Murphys Afterbay
Murphys Afterbay is an earth dam located in Calaveras County, California, built in 1953. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Murphys Afterbay
The primary purpose of Murphys 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 Utica Water & Power Authority (public utility). It impounds the Angels Creek near Murphys.
The dam stands 43 feet tall and stretches 340 feet across, creates a reservoir covering 3 acres, has a maximum storage capacity of 31 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1953, 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 05/31/2023.
At 43 feet, this dam is taller than 89% 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 | Calaveras |
| Nearest City | Murphys |
| River/Stream | Angels Creek |
| Coordinates | 38.15220, -120.43970 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 43 ft |
| Dam Height | 43 ft |
| Dam Length | 340 ft |
| Year Completed | 1953 (73 years old) |
Storage & Hydraulics
| NID Storage | 31 acre-ft |
| Max Storage | 31 acre-ft |
| Normal Storage | 31 acre-ft |
| Surface Area | 3 acres |
| Drainage Area | 2 sq mi |
| Max Discharge | 1,450 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Utica Water & Power Authority |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 05/31/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00410 |
| Federal ID | CA00410 |
| More Info | State Dam Safety Program |