Nantahala Power and Light's West Fork Tuckasegee River Project

This project consists of two developments, Thorpe and Tuckasegee, on the West Fork of the Tuckasegee River, in Jackson County, NC. Thorpe impounds the second largest lake of NP&L's system, Lake Glenville. It is a diversion dam, and just downstream of its powerhouse is the Tuckasegee Dam, also a diversion dam. This project was built by NP&L: Thorpe was started in September 1940 with first generation in October 1941. Tuckasegee was started in April 1949 with first generation May 1950. The project was originally licensed by the FERC (#2686) in 1981.

Thorpe Dam is a rockfill dam, 900 feet long and a maximum of 150 feet high. A rockfill saddle dam adds another 410 feet to the structure; it tops out at 122 feet high. Lake Glenville is 1,462 acres at normal full pool of 3,491.8 feet MSL. Volume is given as 72,000 acre-feet, drainage area is 36.7 square miles and normal infow is 115 cfs.

The spillway has two 25 foot wide by 12 foot high Tainter gates, and six erodible fuse plugs.

Just after the spillway is an abrubt dropoff, which seems to be common in this area!

The diversion conduit is a combination of tunnels and steel pipe totaling 16,287 feet in length. We believe this houses the controls for the intake to the conduit, below is a section of the pipe close to the dam.

The Thorpe Powerhouse is one of the prettiest you will see. Apparently it is being considered for a Historic Site declaration because of the architecture, and Duke evidently spends a little extra time keeping it looking nice. The exterior is the cleanest we have ever seen on any powerhouse, and I don't think I saw any broken windows. And, the lawn looks a lot better than ours!

Thorpe has a single turbine/generator thats good for about 21.6 Megawatts at 1,150 feet of head. Now, where did they come up with 1,150 feet of head?? If you look at the difference between the full pool levels of the two lakes, you come up with about 710 feet of head, and since the Thorpe powerhouse is upstre am of Tuckasegee Lake, its probably even less than that. The "authorized intalled capacity" is 15.5 megawatts. The "dependable capacity" is given as 5 Megawatts for Thorpe, and 0.6 Megawatts for Tuckasegee.

The Thorpe Switchyard handles the output of both Thorpe and Tuckasegee Dams. Apparently the Tuckasegee power is brought here at generator voltage (6.6 KV) before being stepped up for distribution, probably at 161 KV.

Tuckasegee is a concrete thin-arch dam, about a half mile downstream of the Thorpe Powerhouse. It is 254 feet long by 61 feet high, topped with steel "flashboards" and a trashgate. The reservoir is 7.9 acres at full pool of 2778.75 feet MSL. Useful storage is given as 35 acre-feet. The drainage area is 54.7 square miles and normal inflow is about 158 cfs.

The intake to the tunnel is on the far side of the dam. The tunnel is 3,246 feet long.

We didn't get the power house on this trip... we were in traffic as we drove by (i.e. there was a car behind us!). The single turbine/generator can produce up to 3 megawatts with 365 cfs at 118 feet of head.