Plymouth Effluent
Plymouth Effluent is an earth dam located in Amador County, California, built in 1989. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
About Plymouth Effluent
The primary purpose of Plymouth Effluent 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 City Of Plymouth (local government). It impounds the Tr L Indian Cr.
The dam stands 59 feet tall and stretches 545 feet across, creates a reservoir covering 11 acres, has a maximum storage capacity of 185 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1989, the structure is 37 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. An emergency action plan is in place for this dam. The most recent inspection on record was 04/09/2025.
At 59 feet, this dam is taller than 95% of all dams in the United States.
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Location
| State | California |
| County | Amador |
| River/Stream | Tr L Indian Cr |
| Coordinates | 38.47740, -120.88200 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 59 ft |
| Dam Height | 59 ft |
| Dam Length | 545 ft |
| Year Completed | 1989 (37 years old) |
Storage & Hydraulics
| NID Storage | 185 acre-ft |
| Max Storage | 185 acre-ft |
| Surface Area | 11 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Plymouth |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 04/09/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA01189 |
| Federal ID | CA01189 |
| More Info | State Dam Safety Program |