An Energy Transfer subsidiary wants permission to drill beneath the Mississippi River south of St. Louis so a new natural gas lateral can feed Ameren Missouri’s planned Big Hollow Energy Center at the former Rush Island power plant site. The company has asked federal regulators to sign off on a roughly 9.6 mile, 20 inch pipeline that would hook into existing mainlines in Monroe County, Illinois, then cross under the river into Jefferson County, Missouri. If approved, the lateral would supply fuel to Ameren’s proposed 800 megawatt gas plant and co located 400 megawatt battery installation.
The application comes from Enable Mississippi River Transmission LLC, which is seeking a Certificate of Public Convenience and Necessity from the Federal Energy Regulatory Commission, according to a notice in the Federal Register. Local outlets first spotted the filing this week, with KSDK noting that Leader Publications reporter Laura Marlow has been tracking the proposal on the ground. Federal documents describe the project as the gas supply line that would feed Ameren’s Big Hollow facility.
What the project would look like
In its filing, EMRT lays out plans for a roughly 9.6 mile, 20 inch lateral that would include a measurement and regulation station and related facilities such as a pig launcher and receiver. The line would tie into Mainline 2 and Mainline 3 at Mile Post 415.5 in Monroe County, Illinois, then cross beneath the Mississippi into Jefferson County, Missouri. As reported by Pipeline & Gas Journal, construction would follow a standard right of way buildout along the route and a dedicated under river crossing. Company materials outline a broader, temporary construction disturbance area that would shrink to a smaller permanent easement once the line is in operation.
Ameren’s plant and recent approvals
Ameren Missouri unveiled the Big Hollow Energy Center in June 2025 as an approximately 800 megawatt simple cycle natural gas facility paired with a roughly 400 megawatt battery energy storage system at the former Rush Island coal plant site, according to Ameren Missouri. On February 11, the Missouri Public Service Commission approved state level certificates of public convenience and necessity that clear a major regulatory hurdle for the Big Hollow project, according to the commission’s announcement. Ameren says reusing the Rush Island property will bolster grid reliability, create construction jobs and take advantage of existing transmission infrastructure.
Environmental review and local concerns
FERC staff plan to prepare an environmental assessment, or EA, for what is described as the Ameren EMRT Big Hollow Project. The EA is expected to be released for public comment on April 10, 2026, with a 90 day federal authorization decision deadline of July 9, 2026, according to the Federal Register. During the scoping period, the Illinois Department of Natural Resources and nearby landowners raised concerns about air emissions, noise and potential impacts on protected conservation lands. FERC says staff will take up those topics in the EA. The schedule sets up a relatively tight window for regulators and the public to review technical studies and file comments before agencies issue final decisions.
Who is behind the pipeline
Enable Mississippi River Transmission LLC is part of Energy Transfer, the Houston based midstream company that operates a wide interstate pipeline network and filed the proposal through its MRT regulatory channel, according to Energy Transfer’s pipeline information. Industry coverage has described EMRT’s project as a commercial lateral designed to serve Ameren’s planned generating capacity while linking into existing southern supply basins and regional transmission infrastructure. The project paperwork and related regulatory filings are moving through Energy Transfer’s established processes.
What is next for review and landowners
With the environmental assessment scheduled for April, FERC’s review will include a public comment period and coordination with state and federal agencies. Landowners and other interested parties can sign up for updates and submit filings through the FERC eLibrary and eSubscription systems. The federal notice also reminds landowners that the company will seek easements and that, if negotiations fail, the pipeline operator could pursue condemnation under the Natural Gas Act, a standard but often contested step for interstate gas projects. Local officials have highlighted potential construction jobs and reliability benefits, while environmental and community advocates say they intend to scrutinize construction and route impacts during the comment period.
Local reaction and the bigger picture
The proposal arrives as Ameren works to repurpose the Rush Island site following the coal plant’s retirement in 2024, a shift the utility says will help maintain grid reliability while moving its portfolio away from coal, according to company materials and local coverage. Regional reporting on the Missouri PSC decision and community response is available from Spectrum Local News and other outlets. Residents and stakeholders who want to follow the federal process can track Docket No. CP26 2 000 to review filings, watch the environmental review schedule and submit comments before the April window closes.
