O'sullivan Dam
O'sullivan Dam is an earth dam located in Grant County, Washington, built in 1949. It carries a High hazard potential classification.
About O'sullivan Dam
The primary purpose of O'sullivan Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Bureau Of Reclamation (federal). It impounds the Lower Crab Creek near Symina.
The dam stands 200 feet tall and stretches 19,000 feet across, creates a reservoir covering 27,800 acres, has a maximum storage capacity of 546,300 acre-feet, and collects water from a drainage area of 79,162 square miles. Completed in 1949, 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. An emergency action plan is in place for this dam. The most recent inspection on record was 08/18/2023.
At 200 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 Washington 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 | Washington |
| County | Grant |
| Nearest City | Symina |
| River/Stream | Lower Crab Creek |
| Coordinates | 46.98200, -119.29080 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 200 ft |
| Dam Height | 200 ft |
| Dam Length | 19,000 ft |
| Year Completed | 1949 (77 years old) |
Storage & Hydraulics
| NID Storage | 546,300 acre-ft |
| Max Storage | 546,300 acre-ft |
| Normal Storage | 511,700 acre-ft |
| Surface Area | 27,800 acres |
| Drainage Area | 79,162 sq mi |
| Max Discharge | 29,600 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | BUREAU OF RECLAMATION |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 08/18/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00268 |
| Federal ID | WA00268 |
| More Info | State Dam Safety Program |