Union Grove Lake Dam Reservoir Report

Last Updated: December 6, 2025

Union Grove Lake Dam, located in Garwin, Iowa, is a state-regulated structure with a primary purpose of recreation.


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Summary

Completed in 1920, this earth dam stands at a height of 29 feet and has a length of 1205 feet. The dam provides a storage capacity of 2120 acre-feet, with a normal storage level of 770 acre-feet and a surface area of 117 acres.

Managed by the Iowa Department of Natural Resources, Union Grove Lake Dam has a significant hazard potential and was last assessed to be in fair condition in June 2018. The dam features an uncontrolled spillway with a width of 76 feet and is situated on the Deer Creek, within the Detroit District of the US Army Corps of Engineers. With a moderate risk assessment rating of 3, the dam undergoes inspections every five years to ensure its safety and functionality for water resource and climate enthusiasts who enjoy the recreational activities offered at the lake.

Year Completed

1920

Dam Length

1205

Dam Height

29

River Or Stream

DEER CREEK

Primary Dam Type

Earth

Surface Area

117

Drainage Area

11

Nid Storage

2120

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

29
       
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.