Troy Mills Dam Reservoir Report

Last Updated: December 5, 2025

Troy Mills Dam, located in Linn County, Iowa, is a privately owned structure on the Wapsipinicon River with a primary purpose of recreation.


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Summary

Completed in 1989, this gravity-type dam stands at a height of 7 feet and has a length of 300 feet, providing a storage capacity of 640 acre-feet. Despite its relatively low hazard potential and moderate risk assessment, the dam is not currently rated for its condition.

Managed by the Iowa Department of Natural Resources, Troy Mills Dam is subject to state regulations, permitting, inspection, and enforcement. The dam features an uncontrolled spillway and is situated in a scenic area with a surface area of 182 acres and a drainage area of 1210 acres. The dam's risk management measures and emergency action plan status are currently not specified in the available data.

For water resource and climate enthusiasts, Troy Mills Dam presents an intriguing case study of a smaller-scale dam providing recreational benefits while also being subject to state oversight and regulation. With its location in a picturesque setting along the Wapsipinicon River and its relatively low hazard potential, the dam serves as an example of the importance of maintaining and monitoring infrastructure for both human enjoyment and environmental protection in the face of changing climate conditions.

Year Completed

1989

Dam Length

300

Dam Height

7

River Or Stream

WAPSIPINICON RIVER

Primary Dam Type

Gravity

Surface Area

182

Drainage Area

1210

Nid Storage

640

Hazard Potential

Low

Foundations

Soil

Nid Height

7
       
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.