Alto Pass Reservoir Dam
Alto Pass Reservoir Dam is an earth dam located in Union County, Illinois, built in 1964. It carries a High hazard potential classification.
About Alto Pass Reservoir Dam
The primary purpose of Alto Pass Reservoir Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Alto Pass Wd (local government). It impounds the Cave Creek near Alto Pass-offstream.
The dam stands 45 feet tall and stretches 450 feet across, creates a reservoir covering 15 acres, has a maximum storage capacity of 296 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1964, the structure is well into its service life at over 50 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 10/04/2023.
At 45 feet, this dam is taller than 91% 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 | Union |
| Nearest City | Alto Pass-offstream |
| River/Stream | Cave Creek |
| Coordinates | 37.57948, -89.30611 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 45 ft |
| Dam Height | 45 ft |
| Dam Length | 450 ft |
| Year Completed | 1964 (62 years old) |
Storage & Hydraulics
| NID Storage | 296 acre-ft |
| Max Storage | 296 acre-ft |
| Normal Storage | 168 acre-ft |
| Surface Area | 15 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 1,900 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | ALTO PASS WD |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 10/04/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00064 |
| Federal ID | IL00064 |
| More Info | State Dam Safety Program |