Hewittville Reservoir Report
Nearby: Unionville Sissonville
Last Updated: December 18, 2025
Hewittville in Unionville, New York, is a privately owned hydroelectric dam on the Raquette River.
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Summary
Completed in 1870, this concrete dam stands at 17.5 feet tall and has a storage capacity of 360 acre-feet. With a spillway width of 451 feet and the ability to discharge up to 11,500 cubic feet per second, Hewittville plays a crucial role in managing water flow in the region.
Managed by the Federal Energy Regulatory Commission, Hewittville is classified as a low hazard structure with a moderate risk assessment. Despite its age, the dam's condition assessment is not available, highlighting the need for ongoing monitoring and maintenance. The dam has three Tainter (radial) outlet gates and is used for fire protection, stock, small fish pond, and hydroelectric purposes, showcasing its versatility and importance in water resource management.
Located within St. Lawrence County, New York, Hewittville serves as a vital component of the local water infrastructure. With state-regulated permitting, inspection, and enforcement in place, the dam ensures the efficient utilization of water resources while minimizing environmental impact. As a key player in the region's water management system, Hewittville stands as a testament to the intersection of technology, conservation, and climate resilience.
Year Completed |
1870 |
Dam Length |
615 |
Dam Height |
17.5 |
River Or Stream |
Raquette River |
Primary Dam Type |
Concrete |
Surface Area |
109 |
Drainage Area |
1036 |
Nid Storage |
360 |
Outlet Gates |
Tainter (radial) - 3 |
Hazard Potential |
Low |
Foundations |
Rock |
Nid Height |
18 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Raquette River At Raymondville Ny
|
2010cfs |
Grass River At Chase Mills Ny
|
1350cfs |
Raquette River At South Colton Ny
|
360cfs |
W Br St. Regis R Nr Parishville Ny
|
211cfs |
St. Regis River At Brasher Center Ny
|
588cfs |
Oswegatchie River Near Heuvelton Ny
|
1250cfs |
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.
Hewittville