Lewis Dam Reservoir Report
Nearby: Sd Noname 178 Erwin Eisenbraun
Last Updated: December 6, 2025
Lewis Dam, located in Pennington, South Dakota, is a privately owned structure that serves as a vital water resource for the area.
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Summary
Completed in 1961, this earth dam stands at a height of 20 feet and has a storage capacity of 60 acre-feet, with a normal storage level of 42 acre-feet. It is situated on the TR-CHEYENNE river within the jurisdiction of the South Dakota Department of Environment and Natural Resources.
Managed by the Natural Resources Conservation Service, Lewis Dam has a low hazard potential and is currently not rated for its condition assessment. Although the dam does not have a designated primary purpose listed, its importance in providing water storage and flood control to the region cannot be understated. Despite its age, the dam has not undergone any significant modifications over the years, and its last inspection date and condition assessment are currently unavailable.
With a maximum discharge capacity of 1125 cubic feet per second, Lewis Dam plays a crucial role in protecting the surrounding area from potential flooding events. While the structure itself is not owned or funded by any federal agency, its state-regulated status ensures that it is regularly inspected and maintained to meet safety standards. Enthusiasts of water resources and climate management can appreciate Lewis Dam for its role in safeguarding the local community and ecosystem against water-related hazards.
Year Completed |
1961 |
Dam Length |
405 |
Dam Height |
20 |
River Or Stream |
TR-CHEYENNE |
Primary Dam Type |
Earth |
Hydraulic Height |
20 |
Nid Storage |
60 |
Hazard Potential |
Low |
Nid Height |
20 |
Seasonal Comparison
Weather Forecast
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.
Lewis Dam