Mallard Marsh Dam No 3 Reservoir Report

Last Updated: December 6, 2025

Mallard Marsh Dam No 3, located in Cerro Gordo County, Iowa, is a local government-owned structure designed by WALLACE, HOL, KAS&SAHMITT in 1967.


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Summary

This earth dam serves primarily for recreation purposes, with a normal storage capacity of 39 acre-feet and a maximum storage of 129 acre-feet. Situated on the TR-WINNEBAGO RIVER, the dam has a length of 425 feet and a height of 8 feet, with a low hazard potential and a moderate risk assessment rating of 3.

Managed by the Iowa Department of Natural Resources (Iowa DNR), Mallard Marsh Dam No 3 is state-regulated, inspected, and enforced. The dam does not have a spillway and is classified as uncontrolled, with no outlet gates or associated structures. Despite being in a low hazard category, the dam's condition assessment is currently not rated, and there is no available information on emergency action plans or risk management measures. The dam's location in FERTILE, Iowa, offers a surface area of 20 acres and a drainage area of 2.97 square miles, providing valuable recreational opportunities for locals and visitors alike.

Overall, Mallard Marsh Dam No 3 is an important earth dam structure in the St. Paul District, serving as a recreational resource for the community. With its unique design and location on the TR-WINNEBAGO RIVER, the dam plays a crucial role in managing water resources in the area. While the dam's risk assessment is moderate, ongoing monitoring and maintenance by the Iowa DNR ensure the safety and functionality of this vital infrastructure for water resource and climate enthusiasts to explore and appreciate.

Year Completed

1967

Dam Length

425

Dam Height

8

River Or Stream

TR-WINNEBAGO RIVER

Primary Dam Type

Earth

Surface Area

20

Drainage Area

2.97

Nid Storage

129

Hazard Potential

Low

Foundations

Soil

Nid Height

8
       
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.