Thunder Hollow Reservoir Report
Nearby: Big Ridge Wayland Lake
Last Updated: December 13, 2025
Thunder Hollow is a privately owned earth dam located in Union, Tennessee, specifically in the city of Pleasant Grove.
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Summary
Built in 1974, this dam stands at a height of 46 feet, with a hydraulic height of 36.6 feet and a length of 357 feet. It serves as a structure on the Bullrun Creek, providing a storage capacity of 34 acre-feet with a normal storage level of 25 acre-feet.
Despite being privately owned, Thunder Hollow is not regulated by the state and does not have any associated state permitting, inspection, or enforcement. The dam has a significant hazard potential and is classified as having a moderate risk level. It has not been rated for its condition assessment, and the last inspection was conducted in February 2020 with an inspection frequency of every 5 years. The spillway type is uncontrolled, and there are no outlet gates associated with the dam.
For water resource and climate enthusiasts, Thunder Hollow presents an interesting case study of a privately owned dam in Tennessee. Its location on Bullrun Creek and its significance in terms of hazard potential and risk assessment make it a noteworthy site to monitor and study in the context of water resource management and climate resilience. As an earth dam with a moderate risk level, Thunder Hollow highlights the importance of regular inspections and maintenance to ensure the safety and integrity of such structures in the face of changing environmental conditions.
Year Completed |
1974 |
Dam Length |
357 |
River Or Stream |
BULLRUN CREEK |
Primary Dam Type |
Earth |
Surface Area |
1.4 |
Hydraulic Height |
36.6 |
Drainage Area |
0.22 |
Nid Storage |
34 |
Structural Height |
46 |
Outlet Gates |
None |
Hazard Potential |
Significant |
Nid Height |
46 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Bullrun Creek Near Halls Crossroads
|
32cfs |
Beaver Creek At Solway
|
84cfs |
Powell River Near Arthur
|
695cfs |
Little Pigeon River At Sevierville
|
166cfs |
Little River Near Alcoa
|
209cfs |
Clinch River Above Tazewell
|
1200cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Thunder Hollow