Lake Tanglewood Dam

About Lake Tanglewood Dam

The primary purpose of Lake Tanglewood Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Lake Wildwood Association, Inc. (private). It impounds the Trib Sandy Creek near Henry.

The dam stands 40 feet tall and stretches 375 feet across, and has a maximum storage capacity of 161 acre-feet. Completed in 1969, the structure is well into its service life at over 50 years old.

This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. An emergency action plan is in place for this dam. The most recent inspection on record was 05/06/2025.

At 40 feet, this dam is taller than 87% of dams nationwide.

Living Downstream

If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Illinois dam safety program can provide more specific information about emergency planning for this structure.

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