Antietam Reservoir Report

Last Updated: December 5, 2025

Antietam is a vital Earth dam located in Hamiltonban Township, Pennsylvania, serving as a crucial water supply source for the area.


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Summary

Completed in 1953, the dam stands at a height of 70 feet and has a capacity of 866 acre-feet, with a normal storage level of 464 acre-feet. With a surface area of 27 acres and a drainage area of 3.9 square miles, the dam plays a significant role in managing water resources for the region.

Owned and regulated by the Pennsylvania Department of Environmental Protection, Antietam is subject to regular inspections and enforcement to ensure its structural integrity and operational efficiency. Classified with a high hazard potential and assessed to be in fair condition, the dam is monitored closely to mitigate any potential risks and ensure the safety of surrounding communities. Despite its age, Antietam continues to serve its primary purpose of water supply effectively, highlighting the importance of proper maintenance and regulation in safeguarding critical infrastructure in the face of changing climate conditions.

As water resource and climate enthusiasts, understanding the significance of dams like Antietam in managing water supply and mitigating risks is crucial. The dam's location along the East Branch Antietam Creek, in Adams County, Pennsylvania, underscores the interconnectedness of water resources and the environment. With ongoing monitoring and regulatory oversight, Antietam stands as a testament to the importance of sustainable water management practices in the face of evolving climate challenges.

Year Completed

1953

Dam Length

815

Dam Height

70

River Or Stream

EAST BRANCH ANTIETAM CREEK

Primary Dam Type

Earth

Surface Area

27

Drainage Area

3.9

Nid Storage

866

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

70
       
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.