Black Tern Marsh Dam
Black Tern Marsh Dam is an earth dam located in McHenry County, Illinois, built in 1992. It carries a Low hazard potential classification.
About Black Tern Marsh Dam
The primary purpose of Black Tern Marsh Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Illinois Department Of Natural Resources (state). It impounds the Trib Fox River near Mchenry.
The dam stands 7 feet tall and stretches 1,500 feet across, and has a maximum storage capacity of 250 acre-feet. Completed in 1992, the structure is 34 years old.
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 10/31/2023.
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Location
| State | Illinois |
| County | McHenry |
| Nearest City | Mchenry |
| River/Stream | Trib Fox River |
| Coordinates | 42.30533, -88.24556 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 7 ft |
| Dam Height | 7 ft |
| Dam Length | 1,500 ft |
| Year Completed | 1992 (34 years old) |
Storage & Hydraulics
| NID Storage | 250 acre-ft |
| Max Storage | 250 acre-ft |
| Normal Storage | 133 acre-ft |
| Max Discharge | 21 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | ILLINOIS DEPARTMENT OF NATURAL RESOURCES |
| Owner Type | State |
| Hazard Classification | Low |
| Condition Assessment | Not Available |
| Last Inspection | 10/31/2023 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL50320 |
| Federal ID | IL50320 |
| More Info | State Dam Safety Program |