Heishmans Mill Reservoir Report

Last Updated: December 8, 2025

Heishmans Mill, located in West Pennsboro Township, Cumberland County, Pennsylvania, is a historic hydroelectric dam that has been operating since 1815.


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Summary

Owned privately, this concrete dam stands at a height of 10 feet and has a storage capacity of 80 acre-feet. It is situated on the Conodoguinet Creek and serves as a source of renewable energy for the surrounding community.

Managed and regulated by the Pennsylvania Department of Environmental Protection, Heishmans Mill is classified as a low hazard potential structure with a condition assessment that is currently not rated. The dam has a spillway type and width that are unlisted, and its last inspection took place in May 2018 with a scheduled inspection frequency of 5 years. While the emergency action plan status and risk assessment details are not provided, the dam continues to be a vital asset for water resource management in the region.

With its historical significance, operational longevity, and environmental impact as a hydroelectric facility, Heishmans Mill offers a fascinating glimpse into the intersection of water resources, climate considerations, and sustainable energy production. As enthusiasts in these fields, exploring the engineering, regulatory, and conservation aspects of this dam can provide valuable insights into the intricate balance between human development and natural resource management.

Year Completed

1815

Dam Length

140

Dam Height

10

River Or Stream

CONODOGUINET CREEK

Primary Dam Type

Concrete

Surface Area

20

Drainage Area

310

Nid Storage

80

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

10
       
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.