Grassy Sprain Reservoir Dam Reservoir Report
Last Updated: December 14, 2025
Grassy Sprain Reservoir Dam, located in Yonkers, New York, is a significant structure designed for recreational purposes.
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Summary
Constructed in 1876, this earth dam stands at a height of 40 feet and spans a length of 600 feet, with a storage capacity of 3550 acre-feet. The dam overlooks the picturesque Grassy Sprain Brook and serves as a popular spot for water resource and climate enthusiasts to engage in various outdoor activities.
This high-hazard dam is regulated and inspected by the New York State Department of Environmental Conservation to ensure its structural integrity and safety. With a satisfactory condition assessment and a moderate risk rating, the dam is equipped with an uncontrolled spillway and has a maximum discharge capacity of 1025 cubic feet per second. The area surrounding the reservoir spans 150 acres, providing ample space for recreational activities and wildlife habitat preservation.
Water resource and climate enthusiasts can appreciate the historical significance and environmental impact of Grassy Sprain Reservoir Dam. From its construction in the 19th century to its current maintenance and regulation, this dam continues to play a vital role in water storage, flood control, and recreational opportunities in Westchester County. Its presence highlights the importance of sustainable water management practices and the interconnectedness of human activities with the natural environment.
Year Completed |
1876 |
Dam Length |
600 |
Dam Height |
40 |
River Or Stream |
GRASSY SPRAIN BROOK |
Primary Dam Type |
Earth |
Surface Area |
150 |
Drainage Area |
1.91 |
Nid Storage |
3550 |
Hazard Potential |
High |
Nid Height |
40 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
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.
Grassy Sprain Reservoir Dam