Wonder Lake Sediment Dewatering Facility Dam
Wonder Lake Sediment Dewatering Facility Dam is an earth dam located in McHenry County, Illinois, built in 2014. It carries a High hazard potential classification.
About Wonder Lake Sediment Dewatering Facility Dam
Wonder Lake Sediment Dewatering Facility Dam is a dam in McHenry, Illinois. The dam is owned by E-i-e-i-o, Llc (private). It impounds the Galt Creek - Offstream near Wonder Lake.
The dam stands 22 feet tall and stretches 2,300 feet across, creates a reservoir covering 40 acres, and has a maximum storage capacity of 300 acre-feet. Completed in 2014, the structure is relatively new.
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 10/03/2025.
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.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Illinois |
| County | McHenry |
| Nearest City | Wonder Lake |
| River/Stream | Galt Creek - Offstream |
| Coordinates | 42.39851, -88.37691 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 22 ft |
| Dam Height | 22 ft |
| Dam Length | 2,300 ft |
| Year Completed | 2014 (12 years old) |
Storage & Hydraulics
| NID Storage | 300 acre-ft |
| Max Storage | 300 acre-ft |
| Surface Area | 40 acres |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Other |
| Owner | E-I-E-I-O, LLC |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 10/03/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL55153 |
| Federal ID | IL55153 |
| More Info | State Dam Safety Program |