Dejong Bros. 12 Reservoir Report
Nearby: Dejongs Bros. 8 Dejong Bros. 7
Last Updated: December 13, 2025
Dejong Bros.
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Summary
12 is a privately owned dam located in Lyman, South Dakota, along the White River Offstream. Constructed in 1962, this earth dam stands at a height of 28 feet and spans 308 feet in length. With a storage capacity of 18 acre-feet and a maximum discharge rate of 2310 cubic feet per second, this low hazard potential dam serves as a critical water resource infrastructure in the region.
Managed by the Natural Resources Conservation Service and regulated by the South Dakota Department of Environment and Natural Resources, Dejong Bros. 12 undergoes regular inspections and enforcement to ensure its structural integrity and operational efficiency. Despite being in operation for nearly six decades, its condition assessment remains unrated, indicating a need for further evaluation to assess any potential risks and implement necessary risk management measures. Additionally, the dam has not yet been assigned an Emergency Action Plan or inundation maps, highlighting areas for improvement in emergency preparedness and response.
While Dejong Bros. 12 plays a vital role in water resource management in South Dakota, there is still room for enhancement in terms of risk assessment, emergency planning, and overall infrastructure maintenance. With its strategic location and historical significance, it is essential for stakeholders to prioritize the safety and sustainability of this dam to ensure the continued availability of water resources for the surrounding communities and ecosystems.
Year Completed |
1962 |
Dam Length |
308 |
Dam Height |
28 |
River Or Stream |
WHITE RIVER OFFSTREAM |
Primary Dam Type |
Earth |
Hydraulic Height |
28 |
Nid Storage |
18 |
Hazard Potential |
Low |
Nid Height |
28 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
White R Near Oacoma Sd
|
105cfs |
White River Near White River
|
42cfs |
Keya Paha R Near Keyapaha Sd
|
33cfs |
Bad R Near Fort Pierre Sd
|
7cfs |
Little White R Below White River Sd
|
141cfs |
Keya Paha R At Wewela Sd
|
54cfs |
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.
Dejong Bros. 12