Seattle Public Utilities

12th Avenue NW Basin Drainage Project

12th Ave Neighborhood

They City of Seattle will construct drainage improvements in west Broadview.

What & Why

The 12th Ave NW Basin Drainage Improvement Project will improve the drainage system in parts of west Broadview with severe flooding issues.

SPU plans to reduce storm-related flooding by building new storm system improvements where there are none, to slow runoff and improve flows. The project may use a variety of tools in City of Seattle right-of-way along neighborhood streets to address flooding issues including:

  • Converting ditch-and-culvert flow to a piped system
  • Installing large, underground pipes to hold water and prevent flooding during storms
  • Locating improvements to address priority flooding and allow for future expansion
  • Installing natural drainage cells and bioretention in feasible locations

What's happening now?

Project design is just getting started and is anticipated to go through mid-2019.

SPU will work with the community throughout design to both share information and collect input on natural drainage systems.

To learn more about the Broadview program, visit:

Sign up for updates under Connect on the right-hand side of this page.

Project documents


The 12th Ave NW Basin Drainage Improvement Project is part of the first phase of improvements in the Broadview Program.

Program Background

For more information about how SPU selected the 12th Ave NW Basin project, check out the Broadview Program background.

Project goals and benefits

The goals of the Broadview program are to:

  • Reduce sanitary sewer overflows into homes, streets, and creeks
  • Reduce the frequency and quantity of stormwater flooding to areas most impacted, especially building structures.

The 12th Avenue NW Basin Drainage project will focus on reducing storm-related flooding by slowing runoff and improving flows, seeking to maximize benefits with available budget.

Following the outcomes of our program’s options analysis process that included community input, we are now focused on making improvements along neighborhood roads, in City-owned right-of-way. As we move through design, we will work to identify where proposed improvements may require property owners to clear any encroachments beyond their property boundaries that currently extend into the City’s right-of-way (e.g. fencing, landscaping, or parking). Without doing so, we won’t be able to meet our goals.


Grace Manzano, project manager
Call our project information line (206) 409-3651, available weekdays from 8 a.m. to 5 p.m.

Sign up for 12th Avenue NW basin drainage project updates.

Sign up for Broadview program updates.