Sylvan Lake Dam Reservoir Report

Last Updated: December 5, 2025

Sylvan Lake Dam, located in Hill City, South Dakota, is a state-regulated structure on Spring Creek with a height of 37 feet and a length of 57 feet.


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Summary

Completed in 1906, this arch dam has a storage capacity of 240 acre-feet and a maximum discharge rate of 2,880 cubic feet per second. The dam is classified as having a high hazard potential and is currently assessed to be in fair condition as of the last inspection in November 2020.

Managed by the South Dakota Department of Agriculture and Natural Resources (DANR), Sylvan Lake Dam plays a crucial role in water resource management in the region. The dam's primary purpose and associated structures are not specified, but it serves as a key infrastructure for flood control, water supply, and recreational activities in the area. With regular inspections, permitting, and enforcement measures in place, the dam ensures the safety and stability of its surrounding community and environment.

As a significant landmark in Custer County, South Dakota, Sylvan Lake Dam stands as a testament to early 20th-century engineering and continues to serve its intended functions to this day. With its picturesque location and vital role in water resource management, the dam remains a focal point for water resource and climate enthusiasts interested in the history and impact of dam infrastructure in the region.

Year Completed

1906

Dam Length

57

Dam Height

37

River Or Stream

TRIB-SPRING CREEK

Primary Dam Type

Arch

Hydraulic Height

37

Drainage Area

1

Nid Storage

240

Hazard Potential

High

Nid Height

37
       
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.