Dresser Minerals #7 Dam South (dry) is a rockfill dam located in Washington County, Missouri, built in 1950. It carries a High hazard potential classification.
Dam profile
NID height · 35 ft35 ft tall and 4,000 ft long, taller than 80% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic rockfill embankment section and the water level is illustrative.
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 40 years ago — unusually long for a high-hazard dam, which typically requires more frequent inspections.
At 35 feet, this dam is taller than 80% 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.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Missouri |
| County | Washington |
| Nearest City | Blackwell |
| River/Stream | Tr-mill Creek |
| Coordinates | 37.97439, -90.70399 |
Physical Characteristics
| Dam Type | Rockfill |
| NID Height | 35 ft |
| Dam Height | 35 ft |
| Dam Length | 4,000 ft |
| Year Completed | 1950 (76 years old) |
Storage & Hydraulics
| NID Storage | 80 acre-ft |
| Max Storage | 80 acre-ft |
| Normal Storage | 80 acre-ft |
| Surface Area | 37 acres |
| Drainage Area | 37 sq mi |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Tailings |
| Owner | Big River Land Company |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Not assessed |
| Last Inspection | 08/11/1986 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MO31147 |
| Federal ID | MO31147 |
| More Info | State Dam Safety Program |