South Pond Dam Reservoir Report
Last Updated: January 2, 2026
South Pond Dam, located in Rockville Centre, Nassau County, New York, is a state-regulated earth dam completed in 1903 for water supply purposes along the Mill River.
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Summary
With a height of 13 feet and a length of 800 feet, the dam has a storage capacity of 187 acre-feet, with a normal storage level of 83 acre-feet and a maximum discharge capacity of 600 cubic feet per second. The dam features an uncontrolled spillway with a width of 25 feet, contributing to its low hazard potential and moderate risk assessment rating of 3.
Managed by the New York State Department of Environmental Conservation (NYS DEC), South Pond Dam undergoes regular state inspections, permitting, and enforcement measures to ensure its structural integrity and safety. Despite being in operation for over a century, the dam's condition is currently not rated, highlighting the need for ongoing risk management measures and potential updates to its emergency action plan. With its critical role in water resource management in the region, South Pond Dam remains a key infrastructure for maintaining water supply stability and environmental conservation efforts in the area.
Year Completed |
1903 |
Dam Length |
800 |
Dam Height |
13 |
River Or Stream |
MILL RIVER |
Primary Dam Type |
Earth |
Surface Area |
21 |
Drainage Area |
16 |
Nid Storage |
187 |
Hazard Potential |
Low |
Nid Height |
13 |
Seasonal Comparison
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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.
South Pond Dam
Lakeside Drive Hempstead