Michael J. Kirwan Dam Reservoir Report

Last Updated: December 5, 2025

Michael J.


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Summary

Kirwan Dam, located in Ohio, serves as a vital flood risk reduction structure along the West Branch of the Mahoning River. Completed in 1966, this federal-owned earth dam stands at a hydraulic height of 77 feet and a structural height of 83 feet, with a storage capacity of 124,000 acre-feet. Despite its risk management measures and emergency action plans, a moderate hazard potential is associated with the dam due to the possibility of uncontrolled high-volume water releases during extreme storm events.

In the event of a catastrophic failure, downstream communities such as Niles, Newton Falls, Warren, Youngstown in Ohio, and New Castle and Beaver Falls in Pennsylvania could face swift and deep floodwaters that would result in significant property damage and potential loss of life. Risk assessments have identified key scenarios, including a collapse of the concrete spillway, erosion of embankment soils, and dam breach, which could lead to devastating flooding. To mitigate these risks, continuous monitoring and coordination with state and local emergency managers, as well as public engagement efforts, are crucial for enhancing preparedness and response capabilities.

To safeguard public safety, ongoing efforts include close collaboration with the US Geologic Survey and National Weather Service to provide real-time lake level information to the public. By staying proactive in monitoring the dam's condition and responding to potential high water events, the management of Michael J. Kirwan Dam remains committed to reducing the risks posed by this critical infrastructure to downstream communities.

Year Completed

1966

Dam Length

9900

River Or Stream

WEST BRANCH OF THE MAHONING

Primary Dam Type

Earth

Surface Area

2650

Hydraulic Height

77

Drainage Area

81

Nid Storage

124000

Structural Height

83

Outlet Gates

Vertical Lift - 6

Hazard Potential

High

Foundations

Soil

Nid Height

83
       
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.