O'Farrell Dam No. 2 Reservoir Report
Last Updated: December 14, 2025
O'Farrell Dam No.
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Summary
2, located on the TR-N. Fork Whetstone River in Grant, South Dakota, is a privately owned structure designed by KONECHNE ENG. The dam, completed in 2006, stands at 20 feet tall and spans a length of 400 feet, providing a storage capacity of 65 acre-feet. With a low hazard potential and a moderate risk assessment, the dam is regulated by the South Dakota Department of Environment and Natural Resources (DENR) and undergoes state inspections, permitting, and enforcement.
Despite its relatively low hazard potential, O'Farrell Dam No. 2 plays a crucial role in water resource management and climate adaptation in the region. The dam's uncontrolled spillway, with a width of 150 feet, helps regulate the flow of the TR-N. Fork Whetstone River, reducing the risk of flooding and ensuring a stable water supply for nearby communities and agricultural activities. The dam's earth construction and soil foundation contribute to its structural integrity and operational efficiency, making it a key component in the local water infrastructure.
As a part of the Omaha District of the U.S. Army Corps of Engineers, O'Farrell Dam No. 2 serves as a testament to collaborative efforts between private owners and government agencies in ensuring the safety and sustainability of water resources. With its capacity to store 65 acre-feet of water and a normal storage level of 32 acre-feet, the dam plays a vital role in managing water supply during dry periods and mitigating potential risks during heavy rainfall events. Its presence highlights the importance of proactive dam management and the need for continued monitoring and maintenance to safeguard water resources and adapt to changing climate conditions.
Year Completed |
2006 |
Dam Length |
400 |
Dam Height |
20 |
River Or Stream |
TR-N. FORK WHETSTONE |
Primary Dam Type |
Earth |
Hydraulic Height |
20 |
Drainage Area |
1 |
Nid Storage |
65 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
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.
O'Farrell Dam No. 2