Polk County Roadgrade Dam 3-80-24 Reservoir Report

Last Updated: December 11, 2025

Located in Polk County, Iowa, the Polk County Roadgrade Dam 3-80-24 stands as a vital structure regulated by the Iowa Department of Natural Resources.


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Summary

Completed in 1992 by the Polk County Engineer, this earth dam boasts a height of 49 feet and a length of 900 feet, serving a primary purpose classified as "Other." With a storage capacity of 51 acre-feet, the dam plays a crucial role in managing the flow of the TR- Rock Creek and covering a surface area of 3.2 acres.

Despite its low hazard potential, the dam's risk assessment is moderate, emphasizing the need for careful monitoring and management. The condition of the Polk County Roadgrade Dam 3-80-24 is currently labeled as "Not Rated," indicating the necessity for ongoing assessments to ensure its structural integrity. While the dam has not been inspected in recent times, the local government remains responsible for its maintenance, enforcement, and permitting in collaboration with the Iowa DNR.

As enthusiasts of water resources and climate, the Polk County Roadgrade Dam 3-80-24 serves as a reminder of the intricate infrastructure required to manage and protect our natural resources. With its strategic location in Johnston and its role in the Rock Island District, this dam represents a critical piece of the water management puzzle in Iowa, highlighting the ongoing need for vigilance and maintenance to safeguard against potential risks and ensure the safety of surrounding communities.

Year Completed

1992

Dam Length

900

Dam Height

49

River Or Stream

TR- ROCK CREEK

Primary Dam Type

Earth

Surface Area

3.2

Drainage Area

0.07

Nid Storage

51

Hazard Potential

Low

Foundations

Soil

Nid Height

49
       
Seasonal Comparison

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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.