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Map: Ameren's regional multi-value projects

A transmission line has finally been given the green light in Missouri.

It's not the high-profile, 780-mile Grain Belt Express line that has hit snag after snag in its years-long quest for regulatory approval. Instead, Ameren's subsidiary, the Ameren Transmission Company of Illinois, has been granted permission to proceed with its 100-mile Mark Twain Transmission Project in northeast Missouri, the state Public Service Commission ruled Wednesday.

The company aims to have the $250 million project in service by December 2019. Construction is planned to begin in April.

The PSC said its approval was supported by several factors. The commission ruled that the project's benefits will outweigh transmission charges, it will likely lower electric rates in the state, and will help the state meet renewable energy goals by enabling the integration of wind power. It also said the project will generate "significant" property tax revenue for the rural counties along its path.

The project's route will run from Palmyra to Kirksville and north to the Iowa border. In a statement released following the decision, Ameren said it completes "a critical link in the region’s energy infrastructure."

The PSC's decision was the final hurdle the project had to clear. It had already satisfied the more challenging requirement of gaining local approval in counties along its path back in September.

It will pass through Marion, Knox, Adair, Schuyler and Lewis counties, "mostly via existing transmission easements" according to the PSC.

The Mark Twain project had previously been stalled by a court ruling that established local approval as a prerequisite for assent from the PSC. The PSC invoked that ruling in its latest denial of the Grain Belt Express line — a decision many critics have said sets a flawed legal precedent that will deeply complicate efforts to approve future infrastructure projects in the state.

Reporter covering energy and the environment for the St. Louis Post-Dispatch.