Anchor Dam
Highways 120 & 170, 35 miles west of Thermopolis

Anchor Dam, a 200-feet high, thin-arch concrete dam, located approximately 35 miles west of Thermopolis Wyoming, was constructed by the Bureau of Reclamation at a cost exceeding $5 million dollars during the dam building boom of the 1950s and 1960s. Sinkholes and earth fissures within the reservoir area continuously allowed drainage of the reservoir before, during and after construction. Additionally, attempts to plug solution-widened fractures in carbonate strata within the Pennsylvanian Tensleep Formation, which comprised the abutments, resulted in expensive change orders during construction. The reservoir and dam were doomed from the onset. Water continues to leak through the Madison limestone formations, preventing it from filling all the way. Efforts to improve its ability to hold water have reached the point it is able to be filled about halfway in some years.