Assunpink #20 Dam

Assunpink Creek· Mercer, New Jersey· Earth· 26 ft tall

High Hazard Flood Risk Reduction Fish And Wildlife Pond Recreation Local Government

Key Takeaway

Assunpink #20 Dam is classified as high hazard in New Jersey. Its primary use is flood risk reduction. 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	26 ft (taller than 87% in NJ)
Dam Length	4,070 ft
Dam Type	Earth
Max Storage	14.7K acre-ft
Normal Storage	2.7K acre-ft

Surface Area	275 acres
Drainage Area	30 sq mi
Max Discharge	29,450 cfs
NID ID	NJ00552

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: May 26, 2021

State Regulated: Yes

Regulatory Agency: NJDEP

Ownership

County of Mercer Park Commission

Local Government

Nearby Dams

Assunpink #21 Dam

Mercer, NJ

High Hazard 25 ft

Assunpink #8 Dam

Mercer, NJ

High Hazard 20 ft

Colonial Lake Dam

Mercer, NJ

Low Hazard 12 ft

Squibb Dam

Mercer, NJ

Low Hazard 26 ft

Grover'S Mill Dam

Mercer, NJ

Significant Hazard 15 ft

Gropps Lake Dam

Mercer, NJ

Low Hazard 25 ft

Plainsboro Pond Dam

Middlesex, NJ

Significant Hazard 11 ft

Assunpink # 6 Dam

Mercer, NJ

High Hazard 31 ft

Frequently Asked Questions

What is the hazard classification of Assunpink #20 Dam?

Assunpink #20 Dam 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 Assunpink #20 Dam?

Assunpink #20 Dam is owned by County of Mercer Park Commission (Local Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

What is the primary purpose of Assunpink #20 Dam?

Assunpink #20 Dam serves the following purposes: Flood Risk Reduction, Fish And Wildlife Pond, Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is Assunpink #20 Dam?

Assunpink #20 Dam has a dam height of 26 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 Assunpink #20 Dam last inspected?

Assunpink #20 Dam was last inspected on May 26, 2021. 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.