Hales Bar Dam: Many Firsts and Many Lessons

In 1905, the Chattanooga and Tennessee River Power Company began construction of the first privately-owned dam in the United States to span a major, navigable river: The Tennessee. Hales Bar Dam was intended to alleviate notorious navigation issues in the Tennessee River Gorge downstream of Chattanooga and generate hydroelectric power. Construction was to take place at a site chosen for its topography; geologic investigation was considered unnecessary on the presumably sound Bangor Limestone. Eight years, five contractors, and 109 deaths later, the landmark dam and record-breaking lock facility were completed. A troubling death toll and leakage of up to 1,700 cfs, which equates to 10% of the average river flow, remained. By 1963, under the ownership of TVA, continued modification and remediation efforts of Hales Bar Dam were deemed impractical. The once record sized lock was insufficient for contemporary river traffic and despite extensive geologic mapping and geotechnical repairs, the leakage was nearly as significant as the leakage observed in 1913. Hales Bar Dam was replaced by Nickajack Dam six river miles downstream in 1967. Hales Bar contributed two generating units to the new dam, but the lock and spillway were demolished to clear the navigation channel. Its legacy helped shape current safety and site exploration practices and is a case worth studying for dam safety engineers looking to the future.