Tiger Creek Afterbay
Tiger Creek Afterbay is a concrete dam located in Amador County, California, built in 1931. It carries a High hazard potential classification and has a fair condition assessment.
About Tiger Creek Afterbay
The primary purpose of Tiger Creek Afterbay is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Pacific Gas And Electric Company (private). It impounds the North Fork Mokelumne River near Pioneer.
The dam stands 120 feet tall and stretches 448 feet across, creates a reservoir covering 70 acres, has a maximum storage capacity of 2,607 acre-feet, and collects water from a drainage area of 357 square miles. Completed in 1931, 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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 08/21/2025.
At 120 feet, this dam is taller than 98% of all dams in the United States.
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 | Pioneer |
| River/Stream | North Fork Mokelumne River |
| Coordinates | 38.44124, -120.50513 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 120 ft |
| Dam Height | 120 ft |
| Dam Length | 448 ft |
| Year Completed | 1931 (95 years old) |
Storage & Hydraulics
| NID Storage | 2,610 acre-ft |
| Max Storage | 2,607 acre-ft |
| Normal Storage | 2,610 acre-ft |
| Surface Area | 70 acres |
| Drainage Area | 357 sq mi |
| Max Discharge | 194,370 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Pacific Gas and Electric Company |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 08/21/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00401 |
| Federal ID | CA00401 |
| More Info | State Dam Safety Program |