Allegheny River Lock And Dam 9 Reservoir Report

Last Updated: December 6, 2025

Allegheny River Lock and Dam 9, also known as Allegheny River Pool 09, is a gravity dam located in Armstrong County, Pennsylvania.


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Summary

Completed in 1938 by the US Army Corps of Engineers, the dam serves primarily for navigation purposes on the Allegheny River. With a structural height of 55 feet and a hydraulic height of 30 feet, the dam spans 1040 feet in length and has a storage capacity of 13,500 acre-feet.

The dam features a single lock with dimensions of 360 feet in length and 56 feet in width, facilitating the passage of vessels along the river. While the hazard potential of the dam is considered low, it is still subject to regular inspections and risk management measures to ensure its structural integrity and mitigate any potential flood risks associated with the dam. The US Army Corps of Engineers actively monitors the dam's condition, engages with emergency managers, and updates emergency action plans to address any concerns related to the dam's operation and safety.

In the event of severe weather or unforeseen circumstances, the dam may release water to manage levels upstream or downstream, highlighting the importance of ongoing risk assessment and communication with local stakeholders. As part of its commitment to safety and preparedness, the US Army Corps of Engineers continues to implement measures to safeguard the dam and surrounding communities, emphasizing the importance of proactive maintenance and collaboration in mitigating potential risks associated with water resource management and climate variability.

Year Completed

1938

Dam Length

1040

River Or Stream

ALLEGHENY RIVER

Primary Dam Type

Gravity

Surface Area

1040

Length Of Locks

360

Hydraulic Height

30

Drainage Area

8401

Nid Storage

13500

Structural Height

55

Outlet Gates

None - 0, Uncontrolled - 0

Hazard Potential

Low

Foundations

Rock

Nid Height

55
       
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.