Logan Thoene No.1 Reservoir Report
Last Updated: December 13, 2025
Logan Thoene No.1 is a private earth dam located in Gregory, South Dakota, along the Dry Draw River.
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Summary
Completed in 1975, this dam stands at a height of 63 feet and has a storage capacity of 600 acre-feet, with a normal storage level of 480 acre-feet. The dam has a low hazard potential and is currently classified as "Not Rated" in terms of its condition assessment.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Logan Thoene No.1 is under state jurisdiction and is subject to regular inspection, permitting, and enforcement. Although the dam has not been modified in recent years and lacks a formal emergency action plan, it meets the necessary regulatory guidelines to ensure public safety. The dam is situated within the St. Paul District of the U.S. Army Corps of Engineers, but is not federally owned or funded.
Overall, Logan Thoene No.1 serves as a vital water resource infrastructure in the region, providing flood control, water storage, and irrigation benefits. Despite its age, the dam continues to play a crucial role in water management in the area and remains an important asset for the local community. With its low hazard potential and state-regulated status, Logan Thoene No.1 exemplifies the harmonious balance between water resource management and climate resilience.
Year Completed |
1975 |
Dam Length |
882 |
Dam Height |
63 |
River Or Stream |
DRY DRAW |
Primary Dam Type |
Earth |
Hydraulic Height |
63 |
Nid Storage |
600 |
Hazard Potential |
Low |
Nid Height |
63 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Platte Creek Near Platte
|
3cfs |
Niobrara River At Mariaville
|
1650cfs |
Keya Paha R At Wewela Sd
|
54cfs |
Long Pine Creek Near Riverview
|
191cfs |
Niobrara River Nr. Verdel
|
517cfs |
Ponca Creek At Verdel
|
23cfs |
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.
Logan Thoene No.1