Grassy Pond Dam Reservoir Report
Nearby: Bear Pond Dam Hoague - Sprague
Last Updated: December 16, 2025
Grassy Pond Dam, located in Hopkinton, New Hampshire, is a concrete structure with a primary purpose of recreation.
°F
°F
mph
Wind
%
Humidity
Summary
Completed in 1920, this dam stands at a height of 8.5 feet and has a storage capacity of 204 acre-feet. With a surface area of 35 acres and a drainage area of 0.9 square miles, Grassy Pond Dam is a key feature of the surrounding landscape.
Managed by the NHDES Dam Bureau, Grassy Pond Dam is state-regulated, with regular inspections and enforcement measures in place. Despite its low hazard potential and fair condition assessment, the dam poses a moderate risk as per the latest evaluation. The spillway, with an uncontrolled type and a width of 40 feet, plays a crucial role in managing water flow and ensuring safety during high discharge events.
Enthusiasts of water resources and climate will find Grassy Pond Dam an intriguing structure, blending historical significance with modern regulatory standards. Its recreational purpose, combined with its environmental impact on the surrounding intermittent stream, makes it a valuable asset for both the local community and the state of New Hampshire.
Year Completed |
1920 |
Dam Length |
75 |
Dam Height |
8.5 |
River Or Stream |
INTERMITTENT STREAM |
Primary Dam Type |
Concrete |
Surface Area |
35 |
Drainage Area |
0.9 |
Nid Storage |
204 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
9 |
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 Pond Dam
Clement Pond boat launch
Sewall'S Island To Manchester Street Bridge