New Wall Lake Reservoir Report

Last Updated: December 6, 2025

New Wall Lake, located in Pennington County, South Dakota, is a state-regulated dam with a height of 40 feet and a length of 570 feet.


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Summary

Built in 1947, this earth dam serves the primary purpose of water resource management and flood control along the TR-Cheyenne river. With a maximum storage capacity of 460 acre-feet and a normal storage level of 280 acre-feet, the dam plays a crucial role in maintaining water supply and managing peak discharge levels in the area.

Despite being classified as low hazard potential, New Wall Lake dam undergoes regular inspections and maintenance by the South Dakota Department of Agriculture and Natural Resources. The last inspection in September 2017 deemed its condition as "not rated", indicating a need for further assessment. The dam's Emergency Action Plan (EAP) status and risk management measures are currently unspecified, highlighting the need for ongoing monitoring and preparedness in the face of potential emergencies.

Water resource and climate enthusiasts will appreciate the significance of New Wall Lake in the local ecosystem and its role in water management within the St. Paul District. With its strategic location and operational history dating back over seven decades, this dam stands as a testament to the importance of infrastructure in mitigating natural disasters and ensuring sustainable water resource practices in South Dakota.

Year Completed

1947

Dam Length

570

Dam Height

40

River Or Stream

TR-CHEYENNE

Primary Dam Type

Earth

Hydraulic Height

40

Nid Storage

460

Hazard Potential

Low

Nid Height

40
       
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.