Ammons Lake Dam Lower Reservoir Report

Last Updated: December 5, 2025

Ammons Lake Dam Lower, also known as Stonehenge Subdivision Dam or Greystone Lake Dam, is a significant earth dam located in Raleigh, North Carolina.


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Summary

Completed in 1980, this dam serves primarily for recreational purposes and is regulated by the NC Department of Environmental Quality Dam Safety Program. With a hydraulic height of 19 feet and a structural height of 27 feet, the dam stands as a vital structure on the NW Tributary of Mine Creek, offering a storage capacity of 352 acre-feet and a drainage area of 1529 acres.

Despite its satisfactory condition assessment in 2017, Ammons Lake Dam Lower is classified as having a high hazard potential due to its location and design. Regular inspections and enforcement by the regulatory agencies ensure the safety and integrity of this dam, with an inspection frequency of every two years. The dam's emergency action plan (EAP) was last revised in 2011, highlighting the importance of preparedness and risk management measures in case of potential emergencies. With a maximum discharge capacity of 5241 cubic feet per second, the dam plays a crucial role in water resource management and flood control in the region.

In conclusion, Ammons Lake Dam Lower serves as a vital recreational and water management structure in Wake County, North Carolina. Its significance lies in providing storage, flood control, and recreational opportunities while also ensuring the safety and security of the surrounding community. With regular inspections, proper enforcement, and a well-maintained emergency action plan, this dam stands as a testament to responsible water resource management in the face of changing climate conditions.

Year Completed

1980

Dam Length

550

River Or Stream

NW Trib of Mine Creek

Surface Area

8

Hydraulic Height

19

Drainage Area

1529

Nid Storage

352

Structural Height

27

Hazard Potential

High

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.