Algonquin Dam

FOX RIVER· McHenry, Illinois· Built 1947· Concrete· 9 ft tall
Significant Hazard Flood Risk Reduction Recreation State Government

Key Takeaway

Algonquin Dam is classified as significant hazard in Illinois. It was completed in 1947 and is 79 years old. Its primary use is flood risk reduction. Significant hazard means failure could cause economic or environmental damage. Learn more.

Physical Details

Dam Height 9 ft (taller than 3.9% in IL)
Dam Length300 ft
Dam TypeConcrete
Max Storage24.2K acre-ft
Normal Storage0 acre-ft
Year Completed1947 (79 years old)
Year Modified2003
NID IDIL55063

Safety Information

Significant Hazard

No probable loss of human life, but can cause economic loss, environmental damage, or disruption of lifeline facilities.

Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?

Emergency Action Plan: Yes
Last Inspection: April 26, 2023
State Regulated: Yes
Regulatory Agency: IDNR

Ownership

ILLINOIS DEPARTMENT OF NATURAL RESOURCES

State Government

Nearby Dams

Frequently Asked Questions

What is the hazard classification of Algonquin Dam?

Algonquin Dam is classified as Significant Hazard. No probable loss of human life, but can cause economic loss, environmental damage, or disruption of lifeline facilities. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates Algonquin Dam?

Algonquin Dam is owned by ILLINOIS DEPARTMENT OF NATURAL RESOURCES (State Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Algonquin Dam built?

Algonquin Dam was completed in 1947, making it 79 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.

What is the primary purpose of Algonquin Dam?

Algonquin Dam serves the following purposes: Flood Risk Reduction, Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is Algonquin Dam?

Algonquin Dam has a dam height of 9 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.

When was Algonquin Dam last inspected?

Algonquin Dam was last inspected on April 26, 2023. Inspection dates indicate when a formal review occurred, not the results of that inspection.

Data from the National Inventory of Dams (NID) maintained by the US Army Corps of Engineers. Dam conditions may have changed since the last update. This site is not affiliated with USACE. Do not use for emergency planning — contact your local dam safety program.