Merillan Mills Reservoir Report

Last Updated: December 13, 2025

Merillan Mills, located in Merrillan, Wisconsin, is a gravity dam constructed in 1907 primarily for recreational purposes.


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Summary

The dam spans 250 feet in length and has a height of 23 feet, with a storage capacity of 170 acre-feet. Situated on Halls Creek in Jackson County, Wisconsin, the dam serves as a popular spot for outdoor enthusiasts seeking recreational activities such as boating, fishing, and wildlife observation.

Managed by the local government and regulated by the Wisconsin Department of Natural Resources (WIDNR), Merillan Mills has a low hazard potential and is assessed to be in fair condition as of May 2020. The dam's spillway type is uncontrolled, with a maximum discharge capacity of 2750 cubic feet per second. Despite its moderate risk assessment rating, the dam has not been significantly modified or updated in recent years, with its last inspection conducted in July 2016.

For water resource and climate enthusiasts, Merillan Mills offers a glimpse into the historical significance of dam infrastructure in Wisconsin, as well as the importance of balancing recreational use with environmental conservation and safety considerations. With its scenic location and relatively low hazard potential, the dam provides a valuable opportunity for outdoor recreation while highlighting the need for ongoing monitoring and maintenance to ensure its continued functionality and safety.

Year Completed

1907

Dam Length

250

Dam Height

23

River Or Stream

HALLS CREEK

Primary Dam Type

Gravity

Surface Area

16

Hydraulic Height

18

Drainage Area

45

Nid Storage

170

Structural Height

23

Hazard Potential

Low

Nid Height

23
       
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.