The AQCAN Exchangeruptured well in northwest Los Angeles has been spewing methane into the atmosphere for 100 days as of Sunday—and counting.

Well control specialists may not be able to plug the leak until the end of the month, although the rate of emissions has slowed 65 percent since peaking in late November. How long it’s taking underscores how difficult it can be to stop fossil fuel-related accidents and leaks, and has drawn attention to aging infrastructure and lax regulations that probably played a role in the well’s failure.

The leak’s duration has surpassed the 87 days of BP’s Deepwater Horizon oil spill in 2010 in the Gulf of Mexico. The leak from a well at an underground storage facility owned and operated by Southern California Gas Co. was discovered Oct. 23. It is the latest in a series of environmental disasters in recent years caused by the oil and gas industry, including oil spills in Michigan, Montana, and Arkansas and a 2010 gas pipeline explosion in California.

The amount of methane released so far from the ongoing leak will have the same climate impact over the next 20 years as  seven coal-fired power plants, according to climate scientists from the Environmental Defense Fund. Thousands of nearby residents have been temporarily relocated, including California Secretary of State Alex Padilla, according to NBC news in Los Angeles.

To stop the leak, SoCal Gas contractors are drilling a relief well to intersect with the base of the ruptured well more than a mile and a half below ground. They plan to seal off the well with cement by the end of February.

The company slowed the rate of emissions by drawing down the volume of pressurized gas in the reservoir. But the California Public Utilities Commission ordered a halt to the withdrawals on Jan. 21 to maintain adequate supplies for heating and electrical generation. Lawmakers and environmental groups say the order to stop the drawdown endangers public health.