Mannitto Reservoir Report

Last Updated: December 5, 2025

Mannitto is a private dam located in Loyalhanna Township, Westmoreland County, Pennsylvania.


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Summary

Managed by the Pennsylvania Department of Environmental Protection, this earth dam stands at a height of 18 feet and spans a length of 550 feet along the TR Loyalhanna Creek. Originally constructed for recreational purposes, Mannitto has a storage capacity of 95 acre-feet and a surface area of 11 acres.

Despite its low hazard potential, Mannitto has not been rated for its condition assessment. The last inspection took place in June 2017, with a scheduled inspection frequency of every five years. The dam is not associated with any federal agencies and has not undergone any significant modifications since its completion. With its surrounding area covering 0.25 square miles of drainage, Mannitto serves as a vital water resource for the local community.

Enthusiasts of water resources and climate will find Mannitto an intriguing structure due to its unique design and purpose. With its location in a picturesque setting along the Loyalhanna Creek, this dam provides both recreational opportunities and essential water storage for the region. While it has not been rated for condition assessment, Mannitto remains a significant feature in the landscape of Westmoreland County, Pennsylvania, showcasing the intersection of human infrastructure and natural resources in the context of water management and conservation.

Dam Length

550

Dam Height

18

River Or Stream

TR LOYALHANNA CREEK

Primary Dam Type

Earth

Surface Area

11

Drainage Area

0.25

Nid Storage

95

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

18
       
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.