Big Dalton Debris Basin
Big Dalton Debris Basin is an earth dam located in Los Angeles County, California, built in 1960. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Big Dalton Debris Basin
The primary purpose of Big Dalton Debris Basin is debris control. The dam is designed to catch sediment, rocks, and debris carried by flowing water — particularly important in areas prone to mudslides or heavy erosion. The dam is owned by Los Angeles County Department Of Public Works (local government). It impounds the Big Dalton Wash near Glendora.
The dam stands 59 feet tall and stretches 840 feet across, creates a reservoir covering 10 acres, has a maximum storage capacity of 208 acre-feet, and collects water from a drainage area of 7 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 12/02/2025.
At 59 feet, this dam is taller than 95% 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 | Los Angeles |
| Nearest City | Glendora |
| River/Stream | Big Dalton Wash |
| Coordinates | 34.15620, -117.83470 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 59 ft |
| Dam Height | 59 ft |
| Dam Length | 840 ft |
| Year Completed | 1960 (66 years old) |
Storage & Hydraulics
| NID Storage | 208 acre-ft |
| Max Storage | 208 acre-ft |
| Surface Area | 10 acres |
| Drainage Area | 7 sq mi |
Ownership & Safety
| Purpose | Debris Control |
| Owner | Los Angeles County Department Of Public Works |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 12/02/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA01156 |
| Federal ID | CA01156 |
| More Info | State Dam Safety Program |