Souhegan River Site 28 Dam Reservoir Report
Nearby: Burton Pond Dam Souhegan Site 8 Dam
Last Updated: December 17, 2025
Souhegan River Site 28 Dam, also known as Site 28 Floodwater Dam, is a critical flood risk reduction structure located in Lyndeborough, New Hampshire.
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Summary
Built in 1964 by the USDA NRCS, this earth dam stands at a height of 29 feet and spans a length of 590 feet along the TR Stony Brook. With a storage capacity of 187 acre-feet and a maximum discharge rate of 2521 cubic feet per second, the dam plays a crucial role in mitigating potential flooding events in the region.
Managed by the NHDES Dam Bureau, Souhegan River Site 28 Dam is deemed as having a high hazard potential due to its location and the amount of water it can retain. Despite this, the dam's condition assessment in 2017 reported it as being in satisfactory condition, with regular inspections taking place every two years to ensure its structural integrity. While the dam does not feature outlet gates or controlled spillways, its uncontrolled spillway with a width of 3 feet helps manage excess water during peak flow periods.
Water resource and climate enthusiasts will appreciate the significance of Souhegan River Site 28 Dam in protecting the surrounding area from potential flooding events. With a moderate risk assessment rating of 3, the dam serves as a crucial piece of infrastructure designed to reduce flood risks and safeguard the community against the impacts of extreme weather events. Its strategic location, design features, and regular maintenance make it a key asset in the state's flood risk reduction efforts.
Year Completed |
1964 |
Dam Length |
590 |
Dam Height |
29 |
River Or Stream |
TR STONY BROOK |
Primary Dam Type |
Earth |
Surface Area |
2.7 |
Drainage Area |
1.1 |
Nid Storage |
187 |
Outlet Gates |
None |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
29 |
Seasonal Comparison
Weather Forecast
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.
Souhegan River Site 28 Dam
Zephyr Lake boat launch