Holter Dam
Holter Dam is a hydroelectric straight gravity dam on the Missouri River about northeast of Helena, Montana, in the United States. The dam, which was built between 1908 and 1918, is long and high. The reservoir formed by the dam, Holter Lake is long and has a storage capacity of of water when full. The dam is a "run-of-the-river" dam because it can generate electricity without needing to store additional water supplies behind the dam.
Dam and lake
Holter Dam
Holter Dam was built by the United Missouri River Power Company and the Montana Power Company. Samuel Thomas Hauser, a former Territorial Governor of the state of Montana from 1885 to 1887, had had a lengthy career in banking, mining, railroads, ranching, and smelting, but had encountered a series of financial setbacks after the Panic of 1893 which had nearly ruined him financially. In his early 60s, Hauser began to rebuild his finances by branching out into the relatively new industry of hydroelectric power generation. In 1894, he formed the Missouri River Power Company, and won the approval of the United States Congress to build a dam below Stubbs' Ferry. In 1905, Hauser and other directors of the Missouri River Power Company formed the Helena Power Transmission Company. The two companies merged on February 16, 1906, to form the United Missouri River Power Company. The merged company completed Hauser Dam on February 12, 1907. The dam was a steel dam built on masonry footings on top of gravel, with the ends of the dam anchored in bedrock on either side of the river. On April 14, 1908, Hauser Dam failed after water pressure undermined the masonry footings. United Missouri River Power began reconstruction of Hauser Dam in July 1908.The United Missouri River Power Company had begun construction of Holter Dam in 1908 before the failure of Hauser Dam. Hauser had conceived of a dam at the present location in 1906 to supply the newly formed Amalgamated Copper Mining Company with electricity. The dam was named for Anton Holter, president of the Helena Transmission Power Company and by 1908 a director of the United Missouri River Power Company. Hauser formed a subsidiary, the Capital City Improvement Company, to seek investment money and build the dam for the power company. John Ripley Freeman was the dam's design engineer. Stone & Webster, a Boston-based firm, was the construction company. But cost overruns, waning investor enthusiasm, and the liability associated with the collapse of Hauser Dam nearly drove Samuel Hauser into bankruptcy. Amalgamated Copper, which bought 75 percent of United Missouri's power and owned $1 million of its corporate bonds, now began buying its power from Hauser's rival, John D. Ryan's Great Falls Power Company. Construction on Holter Dam was halted in late 1910 after only part of the foundation had been poured. Hauser sold his interest in United Missouri River Power to Ryan, who on October 25, 1912, merged United Missouri River Power with the Butte Electric and Power Company, Billings and Eastern Montana Power Company, and Madison River Power Company to form the Montana Power Company. Montana Power took over not only United Missouri's Canyon Ferry Dam and Hauser Dam but the partially built Holter Dam as well.
Montana Power resumed building the structure in March 1916. The reason for resuming construction was to supply power to the Butte, Anaconda and Pacific Railway and the Chicago, Milwaukee, and St. Paul Railroad. The Chas. T. Main company was hired to revisit the design. Henry A. Herrick, an employee of the power company, was the consulting engineer for Main. The major change implemented by Main and Herrick was to install vertical rather than horizontal turbines, although some changes were made to the wastewater system and the dam's downstream face. Stone & Webster continued to be the construction company, and more than 500 men worked on the project. The S. Morgan Smith Company of York, Pennsylvania, designed the water wheels for the turbines. The 1916-1918 construction camp was the largest ever built by Montana Power. There were more than 115 buildings at the construction site, including a bunkhouse and dormitories for unmarried men, cottages for married men, a dining hall, a bathing house, storage sheds, garages, a photography studio, school, hospital, and sewer. Although most of the structures were tents or wooden buildings intended for short-term use, seven of the structures were renovated into permanent housing for the dam's operators. Two more homes were built for operators after construction ended. Montana Power spent $1.3 million in 1916 and $1.5 million in 1917 to finish the dam. Holter was completed and brought online for power generation in 1918. It was the sixth and last dam completed by the company in that decade.
In its original configuration, Holter Dam was expected to be long and high, but ended up being slightly larger. At the time, Holter was the tallest hydroelectric dam on the Missouri River. The penstocks are below the water level when the reservoir is full. The dam had four vertical single-runner 15,000-horsepower water turbines, seven main electrical generators and three exciters, and was capable of generating 40,000 kilowatts of power. Aside from the powerhouse and water intakes, the dam has three sections: a central section where water is permitted to flow over the dam, and a left and right section anchored to the bedrock where water is not able to flow over the dam. The dam incorporated flashboards into the crest of the dam to permit overflow. The dam has 31 flashboards, each of them high.
As of 1994, Holter Dam, its powerhouse, its nearby operator housing and abandoned construction camp, its railroad switchyard, and the nearby maintenance buildings are one of the most intact historic hydroelectric generating facilities in Montana.
Holter Lake
Holter Dam raised the water level behind it by about, creating the long Holter Lake. Holter Lake has a surface area of. The lake has a mean depth of and a maximum depth of. Holter Lake stores of water when full. The distance between Hauser Dam and Holter Lake is.The Missouri River runs free for between Holter Dam and the five dams at Great Falls, Montana.
Geology beneath and around Holter Dam
forms much of the surface rock through which the Missouri River flows at Holter Dam. The limestone is rich in fossils, mostly brachiopods like clams, mussels, and mollusks. Holter Lake sits atop the Eldorado thrust fault, which juxtaposes Proterozoic Belt Supergroup Greyson Shale over much younger Madison Limestone and is part of the Sevier orogeny.Gates of the Mountains
Holter Lake has two parts, dubbed upper Holter Lake and lower Holter Lake. The central section of the lake is a narrow, neck, marked at its downstream end by the Gates of the Mountains. The Gates of the Rocky Mountains were first recorded when the Lewis and Clark Expedition passed through the area in 1805. Captain Meriwether Lewis wrote on July 19, 1805:The Gates of the Mountains has been tourist attraction since the period 1886 to 1906, when the steamboat Rose of Helena traversed the Missouri River through this area. Although the Missouri River once ran swiftly through the Gates of the Mountains, Holter Dam drastically reduced the flow of water so that now the area has almost no current. Water levels in the Gates are now higher than they were in 1805.
Mann Gulch
Between upper and lower Holter Lake, near the Gates of the Mountains, lies Mann Gulch. The gulch was the site of the 1949 Mann Gulch fire, which claimed the lives of 13 smokejumpers. The incident is the subject of author Norman Maclean's book Young Men and Fire. Today, Mann Gulch is most commonly reached by boat.Operation of the dam
As of 2010, Holter Dam had a 50 megawatt generating capacity. The long-term median flow over and through Holter Dam as of 2005 was per second. Flows into Holter Lake and over Holter Dam are generally considered to be controlled by flows from Canyon Ferry Dam. The total annual discharge from Holter Dam between 1929 and 1988 was an average of per year.The wooden flashboards of Holter Dam were replaced in 1972.
Montana Power shut down electrical generation at Holter Dam in 1984 after a forest fire destroyed a 100,000-volt electric power transmission line.
In June 1999, Montana Power proposed lowering the level of Holter Lake by for six weeks so that the flashboards could be repaired and replaced. Public criticism of the drawdown was extensive, but Montana Power insisted that it go ahead. But in August 1999, Montana Power put its repair plans on hold.
On November 2, 1999, Montana Power announced it was selling all of its dams and other electric power generating plants to PPL, Inc. for $1.6 billion. The sale was expected to generate $30 million in taxes for the state of Montana. Subsequently, in May 2000 PPL announced it would use small steel cofferdams to drain the water around the flashboards and allow their repair without lowering the level of the lake. The cost of using the cofferdams was $300,000. Twenty-one of the dam's 31 flashboards were replaced.
In November 2001, citizens of Montana upset with energy price increases announced by PPL sought passage of a ballot initiative that would require the state of Montana to buy all of PPL's hydroelectric dams, including Holter Dam. Montana voters rejected the initiative in November 2002. Also in 2001, Holter Dam participated in an emergency management training exercise which, in part, planned for the catastrophic failure of Holter Dam.
The public used to be able to walk across the top of Holter Dam, but the dam was closed to the public after the September 11 attacks. Holter Dam was one of the last two such PPL dams to be closed. In 2014, PPL sold Holter Dam and their other Montana dams to NorthWestern Corporation.
While effective at generating electricity, well-designed, and well-engineered, Holter Dam is considered an exceptionally unpleasant structure visually. In 1927, however, the Montana Legislature commissioned painter Ralph E. DeCamp to depict Holter Dam as one of four mural paintings to hang in the state's Law Library. Japanese photographer Toshio Shibata has also photographed the dam, and exhibited this work in 1997 in Chicago at the Museum of Contemporary Art.