St. Marys Lake Dam dam
St. Marys Lake Dam
St. Marys Lake Dam, located in Libertyville, Illinois, is a privately owned gravity dam with a primary purpose of recreation. Built in 1921, this historic dam stands at a height of 12 feet and stretches 389 feet in length, creating a reservoir with a storage capacity of 966 acre-feet. The dam is situated on Bull Creek and is regulated by the Illinois Department of Natural Resources, with state permitting, inspection, and enforcement in place to ensure its safety and compliance with regulations.
With a spillway width of 51 feet and a maximum discharge capacity of 320 cubic feet per second, St. Marys Lake Dam poses a high hazard potential. Despite its age, the condition assessment of the dam is currently listed as not available, highlighting the need for continued monitoring and maintenance. An emergency action plan (EAP) has been prepared, last revised in January 2021, and the dam's risk assessment is categorized as moderate. While the dam meets state guidelines for its EAP and inundation maps, there is room for improvement in risk management measures and overall risk characterization.
For water resource and climate enthusiasts, St. Marys Lake Dam offers a fascinating glimpse into the history and engineering of early 20th-century dam construction. Its location in Lake County, Illinois, surrounded by scenic landscape and recreational opportunities, adds to its allure. As efforts continue to ensure the safety and integrity of this vital infrastructure, the preservation of St. Marys Lake Dam serves as a reminder of the importance of sustainable water resource management in the face of changing climate conditions.
Dam data reference
Condition Assessment
- Satisfactory
- No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
- Fair
- No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action.
- Poor
- A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency.
- Unsatisfactory
- A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
- Not Rated
- The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Hazard Potential Classification
- High
- Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
- Significant
- Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
- Low
- Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
- Undetermined
- Dams for which a downstream hazard potential has not been designated or is not provided.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around St. Marys Lake Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Des Plaines River Near Gurnee | 110 cfs | → |
| Skokie River At Lake Forest | 11 cfs | → |
| Buffalo Creek Near Wheeling | 6 cfs | → |
| Mill Creek At Old Mill Creek | 18 cfs | → |
| North Branch Chicago River At Deerfield | 5 cfs | → |
| Wf Of Nb Chicago River At Northbrook Il | 6 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near St. Marys Lake Dam.
Boat launches
- Des Plaines River Trail Libertyville
- Canoe/Kayak Ramp Vernon Hills
- Des Plaines River Trail Mettawa
- North Sears Boulevard 33435, Grayslake
- North Alleghany Road 116, Grayslake
- North Lake Avenue 39, Third Lake
Campgrounds
- Fourth Lake Resort Campsite
- Camp Reinberg
- The Hollows Conservation Area Campground
- Mud Lake West
- North Branch Conservation Area (Cyclists Only)
- Camp Lakota - A Boyscouts Of America Camp
Fishing spots
Track St. Marys Lake Dam in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About St. Marys Lake Dam
Where does the data for St. Marys Lake Dam come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the High hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of St. Marys Lake Dam.