St. Marys Lake Dam
High HazardNot Available ConditionEmergency Action Plan: Yes
Location
| State | Illinois |
| County | Lake |
| Nearest City | LIBERTYVILLE |
| River/Stream | BULL CREEK |
| Coordinates | 42.28314, -87.98053 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 12 ft |
| Dam Height | 12 ft |
| Dam Length | 389 ft |
| Year Completed | 1921 (105 years old) |
Storage & Hydraulics
| NID Storage | 966 acre-ft |
| Max Storage | 966 acre-ft |
| Normal Storage | 778 acre-ft |
| Surface Area | 96 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 320 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | ARCHDIOCESE OF CHICAGO |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 09/12/2025 |
| Emergency Action Plan | Yes |