Dresser Minerals #7 Dam South (dry)

About Dresser Minerals #7 Dam South (dry)

The primary purpose of Dresser Minerals #7 Dam South (dry) is tailings. Tailings dams contain waste material from mining operations — typically a slurry of finely ground rock left over after valuable minerals have been extracted. These structures require ongoing monitoring because tailings can contain heavy metals and other contaminants. The dam is owned by Big River Land Company (private). It impounds the Tr-mill Creek near Blackwell.

The dam stands 35 feet tall and stretches 4,000 feet across, creates a reservoir covering 37 acres, has a maximum storage capacity of 80 acre-feet, and collects water from a drainage area of 37 square miles. Completed in 1950, the structure is well-established, with more than 75 years of service.

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. The most recent inspection on record was 08/11/1986. That was 39 years ago — unusually long for a high-hazard dam, which typically requires more frequent inspections.

At 35 feet, this dam is taller than 82% of dams nationwide.

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 Missouri dam safety program can provide more specific information about emergency planning for this structure.

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