|An Ancient Method for Modern Times
The Saluda Dam was built of earth because of the soil types that existed in the Dreher Shoals area. Clay soils were ideally suited for the project and readily available in the area near the site. History had shown that earthen dams could stand for centuries. In fact, nature creates her own water-proofing of mud banks under the right conditions, and these conditions existed on the Saluda River.
The first step in the construction of the Saluda development was the preparation of the area in which the "penstocks" and "arch conduit" were to be laid. This was along the north bank of the river and to protect it from high water, a dike some 3,500 feet long was first erected. The entire area was then excavated down to bedrock. In those portions to be occupied by the penstocks, the rock itself was mined to an average depth of about eight feet. When the trenches provided for the penstocks had been completed to grade, concrete "saddles" to support these structures were poured.
|February 11, 1928. After excavating to bedrock, forms for the concrete "saddles" were built.|
The Five Famous Towers
Anyone who has ever crossed Saluda Dam or traversed Lake Murray's "big water" via boat, has seen the five famous towers. These round landmarks are intakes rising 223 feet high. The four smaller towers provide water from the bottom of the lake into the 986-foot-long penstocks. Each penstock is 16 feet in diameter and is built of steel plates sewn together with over 220,000 rivets.
The largest tower feeds water to the massive arch conduit which diverted the river during construction, and afterwards, served as the course for an additional penstock to supply a future turbine.
|Photos of the five, 223-foot towers taken on June 14, 1929 and September 30, 1930. The arch conduit, located under the largest tower, carried the Saluda River's flow during construction.|
The arch conduit has an internal diameter of 48 feet and varies in thickness from about 5 feet to 9 feet. The internal diameter is 20 feet greater than the diameter of New York's Holland Tunnel. In Saluda Dam's arch conduit, six automobiles could drive abreast through its course.
|Workers pose under the arch conduit. Six automobiles could drive abreast through its course. Today this structure is used to draw water from the bottom of Lake Murray.|
Water is drawn from the bottom of the lake into each of the four intake towers. At the bottom of the tower located on the upstream side, trash racks 75 feet high are installed. Inside the racks on the center line of each of the four small towers are a pair of 9-foot by 14-foot "Broome roller gates," weighing 16 tons each. Each pair of gates is operated by a 234-ton hoist. A small brick operating house was built on the top of each tower to house the hoisting equipment. An aerial cableway connects the towers to the mainland.
The fifth tower has a maximum outside diameter of 60 feet and is also 223 feet tall. Six Broome roller gates are installed in this tower. It took 636,000 bags of cement, 122,012 tons of gravel, 62,000 tons of sand, 3,987 tons of steel plate, 329 tons of reinforcing steel, and 1,407 tons of structural steel to construct the five towers. In 1971, SCE&G added a fifth turbine and generator to Saluda Hydro using this larger tower and a new penstock to supply the water. The fifth turbine can generate more than twice as much electricity as any one of the plant's original four.
99 Acres of History
Saluda Dam covers an area of about 99 acres which was completely cleaned of boulders, sod and loam. Wherever bedrock was encountered, such as in the river, all pockets found in the rock were scraped, cleaned and filled with compacted material in the same manner that a dentist would treat a cavity in a tooth.
When completed in 1930, the dam was 208 feet high and nearly a mile and a half long. The maximum width of the dam at the bottom was 1,150 feet and at the crest was 25 feet. During construction, 11,000,000 cubic yards of earth fill had to be placed, requiring 60,000 feet of trestle work and 30 miles of railway tracks.
Earth fill was excavated from "borrow" pits adjacent to the dam site by means of 12 steam-shovels which loaded it onto trains. The transportation equipment consisted of 17 standard gauge locomotives, two narrow gauge locomotives and 180 dump cars. With an average haul of about a mile from the borrow pits to the dam, the daily transportation totaled about 300 train loads or 2,000 cars.
The dam was built in three sections. The upstream and downstream sections, each comprising about a third of the fill, were of ordinary earth with the center of clay placed and packed hydraulically. Work began with two sections of fill being placed 1,000 feet apart and raised until they were 75 feet high.
At this stage, the area of the basin between the two fills was pumped full of water to create a "segregation pool." This pool thereafter was maintained by pumping enough water to take care of evaporation and seepage.
Atop the segregation pool patrolled five scows, each equipped with pumps and a giant nozzle. As trainload after trainload of dirt was unloaded, the scows sprayed 750 gallons of water a minute against the banks at a velocity of 125 feet per second. This process washed down the fine material into the pool, where it deposited to form a dense core for the dam.
Near the top, these sluicing operations were stopped. The final 30 feet were built from selected soils. The upstream face of the dam was then rip-rapped (layered with stone) and on the downstream face 100 acres of Bermuda grass were planted to prevent erosion.
Originally, the dam's spillway was equipped with four Tainter gates, each 37 and-a-half feet long by 25 feet high, which were placed across a gully 500 feet from the Lexington side of the dam. Discharge from the spillway re-enters the Saluda River channel about 3/5 of a mile below the powerhouse. Between 1943 and 1946, the spillway was enlarged. Two additional gates were added and the dam was strengthened by raising the crest three feet. Each November, these spill gates are tested as required by the Federal Energy Regulatory Commission, creating quite a display.