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Mark Twain Transmission Project High Voltage Line Completed

Press Release from the Ameren Corporation

ST. LOUIS (Jan. 6, 2020) – Ameren Transmission Company of Illinois (ATXI), a wholly owned subsidiary of Ameren Corporation (NYSE: AEE), has completed and energized the Mark Twain Transmission Project, a 96-mile, 345,000-volt transmission line and substation in northeast Missouri. The line travels west from Palmyra to Kirksville, Missouri then north to the Iowa border.

The Mark Twain Transmission Project is now providing local and regional benefits, including improved energy grid reliability, increased transmission capacity and greater access to lower cost energy, including renewable sources, such as wind.

“The Mark Twain Transmission Project benefits are many,” said Shawn E. Schukar, chairman and president of ATXI. “In addition to making the energy grid more reliable and promoting renewable and affordable energy such as wind, it will meet energy needs not only for today but well into the future.”

The $267 million project, which includes the Zachary substation in Adair County, Missouri, was placed into service as expected on Dec.19, 2019. Efficient project execution, which included the use of helicopters to install the transmission line, reduced landowner impact and improved construction efficiency.

“The speed and efficiency with which this line was developed and constructed can be attributed to the ongoing collaboration and strong communication efforts we had with landowners, community representatives and Northeast Missouri Electric Power Cooperative,” Schukar said. “Because of our focus on communication, our contract partners were able to quickly move forward on key construction phases, meet crucial deadlines and now energize this important infrastructure project that bolsters the energy grid.”

The Mark Twain Transmission Project has helped enable wind projects under development in Missouri that will provide lower cost energy to the grid, allowing the benefits of this project to far exceed the project costs.

In January 2018, The Missouri Public Service Commission granted ATXI a certificate of convenience and necessity for the project that is now a critical link in the region’s energy infrastructure.

The Mark Twain Transmission Project was approved in 2011 by the Midcontinent Independent System Operator, Inc. (MISO), a regional transmission organization. The project is part of a coordinated, multi-state group of transmission projects – known as Multi-Value Projects – being developed by transmission owners in MISO to improve and strengthen the regional energy grid. Other ATXI Multi-Value Projects include the Spoon River Project in Illinois, which was completed in February of 2018, and the Illinois Rivers Project, with an anticipated in-service date of December 2020.