Preston is an earth dam located in Amador County, California, built in 1949. It carries a High hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 40 ft40 ft tall and 647 ft long, taller than 86% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Preston
The primary purpose of Preston 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 Amador Regional Sanitation Authority (public utility). It impounds the Tr Mule Creek near Ione.
The dam stands 40 feet tall and stretches 647 feet across, creates a reservoir covering 17 acres, has a maximum storage capacity of 268 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1949, 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 11/24/2025.
At 40 feet, this dam is taller than 86% 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 | Amador |
| Nearest City | Ione |
| River/Stream | Tr Mule Creek |
| Coordinates | 38.36980, -120.93980 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 40 ft |
| Dam Height | 40 ft |
| Dam Length | 647 ft |
| Year Completed | 1949 (77 years old) |
Storage & Hydraulics
| NID Storage | 268 acre-ft |
| Max Storage | 268 acre-ft |
| Surface Area | 17 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Amador Regional Sanitation Authority |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/24/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00012 |
| Federal ID | CA00012 |
| More Info | State Dam Safety Program |