Hiram M. Chittenden Locks and Dam is a gravity dam located in King County, Washington, built in 1916. It carries a High hazard potential classification.
Dam profile
NID height · 63 ft63 ft tall and 240 ft long, taller than 95% of U.S. dams with a recorded height. Height is drawn to scale against a ten-story building, about 100 ft; the profile is a generic concrete gravity section and the water level is illustrative.
About Hiram M. Chittenden Locks and Dam
The primary purpose of Hiram M. Chittenden Locks and Dam is navigation. The dam maintains water levels sufficient for boat and barge traffic, supporting commercial or recreational navigation on the waterway. The dam is owned by USACE - Seattle District (federal). It impounds the Cedar River, Sammamish River near Seattle.
The dam stands 63 feet tall and stretches 240 feet across, creates a reservoir covering 25,000 acres, has a maximum storage capacity of 458,000 acre-feet, and collects water from a drainage area of 607 square miles. Completed in 1916, the structure is over a century 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. An emergency action plan is in place for this dam. The most recent inspection on record was 03/10/2022.
At 63 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 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 | King |
| Nearest City | Seattle |
| River/Stream | Cedar River, Sammamish River |
| Coordinates | 47.66529, -122.39725 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 63 ft |
| Dam Length | 240 ft |
| Year Completed | 1916 (110 years old) |
Storage & Hydraulics
| NID Storage | 458,000 acre-ft |
| Max Storage | 458,000 acre-ft |
| Normal Storage | 458,000 acre-ft |
| Surface Area | 25,000 acres |
| Drainage Area | 607 sq mi |
| Max Discharge | 16,000 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Navigation |
| Owner | USACE - Seattle District |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Not assessed |
| Last Inspection | 03/10/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00301 |
| Federal ID | WA00301 |
| More Info | State Dam Safety Program |