Ameren Corp. said Thursday that final approval by state regulators allows construction on its billion-dollar high-voltage power line across central Illinois.

Work on substations for the 380-mile line already are underway and power line construction will begin this year, Ameren said.

Final approval Thursday by the Illinois Commerce Commission of routes and substations allows full-scale work to begin on the line, which will run between Quincy, Ill., and Sugar Creek, Ind. An ICC decision in August determined the need for the 345,000-volt line.

An Ameren subsidy, Ameren Transmission Co. of Illinois, is carrying out the project, called Illinois Rivers. Ameren said Illinois Rivers is its largest transmission project and the longest single transmission line project in Illinois history.

The ICC’s decision Thursday approved final line routes near the Illinois towns of Pawnee, Pana, Mount Zion and Kansas.

Included in the project is a section of high-voltage lines between Quincy and Palmyra, Mo. Steel poles will carry the transmission lines along the entire route to Indiana.