Threw Lake Dam Reservoir Report
Last Updated: December 17, 2025
Threw Lake Dam in Knox, Illinois, is a privately owned structure designed by Hanson Professional Services.
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Summary
The dam, with a height of 43 feet and a length of 700 feet, serves primarily for recreation, offering a storage capacity of 755 acre-feet and covering a surface area of 13 acres. Located on the TRIB NORTH FORK KICKAPOO CR stream, the dam is regulated by the Illinois Department of Natural Resources and is subject to state inspection and enforcement.
Despite being classified as having low hazard potential, Threw Lake Dam poses a moderate risk, with a moderate risk assessment score of 3. The dam features an uncontrolled spillway with a width of 4 feet and has no outlet gates. The last inspection was conducted in September 2018, with a scheduled inspection frequency of 5 years. While the condition assessment is currently not available, the dam's emergency action plan status, inundation maps, and risk management measures are also unspecified.
Water resource and climate enthusiasts will find Threw Lake Dam's structure and function intriguing, as it combines recreational value with considerations for safety and risk assessment. As a privately owned facility in Illinois, the dam's design and regulatory oversight by the state underscore the importance of proper management and maintenance to ensure its continued operation and safety for both recreational users and the surrounding environment. Further monitoring and assessment of the dam's condition and risk profile will be essential for sustainable water resource management in the region.
Dam Length |
700 |
Dam Height |
43 |
River Or Stream |
TRIB NORTH FORK KICKAPOO CR |
Primary Dam Type |
Earth |
Surface Area |
13 |
Drainage Area |
0.54 |
Nid Storage |
755 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
43 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Spoon River At London Mills
|
86cfs |
Illinois River At Kingston Mines
|
8190cfs |
Indian Creek Near Wyoming
|
3cfs |
Fondulac Creek Near East Peoria
|
0cfs |
Spoon River At Seville
|
146cfs |
Farm Creek At Farmdale
|
10cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
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. Investigations and studies are necessary.
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.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams 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, environment 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.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Threw Lake Dam