Lasalle Co. Nuclear Station Cooling Lake Dam
Lasalle Co. Nuclear Station Cooling Lake Dam is an earth dam located in LaSalle County, Illinois, built in 1977. It carries a High hazard potential classification.
About Lasalle Co. Nuclear Station Cooling Lake Dam
Lasalle Co. Nuclear Station Cooling Lake Dam is a dam in LaSalle, Illinois. The dam is owned by Exelon Generation Company, Llc (private). It impounds the Trib Illinois River near Marseilles.
The dam stands 43 feet tall and stretches 37,942 feet across, creates a reservoir covering 2,058 acres, has a maximum storage capacity of 44,167 acre-feet, and collects water from a drainage area of 5 square miles. Completed in 1977, the structure is 49 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 08/27/2025.
At 43 feet, this dam is taller than 89% 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.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Illinois |
| County | LaSalle |
| Nearest City | Marseilles |
| River/Stream | Trib Illinois River |
| Coordinates | 41.26717, -88.64284 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 43 ft |
| Dam Height | 43 ft |
| Dam Length | 37,942 ft |
| Year Completed | 1977 (49 years old) |
Storage & Hydraulics
| NID Storage | 44,167 acre-ft |
| Max Storage | 44,167 acre-ft |
| Normal Storage | 31,706 acre-ft |
| Surface Area | 2,058 acres |
| Drainage Area | 5 sq mi |
| Max Discharge | 5,884 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Other |
| Owner | EXELON GENERATION COMPANY, LLC |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 08/27/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL01102 |
| Federal ID | IL01102 |
| More Info | State Dam Safety Program |