Dresser No.4 Dam

About Dresser No.4 Dam

The primary purpose of Dresser No.4 Dam 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 Mi Drilling Fluids Compa (private). It impounds the Tr-mill Creek near Tiff.

The dam stands 105 feet tall, creates a reservoir covering 77 acres, has a maximum storage capacity of 4,325 acre-feet, and collects water from a drainage area of 528 square miles. Completed in 1975, 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. The most recent inspection on record was 03/24/1979. That was 47 years ago — unusually long for a high-hazard dam, which typically requires more frequent inspections.

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

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