Prairie State Energy Raw Water Dam
Prairie State Energy Raw Water Dam is an earth dam located in Washington County, Illinois, built in 2010. It carries a High hazard potential classification.
About Prairie State Energy Raw Water Dam
The primary purpose of Prairie State Energy Raw Water Dam is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Prairie State Generating Company (public utility). It impounds the Perched near Marissa.
The dam stands 40 feet tall and stretches 6,900 feet across, creates a reservoir covering 0 acres, has a maximum storage capacity of 2,422 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 2010, 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 07/21/2025.
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.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Illinois |
| County | Washington |
| Nearest City | Marissa |
| River/Stream | Perched |
| Coordinates | 38.28095, -89.68224 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 40 ft |
| Dam Height | 40 ft |
| Dam Length | 6,900 ft |
| Year Completed | 2010 (16 years old) |
Storage & Hydraulics
| NID Storage | 2,422 acre-ft |
| Max Storage | 2,422 acre-ft |
| Normal Storage | 1,942 acre-ft |
| Surface Area | 0 acres |
| Drainage Area | 0 sq mi |
| Spillway Type | None |
Ownership & Safety
| Purpose | Water Supply |
| Owner | PRAIRIE STATE GENERATING COMPANY |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 07/21/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL50539 |
| Federal ID | IL50539 |
| More Info | State Dam Safety Program |