L. Koch Reservoir Report

Last Updated: December 7, 2025

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Summary

Koch is a privately owned dam located in Dewey, South Dakota, along the TR-MOREAU river. This earth-type structure was completed in 1957 and stands at a height of 30 feet with a length of 420 feet. The dam has a storage capacity of 132 acre-feet, with a normal storage level of 94 acre-feet. It is regulated by the South Dakota Department of Environment and Natural Resources (DENR) and is subject to state permitting, inspection, and enforcement, ensuring its safety and compliance with regulations.

Despite its low hazard potential, the condition of L. Koch has not been formally assessed, and the Emergency Action Plan (EAP) status is unknown. The dam has not been modified in recent years and does not have any associated locks or spillways. In case of any emergencies, the designated emergency contacts and risk management measures are not specified. The dam falls under the jurisdiction of the St. Paul District of the US Army Corps of Engineers, but is not managed by the federal agency.

L. Koch serves as an essential infrastructure for water resource management in the region, providing storage for irrigation, flood control, and other purposes. Its historical significance and structural integrity make it a key component of the local water management system. Climate enthusiasts and water resource experts may find interest in studying the dam's design, maintenance, and potential impact on the surrounding environment and community.

Year Completed

1957

Dam Length

420

Dam Height

30

River Or Stream

TR-MOREAU

Primary Dam Type

Earth

Hydraulic Height

30

Nid Storage

132

Hazard Potential

Low

Nid Height

30
       
Seasonal Comparison

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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.