Great Stone Reservoir Report
Nearby: Barker Mill Lower Barker Mill Upper
Last Updated: December 15, 2025
Great Stone, also known as Great Falls Dam, is a historic hydroelectric structure located in Lewiston - Auburn, Maine.
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Summary
Built in 1865, this concrete, gravity, and masonry dam stands at a height of 27 feet and spans 955 feet across the Androscoggin River. With a storage capacity of 1600 acre-feet and a surface area of 200 acres, Great Stone serves multiple purposes including hydroelectric power generation and water supply for the region.
Managed by the Federal Energy Regulatory Commission, Great Stone features a spillway width of 814 feet and utilizes seven slide gates for water control. Despite being categorized as having low hazard potential, the dam is subject to regular inspections every three years to ensure its structural integrity and safety. With a moderate risk assessment rating, risk management measures for Great Stone are closely monitored to safeguard against any potential emergencies or hazards that may arise due to its age and location.
As a key landmark in water resource management and hydroelectric power generation in Maine, Great Stone continues to play a vital role in the region's infrastructure. With its historical significance, impressive engineering design, and ongoing operational oversight, Great Stone stands as a testament to the enduring importance of responsible dam management in ensuring water security and sustainable energy production for communities along the Androscoggin River.
Year Completed |
1865 |
Dam Length |
955 |
Dam Height |
27 |
River Or Stream |
Androscoggin River |
Surface Area |
200 |
Drainage Area |
2901 |
Nid Storage |
1600 |
Outlet Gates |
Slide (sluice gate) - 7 |
Hazard Potential |
Low |
Nid Height |
27 |
Seasonal Comparison
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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.
Great Stone
Riverwalk Auburn