Drainage and Wastewater Systems Analysis

What & Why

Seattle Public Utilities is comprehensively examining how our drainage and wastewater systems work. This technical analysis uses modeling and monitors to understand system capacity and problems, so we can plan future projects and improvements. In some cases, Seattle Public Utilities will engage with residents and businesses to get additional information about an issue.

What’s happening now?

We have modeled our wastewater and drainage systems to determine where we have capacity problems. Now we are asking you to tell us more about your drainage and wastewater problems.

Project goals and benefits

This project will provide good data about our systems problems. We need this information so we can plan and make good decisions about future projects and improvements.


Seattle’s drainage and wastewater collection system is a blend of combined, partially-separated and separated systems. See map of Sewer Service Area (pdf). About two-thirds of Seattle is served by a combined or partially-separated sewer system. Completely separated systems serve the other one-third. The city conveys its wastewater to King County facilities for treatment.


2018- 2019