Van Der Molen Dam Reservoir Report

Last Updated: December 5, 2025

Van Der Molen Dam, also known as Van Der Molen Detention Reservoir, is located in Addison, Illinois, along the Westwood Creek.


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Summary

This private dam, designed by Collins Engineers, was completed in 1984 with the primary purpose of flood risk reduction. Standing at a height of 8 feet and a length of 940 feet, the dam has a storage capacity of 99 acre-feet and a maximum discharge of 571 cubic feet per second. The spillway, which is uncontrolled, has a width of 50 feet, and the dam is classified as having a low hazard potential.

Managed by the Illinois Department of Natural Resources (IDNR), Van Der Molen Dam is subject to state regulations, permitting, inspection, and enforcement. The dam is regularly inspected, with the last inspection conducted in August 2020, and it has a moderate risk assessment rating. Although the condition assessment is not currently available, the dam is maintained to meet safety standards and reduce the risk of flooding in the surrounding area. While there are no associated structures or federal agency involvement with the dam, its importance in mitigating flood risks in DuPage County, Illinois, cannot be understated for water resource and climate enthusiasts.

Year Completed

1984

Dam Length

940

Dam Height

8

River Or Stream

WESTWOOD CREEK

Primary Dam Type

Earth

Nid Storage

99

Outlet Gates

None

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

8
       
Seasonal Comparison

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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.