Lower Theisman Dam Reservoir Report

Last Updated: December 5, 2025

Lower Theisman Dam, located in Loudoun, Virginia, is a privately owned earth dam with a primary purpose of recreation.


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Summary

Standing at a height of 20 feet and stretching 660 feet in length, this dam creates a storage capacity of 92.3 acre-feet, providing a serene surface area of 7 acres for visitors to enjoy. Situated on the Limestone Branch tributary, the dam is regulated, permitted, inspected, and enforced by the Department of Conservation and Recreation in Virginia.

Although the dam's hazard potential is currently classified as undetermined and its condition is not rated, Lower Theisman Dam serves as a vital recreational resource for the community. With its picturesque surroundings and ample storage capacity, the dam offers opportunities for outdoor activities and water-based recreation. As water resource and climate enthusiasts, the presence of this dam underscores the importance of sustainable water management practices and the need to balance recreational benefits with dam safety considerations.

As Lower Theisman Dam continues to provide recreational opportunities for visitors, there is a growing emphasis on ensuring its long-term safety and functionality. With the support of regulatory agencies and ongoing inspections, efforts are being made to maintain the dam's integrity and mitigate potential risks. By staying informed and engaged in the management of this essential water resource, enthusiasts can contribute to the preservation of both natural ecosystems and recreational amenities for future generations.

Dam Length

660

Dam Height

20

River Or Stream

Limestone Branch tributary

Primary Dam Type

Earth

Surface Area

7

Hydraulic Height

20

Nid Storage

92.3

Structural Height

20

Hazard Potential

Undetermined

Nid Height

20
       
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.