Midwestern Dam Rehabilitation with Artesian Conditions… What could go wrong?

Lake Katharine Lake was impounded in 1945 when a dam was built on Rock Run Creek in Jackson County, Ohio. The homogenous soil embankment dam is approximately 24 feet tall with a 30-foot wide and 260-foot-long crest. The primary spillway features a 24-foot-wide rock cut along the left abutment. In 2023, the Ohio Department of Natural Resources (ODNR) hired an engineering consultant to investigate the condition of the dam, evaluate the spillway capacity, and develop rehabilitation alternatives. Findings from the investigation included an upgrade to a high hazard classification, identification of artesian conditions at the toe of the dam, and a recommendation to provide overtopping protection in lieu of increasing the spillway capacity to pass the design flood. Ohio law requires that a high hazard dam must pass 100% of the Probable Maximum Flood and Lake Katharine dam was found to only pass about 17%. Articulated concrete blocks (ACBs) and roller-compacted concrete (RCC) were considered for overtopping protection but ultimately the RCC design was selected. During construction additional borings and piezometers were installed to monitor the phreatic surface and artesian conditions. Construction saw several challenges including site access to the remote dam site, the need for an on-site RCC batch plant, complex management of groundwater, and working within an ecologically-sensitive environment.