Mast is an earth dam located in Mendocino County, California, built in 1963. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 85 ft85 ft tall and 580 ft long, taller than 97% of U.S. dams with a recorded height. Height is drawn to scale against a ten-story building, about 100 ft; the profile is a generic embankment section and the water level is illustrative.
About Mast
The primary purpose of Mast is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Stacy Holland (private). It impounds the Tr Cahto Creek.
The dam stands 85 feet tall and stretches 580 feet across, creates a reservoir covering 14 acres, has a maximum storage capacity of 380 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1963, the structure is well into its service life at over 50 years old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. The most recent inspection on record was 05/08/2025.
At 85 feet, this dam is taller than 97% of all dams in the United States.
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Location
| State | California |
| County | Mendocino |
| River/Stream | Tr Cahto Creek |
| Coordinates | 39.66590, -123.52840 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 85 ft |
| Dam Height | 85 ft |
| Dam Length | 580 ft |
| Year Completed | 1963 (63 years old) |
Storage & Hydraulics
| NID Storage | 380 acre-ft |
| Max Storage | 380 acre-ft |
| Surface Area | 14 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Stacy Holland |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 05/08/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | CA00972 |
| Federal ID | CA00972 |
| More Info | State Dam Safety Program |