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Design of Bluestone Dam

Final design of Bluestone Dam was carried out by the Engineering Division of the Huntington District under the direction of the Huntington District Engineer, who was assisted by a "board of eminent consultants." Preliminary studies considered a number of design alternatives, all of which were concrete masonry dams of various design types. In the end, the Board of Consultants and others involved in the project agreed on a straight gravity type dam. The U.S. Army's Chief of Engineers approved the final design.

Numerous flood control dams built by the U.S. Army Corps of Engineers in western Pennsylvania, Virginia, and West Virginia during the 1930s and early 1940s were massive gravity dams. A significant number consisted of earth and rock fill, but many embodied a concrete gravity construction style similar to Bluestone Dam. Chief among them was Tygart Dam, the first major concrete gravity flood control dam built by the Corps of Engineers in West Virginia. Located near Grafton in Taylor County(about 180 miles north of Bluestone Dam), Tygart Dam was under construction when engineers prepared the preliminary drawings for the Bluestone project 1936. Tygart Dam's genesis came in 1933 after Major William Styer of the U.S. Army Corps of Engineers Pittsburgh District recommended building a reservoir dam on the Tygart Riverto assist in flood control and provide supplemental water to the Monongahela River navigation system during periods of low water. The New Deal's Public Works Administration approved Styer's recommendation in October 1933 and allocated funding for Tygart Dam in January 1934. Hence, the first great concrete high dam of the Ohio River watershed flood protection system became a reality between 1934 and 1938.

While Tygart Dam provided no hydroelectric power capability, two privately owned dams built on the New River in the 1930s did, in fact, produce electric power. The first was Hawk's Nest Dam, a 948-foot long concrete gravity structure completed in 1936 on the New River about 40 miles east of Charleston to provide electricity for a ferroalloy plant at Alloy, West Virginia. Next came Claytor Dam on the New River near Radford, Virginia. Constructed between 1937 and 1939, Claytor Dam features a hydroelectric plant capable of generating 76,000 kilowatts of electricity.

Preliminary survey work at the Bluestone Dam site during 1935-1936 included a large amount of core drilling to investigate the suitability of area bedrock for supporting a concrete gravity dam. As drilling continued, the Huntington District was assembling reports on the hydroelectric potential of the site and area flood control needs. The office issued a subsequent project report for Bluestone Dam on December 1, 1936, and adopted plans to erect a concrete gravity dam that would impound a minimum of 623,000 acre-feet of water. The height of the dam was fixed at 165 feet above the streambed to avoid flooding an extant steam generating plant, a major highway, and several bridges in the upper reservoir area.

Some adjustments in dam location were made based on the Huntington District's geological investigations after core samples at the original location revealed heavily weathered sandstone in areas close to the proposed dam. This serious defect shifted dam location 200 feet downstream. Additionally, core samples were also subjected to laboratory analysis to determine the strength of the foundation stone. Although the site was deemed to be a suitable location for a high concrete dam, it was recommended that additional drill testing be completed during construction.  Geologically speaking, the area was composed of interstratified layers of shale and sandstone with much of the rock in the area containing vertical fissures, gaps and crevices.

Hydraulic modeling guided various aspects of Bluestone Dam design, including the overflow section, crest gates, sluice gates, and stilling basins. As mandated by the Huntington District on November 6, 1935, modeling was performed under the Huntington District Engineer at the Hydraulic Laboratory of the Carnegie Institute of Technology in Pittsburgh. Construction of a scale model of the dam allowed the laboratory to test and measure the effects of water on various parts of the dam. Specifically, modeling was used to determine the shape of a number of concrete components, including the spillway section, spillway gate piers, and training walls. Modeling also helped determine the design of the dam's rectangular sluices, needle valve sluice outlets, and protection methods for counteracting erosion at the toe of the dam, the power house tail race, and the left bank of the New River below the stilling weir. Some design solutions employed on Bluestone Dam had already been resolved through model studies for Tygart Dam. Additional model studies were completed in 1946 at the U.S. Army Corps of Engineers Waterways Experiment Station at Vicksburg, Mississippi.

Water can flow through Bluestone Dam via sluice gates or over the dam via crest gates. In a 1936 meeting, the Board of Consultants discussed the types of sluice gates that might be used in the dam. Options included slide gates or roller gates, based on which type could be installed at the lowest cost. Roller gates seemed to have an advantage because they employ rollers on a track to overcome the problem of friction that is often encountered in the use of slide gates. According to Hanna and Kennedy in The Design of Dams, "The roller type of gate is usually used for heads under about 70 feet, but they are applicable to wider spans than slide gates on account of their lesser frictional resistance to motion."

It is unclear when the Corps of Engineers made the initial decision to overturn installing a type of roller gates, but hydraulically operated sluice gates are referred to in the 1941 specifications for Bluestone Dam. Hanna and Kennedy refer to sluice gates as "slide gates" used for controlling the flow over spillways where the quantity of water to be handled is relatively small and the range of fluctuation is about 10 feet or less. They are also used for relatively small discharges through outlets under heads up to about 120 feet.

Gates are usually made of cast iron or cast steel in one piece or rolled-steel plates and sections. The frames of the cast gates are made of the same materials as the gate leaves, and the leaves are reinforced with horizontal and vertical ribs. Hoists are used to operate the gates.

Installation diagram drawings prepared for Bluestone Dam in 1946 delineated 16 sluice gates. Each of the sluices actually has two gates--a service gate and an emergency gate that can be operated in case there is a problem with the service gate. The gate machinery is located in an operating gallery located just above the sluices. A hydraulically powered hoist moves sluice gates up and down to increase or decrease water flowing through each sluice.

Bluestone Dam also contains a set of 21 crest gates. Positioned at the top of the dam, the crest gates allow excess water to flow out of the reservoir in extreme high water conditions. The Board of Consultants elected to have an individual operating system raise and lower each gate, rather than using a movable gantry crane mounted on top of the dam. In addition to increasing overall maintenance costs for the dam, the cost of installing an individual operating mechanism for each gate was estimated to be about $100,000. However, it was decided that this cost was justified since the individual operating machinery would allow more uniform raising of the gates.

The Huntington District originally intended to construct a dam that would perform both flood control and hydroelectric functions, and during the planning process a number of design options incorporated hydroelectric power production. In August 1936 the Corps considered three alternatives; the first specified dam construction exclusively as a flood control project. This option omitted the crest gates and deferred to a later date the design of the hydroelectric powerhouse. Plans being drawn up for the dam in August 1936 followed the second design option, which called for crest gates to be installed but made provisions for building the hydroelectric powerhouse at a later date. A third possibility was to build the dam as a combined flood control and hydroelectric facility by completing the crest gates and powerhouse in the initial construction campaign. As construction began in 1941, option three was favored because of the need for hydroelectric power at that time. When construction resumed in 1946, however, option two became the preferred plan. The powerhouse structure was omitted, although the penstocks needed for hydroelectric power were installed. Crest gates were thus not installed during the initial construction campaign, but they were added separately in 1952.