Large Steel Penstock Relining: The Blue Ridge Dam Rehabilitation

The original Blue Ridge Dam riveted steel penstock was constructed in 1925 and was 168-in diameter and approximately 1050-ft long. Within the penstock was a concrete filled steel cased girder which divided the penstock in two halves for a distance of 160-ft and weighed an estimated 300 tons. The primary components to this relining project involved removal of the girder, removal of a 60-ft long bulge in the floor, and installation of a new steel penstock liner. The new penstock liner was 147-in diameter x 1-in to 0.875-in wall thickness. The project had a critical time line as the emptied penstock was anticipated to become unstable if the reservoir level increased to the regular summertime levels. This paper describes novel remedies required for difficult conditions, including the need for careful coordination of the penstock layout to compliment the means and methods, and assure the rehabilitation could be concluded prior to the increased reservoir levels. Partnering between the owner, designer and contractor (s) was crucial to meeting the milestone requirements of this project.