Ellsworth Power House and Dam

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Ellsworth Power House and Dam
Hydro Electric Power House, showing Leonard Lake and dam, Ellsworth, Maine (66180).jpg
Ellsworth Power House and Dam is located in Maine
Ellsworth Power House and Dam
Ellsworth Power House and Dam is located in the United States
Ellsworth Power House and Dam
LocationUnion River, Ellsworth, Maine
Coordinates44°32′39″N 68°25′50″W / 44.54417°N 68.43056°W / 44.54417; -68.43056Coordinates: 44°32′39″N 68°25′50″W / 44.54417°N 68.43056°W / 44.54417; -68.43056
Area2 acres (0.81 ha)
Built1907 (1907)
Architectural styleRenaissance, Ambursen type
NRHP reference No.85001262[1]
Added to NRHPJune 20, 1985

The Ellsworth Power House and Dam, the latter also known as the Union River Dam, is a hydroelectric power generation facility on the Union River in Ellsworth, Maine. The dam, located just north of downtown Ellsworth, impounds the river to create Leonard Lake, named for project's engineer, James Leonard. The powerhouse is a Renaissance Revival building located at the western end of the dam. The power plant, built in 1907, was one of the first peaking power plants built in the state, and the hollow concrete dam is one of the highest Ambursen-type buttress dams ever built. The facility was listed on the National Register of Historic Places in 1985.[1]

Description and history[edit]

The Ellsworth Dam is located between two bluffs which flank Maine's Union River, and rise to a height of more than 100 feet (30 m). The dam consists of a series of buttresses, spaced about 15 feet (4.6 m) apart, which provide support for two large slabs of steel-reinforced concrete that span the river between the bluffs. The dam is 71 feet (22 m) in height, with a spillway 60 feet (18 m) long. The buttresses, set on a granite bedrock ledge, are three feet thick.[2]

The power station is located at the base of the dam on the west bank of the river. It is a 1-1/2 story structure built out of concrete blocks, with a red tile gabled roof. The Renaissance Revival structure has round-arch windows which are connected by a stone belt course, and there are Palladian windows in the gable ends. An addition on the building's rear was built with similar styling.[2]

The power station was built in 1907 by the Bar Harbor and Union River Power Company, to designs by its engineer, James Leonard. The company was merged in 1925 into the Bangor Hydro-Electric Company, now part of Emera. The plant was acquired by Black Bear Hydro in 2009, and sold to Brookfield Partners in 2014. The dam is in the process of being relicensed; its most recent permit was due to expire in 2017, however, public concern about fish passage and water quality, caused the Federal Energy Regulatory Commission to delay issuing a new permit. The new expiration date is April 2020. In its current configuration, the plant produces about 30,000 megawatt-hours of electricity annually.[3]

(The dam is no longer hollow. During the 1990s. the FERC required installation of post-tensioned anchors deep into ledge and the filling of the hollow dam with concrete, in order to increase dam safety.)

See also[edit]


  1. ^ a b "National Register Information System". National Register of Historic Places. National Park Service. July 9, 2010.
  2. ^ a b "NRHP nomination for Ellsworth Power House and Dam". National Park Service. Retrieved 2015-02-05.
  3. ^ "Company begins five-year effort to relicense Ellsworth hydroelectric dam". Bangor Daily News. August 29, 2012. Retrieved 2015-02-05.