Assabet Reservoir Report
Last Updated: December 18, 2025
Assabet, also known as Powdermill Dam, is a private hydroelectric dam located in Concord, Massachusetts.
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Summary
Constructed in 1921, this masonry dam stands at a height of 13 feet and spans 480 feet across the Assabet River. With a storage capacity of 122 acre-feet and a maximum discharge of 3350 cubic feet per second, Assabet serves as a vital source of renewable energy in the region.
Managed by the Federal Energy Regulatory Commission, Assabet has a significant hazard potential and a moderate risk assessment rating. The dam features an uncontrolled spillway with a width of 80 feet and four slide gates for water release. Despite its age, the condition assessment for Assabet is currently marked as Not Available, highlighting the need for ongoing monitoring and maintenance to ensure its continued safety and functionality.
Enthusiasts of water resources and climate will find Assabet to be a fascinating example of historic infrastructure supporting modern energy needs. With its picturesque location in Middlesex County, Massachusetts, this dam serves as a reminder of the importance of sustainable hydroelectric power generation and the ongoing efforts required to manage and maintain our water resources for future generations.
Year Completed |
1921 |
Dam Length |
480 |
Dam Height |
13 |
River Or Stream |
Assabet River |
Primary Dam Type |
Masonry |
Surface Area |
30 |
Drainage Area |
123 |
Nid Storage |
122 |
Outlet Gates |
Slide (sluice gate) - 4 |
Hazard Potential |
Significant |
Foundations |
Rock |
Nid Height |
13 |
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.
Assabet
Seymour Street 1A, Concord