U.S. energy company Equitrans Midstream Corp. said on Nov. 17 it expected to stop a natural gas leak at its Rager Mountain storage facility in Pennsylvania in the next couple of days.

Equitrans has estimated the size of the leak, which started on Nov. 6 at the facility in Cambria County’s Jackson Township, at about 100 MMcf/d, according to the Pennsylvania Department of Environmental Protection (DEP).

At that rate, the amount of gas leaked could be around 1 Bcf. But the actual leakage per day likely has declined as the company took steps to stop the leak, including relieving pressure at the facility.

For comparison, the leak at Southern California Gas Co.’s Aliso Canyon gas storage facility in California, often cited as the biggest gas leak in U.S. history, released about 4.6 Bcf of gas, or methane, from October 2015 to February 2016.

Equitrans did not estimate the size of the leak in an email to Reuters, but said the gas was escaping from a 1-5/8-inch (4.1-cm) vent on a single storage well. The DEP said the well was called the George L. Reade 1 storage well.

Equitrans said the “vent is working as designed to relieve pressure from the casing, and the well is one of 10 operating storage wells.”

“Work [to stop the leak] will continue until the venting has stopped, which is expected to conclude in the next couple of days,” Equitrans spokesperson Natalie Cox said in the email.

The company said it has hired a specialty well services company, Cudd Well Control, to stop the leak.

Equitrans had no estimate on when the facility would return to service.

There was about 9 Bcf of gas stored in the Rager site, according to a news article from the Pittsburgh Post-Gazette.

The paper said the leaking well is about 1.5-miles (2.4-km) deep and was originally drilled in the 1960s to pull oil and gas out of the ground.

The site was converted to a storage facility after the oil and gas was exhausted.