A national energy transmission company is seeking approval to build a pipeline to carry natural gas under the Mississippi River to a proposed new plant.
In early October, Enable Mississippi River Transmission LLC (MRT) filed an application with the Federal Energy Regulatory Commission to construct a 9.5-mile, 20-inch natural gas pipeline under the Mississippi River as part of Ameren’s proposed Big Hollow Energy Center project in southern Jefferson County.
Energy Transfer is a large Dallas-based energy transportation company, moving fuel across 44 states for industrial, utility and commercial customers. MRT, an Energy Transfer subsidiary, operates a 1,675-mile pipeline system that carries natural gas from supply sources throughout the southern U.S. to customers in the St. Louis metropolitan area. The proposed pipeline lateral would connect with MRT’s main pipeline in Monroe County, Ill., and run under the river to the Big Hollow plant now under construction.
Ameren announced in June 2025 plans to develop a gas-fired electricity generating plant on the site of its former Rush Island coal-fired plant in southern Jefferson County, which closed in October 2024. The Big Hollow site will also feature a separate battery storage facility, where excess energy can be stored until needed.
The pipeline project, which includes a measurement and regulation station, will enable MRT to provide up to 107 million BTU of gas daily to the Big Hollow generating facility, according to the MRT application.
FERC has initiated an environmental review process for the project, with an environmental assessment scheduled for release on April 10.
MRT has requested an overall project approval date of Nov. 1. If approved, pipeline construction will start in early 2027, with completion targeted in time for the new plant to go online in April 2028, Ameren officials say.
Questions pertaining to interstate pipeline facility proceedings may be directed to the FERC’s Office of External Affairs at (202) 502-6088 or toll free at 1-866-208-3372, or by mail at 888 First St. NE, Washington, D.C. 20426.
Ameren Missouri supplies power to approximately 1.3 million electric and 135,000 natural gas customers in central and eastern Missouri. The company’s service area covers approximately 60 counties and more than 500 communities, including the greater St. Louis area. For more information, visit Ameren.com/Missouri.