Twain Harte
Twain Harte is a multi-arch dam located in Tuolumne County, California, built in 1928. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Twain Harte
The primary purpose of Twain Harte 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 Twain Harte Lake Association, Inc. (private). It impounds the Unnamed Creek near Sonora.
The dam stands 36 feet tall and stretches 325 feet across, creates a reservoir covering 12 acres, has a maximum storage capacity of 143 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1928, the structure is well-established, with more than 75 years of service.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 09/12/2024.
At 36 feet, this dam is taller than 83% of dams nationwide.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The California dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | California |
| County | Tuolumne |
| Nearest City | Sonora |
| River/Stream | Unnamed Creek |
| Coordinates | 38.02910, -120.24400 |
Physical Characteristics
| Dam Type | Multi-Arch |
| NID Height | 36 ft |
| Dam Height | 36 ft |
| Dam Length | 325 ft |
| Year Completed | 1928 (98 years old) |
Storage & Hydraulics
| NID Storage | 143 acre-ft |
| Max Storage | 143 acre-ft |
| Surface Area | 12 acres |
| Drainage Area | 1 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Twain Harte Lake Association, Inc. |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 09/12/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00649 |
| Federal ID | CA00649 |
| More Info | State Dam Safety Program |