History

The Terrora Hydroelectric Plant is about three river miles upstream from the Tallulah Falls Plant. It is similar in operation, and an equal feat of engineering for the time.

Terrora's history is similar to Burton's in that its dam, Mathis Dam, was built several years before its powerhouse and for the same original purpose: to create a storage reservoir for the Tallulah Falls Plant. Completed in 1915, the 108-foot high by 660-foot long, Ambursen-type concrete dam impounds Lake Rabun. With a water surface of 834 acres and a shoreline of 25 miles, it is the second largest lake in the North Georgia Hydro Group.

It was expected that a powerhouse with two generating units would later be built into Mathis Dam on Lake Rabun. This plan was abandoned, however, in favor of locating the powerhouse at the head of Tallulah Lake, where it could use the water's 190 foot drop in altitude between these two lakes. Ninety feet of this drop was formed by Mathis Dam; 100 feet by the fall in the Tallulah River. (The force of the original river's steep descent here was, in fact, so furious that the Indians called it "Talula" or "Taruri", meaning "the terrible". From this, the name "Terrora" was taken to identify the new powerhouse.)

To best capture this drop, Charles Adsit, the Georgia Power's chief engineer during construction of Terrora, proposed the building of a mile-long tunnel to take the water from Lake Rabun, just above Mathis Dam, to the powerhouse site. The tunnel would be built through a large mountain with shoulders of solid rock.

In the fall of 1923, two crews started blasting through the mountain from opposite sides. Nine months later, on the Fourth of July, 1924, the two teams met. The exact centers of the two tunnel parts at this intersection missed each other by only a fraction of an inch.

The south end of the tunnel connects with a forebay located on the side of the hill above the powerhouse. From the forebay, two steel penstocks - each nine feet in diameter and 900 feet long - pass the water to two 15,000-horsepower water wheels. Each wheel is directly connected to an 8,000-kilowatt generating unit. The two units were completed and placed in operation in 1925. Together, they give Terrora a total generating capacity of 16,000 kilowatts.