Diablo is a concrete dam located in Whatcom County, Washington, built in 1929. It carries a High hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 389 ft389 ft tall and 1,180 ft long, taller than 99% of U.S. dams with a recorded height. Height is drawn to scale against the Statue of Liberty, 305 ft ground to torch; the profile is a generic concrete gravity section and the water level is illustrative.
About Diablo
The primary purpose of Diablo 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 City of Seattle (local government). It impounds the Skagit River near Newhalem/diablo.
The dam stands 389 feet tall and stretches 1,180 feet across, creates a reservoir covering 770 acres, has a maximum storage capacity of 89,200 acre-feet, and collects water from a drainage area of 1,160 square miles. Completed in 1929, 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 08/16/2022.
At 389 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 | Whatcom |
| Nearest City | Newhalem/diablo |
| River/Stream | Skagit River |
| Coordinates | 48.71340, -121.13180 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 389 ft |
| Dam Height | 389 ft |
| Dam Length | 1,180 ft |
| Year Completed | 1929 (97 years old) |
Storage & Hydraulics
| NID Storage | 89,200 acre-ft |
| Max Storage | 89,200 acre-ft |
| Normal Storage | 50,000 acre-ft |
| Surface Area | 770 acres |
| Drainage Area | 1,160 sq mi |
| Max Discharge | 105,300 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | City of Seattle |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/16/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00170 |
| Federal ID | WA00170 |
| More Info | State Dam Safety Program |