Cliff Lake

Mongaup River· Sullivan, New York· Built 1930· Concrete· 36 ft tall

High Hazard Hydroelectric Recreation Private

Key Takeaway

Cliff Lake is classified as high hazard in New York. It was completed in 1930 and is 96 years old. Its primary use is hydroelectric. High hazard means loss of life is likely if the dam fails — it does not indicate the dam's current condition. Learn more.

Physical Details

Dam Height	36 ft (taller than 85.3% in NY)
Dam Length	610 ft
Dam Type	Concrete
Max Storage	2.9K acre-ft
Normal Storage	2.9K acre-ft

Surface Area	190 acres
Drainage Area	30 sq mi
Max Discharge	13,000 cfs
Year Completed	1930 (96 years old)
NID ID	NY00584

Safety Information

High Hazard

Loss of human life is likely if the dam fails.

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

Emergency Action Plan: Yes

Last Inspection: August 11, 2022

State Regulated: No

Ownership

Eagle Creek Hydro Power, LLC

Private

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Twin Ponds Dam - Lower

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Twin Ponds Dam Upper

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Mongaup

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Toronto

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Frequently Asked Questions

What is the hazard classification of Cliff Lake?

Cliff Lake is classified as High Hazard. Loss of human life is likely if the dam fails. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates Cliff Lake?

Cliff Lake is owned by Eagle Creek Hydro Power, LLC (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Cliff Lake built?

Cliff Lake was completed in 1930, making it 96 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 Cliff Lake?

Cliff Lake serves the following purposes: Hydroelectric, Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is Cliff Lake?

Cliff Lake has a dam height of 36 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 Cliff Lake last inspected?

Cliff Lake was last inspected on August 11, 2022. 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.