state oil and gas regulators as part of risk management plan for the facility. The Department of Energy’s Lawrence Berkeley National Laboratory reviewed the third-party work plan and the credentials of the proposed consultants, according to the state Department of Conservation, which includes the division that oversees the operation and maintenance of oil and natural gas wells.

“Having as much information as possible about the potential seismic hazard at Aliso Canyon can only help regulators achieve the overriding goal of ensuring the facility is operated in a manner that protects public and environmental safety,” said Drysdale, the department spokesman.

The conclusions should be available in June, he said.

ALISO CANYON BACK TO BUSINESS

The Southern California Gas Co. is continuing to work with state oil and gas regulators to complete all well inspections at the Aliso Canyon natural gas storage facility required following the 2015-16 gas leak.

This past summer, SoCalGas resumed injecting natural gas through approved wells there after state regulators completed their comprehensive safety review and gave the company the green light.

As of earlier this month, 52 out of 114 active wells at Aliso Canyon have received final approval for use from oil and gas regulators. Twenty of the 114 wells are in the process of abandonment, while the remainder are in various phases of inspection, according to SoCalGas.

Meanwhile, the company has stressed that it’s made a series of safety improvements at Aliso Canyon to minimize the chance that a massive leak – like the one that happened two years ago – happens again.

SoCalGas, for example, has replaced the inner metal tubing of every approved well, which comes to about 70 miles of new tubing, according to the company. As ordered by the California Public Utilities Commission, the company is now operating the facility at reduced pressure. Injection now occurs through a well’s tubing only, rather than through both the tubing and casing.

In addition, SoCalGas has introduced a number of “advanced leak-detection technologies” to help identify anomalies. They include an infrared fence-line methane detection system, around-the-clock monitoring of the pressure in all wells and twice-daily patrols to examine every well, according to the company.”

FLURRY OF LAWSUITS

A conservative deadline to to file a lawsuit against SoCalGas is on Monday, for those adults who began to feel ill the first day the gas leaks occurred. But the number of claims against the company swelled to more than 25,500 plaintiffs, most pending at the Los Angeles County Superior Court against SoCalGas.

Negligence, property damage, fraud, public and private nuisance, unfair business practices and other complaints are included in those filings.

The massive leak has already cost SoCalGas an estimated $832 million, according to the company’s quarterly report. More than 60 percent of that cost has gone toward relocating residents.

Cases are expected to be heard in December 2018.

LOS ANGELES COUNTY TAKES ON CALIFORNIA

A variety of legal actions by Los Angeles County against the state’s decision to allow SoCalGas to begin re-injections at the Aliso Canyon natural gas wells dominated most of the summer.

Yet despite concerns raised by residents and Los Angeles County leaders, state regulators, and later judges from local to state courts allowed SoCalGas to proceed with natural gas injections. High court judges agreed with a Los Angeles Superior Court judge when he said in late July that he had no jurisdiction to stop the injections because two state statutes barred him from deciding on legal challenges filed by Los Angeles County. As a result, attorneys for Los Angeles County in September decided to try a different tactic.

Porter Ranch homes that come up to the SoCalGas Aliso Canyon Storage Facility. (Photo by Gene Blevins)

SoCalGas crews and outside experts started the coiled tubing rig operation to attempt to work through an ice blockage inside the 2 7/8-inch tubing pipeline of a natural gas storage well at the Aliso Canyon facility on November 6, 2015. If the operation is successful, crews will fill the pipeline with brine solution to stop the flow of gas. (Photo by SoCalGas)

Sound The gallery will resume in seconds

Angry Porter Ranch residents crammed a Woodland Hills Public Utilities Commission meeting, where regulators will hear arguments for and against reopening Southern California GasÕ Aliso Canyon gas field.Woodland Hills, CA 2/1/2017. Photo by John McCoy/Los Angeles Daily News (SCNG)

A map showing the sites of all the wells at the Aliso Canyon Gas facility displayed at a protest of the facility. Sunday was the anniversary of the Aliso Canyon gas leak, a protest was staged at the Holleigh Bernson Memorial Park and proceeded to the facility on Rinaldi street. (Photo by David Crane, Los Angeles Daily News/SCNG)

Roberta Griego and Babetta Juergens wore gas masks at the meeting at Granada Hills Charter High school during the SCAQMD Board Hearing. Officials and residents discussed the So Cal Gas storage facility that is leaking in Porter Ranch, CA 1/16/2016 (photo by John McCoy/Los Angeles News Group)



Porter Ranch residents held a rally at the SoCalGas Aliso Canyon storage facility on Thursday, September 1, 2016, to call on Gov. Jerry Brown and state regulators to keep it closed permanently. Their early morning protest was followed by a press call to release the new review of state regulatorÕs recent Winter Risk Assessment and Action Plan. (Photo by Dean Musgrove, Los Angeles Daily News/SGVN)

SoCalGas crews and outside experts started the coiled tubing rig operation to attempt to work through an ice blockage inside the 2 7/8-inch tubing pipeline of a natural gas storage well at the Aliso Canyon facility on November 6, 2015. If the operation is successful, crews will fill the pipeline with brine solution to stop the flow of gas. (Photo by SoCalGas)

Crews from SoCalGas and outside experts work on a relief well at the Aliso Canyon facility above Porter Ranch on December 9, 2015. Once the relief well is connected to the leaking well, SoCalGas will pump fluids and cement into the bottom of the leaking well to stop the flow of gas and permanently seal the well. (Photo by Dean Musgrove/Los Angeles Daily News)

Matt Pakucko, Save Porter Ranch President, comments on the killed well after the press conference. Numerous officials spoke about the Porter Ranch gas leak kill at a press conference at SoCalGas offices in Chatsworth, CA on Thursday, February 18, 2016. (Photo by Dean Musgrove/Los Angeles Daily News)

Porter Ranch Estates sits below the Aliso Canyon Gas storage facility in Porter Ranch, CA. (Photo by Dean Musgrove/Los Angeles Daily News)



File photo of Jane Fowler of Granada Hills protests with Save Porter Ranch at the corner of Tampa and Rinaldi. (Photo by David Crane, Los Angeles Daily News/SCNG)

(l-r) Issam Najm, Porter Ranch Neighborhood Council Board Member, tries to get order in the room while Caelan McGee who was the Facilitator of the event, lost control of the meeting. Matt Pakucko used a bullhorn to shout out his own agenda. Pakucko, President of Save Porter Ranch, interupted planned speakers as angry Porter Ranch residents cramed a Woodland Hills Public Utilities Commission meeting, where regulators will hear arguments for and against reopening Southern California Gas’ Aliso Canyon gas field. Woodland Hills, CA 2/1/2017. Photo by John McCoy/Los Angeles Daily News (SCNG)

On the one year anniversary, protesters from 350.org, Food and Water Watch LA, SoCal 350 and others, staged a protest on the property of the Aliso Canyon gas storage facility in Porter Ranch Sunday. The group shut down the entrance to the facility for 3 hours before peacefully leaving the property. (Photo by David Crane/Southern California News Group)

This Dec. 17, 2016 photo provided by Earthworks shows an overhead aerial view of the well at the Aliso Canyon facility above the Porter Ranch area of Los Angeles. (Pete Dronkers/Earthworks via AP)

File photo of Argos Scientific Senior Scientist, Dr. Robert Crampton, demonstrates the ultraviolet remote sensing device to monitor critical hazardous and toxic gas detection in the Porter Ranch community. (Photo by Dean Musgrove, Los Angeles Daily News/SCNG)



Well SS-25 well pad a year after SoCalGas plugged the largest natural gas leak in the nation, the utility and state regulators conducted a media tour of the Aliso Canyon natural gas storage field north of Porter Ranch during a comprehensive safety review required by law before reopening the facility on Thursday, January 12, 2017. (Photo by Dean Musgrove, Los Angeles Daily News/SCNG)

SoCalGas worker inspects the Porter 44 well with a FLIR camera. (Photo by Dean Musgrove, Los Angeles Daily News/SCNG)

File photo shows the gas gathering plant on a hilltop at the Southern California Gas Company’s Aliso Canyon storage facility near the Porter Ranch neighborhood of Los Angeles. A third of the wells that inject natural gas into underground storage were taken out of service weeks after a troubled Los Angeles facility restarted following a massive blowout. Southern California Gas Co. said Monday, Sept. 11, 2017, that it notified state regulators in August that 13 of the 39 wells at Aliso Canyon were shut down after detecting a pressure buildup. (AP Photo/Jae C. Hong, File)

File photo of students transplanted from Porter Ranch Community school, due to the ongoing Aliso Canyon gas leak, arrive for their first day at the new school location on the campus of Northridge Middle school in Northridge. The students will finish the school year on the new campus. (Photo by David Crane/Los Angeles News Group)

Reaction to the SoCal Gas announcement that the leaking well has been contained at the Aliso Canyon storage facility above Porter Ranch on Thursday, February 11, 2016. Paula Cracium, Porter Ranch President of Neighborhood Council speaks to the media. (Photo by Dean Musgrove/Los Angeles Daily News)



File photo of Dennis Arriola, President and CEO of SoCalGas speaks during the press conference. Numerous officials spoke about the Porter Ranch gas leak kill at a press conference at SoCalGas offices in Chatsworth, CA on Thursday, February 18, 2016. (Photo by Dean Musgrove/Los Angeles Daily News)

Walker Foley leads chants with a bullhorn. Activists and Porter Ranch area residents gather outside the Hilton to call for the shutting down the Aliso Canyon gas field. The SCAQMD Hearing Board listened to arguments during an evolving agreement between the Southern California Gas Co. and the South Coast Air Quality Management District. Woodland Hills, CA. 1/23/2016, Photo by John McCoy/Los Angeles News Group

View from above the Porter Ranch neighborhood’s that has been affected by the long on going gas leak. The leak started back on October 23, 2015 after a pipe casing a few hundred feet below the ground of a well that goes 8,500 feet underground. Photo by Gene Blevins/LA DailyNews

A screen grab from an infrared camera showed the Aliso Canyon leak in December 2015. Credit via Environmental Defense Fund

“We’ll be going back to the trial court and will ask the Judge to transfer the case to the Court of Appeal or state Supreme Court, so we can get a hearing on the merits of whether the regulators/Gas Co have complied with state law–Senate Bill 380 (passed in 2016) and CEQA,” the California Environmental Quality Act, attorney Skip Miller said in an email response in September.

RESPONSE FROM SACRAMENTO AND WASHINGTON

The leak has prompted a wave of new state and federal laws and regulations designed to bolster safety.

Among them is state Senate Bill 380, which put a moratorium on new gas injections at the site until state gas and energy regulators deemed the remaining wells safe.

But, following a comprehensive safety review, Southern California Gas Co. received the green light from state regulators this past July to resume filling the gas field on a limited basis.

Another state law, Senate Bill 887, established new safety standards for natural gas storage wells across California, including stringent inspections of wells and continuous monitoring for leaks. It also codified the idea that gas storage wells needed to be designed to ensure that no “single point of failure” poses an immediate threat of an uncontrolled leak.

Other state bills related to Aliso Canyon failed to muster the necessary votes in the Legislature.

Senate Bill 57 would have kept the gates closed on new injections at the facility until the official root cause of the nearly four-month leak was determined. It stalled after it fell three votes shy of passing on an urgency basis with the required two-thirds threshold.

“We could have done something more superficial and passed a bill; I didn’t want to,” said Sen. Henry Stern, D-Calabasas, who introduced the bill. “I wanted to send the (state) administration a message. I think they know I’m frustrated and shocked, frankly, that they proceeded on reopening the facility because I didn’t think we were in any rush.”

Coming Monday at dailynews.com: Read about what’s next for Aliso Canyon, and relive the last two years through people affected by the leak.