Pioneer Clarification is an earth dam located in St. Louis County, Minnesota, built in 1961. It carries a Low hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 25 ft25 ft tall and 1,000 ft long, taller than 50% 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 embankment section and the water level is illustrative.
About Pioneer Clarification
The primary purpose of Pioneer Clarification 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 City of Ely (local government). It impounds the Lonsdorf Creek near Local Residents.
The dam stands 25 feet tall and stretches 1,000 feet across, creates a reservoir covering 14 acres, has a maximum storage capacity of 239 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1961, the structure is well into its service life at over 50 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. The most recent inspection on record was 09/19/2023.
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Location
| State | Minnesota |
| County | St. Louis |
| Nearest City | Local Residents |
| River/Stream | Lonsdorf Creek |
| Coordinates | 47.88673, -91.89779 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 25 ft |
| Dam Height | 25 ft |
| Dam Length | 1,000 ft |
| Year Completed | 1961 (65 years old) |
Storage & Hydraulics
| NID Storage | 239 acre-ft |
| Max Storage | 239 acre-ft |
| Normal Storage | 117 acre-ft |
| Surface Area | 14 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 275 cfs |
Ownership & Safety
| Purpose | Tailings |
| Owner | City of Ely |
| Owner Type | Local Government |
| Hazard Classification | Low |
| Condition Assessment | Poor |
| Last Inspection | 09/19/2023 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MN00788 |
| Federal ID | MN00788 |
| More Info | State Dam Safety Program |