Southwest Genesee Street Detention Dam
Southwest Genesee Street Detention Dam is an earth dam located in King County, Washington, built in 1974. It carries a High hazard potential classification and has a fair condition assessment.
About Southwest Genesee Street Detention Dam
The primary purpose of Southwest Genesee Street Detention 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 Seattle Public Utilities (public utility). It impounds the Longfellow Creek near Within Seattle City Limits.
The dam stands 27 feet tall and stretches 230 feet across, creates a reservoir covering 16 acres, has a maximum storage capacity of 52 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1974, 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 09/09/2020.
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 | Within Seattle City Limits |
| River/Stream | Longfellow Creek |
| Coordinates | 47.56488, -122.36751 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 27 ft |
| Dam Length | 230 ft |
| Year Completed | 1974 (52 years old) |
Storage & Hydraulics
| NID Storage | 52 acre-ft |
| Max Storage | 52 acre-ft |
| Normal Storage | 19 acre-ft |
| Surface Area | 16 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 240 cfs |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Seattle Public Utilities |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 09/09/2020 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00380 |
| Federal ID | WA00380 |
| More Info | State Dam Safety Program |