Soo Locks is a concrete dam located in Chippewa County, Michigan, built in 1921. It carries a Significant hazard potential classification.
Dam profile
NID height · 17 ft17 ft tall and 968 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic concrete gravity section and the water level is illustrative.
About Soo Locks
The primary purpose of Soo Locks is navigation. The dam maintains water levels sufficient for boat and barge traffic, supporting commercial or recreational navigation on the waterway. The dam is owned by Canada;usace - Detroit District (federal). It impounds the St Mary S near Sault Ste Marie.
The dam stands 17 feet tall and stretches 968 feet across, creates a reservoir covering 20,255,000 acres, has a maximum storage capacity of 277,540,000 acre-feet, and collects water from a drainage area of 181,000 square miles. Completed in 1921, the structure is over a century old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. An emergency action plan is in place for this dam. The most recent inspection on record was 06/13/2025.
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Location
| State | Michigan |
| County | Chippewa |
| Nearest City | Sault Ste Marie |
| River/Stream | St Mary S |
| Coordinates | 46.50422, -84.34961 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 17 ft |
| Dam Length | 968 ft |
| Year Completed | 1921 (105 years old) |
Storage & Hydraulics
| NID Storage | 277,540,000 acre-ft |
| Max Storage | 277,540,000 acre-ft |
| Normal Storage | 277,540,000 acre-ft |
| Surface Area | 20,255,000 acres |
| Drainage Area | 181,000 sq mi |
| Max Discharge | 68,000 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Navigation |
| Owner | Canada;usace - Detroit District |
| Owner Type | Federal |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 06/13/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MI00650 |
| Federal ID | MI00650 |
| More Info | State Dam Safety Program |