Marseilles Lock And Dam Reservoir Report

Last Updated: December 23, 2025

Marseilles Lock and Dam, located on the Illinois River in LaSalle County, Illinois, is a vital federal water resource structure managed by the US Army Corps of Engineers.


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Summary

Completed in 1933, this concrete gravity dam plays a crucial role in facilitating navigation along the Illinois River, with a single lock measuring 600 feet in length and 110 feet in width. Despite its age, the dam has a structural height of 58 feet and a hydraulic height of 27 feet, ensuring its continued functionality in managing water levels and facilitating safe passage for vessels.

With a storage capacity of 14,000 acre-feet, Marseilles Lock and Dam serves as a key component in the USACE's flood risk management strategy for the Illinois River system. The dam's hazard potential is deemed significant, prompting regular inspections and emergency preparedness measures to mitigate potential risks. Through ongoing monitoring, maintenance, and collaboration with local emergency managers, USACE works diligently to safeguard the surrounding communities and infrastructure from the impacts of severe weather events and fluctuating water levels. As a cornerstone of water resource management in the region, Marseilles Lock and Dam exemplifies the importance of proactive risk management and public safety in the face of changing climate conditions.

Year Completed

1933

Dam Length

2078

River Or Stream

ILLINOIS RIVER

Primary Dam Type

Concrete

Length Of Locks

600

Hydraulic Height

27

Drainage Area

8259

Nid Storage

14000

Structural Height

58

Outlet Gates

Tainter (radial) - 8, Uncontrolled - 0

Hazard Potential

Significant

Foundations

Rock

Nid Height

58
       
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.