Cornwell

WIRE GRASS COULEE· Valley, Montana· Built 1952· Earth· 23 ft tall
Significant Hazard Irrigation Private

Key Takeaway

Cornwell is classified as significant hazard in Montana. It was completed in 1952 and is 74 years old. Its primary use is irrigation. Significant hazard means failure could cause economic or environmental damage. Learn more.

Physical Details

Dam Height 23 ft (taller than 66.4% in MT)
Dam Length400 ft
Dam TypeEarth
Max Storage423 acre-ft
Normal Storage238 acre-ft
Drainage Area2 sq mi
Max Discharge600 cfs
Year Completed1952 (74 years old)
NID IDMT00998

Safety Information

Significant Hazard

No probable loss of human life, but can cause economic loss, environmental damage, or disruption of lifeline facilities.

Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?

Emergency Action Plan: No
State Regulated: Yes
Regulatory Agency: DNRC

Ownership

CORNWELL RANCH

Private

Nearby Dams

Frequently Asked Questions

What is the hazard classification of Cornwell?

Cornwell is classified as Significant Hazard. No probable loss of human life, but can cause economic loss, environmental damage, or disruption of lifeline facilities. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates Cornwell?

Cornwell is owned by CORNWELL RANCH (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Cornwell built?

Cornwell was completed in 1952, making it 74 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.

What is the primary purpose of Cornwell?

Cornwell serves the following purposes: Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is Cornwell?

Cornwell has a dam height of 23 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.

Data from the National Inventory of Dams (NID) maintained by the US Army Corps of Engineers. Dam conditions may have changed since the last update. This site is not affiliated with USACE. Do not use for emergency planning — contact your local dam safety program.