Regulating Basin South Dam
Regulating Basin South Dam is an earth dam located in King County, Washington, built in 1962. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Regulating Basin South Dam
The primary purpose of Regulating Basin South Dam 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 North & South Fork Tolt River near Carnation.
The dam stands 35 feet tall and stretches 250 feet across, has a maximum storage capacity of 882 acre-feet, and collects water from a drainage area of 250 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 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 09/28/2022.
At 35 feet, this dam is taller than 82% of dams nationwide.
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 | North & South Fork Tolt River |
| Coordinates | 47.70060, -121.78270 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 35 ft |
| Dam Height | 35 ft |
| Dam Length | 250 ft |
| Year Completed | 1962 (64 years old) |
Storage & Hydraulics
| NID Storage | 882 acre-ft |
| Max Storage | 882 acre-ft |
| Normal Storage | 1 acre-ft |
| Drainage Area | 250 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Seattle |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 09/28/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00238 |
| Federal ID | WA00238S001 |
| More Info | State Dam Safety Program |