Grinding Rock is an earth dam located in Tuolumne County, California, built in 1979. It carries a Low hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 55 ft55 ft tall and 525 ft long, taller than 94% 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 Grinding Rock
The primary purpose of Grinding Rock 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 Tuolumne City Sanitary District (public utility). It impounds the Tr Turnback Cr.
The dam stands 55 feet tall and stretches 525 feet across, creates a reservoir covering 14 acres, has a maximum storage capacity of 330 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1979, the structure is 47 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected 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 10/21/2025.
At 55 feet, this dam is taller than 94% of dams nationwide.
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Location
| State | California |
| County | Tuolumne |
| River/Stream | Tr Turnback Cr |
| Coordinates | 37.93670, -120.25760 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 55 ft |
| Dam Height | 55 ft |
| Dam Length | 525 ft |
| Year Completed | 1979 (47 years old) |
Storage & Hydraulics
| NID Storage | 330 acre-ft |
| Max Storage | 330 acre-ft |
| Surface Area | 14 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Tuolumne City Sanitary District |
| Owner Type | Public Utility |
| Hazard Classification | Low |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/21/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | CA01184 |
| Federal ID | CA01184 |
| More Info | State Dam Safety Program |