Warren St Detention Reservoir Report

Last Updated: December 6, 2025

Warren St Detention, located in Mankato, Minnesota, is a crucial earth dam structure designed by BARR ENG to manage flood risk along the Minnesota River.


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Summary

Completed in 1997, this dam stands at a height of 45 feet and spans 150 feet in length, with a primary purpose of flood risk reduction. With a storage capacity of 30 acre-feet and a normal storage level of 1.6 feet, the dam plays a vital role in protecting the surrounding Blue Earth County area from potential flooding events.

The structure's hazard potential is classified as low, with a fair condition assessment as of June 2016. The dam features an uncontrolled spillway type with a width of 6 feet, allowing for a maximum discharge of 50 cubic feet per second. Despite its moderate risk rating, Warren St Detention has not been modified in recent years and has demonstrated its effectiveness in managing floodwaters. The dam is inspected every four years to ensure its continued functionality and safety for the community.

Owned and regulated by the local government with oversight from the Minnesota Department of Natural Resources, Warren St Detention serves as a critical infrastructure asset for flood control in the region. Its strategic location and design make it a key component in the overall water resource management system along the Minnesota River, contributing to the resilience of the area against potential climate-related challenges.

Year Completed

1997

Dam Length

150

Dam Height

44

River Or Stream

MINNESOTA RIVER-TR

Primary Dam Type

Earth

Surface Area

3

Drainage Area

1

Nid Storage

30

Structural Height

45

Outlet Gates

Uncontrolled

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

45
       
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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.