Lake Fairfax Dam Reservoir Report

Last Updated: December 5, 2025

Lake Fairfax Dam, located in Fairfax, Virginia, is a local government-owned structure that serves primarily for recreation purposes.


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Summary

The dam, standing at a height of 32 feet, impounds Colvin Run, creating a lake with a normal storage capacity of 182 acre-feet and a maximum storage of 487 acre-feet. With a surface area of 21 acres and a drainage area of 4.3 square miles, the dam plays a significant role in providing water-based recreational activities for visitors.

Managed by the Department of Conservation and Recreation, the dam is regulated by the state of Virginia, ensuring regular inspections and enforcement of safety measures. Despite being classified as having a high hazard potential, the dam's condition assessment as of December 2020 was deemed satisfactory. Emergency action plans are in place, with the last revision dating back to September 2012. The dam's location within the Baltimore District and its association with Congressman Gerald E. Connolly highlights its importance in the region's water resource management and climate resilience efforts.

Lake Fairfax Dam stands as a vital earth structure that not only provides recreational opportunities but also plays a crucial role in water storage and management in the Fairfax County area. As a popular destination for outdoor enthusiasts and nature lovers, the dam's presence along Colvin Run enhances the local ecosystem and contributes to the overall environmental health and well-being. With its strategic location and capacity, Lake Fairfax Dam exemplifies the intersection of water resource management, climate adaptation, and community engagement in ensuring a sustainable future for generations to come.

Dam Length

500

Dam Height

32

River Or Stream

Colvin Run

Primary Dam Type

Earth

Surface Area

21

Hydraulic Height

32

Drainage Area

4.3

Nid Storage

487

Structural Height

32

Hazard Potential

High

Nid Height

32
       
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.