Great Falls Dam Reservoir Report

Last Updated: December 5, 2025

Great Falls Dam, Lock No.


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Summary

20, located in Montgomery County, Maryland, along the C&O Canal, is a historic structure built in 1850 primarily for recreational purposes. The dam, standing at a height of 8 feet, serves as a popular destination for water resource and climate enthusiasts looking to enjoy the scenic beauty of the area. The dam is classified as an earth dam with buttress and stone core types, and it has a low hazard potential according to the latest assessment.

While the dam's condition is currently rated as "Not Rated," it is under the jurisdiction of the Maryland Dam Safety regulatory agency and undergoes regular inspections and enforcement to ensure public safety. The last inspection took place in September 1996, with an inspection frequency of every 7 years. Despite its age, the dam continues to provide valuable recreational opportunities for visitors to the C&O Canal, offering a glimpse into the region's rich history and natural beauty.

Year Completed

1850

Dam Height

8

River Or Stream

C&O Canal

Primary Dam Type

Earth

Nid Storage

51

Hazard Potential

Low

Foundations

Soil

Nid Height

8
       
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.