Mccoy Flat

Susan River· Lassen, California· Built 1891· Earth· 21 ft tall
Low Hazard Water Supply Irrigation Private

Key Takeaway

Mccoy Flat is classified as low hazard in California. It was completed in 1891 and is 135 years old. Its primary use is water supply.

Physical Details

Dam Height 21 ft (taller than 17.3% in CA)
Dam Length650 ft
Dam TypeEarth
Max Storage17.3K acre-ft
Surface Area1,800 acres
Drainage Area110 sq mi
Year Completed1891 (135 years old)
NID IDCA00517

Safety Information

Low Hazard

No probable loss of human life and low economic/environmental losses expected.

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

Emergency Action Plan: No
Last Inspection: May 24, 2022
State Regulated: Yes
Regulatory Agency: DWR, Division of Safety of Dams

Ownership

Lassen Irrigation Company

Private

Nearby Dams

Frequently Asked Questions

What is the hazard classification of Mccoy Flat?

Mccoy Flat is classified as Low Hazard. No probable loss of human life and low economic/environmental losses expected. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates Mccoy Flat?

Mccoy Flat is owned by Lassen Irrigation Company (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Mccoy Flat built?

Mccoy Flat was completed in 1891, making it 135 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 Mccoy Flat?

Mccoy Flat serves the following purposes: Water Supply, Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is Mccoy Flat?

Mccoy Flat has a dam height of 21 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 Mccoy Flat last inspected?

Mccoy Flat was last inspected on May 24, 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.