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California Gov. Jerry Brown declared a state of emergency last week related to a near the Porter Ranch neighborhood of northwest Los Angeles. The Democratic governor  state agencies to protect public health and safety, oversee efforts to stop the 11-week-old leak, and ensure that Southern California Gas Co. is held accountable for costs and any violations.

An official of the California Air Resources Board last week declared the leak at the company's Aliso Canyon natural gas storage facility the to climate change in California. Methane is a greenhouse gas that's dozens of times more potent than carbon dioxide. By one estimate, the leak is the greenhouse gas equivalent of driving each day and will most likely continue for weeks before it can be capped.

Thousands of nearby residents have been evacuated as the blowout has been spewing roughly 62 million cubic feet of the gas into the atmosphere a day. The South Coast Air Quality Management District , a known carcinogen, at levels three to five times higher than those found in urban Los Angeles.

Officials believe the gas is spewing from a damaged 7-inch diameter pipe 500 feet below the surface. From there, the gas likely fills a cavity between the 7-inch pipe and an outer 11¾-inch "casing" pipe that is cemented to the surrounding rock. Because the outer pipe and cement only reach to a depth of 990 feet, engineers suspect the gas is flowing down under the outer casing and seeping through the surrounding rock to the surface, according to Jason Marshall, chief deputy director of the division of oil, gas and geothermal resources at the state Department of Conservation.

When the well tapping into the old oil-bearing formation was completed in 1953, operators weren't required to extend the outer cement casing to the bottom of the well.

"We would not allow something like this by current standards," Marshall said. "But the current standards, when they were adopted, did not say that operators had to shut down all of the pre-existing wells that they were still using and redrill them."

A Warning in 2009

The blowout wasn't entirely unexpected, based on a 2009 review of U.S. underground natural gas storage facilities. The peer-reviewed study concluded there was a high risk of leaks because of weak regulatory oversight. Environmental litigators are now likening the Aliso Canyon blowout to Deepwater Horizon, the 2010 oil spill that continued for months in the Gulf of Mexico.

"Generally, American regulatory agencies have not implemented adequate criteria for comprehensive well integrity analysis to ensure safety at UGS [Underground Gas Storage] facilities," wrote author Brent Miyazaki, now an associate vice president with the civil engineering firm AECOM, in a  published by the Geological Society of London.

In California, where there are several of the largest underground gas storage units, the study found particular fault with the California Public Utilities Commission.

"In California, CPUC conducts regulatory reviews and issues permits for UGS without maintaining staff with the appropriate technical backgrounds and expertise to evaluate hazards and impacts fully," Miyazaki wrote. "Thus UGS operators may face unidentified potential risk and financial liability."

CPUC spokesperson Christopher Chow said the agency does issue permits to owners of natural gas storage facilities. But the Conservation Department's division of oil, gas, and geothermal resources has primary jurisdiction over such facilities and associated wells; maintains a staff of experts in natural gas storage; and conducts inspections.

The last inspection of the Aliso Canyon well before the blowout was October 21, 2014, by the Conservation Department, and no leaks were detected, said Marshall of the department.

Miyazaki could not be reached for comment. Los Angeles County Supervisor Michael Antonovich, who represents the Porter Ranch area, that the leak was the "result of a massive failure on the part of all involved parties" and "exposes the corruption and incompetence of the state's regulatory system."

The Aliso Canyon gas storage unit, in a geological formation that once held crude oil more than 8,000 feet below the surface, is one of the largest of in the Lower 48 states. Gas is piped in from as far away as Canada and is held there for distribution to nearly 22 million customers in the Los Angeles Basin, according to the .

Major leaks at such facilities don't occur frequently, but when they do, the results can be catastrophic. The 2009 study found that "explosions and fires, along with possible exposure to substances such as benzene and toluene, are possible when gas reaches the surface through leaking wells and accumulates inside building voids." Serious previous leaks include:

• In January 2001, natural gas from underground storage in rural Kansas leaked through a damaged well and traveled 7 miles underground before surfacing in Hutchinson, Kan. There, it caused explosions and fires that destroyed buildings and killed two people, according to the 2009 Geological Society study. Nearby residents had to evacuate their homes for 2½ months. An estimated 143 million cubic feet of gas leaked from the storage facility before the well could be plugged.

• In December 2003, residents living 2 miles away from an underground storage facility near Napoleonville, La., had to evacuate their homes for several weeks after gas escaped from a ruptured well.

• In August 2004, a damaged well at an underground gas reservoir 40 miles northeast of Houston caused explosions that shot flames 1,000 feet into the air. The leak forced residents living within three miles to evacuate and caused $30 million to $36 million in lost gas.

Plugging the Leak: No Guarantees

Soon after the Aliso Canyon leak was detected October 23, engineers tried to plug the leak by pumping in pressurized water and mud. After seven attempts, however, the crews stopped out of concern that the pressure they were exerting might do more harm than good.

"That is a balancing act of well control: How hard can you push down the well before the force that you are applying and the shaking cause loss of integrity?" Marshall said. "It would be a far worse thing to break this well as is than it would be to take some of the steps that are being taken now."

On December 4, engineers began drilling a relief well parallel to the leaking well. They plan to use the relief well to pump plugging material into the leaking well near its base 8,500 feet underground. It will take an additional five weeks to complete the relief well, and even then there is no guarantee of success.

"It would be like taking a football and trying to throw it from one end of the end zone and hit the goalpost on the other end at a quarter-inch width," Marshall said.

Meanwhile, the gas company is using other wells to pump stored gas out of the reservoir, decreasing gas pressure and the rate of flow from the blowout. By December 22, the rate had dropped to 30,300 kilograms an hour from an hour as of November 28, according to the state's Air Resources Board.

SoCal Gas is now offering to affected residents and is at the site of the blowout to try to trap an oily mist that nearby residents have detected falling on their homes and vehicles.

Some, however, worry that the efforts may not be enough.

In a Los Angeles County Supervisor meeting last week, Antonovich described the leak as "a mini Chernobyl" and said that the full health effects, which already include , may not be apparent for months or years, according to the .

"In Chernobyl, officials were telling everyone 'there is no problem, there is no problem, there is no problem,' when of course we learned later there was a problem," said Antonovich spokesman Tony Bell.

Editor's Note: On Monday,  they will propose legislative reforms to improve safety at the facility and mitigate emissions.

is a Pulitzer prize-winning, nonprofit, non-partisan news organization that covers clean energy, carbon energy, nuclear energy and environmental science—plus the territory in between where law, policy and public opinion are shaped. Its mission is to produce clear, objective stories that give the public and decision-makers the information they need to navigate the heat and emotion of climate and energy debates.