Black Eagle Dam is a hydroelectric gravity weir dam located on the Missouri River in the city of Great Falls, Montana."Black Eagle Falls (Black Eagle Dam) is the only one in the city." See: "Great Falls Scores a Number of Firsts in Montana." Great Falls Tribune. March 20, 2005. The first dam on the site, built and opened in 1890, was a timber-and-rock crib dam.Peterson, p. 59. This structure was the first hydroelectric dam built in MontanaMarcosson, p. 145; Holmes, Dailey, and Walter, p. 397. and the first built on the Missouri River. The dam helped give the city of Great Falls the nickname "The Electric City.""City's Past Rooted in the River That Runs Through It." Great Falls Tribune. March 24, 2002. A second dam, built of concrete in 1926 and opened in 1927, replaced the first dam, which was not removed and lies submerged in the reservoir. Almost unchanged since 1926, the dam is long and high,PPL Montana, Form S-4, p. A-23. and its powerhouse contains three turbines capable of generating seven megawatts (MW) of power each. The maximum power output of the dam is 18 MW. Montana Power Company built the second dam, PPL Corporation purchased it in 1997 and sold it to NorthWestern Corporation in 2014. The reservoir behind the dam has no official name, but was called the Long Pool for many years.Peterson, p. 116. The reservoir is about long,Peterson, p. 82. and has a storage capacity of "Black Eagle Dam," PPL Montana, 2011. Accessed 2011-04-05. to of water."The FERC order issuing a new license dated September 27, 2000, states that the Black Eagle reservoir has a storage capacity of 1820 AF at normal maximum water surface elevation of 3290 feet." See: Water Right Solutions, Inc., p. 4.
The dam is a "run-of-the-river" dam because it can generate electricity without needing to store additional water supplies behind the dam.
Black Eagle Falls Black Eagle Falls is the first in a series of five waterfalls which constitute the Great Falls of the Missouri River in the state of Montana in the United States. Before being dammed, water dropped over the falls.Cutright and Johnsgard, p. 26.
Black Eagle Falls formed on a fall line unconformity in the Great Falls Tectonic Zone.Botkin, p. 255. The Missouri River in this area flows over and through the Kootenai Formation, a mostly nonmarine sandstone laid down by rivers, glaciers, and lakes in the past. Some of the Kootenai Formation is marine, however, laid down by shallow seas.See, generally, Farshori and Hopkins, 1989; Haney and Schwartz, 2003. The river is eating away at the softer nonmarine sandstone, with the harder rock forming the falls themselves.
The Mandan and the South Piegan Blackfeet, among other Native Americans, knew of the falls.Robbins, 2008, p. 165; Howard, p. 16-17; Federal Writer's Project, p. 353. On June 13, 1805, Meriwether Lewis of the Lewis and Clark Expedition became the first white person to see the Great Falls (the largest of the five waterfalls). On the second day that the expedition camped near the series of falls, Meriwether Lewis discovered Black Eagle Falls. "I arrived at another cataract of 26 feet...below this fall at a little distance a beautiful little Island well timbered is situated about the middle of the river. in this Island on a Cottonwood tree an Eagle has placed her nest; a more inaccessible spot I believe she could not have found; for neither man nor beast dare pass those gulphs which separate her little domain from the shores. the water is also broken in such manner as it descends over this pitch that the mist or sprey rises to a considerable height. this fall is certainly much the greatest I ever beheld except those two which I have mentioned below. it is incomparably a greater cataract and a more noble interesting object than the celebrated falls of Potomac or Soolkiln &c."Lewis and Clark, p. 134-135 (grammar and punctuation in original). It is unclear which member of the expedition named the falls, but the expedition called them "Upper Pitch."Cutright, p. 156.Howard, p. 66. The falls were eventually named for the black eagle which Lewis saw on June 14, 1805.Vaughn, p. 83. In 1872, Thomas P. Roberts, a survey engineer for the Northern Pacific Railway, formally named the cataract "Black Eagle Falls" after the incident recorded in Lewis' journal.Peterson, p. 20.
1890 dam
The Great Falls Water Power & Townsite Company was formed in 1887,The Montana Almanac, p. 381. with the goal of developing the town of Great Falls; providing it with power, sewage, and water; and attracting commerce and industry to the city. Railroad magnate James J. Hill organized the investors, who were primary owners of large amounts of stock in the Great Northern Railway. It was capitalized at $5 million. Hill sold stock to many of his friends, including Philip Danforth Armour, Charles Arthur Broadwater, Marshall Field, John Murray Forbes, Daniel Willis James, John Stewart Kennedy, Leonard Lewisohn and Charles Elliott Perkins.Martin, p. xxi. One of the stockholders in the Great Falls Water Power & Townsite Co. (GFWPTC) was Paris Gibson, a friend of Hill's and the driving force behind the founding of the city of Great Falls.Malone, 1996, p. 132; Guthrie, p. 20; Taliaferro, p. 120-121. Gibson realized that the Great Falls of the Missouri could provide abundant, cheap electricity for industry, and proceeded to promote the town on this basis.Taliaferro, p. 121. But Gibson's plan meant actually building one or more dams to supply the dreamt-of power. The company immediately began purchasing riverside land and water rights along the Missouri River from Black Eagle Falls down to Sheep Creek (a distance of about ). In time, it owned almost all the land set aside for the city of Great Falls as well as an additional of waterside property. GFWPTC employed J.T. Fanning, a hydraulic engineer, to survey Black Eagle Falls in the summer of 1887 to determine the suitability of the falls and the best location for a dam. Plans for a dam were drawn up, but no action was taken at that time.
Black Eagle Dam was built in order to supply power to a copper smelter. The Boston and Montana Consolidated Copper and Silver Mining Company was organized on July 22, 1887, by the merger of Leonard Lewisohn's Lewisohn Brothers (a copper trading company), the Montana Company (a mine holding company), and C. X. Larrabee (owner of the highly productive and famous Larrabee and Mountain View mines)."A Montana Mining Deal." New York Times. July 23, 1887; "Death of Leonard Lewisohn." New York Times. March 6, 1902. On September 12, 1889, the Boston and Montana signed an agreement with GFWPTC in which the power company agreed to build a dam that would supply the mining firm with at least 1,000 horsepower (or 0.75 MW) of power by September 1, 1890, and 5,000 horsepower (or 3.73 MW) of power by January 1, 1891.Hyde, p. 86. In exchange, Boston and Montana agreed to build a $300,000 copper smelter near the dam.
Construction began on Black Eagle Dam in 1890.Peterson, p. 60. GFWPTC engineers designed a rock-and-timber crib weir overflow dam, in which dressed and shaped heavy timbers formed a closed structure filled with rock or rubble. The dam was not a large one. The goal was to merely create a pond behind the dam, which would create enough water pressure (or "head") to turn turbines and generate electricity. The dam was built at a cost of about $515,000Another report claims the cost was only $275,000, but that may be for just the cost of labor and not materials and the associated powerhouses. See: "Great Falls, Mont.," p. 240. (roughly $12,335,000 in inflation-adjusted 2010 dollars) on the upstream brink of the falls (to create the deepest reservoir possible). Construction bids were opened on February 5, 1890, with the request for bids specifying that all work must be finished by December 1, 1890. All the bids were rejected, and mechanical engineer Maurice Parker was employed to design and construct the dam. Coffer dams were constructed in April 1890 to divert the river from the work areas. Work on the dam itself began on April 15. A shanty town named "River Bank" was constructed just upstream of the construction site on the north bank for the river to house the Croat, Scandinavian, Slovak, and Welsh workers who helped construct the dam. (Most of these workers helped found the town of Black Eagle, and earthen foundations for the shanty town can still be seen.) The red sandstone riverbed was leveled as much as possible, and large timbers bolted and cemented (perpendicular to the river's flow) to the rock. Each timber was from the next one downstream, and six cribs were built to form a dam deep at its base.The dam's downstream face had a pitch of 1.05:1. From the crest of the dam, a face (at a pitch of 1:08:1) extended for about before it became vertical. A masonry wall was built on the south end of the dam to form the foundation of and to protect the powerhouse, and the construction worked inward from either end of the dam. Every across the face of the dam, a floodwater spillway made of concrete was created (for a total of eight spillways). Flashboards in height were installed along the entire top of the dam to add water storage capacity. The dam was high and long.
The dam began generating electricity in December 1890.Peterson, p. 86. Water was permitted to flow over the crest of the dam on January 6, 1891, and the dam was considered complete on March 15, 1891.
A two-story brick powerhouse, , was built on the south side of the river. It contained three twin, horizontal "Victor" reaction turbines (to which up to six generators could be mounted), each of which generated 1.27 MW of power. The south bank and a masonry wall some distance offshore created a forebay (or short headrace) which fed the iron-enclosed penstocks, and water flow into the penstocks was partially controlled by a gate at the upstream end of the forebay. The main penstock was long and in diameter, and fed water to the turbines. (Three other penstocks were built but not put into use immediately.)
On the north side of the river was another powerhouse (completed in 1892), which contained seven more Victor turbines, capable of generating a total of 1.94 MW of power. Rock and debris carved from the river bottom was piled near the north bank to create a small island (Tailrace Island), and the powerhouse was built on this manmade shore.Talwani, Sanjay. "Race Is On at Tailrace Island." Great Falls Tribune. May 7, 1999. The island and the north bank of the Missouri River formed the tailrace (or channel for water leaving the powerhouse) of Black Eagle Dam. Tailrace Island was jointly owned by the power company and the Boston and Montana. A wooden pedestrian bridge was built to the island to connect the powerhouse with the smelter above. The north bank and a masonry wall offshore formed a long, concrete-lined forebay ( across at its widest part) for the northern powerhouse. The flow of water into this forebay was also controlled by gates. Three iron-enclosed penstocks were built to feed the northern powerhouse. The mechanical power generated by the turbines in the north powerhouse was not converted into electricity, however. Most of the power was transferred mechanically to the smelter's equipment via a system of ropes and pulleys.
Thomson-Houston generators were used to transform some of the mechanical energy generated by the two powerhouses into electricity. A single person could operate the powerhouse during an eight-hour shift. A secondary powerhouse, which contained an Armington & Sims steam-powered turbine and generator, was built next to the south powerhouse and used to provide electricity to clients whenever the main turbines were shut off. A funicular (or inclined railway) provided access to the south powerhouse from the bluff above. A , pedestrian suspension bridge ran from the bluffs above each powerhouse over the river. The dam's life expectancy was estimated at 50 years.