Cochrane

Cochrane is a gravity dam located in Cascade County, Montana, built in 1957. It carries a High hazard potential classification and has a fair condition assessment.

About Cochrane

The primary purpose of Cochrane is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Northwestern Energy (private). It impounds the Missouri River near Fort Benton.

The dam stands 105 feet tall and stretches 856 feet across, creates a reservoir covering 249 acres, has a storage capacity of 8,464 acre-feet, and collects water from a drainage area of 23,270 square miles. Completed in 1957, 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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 08/12/2022.

At 105 feet, this dam is taller than 98% 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.

High HazardFair ConditionEmergency Action Plan: Yes

Location

StateMontana
CountyCascade
Nearest CityFort Benton
River/StreamMissouri River
Coordinates47.55290, -111.14900

Physical Characteristics

Dam TypeGravity
NID Height105 ft
Dam Height100 ft
Dam Length856 ft
Year Completed1957 (69 years old)

Storage & Hydraulics

NID Storage8,464 acre-ft
Normal Storage8,464 acre-ft
Surface Area249 acres
Drainage Area23,270 sq mi
Max Discharge140,000 cfs
Spillway TypeControlled

Ownership & Safety

PurposeHydroelectric
OwnerNorthWestern Energy
Owner TypePrivate
Hazard ClassificationHigh
Condition AssessmentFair
Last Inspection08/12/2022
Emergency Action PlanYes

Identifiers

NID IDMT00556
Federal IDMT00556
More InfoState Dam Safety Program

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