Mario Johnson Reservoir Report
Nearby: Marlo Johnson Morris Jensen
Last Updated: December 6, 2025
Mario Johnson is a private dam located in Perkins, South Dakota, along the TR SOUTH GRAND RIVER.
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Summary
Built in 1952, this Earth-type dam stands at a height of 21 feet and has a storage capacity of 78 acre-feet, with a normal storage of 60 acre-feet. Despite its age, Mario Johnson has a low hazard potential and is currently not rated in terms of its condition assessment.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Mario Johnson is subject to state regulations, permitting, inspection, and enforcement. The dam is not federally owned or funded, and its operations and maintenance fall under the responsibility of the private owner. The dam poses minimal risk and does not have an Emergency Action Plan (EAP) in place, indicating a need for further preparedness measures in case of emergencies.
Situated within the St. Paul District of the US Army Corps of Engineers, Mario Johnson plays a crucial role in water resource management in the region. With a historical significance dating back to the mid-20th century, this dam serves as a testament to the engineering capabilities of its time and continues to contribute to the overall ecosystem health and water supply for the local community.
Year Completed |
1952 |
Dam Length |
380 |
Dam Height |
21 |
River Or Stream |
TR SOUTH GRAND RIVER |
Primary Dam Type |
Earth |
Hydraulic Height |
21 |
Nid Storage |
78 |
Hazard Potential |
Low |
Nid Height |
21 |
Seasonal Comparison
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Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Mario Johnson