Upper Reservoir Report
Nearby: Spragues Mill Whitney Irrigation Pond
Last Updated: December 19, 2025
Upper is a hydroelectric dam located on the East Branch Sebasticook river in Penobscot, Maine.
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Summary
Built in 1900, this concrete structure stands at 10 feet in height and spans 160 feet in length, with a storage capacity of 1600 acre-feet. Despite its age, Upper has been deemed to have a low hazard potential, but its condition assessment is rated as poor as of 2012.
Owned and regulated by the local government and the Maine Emergency Management Agency, Upper plays a crucial role in water resource management in the region. With a normal storage capacity of 736 acre-feet and a drainage area of 30 square miles, the dam serves multiple purposes beyond hydroelectricity, such as flood control and water supply.
Although in need of improvement in terms of its condition, Upper continues to operate under state regulation and inspection. With its historical significance and impact on the local ecosystem, efforts to enhance its structural integrity and overall performance are essential for ensuring the sustainable management of water resources and climate resilience in the area.
Year Completed |
1900 |
Dam Length |
160 |
Dam Height |
10 |
River Or Stream |
East Branch Sebasticook |
Primary Dam Type |
Concrete |
Surface Area |
233 |
Hydraulic Height |
10 |
Drainage Area |
30 |
Nid Storage |
1600 |
Structural Height |
10 |
Hazard Potential |
Low |
Nid Height |
10 |
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.
Upper