Sylvan Lake Dam Reservoir Report

Last Updated: December 5, 2025

Sylvan Lake Dam, located in Long Grove, Illinois, was completed in 1920 and serves as a private recreational area for water enthusiasts.


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Summary

This earth dam stands at a height of 15 feet and has a length of 120 feet, providing storage of up to 207 acre-feet of water. The dam overlooks the scenic Trib Indian Creek and offers opportunities for boating, fishing, and other water-based activities.

Managed by the Illinois Department of Natural Resources, Sylvan Lake Dam is considered to have a significant hazard potential and undergoes inspections every three years to ensure its safety. While the dam has an uncontrolled spillway with a width of 4 feet, it does not feature any outlet gates. Despite its age, the dam's condition assessment is listed as "Not Available," highlighting the need for ongoing monitoring and maintenance to mitigate any potential risks associated with its operation.

With its historical significance and importance for local recreation, Sylvan Lake Dam represents a key feature in the water resource landscape of Lake County, Illinois. As climate change impacts continue to affect water availability and quality, maintaining the integrity of dams like Sylvan Lake becomes crucial for ensuring sustainable water management practices in the region. Enthusiasts and stakeholders alike can appreciate the beauty and functionality of this dam while also recognizing the need for ongoing stewardship to protect both the environment and the communities that rely on its benefits.

Year Completed

1920

Dam Length

120

Dam Height

15

River Or Stream

TRIB INDIAN CREEK

Primary Dam Type

Earth

Nid Storage

207

Outlet Gates

None

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

15
       
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.