Montello Granite Reservoir Report
Nearby: Buffalo Lake Dam Duffy's Marsh
Last Updated: December 5, 2025
Montello Granite, located in Marquette, Wisconsin, is a concrete dam constructed in 1914 for hydroelectric and recreational purposes.
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Summary
With a height of 24 feet and a hydraulic height of 18.4 feet, this dam spans 55 feet in length and has a storage capacity of 3,300 acre-feet. Situated on the Montello River, this dam not only serves as a source of water storage but also provides opportunities for recreation in the area.
Despite its age, Montello Granite is maintained by the Wisconsin Department of Natural Resources, with regular inspections ensuring its structural integrity. The dam has a controlled spillway with a width of 17 feet, allowing for the safe release of excess water during periods of high flow. The hazard potential is rated as high, but the condition assessment in 2020 deemed it to be fair, indicating that necessary maintenance and upgrades are being carried out to mitigate risks and ensure public safety.
In summary, Montello Granite is a historic dam that continues to play a vital role in water resource management and recreation in the region. With a rich history dating back over a century, this concrete structure stands as a testament to the ingenuity of past generations in harnessing the power of water for multiple purposes. As climate change poses new challenges to water management, the maintenance and monitoring of dams like Montello Granite are essential to safeguarding communities and ecosystems in the face of evolving environmental conditions.
Years Modified |
2012 - Other |
Year Completed |
1914 |
Dam Length |
55 |
Dam Height |
24 |
River Or Stream |
MONTELLO RIVER |
Primary Dam Type |
Concrete |
Surface Area |
286 |
Hydraulic Height |
18.4 |
Drainage Area |
160 |
Nid Storage |
3300 |
Structural Height |
24 |
Hazard Potential |
High |
Foundations |
Rock |
Nid Height |
24 |
Seasonal Comparison
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Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Montello Granite
Lakeshore Drive 137, Montello