The regional operator Midcontinent Independent System Operator (MISO) selected a consortium comprising Ameren Transmission Company of Illinois (ATXI), GridLiance Heartland, Dairyland Power Cooperative, and the Illinois Municipal Electric Agency (IMEA) to develop two major electric transmission projects in Illinois valued at approximately $1.658 billion.
The projects are part of MISO’s long-range transmission expansion plan and aim to strengthen the reliability of the U.S. Midwest electric system through a new 765-kilovolt (kV) transmission backbone.
Two transmission projects for the Midwest grid
The first project, called Sub T – Iowa/Illinois State Line – Woodford County (STIW), involves the construction of two 765 kV transmission lines spanning approximately 149 miles. The infrastructure will connect the Woodford County substation in Illinois with the Sub T substation in Iowa.
MISO estimates that this project will require an investment of around $940 million.
Meanwhile, the Woodford County – Illinois/Indiana State Line (WIIL) project includes two new 765 kV transmission lines spanning about 88 miles, along with a new 765/345 kV substation. The estimated cost is $718 million.
Both projects are scheduled to enter operation in 2034 after completing regulatory and community engagement processes.
Ameren and GridLiance will lead the development
ATXI and GridLiance will lead the development and execution of the works, while Dairyland and IMEA will participate as partial owners once the projects enter service.
The agreed ownership structure includes 43% stakes for ATXI and GridLiance, respectively, while Dairyland will hold 11% and IMEA 3%.
Shawn Schukar, President of ATXI, noted that the partnership will enable critical infrastructure to be built efficiently while supporting regional energy growth.
Likewise, Matt Valle, President of NextEra Energy Transmission, emphasized that the projects will be essential to building a more resilient transmission grid prepared to respond to rising energy demand in the Midwest.
Key infrastructure to integrate new energy resources
Expanding the transmission grid has become a priority for U.S. electric operators due to growing energy consumption and the integration of new generation sources.
In this context, the projects selected by MISO will improve interstate power transfer capacity while also strengthening the operational stability of the regional system.
Dairyland Power Cooperative underscored that the infrastructure will provide greater flexibility and reliability for future generations, while IMEA highlighted the strategic role of transmission in supporting Illinois’ economic development and energy resilience.
MISO accelerates modernization of the regional electric system
The STIW and WIIL projects are part of Tranche 2.1 of MISO’s Long Range Transmission Planning, approved in December 2024. This initiative seeks to adapt the Midwest power grid to scenarios of greater electrification, industrial growth, and expansion of renewable energy.
With this decision, MISO moves forward in building a high-capacity transmission grid capable of meeting the energy needs of the coming decades in one of the most important industrial regions of the United States.
Source: NextEra Energy
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