Old Lyme — Repairs to the Rogers Lake Dam that began this summer are slated to be completed by the end of September.

The project will install a new fish ladder for migrating alewives and replace the dam’s damaged slide gate.

Twelve years ago, the then-Department of Environmental Protection said the dam needed to be repaired. The town has since been awarded a Small Town Economic Assistance Program grant and received funding from the Connecticut River Watershed Council for the repairs.

The town has notified nearby residents by letter that the repairs will entail lowering the Rogers Lake water level at times by about 10 inches to possibly up to 18 inches, according to First Selectwoman Bonnie Reemsnyder.

Reemsnyder explained at last week’s Board of Selectmen meeting that repairing the dam during the summer avoids such risks as storms in the fall or having to pour concrete in cold weather.

“Once repaired, we hope we won’t have to deal with this again in our lifetime,” she said.