It wasn’t until 1991 that the dam received what would become its most distinctive feature. That year, as part of TVA’s Lake Improvement Plan, an aerating labyrinth weir was constructed about a mile-and-a-half below the dam on the South Fork Holston River. The aim of the Lake Improvement Plan was to improve dissolved oxygen concentrations in the downstream tailwater, and to increase minimum flow in the tailwater between periods of generation. Both goals would benefit aquatic life, as post-generation tailwaters tend to be cold, dense and oxygen-depleted.
In addition to lake improvement initiatives, the South Holston weir also was designed to provide less backwater on upstream turbines at the dam’s generating unit, and to minimize the intensity of downstream water recirculation such that it would be safe for recreational river users, including boaters and fishermen.