Jensen No.9 Reservoir Report
Nearby: Jarl No.1 Jensen No. 2
Last Updated: December 8, 2025
Jensen No.9, located in Mellette, South Dakota, is a privately owned dam that was completed in 1958.
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Summary
This earth dam has a height of 32 feet and a length of 424 feet, with a maximum storage capacity of 58 acre-feet. The dam is regulated by the South Dakota Department of Environment and Natural Resources (DENR) and undergoes regular inspections to ensure compliance with state regulations.
Situated on the TR Cottonwood Offstream, Jensen No.9 has a low hazard potential and is currently rated as "Not Rated" in terms of its condition assessment. Despite its age, the dam continues to serve its primary purpose effectively. The dam's emergency action plan (EAP) status and risk assessment information are currently not available, but the dam is equipped with necessary measures for risk management.
Jensen No.9 is a vital structure in the St. Paul District, ensuring water resource management and flood control in the region. With its functional design and adherence to state regulations, this dam plays a crucial role in maintaining the safety and sustainability of the surrounding area for both water resources and climate enthusiasts to appreciate.
Year Completed |
1958 |
Dam Length |
424 |
Dam Height |
32 |
River Or Stream |
TR COTTONWOOD OFFSTREAM |
Primary Dam Type |
Earth |
Hydraulic Height |
32 |
Nid Storage |
58 |
Hazard Potential |
Low |
Nid Height |
32 |
Seasonal Comparison
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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.
Jensen No.9