Sandstone Rapids Reservoir Report

Last Updated: December 8, 2025

Sandstone Rapids, located in Marinette County, Wisconsin, is a gravity dam on the Peshtigo River with a primary purpose of hydroelectric power generation.


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Summary

Constructed in 1925 by designers Mead & Scastone, this dam stands at a height of 42 feet and has a storage capacity of 1650 acre-feet. With a maximum discharge of 20,000 cubic feet per second, the dam boasts a controlled spillway with a width of 184 feet.

The dam, owned by a public utility, serves as both a source of renewable energy and a recreational spot for visitors. Despite its historical significance and engineering marvel, Sandstone Rapids poses a high hazard potential and is categorized with a very high risk assessment rating. While the dam is regulated by the Federal Energy Regulatory Commission, state inspection and enforcement are not currently in place.

As an integral part of the water resource infrastructure in the region, Sandstone Rapids provides a glimpse into the intersection of human ingenuity and environmental stewardship. Its presence along the Peshtigo River not only contributes to the local economy through energy generation but also offers opportunities for outdoor recreation. However, the high hazard potential underscores the importance of ongoing maintenance and risk management to ensure the safety and sustainability of this vital water resource structure.

Year Completed

1925

Dam Length

420

Dam Height

42

River Or Stream

Peshtigo River

Primary Dam Type

Gravity

Surface Area

150

Hydraulic Height

42

Drainage Area

675

Nid Storage

1650

Structural Height

42

Outlet Gates

Tainter (radial) - 6

Hazard Potential

High

Foundations

Rock

Nid Height

42
       
Seasonal Comparison

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Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.