Lyons Falls - Mill 3 Reservoir Report

Last Updated: December 10, 2025

Lyons Falls - Mill 3 is a captivating hydroelectric dam located in Lewis, New York, along the Black River.


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Summary

Constructed in 1922, this concrete gravity dam stands at a height of 10 feet and spans 430 feet in length. With a storage capacity of 730 acre-feet and a maximum discharge of 35,513 cubic feet per second, this dam plays a crucial role in harnessing the power of water for hydroelectric purposes.

Managed by a private owner, Lyons Falls - Mill 3 is not regulated by the state but falls under the jurisdiction of the Federal Energy Regulatory Commission (FERC). The dam has a low hazard potential and a very high risk assessment rating, signifying its importance in the region's water resource management and energy production. With two slide (sluice gate) outlet gates and a controlled spillway width of 360 feet, this dam is equipped to handle various water flow conditions and ensure the safety of downstream areas.

Despite its age, Lyons Falls - Mill 3 continues to operate efficiently, with regular inspections conducted by the FERC to ensure its structural integrity. The dam's location in the picturesque city of Lyons Falls further adds to its appeal for water resource and climate enthusiasts, offering a unique opportunity to witness the intersection of natural beauty and sustainable energy generation in action.

Year Completed

1922

Dam Length

430

Dam Height

10

River Or Stream

Black River

Primary Dam Type

Concrete

Surface Area

130

Drainage Area

870

Nid Storage

730

Outlet Gates

Slide (sluice gate) - 2

Hazard Potential

Low

Foundations

Rock

Nid Height

10
       
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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.