Built to Last

Hydro Project Helps Ensure Reliability, Resiliency

At Watauga Dam in northeast Tennessee, the river enters a gorge bordered by steep, rocky bluffs that rise upwards of 700 feet above the riverbed.

This striking terrain is home to TVA’s tallest earth and rock-fill dam.

Integral to the dam’s operation is an 18-foot-wide pipe that carves its way 3,700 feet through Iron Mountain, a subrange of the Blue Ridge Mountains. Called the “power conduit” in technical reports from 1948, the pipe is today referred to as a penstock.

It carries water from the lake above to the powerhouse below – the vertical drop creating an immense amount of pressure and, ultimately, more megawatts.

As the penstock nears the powerhouse, the diameter gets smaller and the penstock splits into two lines. That’s where the water meets the butterfly valve, a large circular disk inside the water pipe that rotates on a central axis to block or allow flow.

Watauga is currently undergoing a comprehensive reliability and safety upgrade across several projects: refurbishing wicket gates and bushings, modernizing electrical components and completely replacing two 11-foot butterfly valves.

“There’s an original photo showing them sliding the valve into place,” said Jordan Clark, Generation Projects construction manager. “These brown and blue books give a detailed explanation of how they constructed this plant and some detailed drawings.”

The historic blue books and brown books are TVA’s original plant documentation – collections of construction drawings, engineering notes and historical records that show how facilities like Watauga were designed and built. They contain invaluable archived knowledge, preserving detailed information about components, installation methods and early construction techniques. Crews still use them to understand original design intentions and confirm historical measurements that guide modern rehabilitation work.

The original design riveted the butterfly valve to the penstock, so the team had to cut the entire pipe to remove the old valve.

“We shifted from rivets to bolted dismantling joints so the valve can be removed without cutting,” said Thomas Bell, project manager. “We are designing for the future and maintainability.”

Whether responding to storms, upgrading aging assets or managing water flows across the Valley region, the goal is always the same: reliability.

“Managing the river system is complex,” Bell said. “It’s important that we never take it for granted. This team does a great job keeping everything running smoothly."