Bagnell Dam and Osage Energy Center at Missouri's Lake of the Ozarks will get a $52 million upgrade starting this spring.
Ameren Missouri said Tuesday that new anchors and concrete will be installed on the downstream side of the dam that provides power to 42,000 homes.
Ameren officials say the last major structural update at Bagnell Dam was completed more than 30 years ago.
The new project is expected to take about 18 months. Ameren says the new anchors will help hold the dam to underlying bedrock, and more than 66 million pounds of new concrete will be added.