About 42 kilometres from Los Angeles, above the houses nestled in the mountains of Porter Ranch, Calif., a plume of methane is shooting into the sky. The cloud is invisible but it stretches for kilometres, as though a forest fire has been continually burning for months. All of this is emanating from a tiny pipe about 20 centimetres wide, more than a kilometre underground.

"The amount of methane and natural gas that's coming out of the Aliso Canyon Facility really is probably one of the largest volumes of gas ever recorded from a single leak," says Tim O'Connor, an oil and gas specialist with the non-profit Environmental Defense Fund (EDF).

SoCalGas spokesman Mike Mizrahi says the company 'has observed all of the safety protocols.' (Kim Brunhuber/CBC)

The Aliso Canyon Natural Gas Storage Facility, owned by SoCalGas, is the fifth biggest of its kind in U.S. But in late October, the company realized one of its wells was leaking. At first the company tried to close the leak using the conventional method of pouring fluids and mud down the well.

"We have tried that seven times and have been unsuccessful in trying to stop the leak," said SoCalGas spokesman Michael Mizrahi. "I have to say more than likely it's [because] the pressures that are coming up from the leaking well are so intense."

The company says it doesn't know exactly how much gas is escaping. But environmentalists estimate the effect is comparable to the tailpipes of up to seven million cars venting directly into the atmosphere every day.

Environmental Defense Fund oil and gas specialist Tim O'Connor says the leak is 'probably one of the largest volumes of gas ever recorded from a single leak.' (Kim Brunhuber/CBC)

"Methane is a very potent greenhouse gas; over the first 20 years it's released, it has a climate impact 84 times that of carbon dioxide," said O'Connor. "There's no telling what the far reaches of the overall end results are going to be. Air quality, public health, ecological — it's all on the table."

The Federal Aviation Administration has imposed a no-fly zone because of the small risk that a plane could ignite a pocket of methane. And then there's the smell.

Outside the gate of the facility, about 1.5 kilometres away from the leak, the smell is far from overpowering; in fact it's often impossible to detect. Then the wind shifts, and there it is: It smells as though someone nearby is cooking cabbage.

"It's that odourant that's causing some people to have some temporary ill effects," said Mizrahi. "We fully recognize that some people are more susceptible to that smell than others. And we are really apologetic about that."

Laurie Rosenberg is among the many Porter Ranch residents who say the chemicals are causing them health problems.

Porter Ranch resident Laurie Rosenberg will be moving to temporary housing in January because she worries about the leak's long-term effects. (Kim Brunhuber/CBC)

"I've had migraine headaches … itchy eyes, and runny nose 24/7," she said. "And the two schools in the area that my grandsons go to are closed. So I think there's more up there than they're really willing to admit. I'm not really confident about the long-term effects of this."

Mizrahi says experts are sampling the air twice a day in ten different locations to make sure the levels aren't harmful, but says the company will temporarily relocate anyone who wants to move.

"We are working as fast as we can, and we don't want anybody to be in their homes any longer than they want to be in their homes," Mizrahi said.

SoCalGas is drilling a relief well which will enable them to seal the leak, but that could take up to four months.

Porter Ranch residents Natalie and Kyle Norman say they can't wait that long. Natalie says she's been suffering from a variety of problems.

"Mainly migraines, nosebleeds," Natalie said, while she and Kyle stood in line at a temporary resource center, set up by SoCalGas, to deal with the more than 7,000 people who have asked the company for information about relocating.

"I don't want to move," she says, "but also I don't want to be in pain every day."

Kyle says even their two dogs have been vomiting more than usual.

SoCalGas is drilling a relief well which will allow it to pump liquids, and then cement, into the leaking well to close and seal it. The company says it could take another four months. (SoCalGas)

More than two months after SoCalGas discovered the leak, the company says it still doesn't know what caused it.

"We won't be able to determine that definitively until we actually complete the relief well process," said Mizrahi. "SoCalGas has observed all of the safety protocols. These wells are inspected every day. They have an in-depth annual inspection once a year, in fact this well was due for its next annual inspection just before the leak happened."

"Since we have a major catastrophe, something certainly went wrong and we need to get to the bottom of it," said O'Connor, the specialist with the EDF. He believes either the company is at fault or current regulations for underground gas storage are too lax.

"We need systems in place to make sure we have inspections and maintenance and construction requirements that both prevent the leaks that happen every day — the 'little guys' — but that can also prevent these big environmental catastrophes," says O'Connor.

The irony, he says, is that California is about to enact methane reduction legislation across all sectors of the economy.

"And yet we have one leak that's pumping out more methane pollution every day than all of the other oil and gas sources [in California] combined."