Twelve Mile Creek Watershed Site M-1

About Twelve Mile Creek Watershed Site M-1

The primary purpose of Twelve Mile Creek Watershed Site M-1 is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Creston Waterworks (local government). It impounds the Twelve Mile Creek near Afton.

The dam stands 66 feet tall and stretches 2,100 feet across, creates a reservoir covering 633 acres, has a maximum storage capacity of 27,200 acre-feet, and collects water from a drainage area of 23 square miles. Completed in 1983, the structure is 43 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 08/15/2023.

At 66 feet, this dam is taller than 96% 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 Iowa dam safety program can provide more specific information about emergency planning for this structure.

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