24th Ave NW Sewer & Drainage Improvements

Project description

Seattle Public Utilities (SPU) is planning sewer and drainage system improvements in the North Beach area to address flooding and overflows along 24th Ave NW and NW Neptune Pl. These improvements will add capacity to the drainage and sewer systems, reduce risks of floods and sewer backups, and provide robust infrastructure to handle future growth and climate change. SPU coordinates these improvements with other city departments including Seattle City Light and Seattle Department of Transportation.

Location

The area being assessed for improvements includes the sewer and drainage basin to the east of 24th Ave NW, in the North Beach Neighborhood. Once the project team has adequately assessed the area, the map will be updated with a project specific area detailing where the improvements will take place.

Community benefits

North Beach drainage and sewer improvements will contribute to a healthier and safer community by:

• Reducing the risk of flooding and sewer backups in streets, homes and business
• Increase drainage and sewer capacity to handle increased rainfall projections caused by climate change
• Direct groundwater into drainage system to avoid dangerous ice forming near North Beach Elementary School
• Include street improvements near school to add sidewalks and safety/ADA features

What's happening now?

The North Beach neighborhood has significant drainage and sewer challenges. SPU is currently working to understand and map the complex drainage and sewer system in the study area shown above. In early 2027, SPU will work to develop engineered design options  in coordination with SDOT sidewalk improvements. Construction is planned to start in 2030.

Seattle Public Utilities (SPU) will be inspecting sewer lines in your neighborhood using water vapor in August 2026. The testing helps SPU identify leaks and pipe connection issues.

This is a first step in identifying the details of the sewer system layout. Once data is collected, SPU teams will use the information to develop workable neighborhood solutions to prevent flooding.

What is Water Vapor Testing?

Water vapor testing is a common practice where water vapor is released into sewer pipes to help crews locate leaks and pipe connection issues. The water vapor is sent through the sewer system so crews can visually track where it comes out through sewer vents, maintenance holes, and the ground. 

What to Expect

• No Utility Service interruptions: Homes and businesses will continue to receive normal water and sewer services throughout the inspection period.
• Preparing Your Home: To prevent the water vapor from entering your home, residents are advised to run water for 30 seconds in all sinks, baths, and showers, and pour water into exposed floor drains prior to the testing. This ensures that drains are filled with water, which acts as a seal.
• Normal Observations: It is normal to see or smell the water vapor coming from maintenance holes in the street or right-of-way, sewer vents from roofs, or emerging from the ground. In such cases, no action is required.
• If Water Vapor Enters Your Home: If you detect or smell water vapor inside your house or building, open doors or windows to increase ventilation. The vapor should clear within a few minutes.
• Persistent Water Vapor Inside: If water vapor continues to remain in your building for more than five minutes, you should speak with the on-site field representatives or workers conducting the inspections.  You can also contact SPU’s emergency Operations Response Center (ORC) at (206) 386-1800.

For more information, please see the Water Vapor Testing Frequently Asked Questions (FAQ’s).

Schedule

2026

• 2026-Water Vapor Testing

2027

• Project Options Analysis

2028-2030

• Project Design