Loyalhanna Dam Reservoir Report

Last Updated: December 5, 2025

Loyalhanna Dam, also known as Loyalhanna Lake, is a gravity dam located in Westmoreland, Pennsylvania, along the Loyalhanna Creek.


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Summary

Built in 1942 by the US Army Corps of Engineers, the primary purpose of this dam is flood risk reduction, with additional purposes including recreation. The dam stands at a structural height of 120 feet, with a hydraulic height of 114 feet, and a length of 960 feet. It has a maximum storage capacity of 127,556 acre-feet and a normal storage capacity of 2,000 acre-feet.

The dam is equipped with a controlled spillway and a variety of outlet gates to manage water levels. It has a high hazard potential and is subject to regular inspections and risk management measures. The US Army Corps of Engineers works diligently to monitor the dam's condition, prioritize risk-reducing activities, and collaborate with local emergency managers and the public to ensure preparedness in case of a dam-related emergency. Despite its flood risk reduction capabilities, the dam cannot eliminate all risks of flooding, especially during severe weather events that may overwhelm its capacity.

In summary, Loyalhanna Dam serves as a critical infrastructure for flood risk reduction in the region. With a focus on safety and risk management, the US Army Corps of Engineers implements measures to ensure the dam's structural integrity and collaborates with local stakeholders to enhance emergency preparedness. As a key component of water resource management, Loyalhanna Dam plays a vital role in protecting communities downstream from potential flooding events.

Year Completed

1942

Dam Length

960

River Or Stream

LOYALHANNA CREEK

Primary Dam Type

Gravity

Surface Area

210

Hydraulic Height

114

Drainage Area

290

Nid Storage

127556

Structural Height

120

Outlet Gates

Slide (sluice gate) - 9, Valve - 1, Vertical Lift - 5

Hazard Potential

High

Foundations

Rock

Nid Height

120
       
Seasonal Comparison

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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.