Post Avenue Bridge Replacement Project

What's happening now?

In recent days cellular concrete, a lighter and more appropriate substance than regular concrete for the landfill base of Post Ave, has been poured into the west side of Post Ave. The cellular concrete is being poured to a depth of 4', which will then be topped with 6" of aggregate stone, before the final concrete pour to come at the end of the project.

Next, the construction crew is beginning the excavation of the east side of Post Ave and sidewalk from Columbia St to the entrance of Owl'n'Thistle. Access to both the Owl'n'Thistle and the trash room of the Colman Building will then be provided via two east/west land bridges from the sidewalk on the west side of Post Ave. Both should be in place by the end of this week.

The demolition and excavation of the remainder of the east side of Post Ave and the sidewalk north of Owl'n'Thistle will begin the week of November 6, at which point two additional east/west land bridges will be installed to provide access to The Good Coffee Company and the Colman Building Barber Shop (as well as the Post Ave entrance to the building from the sidewalk on the west side of Post Ave).

Active construction - October 30

Project Overview

We expect to replace the Post Ave Bridge, located between Marion St and Columbia St over a period of about 4 months.  

Project Area

Built in 1911, the bridge is one of the few remaining timber pile structures supporting a roadway in Seattle.  The waterfront west of First Avenue, then called Front Street, is where the Colman Building and Post Avenue are now.

Historic photo

The bridge itself is no longer visible from the surface, as its wood deck has long since been covered with a reinforced concrete surface and an asphalt wearing surface. The timber structure has sunk over time, and the roadway surface is significantly lower than it once was.  This movement has also affected the adjoining sidewalk to the east, adjacent to the Colman Building, leading to sidewalks with a very steep cross-slope . 

SDOT will remove the 240' long bridge, replace the soil below with a low -density fill material, and build a new roadway and sidewalk adjacent to the Colman Building.  The new sidewalk will be wider than the existing one to meet requirements of the Americans with Disabilities Act (ADA), and will also incorporate concrete steps along the length of the street leading to the curb edge.  (See cross section and detail below - looking north.)

East Detail

Cross section

The sidewalk to the west will not require replacement as this was done in conjunction with the development of The Post - a 16 story mixed-use building finished in 2012.

Construction Impacts

  • Post Ave will be closed to thru traffic for all vehicles for approximately 3 months
  • Pedestrian access to both the Colman and Post buildings will be maintained at all times, with detours as needed
  • Construction crews will maintain or provide services to Colman Building tenants - including deliveries of mail, parcels, merchandise, restaurant supplies, and the removal of trash, recycling, and compost
  • Noise, vibration, and dust will be present at times
  • Construction is expected to occur during regular weekday work hours, with occasional night or weekend work ; we will provide advanced notice
  • A portion of Marion St adjacent to Post Ave will be closed for repaving

Once the project is complete, Post Ave will continue to have a single southbound travel lane, but parking will be limited to the east side.  This is because the roadway has to be narrowed from 30' to 25' to accommodate the widened sidewalk and stepped surface between the Colman Building and Post Avenue's eastern curb edge. The remaining parking will be restricted to loading and unloading during business hours.

As part of the work, voids below the sidewalk adjacent to the foundation of the Colman Building will be filled as well - including areas under the Marion Str Pedestrian Bridge which connects 1st Ave to the Washington Colman Ferry Dock.

The project is outside the Pioneer Square Historical Preservation District and has been granted a Determination of Non-Significance.  Consulting archeologists will document the project during the demolition and monitor the work for anything of interest.

Schedule

We expect construction to begin in October of 2017 and take about 4 months to complete.  Once the contract for the work has been signed, more complete information about the schedule will be available here.

Funding

The project budget is approximately $2 million, funded by a grant from the Federal Highway Bridge Program and local funding.

Project Materials

Current photo

Contact Infomation

If you have questions or comments about the Post Avenue Bridge Replacement Project, or if you would like to receive updates about the project by email, please contact Paul Elliott at paul.elliott@seattle.gov .

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