Lake Zumbro Hydroelectric Generating Plant

The Lake Zumbro Hydroelectric Generating Plant, also known as the City of Rochester Municipal Hydro-Electric Plant, is a hydroelectric facility on the Zumbro River in Mazeppa and Zumbro Townships in the U. S. State of Minnesota. The facility consists of a gravity dam and a powerhouse, and formerly included three houses for the plant operators. The houses were removed in the 1960s when the dam was retrofitted to allow remote operation of the generating equipment from Rochester. The impoundment created is called Lake Zumbro. This dam spans 904 feet (276 m) and is 66 feet (20 m) high, creating a reservoir with about 55 feet (17 m) of hydraulic head.[2]

Lake Zumbro Hydroelectric Generating Plant
The Lake Zumbro Hydroelectric Generating Plant and Dam viewed from the north
Country	United States
Location	Off County Road 21 at north end of Lake Zumbro, Mazeppa Township, Minnesota
Coordinates	44°12′46″N 92°28′46″W
Purpose	Power
Status	Operational
Construction began	1917 (1917)
Opening date	1919 (1919)
Construction cost	$1,019,160.95 (equivalent to $23,279,224 in 2022)
Built by	Omaha Structural Steel Bridge Company
Designed by	Hugh Lincoln Cooper
Owner(s)	City of Rochester, Minnesota
Operator(s)	Rochester Public Utilities
Dam and spillways
Type of dam	Gravity dam
Impounds	Zumbro River
Height (foundation)	66 ft (20 m)
Length	904 ft (276 m)
Width (crest)	7 ft (2.1 m)
Width (base)	70 ft (21 m)
Spillways	1
Spillway type	Uncontrolled
Spillway length	426 ft (130 m)
Reservoir
Creates	Lake Zumbro
Surface area	714.55 acres
Maximum water depth	43 ft (13 m)
Type	Run-of-the-river
Hydraulic head	55 ft (17 m)
Turbines	2 × Francis-type
Installed capacity	2.3 MW
Annual generation	12.5 GW·h
Lake Zumbro Hydroelectric Generating Plant
U.S. National Register of Historic Places
Sign on the Lake Zumbro Hydroelectric Generating Plant
Area	2 acres (0.81 ha)
Built	1917–1919
Architectural style	Neoclassical
MPS	Minnesota Hydroelectric Generating Facilities MPS
NRHP reference No.	91000243[1]
Designated NRHP	March 14, 1991

The idea of building a hydroelectric plant on the Zumbro River north of Rochester had been discussed at least as far back as 1904, when several entrepreneurs surveyed the river, going so far as to buy land for a dam site. An effort was made to secure funding for a 60-foot (18 m) dam and transmission line to enable sale of electricity to the city, but the city council declined the arrangement as they did not feel that Rochester's power consumption would justify it. In 1915, a bond issue for a new hydroelectric plant was put before the city council, possibly spurred by the recent loss of the coal-fired municipal power plant in a fire. Voters overwhelmingly approved a $360,000 (equivalent to $8,222,961 in 2022) bond issue in a special election held in January, 1916.[3]

The facility was designed by pioneering hydroelectric engineer Hugh Lincoln Cooper (1865–1937), a Minnesota native with strong ties to the city of Rochester, and was built from 1917 to 1919.[2] It is still operated by its original owner, Rochester Public Utilities (RPU), to supply power to Rochester, Minnesota, 15 miles (24 km) to the south. The Lake Zumbro Hydroelectric Generating Plant was listed on the National Register of Historic Places in 1991 for its state-level significance in the theme of engineering.[4] It was nominated as a representative work of Cooper—one of the nation's leading hydroelectric engineers in the early 20th century—and his only project in his home state of Minnesota.[2]

On the night of August 24, 2019, a pontoon boat with three people on board went over the dam. They were casting off from the lake shore after patronizing a business below the dam but got caught on the lip of the spillway. A fourth person jumped off and swam to a buoy, where she yelled for help, while the other three went over the edge in the boat. It lodged right-side-up near the base of the dam, causing the people on board only minor injuries. Firefighters, sheriff's deputies, and civilian boaters rescued all four individuals. The Wabasha County Sheriff's Office ascribed the incident to alcohol and darkness, charging the driver with boating while intoxicated.[5][6]