Three Mile Creek Watershed Site U-7 Reservoir Report

Last Updated: December 12, 2025

Located in Union County, Iowa, the Three Mile Creek Watershed Site U-7 is a crucial water resource managed by the local government for fire protection, stock, and small fish pond purposes.


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Summary

Built in 1980 by the USDA NRCS, this earth dam stands at a height of 27 feet and spans 450 feet in length, with a storage capacity of 137 acre-feet. Despite its low hazard potential and moderate risk assessment, the dam has not been rated for its condition and lacks an emergency action plan.

The dam's primary purpose of flood risk reduction underscores its importance in mitigating potential water-related disasters in the region. Managed by the Iowa DNR, the dam is subject to state regulation, permitting, inspection, and enforcement to ensure its structural integrity and safety. With a drainage area of 0.4 square miles and a surface area of 3.5 acres, the dam plays a vital role in managing water flow and protecting the surrounding environment and communities from flooding events.

As part of the Rock Island District, the Three Mile Creek Watershed Site U-7 serves as a key water management infrastructure in the area, contributing to the overall resilience of the watershed and ecosystem. Despite its age, the dam continues to provide essential water resource services while highlighting the importance of ongoing monitoring, maintenance, and emergency preparedness to safeguard against potential risks and ensure sustainable water management practices in the region.

Year Completed

1980

Dam Length

450

Dam Height

27

River Or Stream

TR-THREE MILE CREEK

Primary Dam Type

Earth

Surface Area

3.5

Drainage Area

0.4

Nid Storage

137

Hazard Potential

Low

Foundations

Soil

Nid Height

27
       
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.