Thomson Dam, also known as the Thomson Hydro Station or Thomson Water Project, is an

embankment Embankment may refer to: Geology and geography * A levee, an artificial bank raised above the immediately surrounding land to redirect or prevent flooding by a river, lake or sea * Embankment (earthworks), a raised bank to carry a road, railway ...

and concrete gravity dam on the Saint Louis River near the town of

Thomson Thomson may refer to: Names * Thomson (surname), a list of people with this name and a description of its origin * Thomson baronets, four baronetcies created for persons with the surname Thomson Businesses and organizations * SGS-Thomson M ...

in northeastern

Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. It consists of a 1600-foot (488 m) long primary structure and multiple supplementary dams which, together with

precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...

rock outcrops known as the Thomson formation, impound the river to create Thomson Reservoir. The tallest dam in the complex is 51.6 feet (16 m) and the longest is 3500 feet (1067 m). A series of gate houses, a canal, forebay, and underground

penstock A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydro turbines and sewerage systems. The term is of Scots origin, and was inherited from the earlier technology of mill pond ...

s supply a

hydropower plant Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other renewable sources combined and also mo ...

located 3 miles away in

Jay Cooke State Park Jay Cooke State Park is a state park of Minnesota, United States, protecting the lower reaches of the Saint Louis River. The park is located about southwest of Duluth and is one of the ten most visited state parks in Minnesota. The weste ...

. With an installed capacity of 72 MW and an annual generation of approximately 280

GWh A kilowatt-hour ( unit symbol: kW⋅h or kW h; commonly written as kWh) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour. Kilowatt-hours are a commo ...

, the Thomson project is the largest

hydroelectric Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...

facility in the state.

History

Thomson Dam was completed in 1907 by Great Northern Power, an operating division of the

Great Northern Railway Great Northern Railway or Great Northern Railroad may refer to: Australia * Great Northern Railway (Queensland) in Australia * Great Northern Rail Services in Victoria, Australia *Central Australia Railway was known as the great Northern Railway ...

. The generating station was expanded in 1914 with the addition of Unit 4. Unit 5 was added in 1918 and Unit 6 in 1948. Railroad tracks built into the generator floor allowed for installation and maintenance of the equipment. The complex was later transferred to the Saint Louis Power Company. Today it is owned by Minnesota Power, a division of Allete, Inc. Heavy rains in June 2012 created an historic flood in the region which overtopped the dam, breached the forebay canal and severely damaged the hydroelectric station. Following $90 million in reconstruction and upgrades, including the addition of a new emergency spillway, the facility came back online in November, 2014. Additional upgrades will continue through 2018, including removal of the original 46kV transmission line equipment in favor of other, higher voltage equipment that was added later.

Structures

The most visible part of Thomson Dam is the primary structure straddling the Saint Louis River channel near

Minnesota State Highway 210 Minnesota State Highway 210 (MN 210) is a state highway in west-central, central, and northeast Minnesota, which runs from North Dakota Highway 210 (ND 210) at the North Dakota state line (at Breckenridge), and continues east to its e ...

. However, the Thomson Project is actually composed of multiple dams and control structures, several of which have been rebuilt and merged over the years. Today the

United States Army Corps of Engineers The United States Army Corps of Engineers (USACE) is the military engineering branch of the United States Army. A direct reporting unit (DRU), it has three primary mission areas: Engineer Regiment, military construction, and civil wo ...

National Inventory of Dams (NID) counts 18 structures as part of the complex, with 14 formally listed as separate.

References

{{Reflist Dams in Minnesota Hydroelectric power plants in Minnesota Buildings and structures in Carlton County, Minnesota 1907 establishments in Minnesota Dams completed in 1907

History

Structures

See also

References