North Twin - Dike 1 Reservoir Report

Last Updated: December 22, 2025

North Twin - Dike 1 is a significant earth dam located in Millinocket, Maine, along the West Branch Penobscot River.


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Summary

Completed in 1934, this hydroelectric structure stands at a height of 11 feet and stretches 416 feet in length, with a storage capacity of 346,000 acre-feet and a surface area of 17,790 acres. While it serves multiple purposes including flood risk reduction, navigation, recreation, and water supply, its primary function is hydroelectric power generation.

Managed by the Federal Energy Regulatory Commission, North Twin - Dike 1 has a high hazard potential and a significant risk assessment rating of 2. Despite its age, the dam's condition assessment is not currently available, highlighting the need for ongoing monitoring and maintenance to ensure its structural integrity and continued safe operation. With its location in a picturesque natural setting and crucial role in water resource management, this dam is of great interest to water resource and climate enthusiasts alike, serving as a vital piece of infrastructure in the region.

As part of the New England District, North Twin - Dike 1 is a key component in the local water management system, contributing to fish and wildlife conservation efforts while providing essential water storage capacity for the surrounding area. With its historical significance and ongoing importance in the region, this dam represents a balancing act between harnessing natural resources for energy production and protecting the environment for future generations.

Year Completed

1934

Dam Length

416

Dam Height

11

River Or Stream

West Branch Penobscot River

Surface Area

17790

Drainage Area

1877

Nid Storage

346000

Hazard Potential

Significant

Nid Height

11
       
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.