Corps Clears Next Phase of Modifications to Rough River Dam in Kentucky

The U.S. Army Corps of Engineers estimates the cost of the project at between $320 and $655 million

The U.S. Army Corps of Engineers Louisville District gave the go-ahead for the second phase of the Rough River Dam Safety Modification project in southwest Kentucky that aims to restore the dam’s long-term structural integrity and safeguard downstream communities in the largely rural area.

The Phase 2 base $320-million firm fixed-price contract to Thalle-Bauer LLC., Hillsborough, N.C., includes options that could increase its total value to $655 million, according to the Corps. Groundbreaking for the project, 95 miles southwest of Louisville, is set to take place this spring and construction would take up to seven years.

Thalle-Bauer will construct a new outlet works on the dam’s left abutment, including a new control tower and stilling basin connected by a tunnel. Once the new outlet works is operational, a cutoff wall will be constructed across the crest of the dam, varying in depth from 75 ft to 180 ft. The project’s final portion relocates Kentucky State Highway 79 to the top of the dam.

Constructed between 1955 and 1961, the Corps-maintained 1,590-ft long, 135-ft-high embankment dam, creates Rough River Lake, a 5,100-acre recreational lake that’s the centerpiece of a state-operated park. Following a 2012 report that highlighted unacceptable risk due to the dam’s foundation being constructed on karst geology, the Corps launched a multi-phase rehabilitation effort.

Karst geology is a type of landscape formed when water dissolves soluble rock, most commonly limestone, but also dolomite or gypsum. Over long periods of time, slightly acidic rainwater and groundwater eat away at the rock, creating distinctive landforms both above and below ground such as sinkholes, caves and caverns, disappearing streams, springs and thin, rocky soil.

Phase 1, completed in May 2017, included relocation of the road across the dam’s crest, and exploratory drilling and grouting across the structure’s centerline.

According to the Corps’ project page, subsequent instrumentation and visual observations indicated continuing foundation deterioration, leading to the 2023 implementation interim risk reduction measures, such as lowering reservoir water levels to relieve pressure on the dam, pending completion of long-term repairs.

Extreme flooding in April 2025 caused water from the dam to flow into the spillway, but the Corps said it was tracking the event.

"Due to known concerns with the foundation of the dam, lowering the frequency of events [such as flooding] that stress the structure is our goal," said Jackie Henn, dam safety program manager for the Corps, at the time.

She said that automated instrumentation systems allow the Corps to monitor the integrity of the dam at all times.