Fair Lakes Dam #1 Reservoir Report

Last Updated: December 5, 2025

Fair Lakes Dam #1, also known as Seven Fair Lakes Dam, is a privately owned structure located in Fairfax, Virginia.


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Summary

This earthen dam stands at a height of 25 feet and stretches 980 feet in length, serving the primary purpose of flood risk reduction along the Big Rocky Run tributary. With a storage capacity of 99.43 acre-feet and a surface area of 3.81 acres, this dam plays a crucial role in managing water resources in the area.

Managed by the Department of Conservation and Recreation in Virginia, Fair Lakes Dam #1 has a high hazard potential but is currently assessed to be in satisfactory condition. Regular inspections take place to ensure its operational integrity, with the last assessment conducted in February 2020. Despite its critical role in flood risk reduction, there is limited information on its construction date or any modifications over the years, highlighting the importance of continued monitoring and maintenance to safeguard against potential risks and ensure its efficacy in the face of changing climate dynamics.

With the dam's location in a densely populated area and its vital function in mitigating flood risks, Fair Lakes Dam #1 serves as a key infrastructure for water resource and climate enthusiasts to study and monitor. As climate change impacts become more pronounced, understanding and maintaining such structures will be crucial in safeguarding communities and ecosystems from the escalating threats of extreme weather events and water resource management challenges.

Dam Length

980

Dam Height

25

River Or Stream

Big Rocky Run tributary

Primary Dam Type

Earth

Surface Area

3.81

Hydraulic Height

25

Drainage Area

0.78

Nid Storage

99.43

Structural Height

25

Hazard Potential

High

Nid Height

25
       
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.