Riverdale Mills Reservoir Report
Last Updated: December 16, 2025
Riverdale Mills, also known as Knott Dam, is a private hydroelectric facility located in Northbridge, Massachusetts along the Blackstone River.
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Summary
Built in 1957, this concrete dam stands at a height of 9.5 feet and has a length of 142 feet, serving multiple purposes including flood risk reduction, hydroelectric power generation, and water supply. With a storage capacity of 89 acre-feet and a maximum discharge of 19,400 cubic feet per second, Riverdale Mills plays a crucial role in managing water resources in the region.
Managed by the Federal Energy Regulatory Commission, Riverdale Mills has a low hazard potential and a very high risk assessment rating. Despite its age, the dam's condition assessment is not currently available, and its emergency action plan has not been updated since 2009. The dam features controlled spillways and outlet gates for efficient water management, serving as an important infrastructure for both environmental and energy needs in the area. For water resource and climate enthusiasts, Riverdale Mills represents a unique blend of history, engineering, and sustainable practices in harnessing the power of water for the benefit of the community.
Overall, Riverdale Mills stands as a testament to the importance of hydroelectric infrastructure in managing water resources and supporting sustainable energy practices. Its location along the Blackstone River in Worcester County, Massachusetts, underscores its significance in the region's water management efforts. With a focus on flood risk reduction, hydroelectric power generation, and water supply, Riverdale Mills exemplifies the intersection of technology, nature, and innovation in meeting the challenges of climate change and water resource sustainability.
Year Completed |
1957 |
Dam Length |
142 |
Dam Height |
9.5 |
River Or Stream |
Blackstone River |
Primary Dam Type |
Concrete |
Surface Area |
12 |
Drainage Area |
142 |
Nid Storage |
89 |
Outlet Gates |
Flap - 1, Other Controlled - 5 |
Hazard Potential |
Low |
Foundations |
Rock |
Nid Height |
10 |
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.
Riverdale Mills
Brigham Hill Road Grafton