Stone Dam - Dike 7 Reservoir Report

Last Updated: December 21, 2025

Stone Dam - Dike 7, located in Millinocket, Maine, is a crucial structure along the West Branch Penobscot River with a primary purpose of hydroelectric power generation.


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Summary

Built in 1900, this earth dam stands at 9 feet high and spans 235 feet in length, providing a storage capacity of 8100 acre-feet. The dam also serves various other purposes including flood risk reduction, recreation, and water supply for the surrounding area.

Managed by the Federal Energy Regulatory Commission, Stone Dam - Dike 7 has a low hazard potential and a high risk assessment rating of 2. Despite its age, the condition assessment of the dam is not available, highlighting the need for ongoing monitoring and inspection. The Emergency Action Plan for the dam was last revised in December 2018, emphasizing the importance of preparedness in case of any unforeseen events. With a drainage area of 1890 square miles, the dam plays a crucial role in regulating water flow and providing environmental benefits to the region.

Overall, Stone Dam - Dike 7 stands as a significant infrastructure for water resource management and climate resilience in Maine. As a key component in the hydroelectric power generation network, this dam plays a vital role in supporting various sectors while also ensuring the safety and well-being of the local communities. Ongoing maintenance and monitoring efforts will be essential to ensure the continued effectiveness and safety of this important structure in the years to come.

Year Completed

1900

Dam Length

235

Dam Height

9

River Or Stream

West Branch Penobscot River

Surface Area

1344

Drainage Area

1890

Nid Storage

8100

Hazard Potential

Low

Nid Height

9
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.