Thornley Pond Dam Reservoir Report

Last Updated: December 5, 2025

Thornley Pond Dam, located in Berkeley County, South Carolina, was completed in 1940 and serves primarily for recreational purposes.


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Summary

This earth dam, with a height of 14 feet and a length of 775 feet, has a storage capacity of 156 acre-feet and covers a surface area of 20 acres. Despite being privately owned, the dam is regulated by the South Carolina Department of Health and Environmental Control (DHEC) and undergoes regular inspections to ensure its safety and compliance with state regulations.

The dam poses a high hazard potential due to its condition being assessed as fair during the last inspection in March 2020. With an inspection frequency of every two years, efforts are being made to maintain the dam's integrity and address any potential risks. Although no emergency action plan (EAP) or guidelines for inundation maps have been prepared, the dam remains under the jurisdiction of the state and is subject to enforcement and oversight by the regulatory agency.

Situated on the TR-West Branch Cooper River, Thornley Pond Dam contributes to the local ecosystem and provides opportunities for outdoor recreation. As water resource and climate enthusiasts, it is important to monitor and support the maintenance of such infrastructure to ensure the safety of communities and the preservation of the natural environment.

Year Completed

1940

Dam Length

775

Dam Height

14

River Or Stream

TR-WEST BRANCH COOPER RIVER

Primary Dam Type

Earth

Surface Area

20

Nid Storage

156

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

14
       
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.