Cedar Rapids Milldam (5 In 1) Reservoir Report

Last Updated: December 5, 2025

Cedar Rapids Milldam (5 In 1) is a captivating structure located in Linn County, Iowa, along the Cedar River.


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Summary

Built in 1978, this gravity dam stands at a height of 14 feet and has a hydraulic height of 11 feet. Its primary purpose is hydroelectric power generation, with a normal storage capacity of 9,843 acre-feet and a surface area of 985 acres.

Managed by the local government and regulated by the Iowa Department of Natural Resources, Cedar Rapids Milldam is classified as a low hazard potential dam with a satisfactory condition assessment. The dam features a controlled spillway with a width of 605 feet, serving as a crucial component of the region's water resource infrastructure. Despite its age, the dam's risk assessment remains very high due to its structural complexity and the potential impact of a failure event.

With its rich history and significant contribution to hydroelectric power generation, Cedar Rapids Milldam (5 In 1) stands as a testament to the innovative engineering practices of its designers, Howard, Needles, T&B. As a focal point for water resource and climate enthusiasts, this dam represents a harmonious blend of technology and nature, showcasing the importance of sustainable water management practices in a changing climate landscape.

Year Completed

1978

Dam Length

680

Dam Height

14

River Or Stream

CEDAR RIVER

Primary Dam Type

Gravity

Surface Area

985

Hydraulic Height

11

Drainage Area

6510

Nid Storage

9843

Structural Height

16

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

16
       
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.