Upper South Dam Reservoir Report
Nearby: Hillman Brush Creek Dam
Last Updated: December 5, 2025
Upper South Dam, located in Lachine, Michigan, is a gravity and earth dam with a primary purpose of hydroelectric power generation.
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Summary
Completed in 1930, this structure stands at a height of 20 feet and spans 350 feet across Thunder Bay. With a storage capacity of 55,000 acre-feet, it serves as a vital resource for water management in the region.
Managed by the Federal Energy Regulatory Commission, Upper South Dam boasts a controlled spillway with a width of 32 feet and four needle outlet gates. Despite its low hazard potential, the dam is subject to regular inspections and has a very high risk assessment rating. Its normal storage capacity of 40,100 acre-feet supports recreation activities in addition to its hydroelectric functions, making it a versatile asset for the community.
While the dam's condition assessment is not available, its emergency action plan was last revised in December 2019. With a strong focus on risk management and safety measures, Upper South Dam plays a crucial role in water resource management and climate adaptation efforts within the region.
Year Completed |
1930 |
Dam Length |
350 |
Dam Height |
20 |
River Or Stream |
Thunder Bay |
Surface Area |
7000 |
Drainage Area |
182 |
Nid Storage |
55000 |
Outlet Gates |
Needle - 4 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
20 |
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 South Dam