The expansion of hub in Mississippi where salt caverns are used to store natural gas is one step closer to approval after a review by the Federal Energy Regulatory Commission (FERC).

On Oct. 30, FERC issued its final environmental assessment for an expansion of the Mississippi Hub Storage Facility, where Enstor Gas is planning to build three new salt storage caverns and expand two existing caverns. If approved, it would add up to 1 billion cubic feet per day of storage capacity.

Salt caverns are created by drilling a hole into a naturally occurring underground rock salt formation called a “salt dome” between layers of sedimentary rock. Companies then inject water to dissolve the salt and pump out the saltwater solution. This leaves behind an empty space that can be filled with natural gas or other fuels. Companies withdraw from the cavern by pumping in water, forcing the fuel upwards.

In the assessment, FERC’s staff concluded that as long as Enstor obtains all its required permits and approvals and files additional paperwork, the project would not significantly affect “the quality of the human environment.”

Mississippi Storage Hub is one of three salt cavern storage expansion projects proposed recently that would together add about 58 billion cubic feet of underground storage capacity, or about 8 percent more than that amount currently stored this way in the U.S. The other two are in Beaumont and Pecos County, both in Texas.

FERC is accepting comments on the environmental assessment by 5 p.m. Eastern on Nov. 29, 2024. See the public notice for more information.