A new spill gate at one of TVA’s oldest dams will allow better access and greater safety through more accurate inspections.
FEBRUARY 25, 2019 — One of TVA’s oldest dams has recently been outfitted with a new spill gate to allow more thorough inspections so that it meets TVA dam safety standards and operates safely and as intended.
Nolichucky Dam was built in 1913 and acquired by TVA in 1945. Located on the Nolichucky River just southeast of Greenville, Tennessee, it impounds Davy Crockett reservoir. The dam stopped generating hydropower in 1972. After ongoing maintenance issues, its spill gate was permanently closed by installing a reinforced concrete bulkhead on its upstream side.
As years passed, TVA’s increased focus on dam safety called for more thorough inspections, which were not possible with the spill gate sealed and water continuously spilling over the dam. TVA’s Dam Safety engineers determined that a new spill gate was needed to drop the reservoir so that the dam could be closely inspected for deterioration and scour.
A joint project team effort between TVA organizations began with Dam Safety designing the 12 feet tall and 25 feet wide gate and its electrical and mechanical systems. TVA Environmental Compliance and Operations organization completed an environmental assessment. TVA Power Services Shops built the new gate in Muscle Shoals, Alabama, refurbished existing mechanical components and transported it to the Nolichucky site. TVA Generation Construction Projects & Services and Facilities team oversaw all project management duties and construction activities, including removal of the existing gate/concrete bulkhead.
One challenge in particular had to be met: moving the 40,000 pound gate 120 feet across the dam and fitting it with exacting precision into the existing spillway slot.
“Using an overhead crane was not possible due to the size of crane needed to lift and set the 40,000 lb. gate, large trees that could not be disturbed and a small area to work with,” said Darrell Moses, GCPS&F construction manager for the project. “We worked with the Power Services Shops to devise a plan to build a rail on top of the dam to safely lift and move the new gate to the spillway gate slot.”
The TVA teams collaborated successfully to build a custom designed rail and lift to make the work possible. Jim Bryant, senior program manager for Dam Safety, explained, “All of the design work, fabrication, and labor for the gate was done in house by TVA. It truly took a team to remove the existing 40,000 pound gate and to devise a plan to create and install a new, working gate. Now we can add an important routine inspection at our dam, which was not accessible to us before.”
Moving the gate still had its challenges, as the team had to deal with high winds for four days before they could get the gate to the slot in a safe manner. But the new gate was installed safely on January 25 and is expected to be operational by mid-February. Dam Safety inspections of the dam for assurance and safety will follow shortly after.
“This project is a testimony to TVA’s talents,” said Dolly Novak project manager for the Nolichucky project. “Everyone worked together to create the best possible product.”
TVA also performs monthly, biannual and annual inspections of all of its river dams to identify any potential issues or concerns. More thorough detailed inspections are performed every five years by a diverse team of dam safety subject matter experts, operators and inspectors. The inspections may also include testing of electrical and mechanical equipment, and rigorous structural and geological assessments.
TVA has spent about $400 million since 2010 on Dam Safety. That includes current projects at Nolichucky, Boone, Pickwick and other sites.