Rocky Pen Run #4a Reservoir Report

Last Updated: December 6, 2025

Rocky Pen Run #4a is a state-regulated dam located in Stafford, Virginia, along the Rocky Pen Run river.


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Summary

The dam serves the primary purpose of flood risk reduction and water supply, standing at a height of 27 feet and with a storage capacity of 128 acre-feet. Despite its low hazard potential, the dam has a satisfactory condition assessment as of the last inspection in September 2019.

Managed by the Department of Conservation and Recreation, this earth dam has a structural length of 220 feet and covers a drainage area of 0.61 square miles. With a normal storage capacity of 34.87 acre-feet and a surface area of 7.32 acres, Rocky Pen Run #4a plays a crucial role in mitigating flood risks in the region. The dam has not undergone any modifications in recent years and meets state regulatory standards for inspection, enforcement, and permitting.

For water resource and climate enthusiasts, Rocky Pen Run #4a offers a fascinating case study in dam infrastructure management and its impact on local water systems. With its dual purpose of flood risk reduction and water supply, this dam is a vital component of the region's water management strategy. As climate change continues to pose challenges to water resources, understanding the role of structures like Rocky Pen Run #4a becomes increasingly important in ensuring the resilience of communities and ecosystems in the face of changing environmental conditions.

Dam Length

220

Dam Height

27

River Or Stream

Rocky Pen Run

Surface Area

7.32

Hydraulic Height

27

Drainage Area

0.61

Nid Storage

128

Structural Height

27

Hazard Potential

Low

Nid Height

27
       
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.