Mcmahon
Mcmahon is an earth dam located in Mariposa County, California, built in 1957. It carries a Low hazard potential classification and has a satisfactory condition assessment.
About Mcmahon
The primary purpose of Mcmahon 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 Kym Carpenter (private). It impounds the Maxwell Creek.
The dam stands 52 feet tall and stretches 705 feet across, creates a reservoir covering 26 acres, has a maximum storage capacity of 520 acre-feet, and collects water from a drainage area of 18 square miles. Completed in 1957, the structure is well into its service life at over 50 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. The most recent inspection on record was 05/28/2025.
At 52 feet, this dam is taller than 93% of dams nationwide.
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Location
| State | California |
| County | Mariposa |
| River/Stream | Maxwell Creek |
| Coordinates | 37.69916, -120.19824 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 52 ft |
| Dam Height | 52 ft |
| Dam Length | 705 ft |
| Year Completed | 1957 (69 years old) |
Storage & Hydraulics
| NID Storage | 520 acre-ft |
| Max Storage | 520 acre-ft |
| Surface Area | 26 acres |
| Drainage Area | 18 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Kym Carpenter |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Satisfactory |
| Last Inspection | 05/28/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | CA00701 |
| Federal ID | CA00701 |
| More Info | State Dam Safety Program |