Thorn Run Reservoir Report

Last Updated: December 6, 2025

Thorn Run, located in Oakland Township, Butler, Pennsylvania, is a privately owned Earth dam completed in 1903 for water supply purposes.


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Summary

The dam stands at a height of 39.7 feet and has a length of 660 feet, with a storage capacity of 960 acre-feet. It serves a drainage area of 6.3 square miles and has a surface area of 49 acres, making it a crucial water resource in the region.

Managed by the Pennsylvania Department of Environmental Protection, Thorn Run is regulated, permitted, inspected, and enforced to ensure its structural integrity and operational efficiency. The dam has a high hazard potential but is currently in satisfactory condition, as per the last inspection in June 2020. It has undergone modifications in 2012 for hydraulic improvements, further enhancing its ability to manage water flow and storage.

With its vital role in water supply and its historical significance dating back over a century, Thorn Run represents a significant piece of infrastructure in the region. Climate and water resource enthusiasts can appreciate its design, purpose, and the effort put into its maintenance to ensure the safety and reliability of the dam for the community it serves.

Years Modified

2012 - Hydraulic

Year Completed

1903

Dam Length

660

Dam Height

39.7

River Or Stream

THORN RUN

Primary Dam Type

Earth

Surface Area

49

Drainage Area

6.3

Nid Storage

960

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

40
       
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.