The nine low head dams present in the 46.1 river miles of the lower Mahoning River (from PA/OH border up to Leavittsburg dam) have been impounding the river for several decades, altering the river habitat significantly (USACE, 2006). Several studies have been done by federal and state agencies such as the United States Army Corps of Engineers (USACE) and Ohio Environmental Protection Agency (OEPA) to determine the levels of sediment contamination, fish contamination, sources of contamination and the volume and cost of sediment dredging as well as dam removal.
Studies of the dams and their upstream pools were performed by a literature review, field visits, dam removal cost analysis and a HEC-RAS simulation for the lower Mahoning River water profile for pre- and post-dam removal conditions. The outputs of the study were used to rank eight of the nine low head dams using a rating system based on three major criteria - economics, environmental and other factors. Leavittsburg dam was not included in environmental criteria and two sub-criteria of other factors due to lack of sufficient information for HEC-RAS simulation. Ranking scores were allocated to each dam based on a weighted significance of the criteria with a maximum possible total of 100 points.
The free flowing and impounded river length for each of the eight dam pools were predicted using the HEC-RAS outputs. The improvement in the fish population (Index of Biotic Integrity) and potential for bridge pier scouring after dam removal were also predicted from HEC-RAS output. The Struthers dam was predicted to have the highest priority for removal, followed by the Girard Liberty St. dam and Crescent St. dam, while the Warren Summit St. dam showed the lowest priority for removal.