Rapidan Dam
Blue Earth County, MN
Introduction
The Rapidan Dam was built over 100 years ago (built in 1910) and has been managed by Blue Earth County for the last 46 years. Blue Earth County recently completed studies that evaluated two options: repair or remove the dam. This decision cannot be made without your help. Learn about the dam below.
Rapidan Dam: Repair or Replace?
About the Dam
The Rapidan Dam was built over 110 years ago in 1910. It is located in the Rapidan Township on the Blue Earth River and has been managed by Blue Earth County for the past 46 years. Throughout the years, the dam has experienced regular flooding — the second-highest flood on record occurred as recently as 2019. These flood events and the toll of time have caused significant damage to the dam's structure and usability.
Because of this, doing nothing is no longer a long-term solution. Action needs to be taken to address the current conditions of the dam.
Rapidam Dam Facts
- The dam is over 100 years old with construction being completed in 1910. Blue Earth County has only owned the dam and resevoir for the last 46 years.
- The dam makes energy from two turbines that are powered by falling water.
- When functioning at full capacity, the dam can produce 23 million kilowatt hours of clean energy a year. That's enough to power 2,000-3,000 residences a year.
- High water events in 2010, 2019, and 2020 have caused damage to the dam. The dam has not produced any energy since 2019.
What is a hydroelectyric dam?
A hydroelectric dam is a system with three parts: a power plant where the electricity is poduced, a dam that can be opened or closed to control water flow, and a reservoir where water is stored. The water behind the dam flows through an intake and pushes against blades in a turbine, causing them to turn. This thenproduces energy.
The image above shows the key parts to a hydroelectric dam, including the intake, generator, and turbine.
Did you know?
- The dam makes energy from two turbines that are powered by falling water. This dam is over 100 years old. Blue Earth County has only owned the dam and resevoir for the last 46 years.
- When functioning at full capacity, the dam can produce 23 million kilowatthours of clean energy a year. That’s enough energy to power 2,000-3,000 residences a year.
- In 2021, hydroelectric power generated 6.3% of total U.S. electricity. This is the second highest renewable source behind wind at 9.2%. (Source: U.S. Energy Information Administration).
- High water events in 2010, 2019 and 2020 have caused damage to the dam. The dam has not produced any energy since 2019.
Key facts about the Rapidan Dam.
Possible Solutions
To find a solution for the ongoing problems the Rapidam Dam is experiencing, Blue Earth County worked with Barr Engineering in 2021 to conduct a study for two potential solutions: repair or remove the dam.
Repairing the Dam
Key Facts:
- The dam has not generated power since 2019
- Returning the dam to working condition would cost an estimated 15 million dollars and take about 4 years to make repairs
- Will require ongoing maintenance and inspection costs
What repairs need to be made?
Many repairs would need to be made to the structure, include apron, basin, and gate repairs. A large amount of repairs would be needed for the generator as well, including bearings, controls, balancing and hydraulics.
Timeframe: Approximately 4 years
Cost: Estimated 15 million dollars
While a payment plan has not been determined for either option, the county will seek federal and state funding to assist with payment for these improvements and may also require the use of local resources.
Removing the Dam
Key Facts:
- Removing the dam would cost an estimated 82 million dollars and take approximately 10 years for permitting and removal
- Also includes re-establishing the river and replacing the County Road 9 bridge south of the dam
- While this option costs more, it would not require any future maintenance costs
- Removing the dam would restore the flow of the Blue Earth River for fish and recreational uses such as kayaking and canoeing
- Could be transformed into a destination for horseback riding, multi-use trails, or other activities
Timeframe: Approximately 10 years
Cost: Estimated 82 million dollars
While a payment plan has not been determined for either option, the county will seek federal and state funding to assist with payment for these improvements and may also require the use of local resources.
Public Engagement Timeline
Survey Released
April 6, 2022
Open House
April 19
Virtual Learning Platform released on website
April 19, 2022
Pop up at the HUB Food Park
April 30 - 11-3 p.m. - 512 N. Riverfront Dr. Mankato
Pop up at River Valley Running 5K
May 7 - 7:30 a.m. - 605 N Riverfront Dr, Mankato
Focus Group Meetings
Mid-May
Pop up at CruzIN Lake Crystal
May 19 - 4-8 p.m. - Lake Crystal Main Street
Pop up at Moon Dogs game
June 2 - 6:30 p.m. - 1221 Caledonia St, Mankato
Comment Period Closes
Late Summer 2022
Final Report of Findings Presented to County Board
Fall 2022
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