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Hennepin Island
Location: Downtown Minneapolis, Minnesota, on the Mississippi River at St. Anthony Falls.
Plant Description: Hennepin Island is a five-unit hydro plant, with each turbine accommodating river flows of up to 3,800 cubic feet a second. Hennepin Island also is home to a major electric distribution center – Main Street substation – serving downtown Minneapolis.
Power production capability (in-service dates): 12 Mw total
Units 1,2, 3 and 4 (1954); Unit 5 (1955)
The five units produce 2.4 Mw each.
Fuel Sources: Falling water that flows through each turbine, which turns a generator to produce electricity. A 1,900-foot-long, 14-foot-high dam, situated on the upper portion of St. Anthony Falls, creates a 450-acre reservoir that provides fuel for the plant. The dam and falls create 49 feet of “head,” or the height from the water surface to the turbines. The amount of electricity generated is determined by the amount of head and volume of water flow.
Plant History: Hennepin Island gets its name from Belgian explorer Father Louis Hennepin, who upon seeing the adjacent falls named them after his patron saint, St. Anthony of Padua. To Father Hennepin, the falls stood for the riches and power of the New World.
By the mid-1800s, the falls had become the birthplace of Minneapolis – home to flour mills and saw mills, and a fashionable spot for vacationers seeking to escape the summer heat. One of the nation’s first hydroelectricity plants and ultimately Northern States Power Company – the predecessor to Xcel Energy – sprung from the original limestone dam at St. Anthony Falls, built in 1882. The area has survived several floods over the years, and while flour milling along the river had largely declined by 1965, Hennepin Island continues to generate hydropower almost 120 years after the site was developed. To preserve the heritage of Minneapolis and the state of Minnesota, the St. Anthony historic district was established in 1971.
Interesting Features: The aging St. Anthony Falls dam was replaced in 2000-2001 with a new dam about 30 feet upriver of the existing structure. We recently completed the re-licensing process for our Hennepin Island plant that ensures continued hydro operations at one of our original plant sites. The re-licensing also includes provisions for development of the upper island into a park with an access bridge that will give the public an upfront view of the main spillway, horseshoe dam and the downtown skyline.
Environmental Highlights: Hydro is a clean, renewable fuel, and Xcel Energy manages its dam operations to protect the aquatic environment and improve recreational opportunities.
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