The Mill Creek will soon flow freely from its headwaters in Butler County down to the Ohio River once again.
For decades, low head dams that enclose sewer lines have obstructed the creek and prevented fish from migrating upstream.
Now, the nonprofit Mill Creek Alliance is getting ready to modify the largest remaining two dams by building riffles that raise the water level over the structures.
“It returns the stream not to an absolutely pristine state, but to a more natural ecological condition, where all parts of the stream are connected to each other both physically and ecologically,” said Dave Schmitt, executive director of Mill Creek Alliance.
RELATED: A look at the biggest greenhouse gas polluters in Kentucky, Indiana and nearby states
Schmitt says as the creek has been cleaned up from centuries of industrial pollution, populations of fish, crawdads, turtles and other animals have rebounded. But the low head dams remained obstacles for wildlife.
Aquatic life returned shortly after the Alliance built the riffles over the past few years.
“It's like they're waiting for us,” Schmitt said. “As soon as we can mitigate one of these low head dams and clear the path, they appear and they just instantly start moving upstream.”
The two large remaining dams are located in the Mill Creek near Galbraith Road in Carthage and Columbia Avenue in Reading.
There, crews will build new riffles, which Schmitt likens to underwater ramps.
“You bring in a bunch of native rock and you build a very gradual sloping ramp in the stream,” Schmitt said. “The top of your riffle is the same elevation as the top of the dam, and it creates a nice pool of water just below the dam. Fish, turtles and other critters can really just swim up the ramp and keep right on going past the dam.”
Removing the low head dams will also make recreation on the creek safer for people.
Construction is expected to start this year and wrap up by spring 2026.