Lake Grinnell Dam

Wallkill River-TR· Sussex, New Jersey· Built 1900· Earth· 12 ft tall
Significant Hazard Recreation Private

Key Takeaway

Lake Grinnell Dam is classified as significant hazard in New Jersey. It was completed in 1900 and is 126 years old. Its primary use is recreation. Significant hazard means failure could cause economic or environmental damage. Learn more.

Physical Details

Dam Height 12 ft (taller than 31.2% in NJ)
Dam Length195 ft
Dam TypeEarth
Normal Storage150 acre-ft
Surface Area46 acres
Drainage Area3 sq mi
Max Discharge30 cfs
Year Completed1900 (126 years old)
NID IDNJ00289

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 5, 2021
State Regulated: Yes
Regulatory Agency: NJDEP

Ownership

Lake Grinnell Homeowners Association

Private

Nearby Dams

Frequently Asked Questions

What is the hazard classification of Lake Grinnell Dam?

Lake Grinnell 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 Lake Grinnell Dam?

Lake Grinnell Dam is owned by Lake Grinnell Homeowners Association (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Lake Grinnell Dam built?

Lake Grinnell Dam was completed in 1900, making it 126 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 Lake Grinnell Dam?

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

How tall is Lake Grinnell Dam?

Lake Grinnell Dam has a dam height of 12 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 Lake Grinnell Dam last inspected?

Lake Grinnell Dam was last inspected on April 5, 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.