Broadview SPU Updates

Our project team has conducted surveys and tested soils in 12th Ave NW Basin over the last few months to identify feasible locations for natural drainage installations. Initially we studied 24 blocks near the top of the drainage basin where capturing surface stormwater flows would be most effective. In early June, we went door-to-door to talk to residents about the possibility of siting natural drainage systems (NDS) in the area.

Narrowing down where we can install NDS

Natural drainage systems require well-draining, granular soils (comprised mostly of sand or a mix of sand and gravel). We found that the most favorable soils for NDS are east of 3rd Avenue NW (inside the green, solid rectangle on the attached map). Other blocks in the original study area (shown inside the blue-dashed line on the map) had significant fine-grained soils, which have low infiltration rates and are not considered suitable for NDS. We are no longer considering these blocks for NDS installations.

What we heard from talking to the community

• Many community members have issues with flooding in their yards and homes.
• Many community members were excited about NDS and expressed an interest in aesthetic improvements and traffic calming.
• Many community members were concerned with safety, including how NDS could impact sightlines.
• Maintaining convenient parking is important.
• Consideration should be given to keeping mature trees and landscaping in the public right-of-way.

Next steps

• We will continue to study the soils along the blocks in the smaller study area (inside the green, solid rectangle on the attached map) in addition to the location of other utilities, existing infrastructure and the feedback from our community survey and door-knocking efforts.
• We will present possible NDS locations to the neighborhood for review later this fall at a drop-in session. Stay tuned for an invite!
• We are also continuing to design new underground stormwater pipes (see pipe alignment in navy on this map on the website). These new underground stormwater pipes help capture stormwater and reduce flooding.

 Stay connected

• Visit our project website, which includes a new listserv: www.seattle.gov/util/12thBasin
• Sign up for 12th Ave NW Basin specific email updates
• Email us at SPU_BroadviewProjects@seattle.gov

Warm regards,

Broadview Sewer and Drainage Improvement Project Team
206-409-3651