Main Street Triangle Dam is a concrete dam located in Cook County, Illinois. It carries a Significant hazard potential classification.
Dam profile
NID height · 9 ft9 ft tall and 395 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic concrete gravity section and the water level is illustrative.
About Main Street Triangle Dam
The primary purpose of Main Street Triangle Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Village of Orland Park (local government). It impounds the Mill Creek - Offstream near Orland Park.
The dam stands 9 feet tall and stretches 395 feet across, creates a reservoir covering 1 acres, and collects water from a drainage area of 0 square miles.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. The most recent inspection on record was 10/29/2025.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Illinois |
| County | Cook |
| Nearest City | Orland Park |
| River/Stream | Mill Creek - Offstream |
| Coordinates | 41.63431, -87.85431 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 9 ft |
| Dam Height | 9 ft |
| Dam Length | 395 ft |
Storage & Hydraulics
| Surface Area | 1 acres |
| Drainage Area | 0 sq mi |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Village of Orland Park |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 10/29/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL55123 |
| Federal ID | IL55123 |
| More Info | State Dam Safety Program |