Lake Antietam Reservoir Report

Last Updated: December 6, 2025

Lake Antietam, located in Lower Alsace Township, Pennsylvania, is a vital water supply source with a primary purpose of providing water to the local community.


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Summary

The earth dam, standing at a height of 60 feet and stretching 230 feet in length, was completed in 1880 and has a storage capacity of 430 acre-feet. The dam's normal storage capacity is 310 acre-feet, covering a surface area of 16 acres and serving a drainage area of 5.4 square miles.

Managed by the Pennsylvania Department of Environmental Protection, Lake Antietam is regulated, inspected, and enforced to ensure its structural integrity and operational safety. The dam has a high hazard potential but is currently assessed as satisfactory in condition. Despite its age, the dam continues to meet guidelines for emergency action plans, although specific dates for assessments and management measures are not provided in the data.

With its historical significance and crucial role in providing water to the region, Lake Antietam serves as a reminder of the importance of maintaining and safeguarding water resources in the face of changing climate conditions. The dam stands as a testament to the engineering feats of its time and the ongoing efforts to protect communities from potential hazards associated with water infrastructure.

Year Completed

1880

Dam Length

230

Dam Height

60

River Or Stream

ANTIEEAM CREEK

Primary Dam Type

Earth

Surface Area

16

Drainage Area

5.4

Nid Storage

430

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

60
       
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.