Cedarburg Woolen Mill Reservoir Report

Last Updated: December 5, 2025

The Cedarburg Woolen Mill, located on Cedar Creek in Ozaukee, Wisconsin, was completed in 1864 and serves primarily for recreation purposes.


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Summary

The dam, with a height of 18 feet and a length of 130 feet, creates a surface area of 6 acres and a drainage area of 119 square miles. Despite its historical significance, the dam's condition is assessed as poor, with a significant hazard potential due to its age and maintenance issues.

The Cedarburg Woolen Mill dam is regulated by the Wisconsin Department of Natural Resources, with state permitting, inspection, and enforcement in place. The spillway type is uncontrolled, and the dam's maximum discharge capacity is 4300 cubic feet per second. The last inspection conducted in June 2018 found the dam to be in poor condition, indicating a need for immediate attention to address safety concerns and prevent potential risks to the surrounding community and environment.

With its unique gravity design and historical significance, the Cedarburg Woolen Mill dam presents both challenges and opportunities for water resource and climate enthusiasts. As efforts are made to address the dam's poor condition, there is potential for collaboration between local government and environmental agencies to ensure the preservation of this iconic structure while safeguarding the surrounding ecosystem and water resources for future generations.

Years Modified

1939 - Other

Year Completed

1864

Dam Length

130

Dam Height

18

River Or Stream

Cedar Creek

Primary Dam Type

Gravity

Surface Area

6

Hydraulic Height

12

Drainage Area

119

Nid Storage

50

Structural Height

18

Hazard Potential

Significant

Nid Height

18
       
Seasonal Comparison

Weather Forecast

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.