Structure No. 12 Reservoir Report

Last Updated: December 5, 2025

Structure No.


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Summary

12, also known as Dutchman Lake, is a federal-owned dam located in Johnson County, Illinois. Managed by the USDA NRCS, this earth dam was completed in 1974 for the primary purposes of recreation and water supply. With a height of 54 feet and a length of 1450 feet, the dam provides a maximum storage capacity of 4432 acre-feet and serves a drainage area of 11 square miles.

The dam's spillway type is controlled with a width of 300 feet, and the outlet gates are equipped with valves for water release. Despite being classified as having a significant hazard potential and a very high risk assessment level, the dam's condition assessment is currently listed as not rated. The last inspection was conducted in September 2016, with no specific inspection frequency provided.

This structure, situated along Dutchman Creek, is under the regulation of the IDNR and the Forest Service, with funding and construction support from various federal agencies. As a popular recreational spot in the area, Structure No. 12 plays a crucial role in water supply management and offers opportunities for outdoor activities amid its natural surroundings.

Year Completed

1974

Dam Length

1450

Dam Height

54

River Or Stream

DUTCHMAN CREEK

Primary Dam Type

Earth

Surface Area

186

Hydraulic Height

35

Drainage Area

11

Nid Storage

4432

Structural Height

51

Outlet Gates

Valve

Hazard Potential

Significant

Nid Height

54
       
Seasonal Comparison

Weather Forecast

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. 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

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, 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.