Rio

Mongaup River· Sullivan, New York· Built 1927· Gravity· 101 ft tall

High Hazard Hydroelectric Recreation Private

Key Takeaway

Rio is classified as high hazard in New York. It was completed in 1927 and is 99 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	101 ft (taller than 98.5% in NY)
Dam Length	1,487 ft
Dam Type	Gravity
Max Storage	15.0K acre-ft
Normal Storage	15.0K acre-ft

Surface Area	460 acres
Drainage Area	195 sq mi
Max Discharge	56,700 cfs
Year Completed	1927 (99 years old)
NID ID	NY00497

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 12, 2022

State Regulated: No

Ownership

Eagle Creek Hydro Power, LLC

Private

Nearby Dams

Lower Lake Metaugue Dam

Sullivan, NY

Low Hazard 10 ft

Hartwood Club Dam

Sullivan, NY

Low Hazard 8 ft

Hemlock Lake Dam

Sullivan, NY

Significant Hazard 27 ft

Burnt Hope Dam

Sullivan, NY

Low Hazard 19 ft

Dormans Pond Dam

Orange, NY

Significant Hazard 9 ft

Mogisca Lake Dam

Sullivan, NY

Significant Hazard 36 ft

Mongaup

Sullivan, NY

High Hazard 45 ft

Camp Diana Dalmqua Pond Dam

Sullivan, NY

Low Hazard 7 ft

Frequently Asked Questions

What is the hazard classification of Rio?

Rio 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 Rio?

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

When was Rio built?

Rio was completed in 1927, making it 99 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 Rio?

Rio 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 Rio?

Rio has a dam height of 101 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 Rio last inspected?

Rio was last inspected on August 12, 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.