Mallard

Offstream· Contra Costa, California· Built 1930· Earth· 30 ft tall

High Hazard Water Supply Irrigation Public Utility

Key Takeaway

Mallard is classified as high hazard in California. It was completed in 1930 and is 96 years old. Its primary use is water supply. 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	30 ft (taller than 30.4% in CA)
Dam Length	11,000 ft
Dam Type	Earth
Max Storage	3.1K acre-ft

Surface Area	213 acres
Drainage Area	0 sq mi
Year Completed	1930 (96 years old)
NID ID	CA00838

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: April 20, 2022

State Regulated: Yes

Regulatory Agency: DWR, Division of Safety of Dams

Ownership

Contra Costa Water District

Public Utility

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Frequently Asked Questions

What is the hazard classification of Mallard?

Mallard 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 Mallard?

Mallard is owned by Contra Costa Water District (Public Utility). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Mallard built?

Mallard 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 Mallard?

Mallard 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 Mallard?

Mallard has a dam height of 30 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 Mallard last inspected?

Mallard was last inspected on April 20, 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.