Black Lake
Black Lake is an earth dam located in Missoula County, Montana, built in 1967. It carries a High hazard potential classification and has a unsatisfactory condition assessment.
About Black Lake
The primary purpose of Black Lake is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Bia (federal). It impounds the Jocko River near Arlee.
The dam stands 75 feet tall and stretches 530 feet across, creates a reservoir covering 143 acres, has a maximum storage capacity of 6,800 acre-feet, and collects water from a drainage area of 4 square miles. Completed in 1967, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated unsatisfactory, indicating serious safety deficiencies exist that require immediate attention or remedial action. An emergency action plan is in place for this dam. The most recent inspection on record was 10/05/2020.
At 75 feet, this dam is taller than 97% of all dams in the United States.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Montana dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Montana |
| County | Missoula |
| Nearest City | Arlee |
| River/Stream | Jocko River |
| Coordinates | 47.20130, -113.73250 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 75 ft |
| Dam Height | 60 ft |
| Dam Length | 530 ft |
| Year Completed | 1967 (59 years old) |
Storage & Hydraulics
| NID Storage | 6,800 acre-ft |
| Max Storage | 6,800 acre-ft |
| Normal Storage | 5,200 acre-ft |
| Surface Area | 143 acres |
| Drainage Area | 4 sq mi |
| Max Discharge | 21,625 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | BIA |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Unsatisfactory |
| Last Inspection | 10/05/2020 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MT00587 |
| Federal ID | MT00587 |
| More Info | State Dam Safety Program |