North Twin - Dike 4 Reservoir Report
Last Updated: December 23, 2025
North Twin - Dike 4, located in Millinocket, Maine, along the West Branch Penobscot River, is a significant earth dam completed in 1934 for hydroelectric purposes.
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Summary
Standing at a height of 11 feet and stretching 197 feet in length, the dam has a storage capacity of 346,000 acre-feet and covers a surface area of 17,790 acres. Despite being regulated by the Federal Energy Regulatory Commission, the dam does not have a spillway, increasing its hazard potential to a significant level.
The dam's primary purposes include flood risk reduction, water supply, and recreation, while also supporting fish and wildlife habitats. With a drainage area of 1,877 square miles, the dam plays a crucial role in managing water resources in the region. While the dam has not been modified in recent years, its risk assessment remains high, underscoring the importance of ongoing monitoring and maintenance to ensure its structural integrity and continued efficient operation.
As a key infrastructure for the local community and the region, North Twin - Dike 4 serves as a vital component in the water management system along the West Branch Penobscot River. With its rich history dating back to the 1930s, the dam continues to be a cornerstone for hydroelectric power generation and environmental conservation efforts in the area. As water resource and climate enthusiasts, understanding the dam's significance and risk profile helps to appreciate its role in sustaining both natural ecosystems and human activities dependent on its regulated water supply.
Year Completed |
1934 |
Dam Length |
197 |
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
Nearby Streamflow Levels
East Branch Penobscot River At Grindstone
|
943cfs |
Mattawamkeag River Near Mattawamkeag
|
1130cfs |
Piscataquis River At Medford
|
880cfs |
Penobscot River At West Enfield
|
17000cfs |
Seboeis River Near Shin Pond
|
156cfs |
Piscataquis River Near Dover-Foxcroft
|
1160cfs |
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.
Area Campgrounds
| Location | Reservations | Toilets |
|---|---|---|
Remote Site 5K
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Remote Site 5J
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Remote Site 4I
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Remote Site 3H
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Remote Sit 3G
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Remote Site 2F
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North Twin - Dike 4
trail Penobscot County
Ambajejus Falls
To The End Of North And South Twin Lakes