Souhegan River Site 10a Dam Reservoir Report
Last Updated: December 17, 2025
Souhegan River Site 10a Dam, also known as Mill Brook Dam, is a state-owned structure in Wilton, New Hampshire, designed by USDA NRCS to serve the primary purpose of flood risk reduction.
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Summary
Completed in 1966, this earth dam stands at a height of 59 feet and stretches over 1,281 feet, with a storage capacity of 2,770 acre-feet and a drainage area of 6.4 square miles. The dam has a high hazard potential but is currently in satisfactory condition, with the last inspection conducted in December 2019.
Located on the Mill Brook, this dam is regulated by the NHDES Dam Bureau and is subject to state permitting, inspection, and enforcement. Despite its uncontrolled spillway type, the dam's risk assessment is moderate, indicating a level 3 risk rating. The emergency action plan (EAP) for the dam was last revised in July 2016, and the structure is not associated with the US Army Corps of Engineers. With its significant flood mitigation capabilities and relatively stable condition, Souhegan River Site 10a Dam remains a crucial asset for water resource management in the region.
Year Completed |
1966 |
Dam Length |
1281 |
Dam Height |
59 |
River Or Stream |
MILL BROOK |
Primary Dam Type |
Earth |
Surface Area |
7.6 |
Drainage Area |
6.4 |
Nid Storage |
2770 |
Outlet Gates |
None |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
59 |
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.
Souhegan River Site 10a Dam
Cunningham Pond boat launch