Natural gas has been spewing from a ruptured well at SoCal Gas' Aliso Canyon Storage Facility near Porter Ranch, leading to thousands of residents relocating from the area, with some complaining of health problems. Two schools in Porter Ranch have closed, with students moved to alternate campuses.



Here are some frequently asked questions:

When will the gas leak be stopped?

A relief well that the Southern California Gas Company began drilling in early December should reach the bottom of the 8,500-foot-deep well by late February or sooner, when it will be permanently taken out of service, according to the company. "We are focused on stopping the leak as quickly and safely as possible, mitigating the environmental impact, and supporting the community," said Jimmie Cho, the engineering head. "Our schedule to control and stop the leak in February is consistent with the updated plan we have submitted to state regulators." Gas company attorney Robert Wyman of the firm Latham & Watkins LLP stated that the leak was "being addressed as safely and expeditiously as possible. This is SoCalGas's highest priority." Earlier estimates put the date sometime in March. Some are skeptical of the new timeline. The gas company also said it has abandoned a plan to capture and burn the leaking natural gas. The announcement came just two days after the South Coast Air Quality Management District announced that the company's proposal to burn the gas would be placed on hold because of the risk of a catastrophic explosion.

What's being emitted from the well?

An estimated 77 million kilograms of methane have been flowing over Porter Ranch since Southern California Gas Company discovered the leak on Oct. 23. The leak is producing greenhouse gas emissions equivalent to 3.3 million cars.

How did it start?

No official cause has been given.

What's the health threat?

A study by the South Coast Air Quality Management District estimates that six months of exposure to benzene from the gas leak poses to Porter Ranch residents an increased cancer risk of up to 2 in a million, a level that is at or below benzene risk throughout the region, according to the Los Angeles Times. Los Angeles County health officials have cautioned that levels of chemicals tracked so far in Porter Ranch are not believed to be associated with long-term health problems.

What are residents doing to mitigate the effects?

More than 2,800 households have moved to motels and officials have moved students from two schools into other campuses out of the area.

What is the Aliso Canyon storage field?

The Aliso Canyon storage field, the largest facility of its kind west of the Mississippi River, is "the largest of four natural gas storage fields that SoCalGas operates in Southern California" and provides fuel to "homes, manufacturers, hospitals, universities, small businesses and all customers who rely on a ready supply of energy from natural gas." Many of the pipes being used are from the 1950s and from the absence of surface safety valves, which had been removed in 1979 and never replaced.

How much money has the effort to plug the leak cost?

By the end of December the Southern California Gas Company had spent some $50 million in its efforts to stop the leak and mitigate its effects and Gov. Jerry Brown declared a state of emergency over its emissions.

How are lawmakers responding?

A group of state legislators unveiled a package of proposed legislation calling for an immediate moratorium on injecting any more gas into the well and calling for stepped-up inspections of aging wells statewide. Pavley and other legislators noted that while seven state agencies are involved in monitoring or investigating the leak, there is no single agency with responsibility for oversight of such facilities. Such oversight is called for in one of the bills the legislators plan to introduce. The bill also would require a utility responsible for environmental damage to bear the full cost of remediation without passing the bill to ratepayers. The senators also plan to introduce a bill that would ban new injections of gas into Aliso Canyon and bar the use of aging wells at the site until they can be inspected to determine they do not pose any public safety risk.

How big is this leak in comparison with other major leaks?

The ongoing gas leak is one of the biggest environmental disasters in the United States since the 2010 BP oil leak in the Gulf of Mexico. Los Angeles Eric Garcetti described the leak as a "disaster on the scale of what we saw with Deepwater Horizon."

How do I contact SoCal Gas?

The company has a contact page here