Clark Mills (Pa-490) Reservoir Report
Last Updated: December 13, 2025
Clark Mills (Pa-490) is a local government-owned earth dam located in Perry Township, Mercer, Pennsylvania.
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Summary
Built in 1971 by the USDA NRCS, this dam on Calvin Clark Run serves the primary purpose of flood risk reduction. Standing at a height of 45 feet and with a length of 430 feet, it has a storage capacity of 790 acre-feet and covers a surface area of 4 acres.
This dam is regulated by the Pennsylvania Department of Environmental Protection, with state permitting, inspection, and enforcement in place. Despite being classified as having a high hazard potential, the dam is currently in fair condition, as assessed in the last inspection conducted in September 2020. With a drainage area of 3.29 square miles, Clark Mills plays a crucial role in managing water resources in the region and mitigating flood risks for the local community.
Enthusiasts of water resources and climate will find Clark Mills (Pa-490) to be an intriguing case study in dam infrastructure. With its historical significance, design by the USDA NRCS, and state regulation ensuring its safety and functionality, this dam serves as a vital asset for flood risk reduction in Mercer, Pennsylvania. As efforts continue to maintain and improve its condition, Clark Mills stands as a testament to the importance of effective water resource management in addressing the challenges of a changing climate.
Year Completed |
1971 |
Dam Length |
430 |
Dam Height |
45 |
River Or Stream |
CALVIN CLARK RUN |
Primary Dam Type |
Earth |
Surface Area |
4 |
Drainage Area |
3.29 |
Nid Storage |
790 |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
45 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Ohoopee River Near Reidsville
|
195cfs |
Altamaha River Near Baxley
|
4410cfs |
Canoochee River Near Claxton
|
69cfs |
Oconee River Near Mount Vernon
|
1280cfs |
Ocmulgee River At Lumber City
|
2740cfs |
Altamaha River At Doctortown
|
5070cfs |
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.
Chicken Yard Pond Dam