Southern California Gas Company has been trying to plug a massive natural gas leak for more than two months, and now we have some new perspective on the scale of the leak. The non-profit organization Environmental Defense Fund (EDF) has released an infrared aerial video showing the plume created by the normally invisible methane seeping out of the former oil well in the hills north of Los Angeles. The video puts in sharp relief the gravity of the situation caused by the rupture, which was discovered on October 23 and has been estimated to be releasing tens of thousands of kilograms of methane into the air every hour.

The leak at SoCal Gas’ Aliso Canyon site is northwest of Los Angeles and just adjacent to the Porter Ranch community. Although the Los Angeles County Department of Health and SoCal Gas have assured residents that the leak poses no harm to human health, the highly flammable, odorless gas has been treated with chemicals to give it a “rotten-eggs” smell, which can cause headaches, nausea, and nosebleeds. Because of this, SoCal Gas has relocated families in Porter Ranch to motels and offered to reimburse them for household air purifiers, per an agreement with Los Angeles officials.

The most concerning result of the leak, however, is that methane is a potent greenhouse gas, according to the California Air Resources Board (CARB). It is many times more harmful than CO 2 with respect to climate change in the near-term. CARB estimated in November that the Aliso Canyon leak has released methane approximately equivalent to one-quarter of California’s normal methane emissions.

To get the situation under control, SoCal Gas started drilling a relief well to stop the leak in November after other attempts to plug the injection well failed.

On Sunday, Southern California Gas Company told the Los Angeles Times that the relief well it's been drilling has passed near the original injection well, making a critical step toward stopping the natural gas leak. Engineers detected the 7-inch-wide injection well nearly 3,800 feet underground using a "magnetic ranging tool." The process involves an extra layer of difficulty, given that workers had to drill the relief well from far enough away from the site of the leak to prevent stray sparks from causing the leaking methane to go up in flames.

The leaking well descends 8,700 feet to an underground sandstone reservoir, and SoCal Gas originally pumped the natural gas there for storage (Aliso Canyon is one of the largest natural gas storage facilities in the US). From here on, SoCal Gas will continue drilling in parallel to the 7-inch well, until the relief well gets to about 8,000 feet deep. At that point, the new well will intercept the leaking one, and fluids and cement will be injected to plug up both. (A Los Angeles Times infographic gives a good visual representation of how the relief well will be installed).

SoCal Gas maintains that its efforts to plug the leak won’t come to fruition until late February to late March. It also plans to start drilling a back-up relief well in January.

The cost of plugging the massive leak, how much methane will be released into the atmosphere, and the exact cause of the leak, are still unknowns and likely will remain so until after the leak is plugged. According to The Washington Post, "company officials believe the problem began when an underground well casing failed, allowing the pressurized gas to push through geological cracks to the surface near the community of Porter Ranch."

Ars contacted SoCal Gas but has not received a response.

Listing image by Earthworks