A rendering provided by Ameren shows the proposed Big Hollow Energy Center, which would be developed on the site of the company’s former coal-fired Rush Island Energy Center. The utility hopes to have the facility completed and operational by 2028.
Ameren is looking to build a natural gas-fired power plant and the company’s first large lithium-ion battery facility on the Jefferson County site of its former coal-based Rush Island Energy Center, which closed last year after continuous Clean Air Act violations.
The ӣƵ-based electric utility will call the complex the Big Hollow Energy Center, the company announced late last month. Collectively, the 800-megawatt gas plant and the 400-megawatt battery storage facility would roughly match the generating potential that Rush Island had, taking advantage of the site’s existing transmission capacity and access to the power grid.
“That was the idea,” said Ajay Arora, Ameren Missouri’s senior vice president and chief development officer. “The infrastructure is extremely valuable … certainly the transmission aspect of it.”
The proposed switch to gas at one of its former coal plant sites follows a familiar playbook for Ameren. The utility is also building an 800-megawatt gas plant — called the Castle Bluff Energy Center — for about $800 million at the former site of its smallest and oldest coal plant, the Meramec Energy Center in south ӣƵ County, which closed at the end of 2022.
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The Rush Island plant was used fairly sparingly in its later years — primarily as a “peaker” plant, when power demand was greatest.
Ameren said it intends for the new facility to play a similar role, “as a reliable backup source of energy,” with the gas plant designed to provide power when demand peaks on cold winter days, hot summer afternoons, and to support the grid when renewable generation is unavailable.
Meanwhile, the project’s energy storage component would do much of the same. For instance, the batteries could be charged when cheap, excess energy is on the grid and then used when needed, in any weather conditions.
“Fully charged, the entire array could power thousands of homes for hours and help overall grid reliability, especially during times of peak energy needs,” Ameren said in its announcement.
While the site offers plenty of existing attributes, such as its readymade transmission access, Ameren said that the Rush Island building could not be retrofitted to accommodate the new projects, and that its demolition is already underway.
Ameren still needs approval from state utility regulators before proceeding with its Big Hollow proposal, which it hopes to receive by March. The company then aims to complete the project by 2028.
The utility said that the estimated cost of the project is currently confidential.
‘About time’ for battery storage
Ameren’s plans for the Rush Island site’s redevelopment have elicited some mixed reactions from energy experts — and raised questions about costs.
For example, the company’s push to build new generation and aid grid reliability comes as it says it faces a wave of demand from prospective developers of highly energy-intensive projects, like data centers.
Utilities are fielding similar requests nationwide, although Missouri has not yet seen the explosions in energy demand that so far have been concentrated in scattershot places across the map, such as Virginia, Texas and North Dakota.
Predicting if or when that wave of demand could materialize in Missouri is one challenge that now confronts regional utilities and state regulators, raising questions about how to shoulder costs of energy projects that largely cater to heavy users, and carrying risks of a possible “overbuild” that leaves customers on the hook for hefty investments.
“The question is what supply should be built and how do you pay for it?” said Ashok Gupta, a Kansas City-based energy economist for the Natural Resources Defense Council.
While the payment question will eventually be part of the regulatory review process for Ameren’s Big Hollow proposal, it is also being broadly examined and debated in separate cases before the Missouri Public Service Commission. For example, outside groups and watchdog agencies that police utility spending will soon weigh in on cases about how to serve large-load customers seeking power from the state’s biggest electric utilities: Ameren and Kansas City-based Evergy.
Federal energy policy whiplash out of Washington now “makes the calculus even harder” in determining what to build and when to build it, Gupta said, as tax credits for wind and solar projects are now set to lapse within a couple years — projects that represent the bulk of new power generation in the U.S.
But costs at Big Hollow could at least partially be reduced by federal tax credits for battery storage projects. Unlike the tax credits for wind and solar, those for battery storage projects were spared the widespread cuts contained in the massive spending bill passed by Congressional Republicans this month, and signed by President Donald Trump.
Some, like Gupta, cheered the battery portion of the proposed project.
“It’s about time,” said Gupta, noting that storage can nicely complement renewable energy and smooth out issues with intermittent generation, whenever solar or wind generation stops or slows. “It’s exciting, it’s necessary.”
Ameren said its battery investment aligns with industry trends and that it can learn from other utilities that adopted the technology earlier.
“A lot of our peer utilities are investing heavily in batteries,” said Arora, the Ameren senior vice president. “The technology has matured.”
The proposed gas plant faces questions from some, for reasons beyond making a large financial investment in fossil fuels that contribute to climate change.
Gas has had issues with reliability and affordability at times, particularly in the extreme weather conditions when peaker plants are needed, as illustrated during Winter Storm Uri in 2021, when gas plants faltered and fuel prices skyrocketed.
And building gas plants, themselves, has become considerably more expensive in recent years, with costs tripling amid high demand and long waits for gas turbines, said John Ketchum, the CEO of NextEra Energy, a giant Florida-based utility, at recent energy conferences in and .
Gupta, of the Natural Resources Defense Council, questioned Ameren’s choice to pursue a simple-cycle gas plant — a less efficient alternative than combined-cycle gas plants, which recover exhaust heat and use it to generate additional power.
“You’re gonna burn all this gas. Let’s get as much energy as possible,” Gupta said.
Ameren, though, said that simple-cycle plants are better for peaker plants, rather than those relied on for baseload power generation.
Some would also prefer to see more emphasis on energy efficiency, rather than focusing on building new power plants.
“The lowest-cost resource is still energy efficiency,” said Gupta. “We should be doing hundreds if not thousands of megawatts of energy efficiency to keep energy affordable.”
Filling the void
The proposed next chapter for the site would mark the coda to Rush Island’s unique — and criminal — background. Between 2007 and 2010, Ameren illegally modified the plant’s generators near the end of their intended lifespan without obtaining permits — enabling them to produce more energy and emit more air pollutants, and sparking a decade-plus lawsuit from the U.S. Department of Justice.
The plant was one of a dwindling number of U.S. coal plants that did not have widely adopted pollution controls, called scrubbers, that remove sulfur dioxide, or SO2, from emissions. Ameren’s biggest coal plant, the Labadie Energy Center west of ӣƵ, also lacks scrubbers and emits far more SO2 than any other U.S. coal plant.
A judge in the marathon legal case over the plant’s air pollution sought to have the company offset Rush Island’s illegal SO2 emissions by reducing Labadie’s emissions by an equal amount. But an appeals court scrapped that order, saying that Ameren was never given notice of an alleged Clean Air Act violation at Labadie — despite the fact that the Environmental Protection Agency had issued “Notices of Violation” to the company about that very issue at Labadie, years ago.
The company ultimately reached an agreement to pay $61 million for electric school buses and charging equipment, as well as the distribution of air purifiers to residential customers, prioritizing low-income households.
The new plans for the site bring potential relief to local leaders dealing with lost tax revenue from Rush Island’s closure. For instance, the Jefferson R-VII School District will see a budget reduction of $1.1 million in the upcoming school year, thanks to the plant’s retirement.
“It’s a tough number to look at,” said David Haug, the district superintendent.
But the site’s planned redevelopment figures to eventually bring the money back. And it would provide longer-term certainty and stability compared to Rush Island, with Haug saying it felt as if the “clock was ticking” throughout the aging plant’s later years, as both the facility and the school district’s finances faced an unclear future.
“It was certainly a good day when we became aware that this was official,” Haug said. “This is a big, long-term win for the district.”
Post-Dispatch photographers capture tens of thousands of images every year. See some of their best work that was either taken in June 2025 in this video. Edited by Jenna Jones.
