Bay Creek Structure 5 Dam Reservoir Report

Last Updated: December 5, 2025

Bay Creek Structure 5 Dam, also known as Millstone Lake, is a significant earth dam located in Pope County, Illinois.


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Summary

Completed in 1976, this dam serves the primary purpose of recreation and is owned by the local government. Managed by the USDA NRCS, it stands at a height of 51 feet and has a length of 911 feet, with a storage capacity of 13,779 acre-feet.

With a spillway width of 130 feet and uncontrolled outlets, Bay Creek Structure 5 Dam poses a significant hazard potential and is classified as having a moderate risk level. Inspected regularly by the IDNR, this dam is equipped with emergency action plans and meets regulatory guidelines. Despite its condition assessment not being available, the dam continues to provide recreational opportunities while ensuring the safety and well-being of surrounding communities in Illinois.

Year Completed

1976

Dam Length

911

Dam Height

51

River Or Stream

BAY CREEK

Primary Dam Type

Earth

Nid Storage

13779

Outlet Gates

Uncontrolled

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

51
       
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.