Tolt River - South Fork
Tolt River - South Fork is an earth dam located in King County, Washington, built in 1962. It carries a High hazard potential classification and has a fair condition assessment.
About Tolt River - South Fork
The primary purpose of Tolt River - South Fork is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by City Of Seattle (local government). It impounds the South Fork Tolt River near Carnation.
The dam stands 200 feet tall and stretches 980 feet across, creates a reservoir covering 1,040 acres, has a maximum storage capacity of 68,400 acre-feet, and collects water from a drainage area of 18 square miles. Completed in 1962, 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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 09/28/2022.
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 | King |
| Nearest City | Carnation |
| River/Stream | South Fork Tolt River |
| Coordinates | 47.69300, -121.68870 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 200 ft |
| Dam Height | 200 ft |
| Dam Length | 980 ft |
| Year Completed | 1962 (64 years old) |
Storage & Hydraulics
| NID Storage | 68,400 acre-ft |
| Max Storage | 68,400 acre-ft |
| Normal Storage | 57,500 acre-ft |
| Surface Area | 1,040 acres |
| Drainage Area | 18 sq mi |
| Max Discharge | 13,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Seattle |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 09/28/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00177 |
| Federal ID | WA00177 |
| More Info | State Dam Safety Program |