Mammoth Pool
Mammoth Pool is an earth dam located in Madera County, California, built in 1960. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Mammoth Pool
The primary purpose of Mammoth Pool 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 Southern California Edison Company (private). It impounds the San Joaquin River near Big Creek.
The dam stands 411 feet tall and stretches 820 feet across, creates a reservoir covering 1,100 acres, has a maximum storage capacity of 122,175 acre-feet, and collects water from a drainage area of 995 square miles. Completed in 1960, the structure is well into its service life at over 50 years old.
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 08/29/2023.
At 411 feet, this dam is taller than 99% 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 | Madera |
| Nearest City | Big Creek |
| River/Stream | San Joaquin River |
| Coordinates | 37.32310, -119.31720 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 411 ft |
| Dam Height | 411 ft |
| Dam Length | 820 ft |
| Year Completed | 1960 (66 years old) |
Storage & Hydraulics
| NID Storage | 122,175 acre-ft |
| Max Storage | 122,175 acre-ft |
| Normal Storage | 120,000 acre-ft |
| Surface Area | 1,100 acres |
| Drainage Area | 995 sq mi |
| Max Discharge | 235,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Southern California Edison Company |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/29/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00443 |
| Federal ID | CA00443 |
| More Info | State Dam Safety Program |