Cone Dam Reservoir Report

Last Updated: December 12, 2025

Cone Dam, located in Lyman, South Dakota, is a privately owned earth dam on TR.


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Summary

MEDICINE CREEK with a height of 14 feet and a length of 1055 feet. Completed in 2013, this dam has a storage capacity of 246 acre-feet and a maximum discharge of 1080 cubic feet per second. With a spillway width of 80 feet and a hazard potential rated as low, Cone Dam poses a moderate risk and is not currently rated for its condition assessment.

Managed by the South Dakota Department of Environment and Natural Resources, Cone Dam is regulated, permitted, inspected, and enforced by the state agency. The dam does not have any associated structures or outlet gates, and it does not currently have an emergency action plan in place. Despite the lack of an official condition assessment, Cone Dam is considered to have a moderate risk level based on available data.

Overall, Cone Dam serves as a critical infrastructure for water resource management in the region, providing storage and flood control capabilities for TR. MEDICINE CREEK. With its low hazard potential and moderate risk level, continued monitoring and maintenance of Cone Dam are essential to ensure its long-term safety and effectiveness in mitigating potential climate-related impacts.

Year Completed

2013

Dam Length

1055

Dam Height

14

River Or Stream

TR. MEDICINE CREEK

Primary Dam Type

Earth

Hydraulic Height

14

Drainage Area

3

Nid Storage

246

Outlet Gates

None

Hazard Potential

Low

Foundations

Soil

Nid Height

14
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.