Island Lake Dam is an earth dam located in McHenry County, Illinois, built in 1940. It carries a Low hazard potential classification.
Dam profile
NID height · 12 ft12 ft tall and 160 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Island Lake Dam
The primary purpose of Island Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Village of Island Lake (local government). It impounds the Cotton Creek near Island Lake.
The dam stands 12 feet tall and stretches 160 feet across, and has a maximum storage capacity of 470 acre-feet. Completed in 1940, the structure is well-established, with more than 75 years of service.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. The most recent inspection on record was 08/11/2025.
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 | Island Lake |
| River/Stream | Cotton Creek |
| Coordinates | 42.27522, -88.20185 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 12 ft |
| Dam Height | 12 ft |
| Dam Length | 160 ft |
| Year Completed | 1940 (86 years old) |
Storage & Hydraulics
| NID Storage | 470 acre-ft |
| Max Storage | 470 acre-ft |
| Normal Storage | 373 acre-ft |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Village of Island Lake |
| Owner Type | Local Government |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 08/11/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL00580 |
| Federal ID | IL00580 |
| More Info | State Dam Safety Program |