Southern California Gas Co. knew of deteriorating wells at its underground methane storage facilities and warned state regulators of the risks almost a year before a massive, uncontrolled leak was discovered at its Aliso Canyon unit on the outskirts of Los Angeles.

The gas company disclosed the risk as part of a state regulatory filing and requested a rate increase to pass along the cost of more inspections and well repairs to customers. The regulators and the gas company failed to act.

Now, as pressure mounts to end the three-month-old disaster, California officials have intensified efforts to hold SoCal Gas accountable as well as the state regulators who didn't heed warning signs. Last week, lawmakers at a state assembly committee hearing grilled officials from SoCal Gas and the California Public Utilities Commission (CPUC) about what they knew before the leak began. On Tuesday, the South Coast Air Quality Management District (SCAQMD), the air pollution control agency for much of southern California, sued the gas company for negligence.

The SoCal Gas leak is the latest in a series of recent environmental disasters caused by the oil and gas industry. BP's Deepwater Horizon explosion and 87-day oil spill into the Gulf of Mexico in 2010 was the biggest and most publicized, but the list also includes the Kalamazoo River oil spill in Michigan in 2010; the San Bruno natural gas pipeline explosion in California in 2010; oil spills in the Yellowstone River in 2011 and 2015; and an oil spill in Mayflower, Ark., in 2013. A flurry of government activity after such a catastrophe is all too common, according to one industry watchdog.

"No one gets out in front of these issues; they wait for a tragedy," said Carl Weimer, executive director of the Pipeline Safety Trust in Bellingham, Wash.

The SoCal Gas warning to the CPUC of deteriorating wells was part of a November 2014 rate request. The Aliso Canyon leak was discovered Oct. 23.

"I think you have a complete failure of the system," said Mike Gatto, the Democratic chairman of the California State Assembly Committee on Utilities and Commerce, who convened last week's hearing.

The gas company's rate request cited multiple cases of corrosion and advanced aging of wells at SoCal Gas's four underground storage facilities, the largest of which is Aliso Canyon. According to written testimony, Phillip Baker, SoCal Gas's director of storage, said:

Ultrasonic surveys of storage wells during repair work from 2008 to 2013 identified internal and external casing corrosion or mechanical damage in 15 wells.

SoCal Gas had 52 storage wells in service that were more than 70 years old. Half of its 229 storage wells were more than 57 years old as of July 2014.

A rising number of well integrity issues starting in 2008 were attributed primarily to frequency of use, operating environment, age and length of time the wells had been in service.

"We believe that it is critical that we adopt a more proactive and in-depth approach," Baker said in his written testimony. Otherwise, he said, the company would continue to "operate in a reactive mode" with the potential for even higher costs for ratepayers "to address sudden failures of old equipment." He also said the company and its customers "could experience major failures and service interruptions from potential hazards that currently remain undetected."

Given SoCal Gas's knowledge of the failing state of its infrastructure and the company's insistence on the need to be more proactive, Gatto asked last Thursday in the hearing, "How did this happen?"

"We don't know," said SoCal Gas senior vice president Jimmie Cho. "I think the thing we have to rely on is the fact that there will be an investigation, and we need to let the facts come out through that investigation."

The 2014 rate request is still pending with the CPUC.

"I think there is absolutely more that could have been done," said Elizaveta Malashenko, the CPUC's safety and enforcement division director, at the hearing.

The leak has emitted an estimated 90,000 metric tons of methane into the atmosphere since it was detected 98 days ago. The emissions are the greenhouse gas equivalent of burning 847 million gallons of gasoline , according to the Environmental Defense Fund. Short-term exposure to mercaptan, an odorant added to natural gas to aid in leak detection, can cause adverse health effects "including, but not limited to, headaches, dizziness, nausea, vomiting, pulmonary irritation, expiratory wheezing, rapid heartbeat, and irritation of the eyes, skin, and mucus membranes" according to the SCAQMD.

"If I submitted a public document of testimony saying that there was corrosion at a natural gas well, the very next act that I would have done as a company and the very next act I that would have done as a regulator would be to go out there and test every single well and close them down where applicable," Gatto said.

SoCal Gas said Wednesday that it has temporarily shut down 18 older wells at Aliso Canyon for inspection. Earlier in the day, the Los Angeles Times reported that the CPUC is considering the permanent closure of the Aliso Canyon storage facility. Residents of the Porter Ranch neighborhood adjacent to the leaking well and environmental groups have been campaigning for a shutdown under the social media hashtag "#ShutItAllDown" with demonstrations, petition drives and meetings with government officials.

The lawsuit filed Tuesday in Los Angeles County court by the SCAQMD alleges gas company negligence in the design, construction, operation and inspections of SS-25, the name of the ruptured well at the Aliso Canyon unit. The suit also faults SoCal Gas for a slow response to the leak.

The SCAQMD has received more than 2,000 complaints from those living and working near the Aliso Canyon unit, according to the suit. The agency alleges that SoCal Gas violated multiple state Health and Safety Code regulations and seeks up to $250,000 per violation for each day that the violation occurred.

The complaint is one of more than 25 suits filed against the company since the leak began, according to the Los Angeles Daily News. "It's certainly the most significant public nuisance I've seen in my career," Kurt Wiese, SCAQMD'S general counsel, told the paper.

Kristine Lloyd, a spokeswoman for SoCal Gas, said, "We do not comment on pending litigation and will respond to the lawsuit through the judicial process."

"There's an alphabet soup of state regulators across California, and we are happy that at least one of them is taking the necessary step to hold SoCal Gas accountable for the gas leak in Aliso Canyon," Gatto said in a written response to the SCAQMD's suit.

However, Gatto said he would prefer a stronger regulatory and inspection regime to prevent such incidents.

"The fact that there weren't even questions asked, there wasn't even an inspection team sent out there, neither by the company nor the regulators, that to me is just unbelievable," Gatto said. "It's like telling somebody, 'Gee our car, the wheels could fall off on the freeway,' and that document goes in front of all these people and no one says, 'Well shouldn't we at least bring it to the mechanic?'"