Seattle Public Utilities Mami Hara, General Manager/CEO

Broadview Sewer & Drainage Improvements


We’ll be making sewer and drainage improvements in Broadview neighborhood.



  • 2016 – 2017
    12th Avenue NW Drainage Improvement and Dayton Ave N Sewer Improvement design
  • 2018
    12th Avenue NW Drainage Improvement construction
  • 2018 – 2019
    Dayton Ave N Sewer Improvement construction
  • 2018 – 2021
    Broadview Program post project monitoring

Past project updates

Project update – October 16, 2015

The project team is completing a detailed analysis to make recommendations for the preferred project alternatives. Since July, we have also been coordinating closely with King County. Our work with King County includes modeling to help understand how each alternative would affect the overall sewer and drainage system.

In our analysis, we consider the social, financial, and environmental impacts of each options, including:

  • Construction-related traffic impacts,
  • Long-term environmental impacts,
  • Community preferences, and
  • Impacts to ratepayers.

We also carefully consider the entire Broadview basin in this process to ensure drainage improvements are designed to do no harm to downstream communities or resources. Based on comments from the community over the last year, stormwater ponds are no longer being considered as a drainage option for Broadview.

Project update – March 19, 2015

Over the past few months, our technical team has been analyzing a potential new regional sewer alternative for the 12th Avenue basin (western Broadview) and Dayton Avenue basin (eastern and southern Broadview). Preliminary work on this regional sewer alternative includes policy-level discussions among agencies, developing preliminary cost estimates, and studies of feasibility. This work will help the team determine if this potential regional sewer alternative should be considered in Broadview.

In addition, our team has been studying a new drainage alternative for the 12th Avenue basin that would use the right-of-way for drainage improvements and reduce property acquisition needs. This alternative has been developed in response to requests from the community.

Project update – September 24, 2014

Dayton Ave N Basin
SPU is working to identify preferred sewer and drainage improvements for the Dayton Ave N basin in the spring of 2015. In late 2014 we will evaluate drainage alternatives for this portion of Broadview. We will then pair leading sewer and drainage alternatives for the basin. Throughout this project, we will engage the community and seek input on key project elements.

Project phasing
SPU will develop a funding plan for phased implementation of sewer and drainage improvements in both the 12th Ave NW and Dayton Ave N basins. Early cost estimates for both basins indicate that paired sewer and drainage improvements will cost considerably more than is currently available. Refer to the September 23 community meeting materials (link above) for more information on anticipated project costs and funding.

Geotechnical study and groundwater monitoring work in Dayton Ave N Basin
As part of the project, we installed groundwater monitoring equipment in locations throughout southern and eastern Broadview. This data will help SPU understand groundwater conditions as we plan for improvements to the sewer and drainage systems in the Dayton Ave N basin.

Project update – March 24, 2014

SPU continues to plan for improvements to the sewer and drainage systems in Broadview. We are currently evaluating alternatives for sewer solutions in the 12th Avenue basin in western Broadview. Next we will pair leading sewer improvement alternatives with drainage improvement alternatives for this area, which has the highest frequency of sewer backups in Broadview. We are also concurrently planning for sewer and drainage improvements in southern and eastern Broadview (Dayton Avenue basin).

Project update – October 10, 2013

Recent draft geotechnical study completed in western portion of Broadview
In the summer of 2013 a geotechnical study in the western portion of Broadview was completed by SPU’s contractors to gain a better understanding of the hydrology in the area. A good understanding of the groundwater conditions and flows is necessary for SPU to develop effective sewer and drainage solutions. The western portion of Broadview has the highest frequency of sewer backups in all of Broadview. This study was needed because of the high ground water table and steep slopes in this area.

Next steps sewer and drainage options analysis for western portion of Broadview
SPU is analyzing the most viable sewer and drainage solutions in Broadview. SPU is evaluating alternatives for regional and local solutions to sewer backups and stormwater flooding in the western portion of Broadview (named 12th Ave basin). We will examine potential options in terms of cost, time to implement, potential effects to residents during construction, environmental benefits/impacts, and other key factors. As we analyze alternatives, we will work with the community for input on recommended solutions. We anticipate beginning design for these capital improvements in the 12th Ave basin toward the end of 2014. We are currently projecting to break ground on the capital improvement project in Broadview in 2016.

Sewer and drainage options analysis for eastern portion of Broadview
SPU will also be conducting a similar Options Analysis for the eastern half of Broadview (named the Dayton Ave. basin) which will begin after we complete the analysis on the western portion of Broadview. The reason for this timing (as noted above) is because the 12th Ave basin has a significantly higher frequency of sewer backups. Design for Dayton Ave basin sewer and drainage improvements is currently projected to begin in early 2015.


Grace Manzano, project manager
(206) 233-1534

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