Orville

Angwin Creek· Napa, California· Built 1959· Earth· 28 ft tall
High Hazard Water Supply Irrigation Recreation Private

Key Takeaway

Orville is classified as high hazard in California. It was completed in 1959 and is 67 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 28 ft (taller than 27.2% in CA)
Dam Length725 ft
Dam TypeEarth
Max Storage89 acre-ft
Surface Area10 acres
Drainage Area1 sq mi
Year Completed1959 (67 years old)
NID IDCA00580

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: September 14, 2022
State Regulated: Yes
Regulatory Agency: DWR, Division of Safety of Dams

Ownership

Howell Mountain Mutual Water Company

Private

Nearby Dams

Frequently Asked Questions

What is the hazard classification of Orville?

Orville 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 Orville?

Orville is owned by Howell Mountain Mutual Water Company (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Orville built?

Orville was completed in 1959, making it 67 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 Orville?

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

How tall is Orville?

Orville has a dam height of 28 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 Orville last inspected?

Orville was last inspected on September 14, 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.