Boone Milldam Reservoir Report

Last Updated: December 13, 2025

Boone Milldam, located in Boone, Iowa, is a gravity dam constructed in 1932 for the primary purpose of water supply.


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Summary

The dam stands at 7 feet high and spans 355 feet in length, with a storage capacity of 387 acre-feet and a surface area of 110 acres. It is situated on the Des Moines River, within the Rock Island District, and is owned and regulated by the local government, with oversight from the Iowa Department of Natural Resources.

Despite being classified as having a low hazard potential, Boone Milldam is considered to have a moderate risk level, with a risk assessment rating of 3. The dam has not been rated for its condition assessment and last underwent an inspection in September 1989. While the dam has not been modified in recent years, it is subject to state regulatory oversight, including permitting, inspection, and enforcement by the Iowa DNR. The dam's emergency action plan status and risk management measures are currently not specified.

Boone Milldam serves not only as a vital water supply structure but also offers recreational opportunities within the surrounding area. With its historical significance and environmental impact on the Des Moines River, the dam provides a focal point for water resource and climate enthusiasts interested in understanding the intersection of human infrastructure with natural ecosystems.

Year Completed

1932

Dam Length

355

Dam Height

7

River Or Stream

DES MOINES RIVER

Primary Dam Type

Gravity

Surface Area

110

Drainage Area

5510

Nid Storage

387

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.