Puddingstone Diversion
Puddingstone Diversion is an earth dam located in Los Angeles County, California, built in 1928. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Puddingstone Diversion
Puddingstone Diversion is a dam in Los Angeles, California. The dam is owned by Los Angeles County Department Of Public Works (local government). It impounds the San Dimas Wash near San Dimas.
The dam stands 34 feet tall and stretches 825 feet across, creates a reservoir covering 16 acres, has a maximum storage capacity of 150 acre-feet, and collects water from a drainage area of 19 square miles. Completed in 1928, 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 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 11/18/2025.
At 34 feet, this dam is taller than 80% 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 | Los Angeles |
| Nearest City | San Dimas |
| River/Stream | San Dimas Wash |
| Coordinates | 34.13270, -117.78290 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 34 ft |
| Dam Height | 34 ft |
| Dam Length | 825 ft |
| Year Completed | 1928 (98 years old) |
Storage & Hydraulics
| NID Storage | 150 acre-ft |
| Max Storage | 150 acre-ft |
| Surface Area | 16 acres |
| Drainage Area | 19 sq mi |
Ownership & Safety
| Purpose | Other |
| Owner | Los Angeles County Department Of Public Works |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/18/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00199 |
| Federal ID | CA00199 |
| More Info | State Dam Safety Program |