Pactola Dike 1 Reservoir Report

Last Updated: December 5, 2025

Pactola Dike 1, located in Rapid City, South Dakota, is a federally owned earth dam constructed in 1959 by the Bureau of Reclamation.


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Summary

Standing at a height of 115 feet, this structure serves as a critical component for managing water resources in the area, particularly along the Rapid Creek. With a storage capacity of 140,898 acre-feet and a surface area of 1,557 acres, Pactola Dike 1 plays a pivotal role in flood control and water supply management for the region.

Despite being under the jurisdiction of the Bureau of Reclamation, Pactola Dike 1 is not state regulated or permitted, showcasing the federal agency's responsibility in overseeing its operations, inspections, and regulatory aspects. The dam's hazard potential is classified as high, with a very high risk assessment rating, emphasizing the importance of maintaining its structural integrity and emergency preparedness protocols. With its controlled spillway and rock foundation, Pactola Dike 1 stands as a testament to engineering excellence and the critical role of water infrastructure in mitigating climate-related risks in the region.

As a key component of the water management system in Pennington County, Pactola Dike 1 not only provides flood protection but also contributes to the overall resilience of the community in the face of changing climate patterns. With its arch core design and significant storage capacity, this earth dam symbolizes the ongoing efforts to safeguard water resources and ensure sustainable development in South Dakota. As climate enthusiasts, it is essential to recognize the importance of infrastructure like Pactola Dike 1 in adapting to and mitigating the impacts of climate change on water resources and communities.

Year Completed

1959

Dam Length

1806

Dam Height

115

River Or Stream

RAPID CREEK

Primary Dam Type

Earth

Surface Area

1557

Hydraulic Height

86

Drainage Area

229

Nid Storage

140898

Structural Height

115

Hazard Potential

High

Foundations

Rock

Nid Height

115
       
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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.