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Portage Bay Bridge Construction Issues

Portage Bay- Roanoke Park and Montlake Residents,


The COVID-19 pandemic has interrupted all our lives. It has also caused delays in WSDOT’s development and construction schedule for the replacement of the Portage Bay Bridge and its connections. This last project phase extends from Montlake Boulevard westward to I -5.  It includes completion of the previously designed Delmar Lid.  WSDOT has scheduled a meeting on the planning process at the end of this summer.  WSDOT also plans to submit a required Seattle Shoreline Permit early in 2021. 


This last phase of construction is planned to start in 2023 and end six years later in 2029. 

The final phase will be preceded by the construction of a High Occupancy Vehicle (HOV) lane connection from SR 520 to the I-5 express lanes. This work includes new ramp construction plus limited retaining wall replacement and highway widening on the northside of SR 520. The City has approved a nighttime noise variance for this work.


This last phase will have enormous impacts on the livability of our neighborhoods throughout the long construction period. There also is an opportunity to provide input on these impacts and on mitigation enhancements along the South Portage Bay shoreline. The COVID-19 work delay will provide more time to develop community input into the project development process.


We again need to establish cohesive neighborhood support on the various project development issues. Following is an overview of these issues and a survey of our neighborhood resident interest in them. 


Please review this information and share it with your neighbors.  If you have any questions about it or need more information, please send an e-mail to Ron Melnikoff ( .


Project Development Issues


Bridge Design - The Seattle Design Commission approved the bridge design.  For the roadway this includes adding a 3rd HOV lane and a bike/pedestrian pathway. The approval also includes the bridge’s pier design and spacing, support structure, noise containment side walls and lighting. Final design elements like lighting should have more review.


Noise and Vibration Mitigation During SR 520 Construction - WSDOT plans to build the replacement bridge in two phases.  A westbound, northside half bridge structure will be completed first.  Months of pile driving may create high noise level and vibration impacts.  These impacts may be influenced by the bowl-shaped topography surrounding the construction corridor.  Noise impacts carry farther over open water and soft soils in the bay may increase vibration impacts on vulnerable foundations of nearby residences. 


Pile driving is allowed by City code without a variance during the day.  The City has approved two nighttime hour noise variances for previous project phases.  WSDOT has proposed noise mitigation measures to be determined by the construction contractor. They include providing hotel rooms and ear plugs for severely impacted residents.  The legislature provided separate funding for measures such as window upgrades sound drapes and air conditioning. 


Construction vehicle access will also raise noise levels.  It is not clear that a cost-benefit analysis (including construction traffic effects) has been performed that could assure the public that the harm caused is minimized.  Alternatively, an option for use of barges can have lower noise and vibration impacts.  WSDOT apparently considers barge-based construction infeasible even though this option was used for the original construction in the 1960’s.


There will be an opportunity for neighborhood resident comment on the next WSDOT City night time noise variance and the WSDOT Contractor noise management plan.

Neighborhood Traffic Management Plan - Those living closest to the highway construction corridor, haul routes and staging areas will see the greatest impacts during construction. There will be temporary closures of 10th Ave. East and Fuhrman-Boyer for both bridge, highway and lid construction. Additional impacts will result from construction vehicle traffic and detours that will impact Harvard - 10th Ave. East, Fuhrman-Boyer, Roanoke, Delmar, Lynn, and 19th Ave. East.  Cut through traffic on residential streets (such as from Roanoke to Boyer on 11th Ave. East) needs control.  Pedestrian crossings and signalization are an important consideration.  During construction of the Delmar lid, WSDOT has considered keeping one lane of Delmar open with stoplight control.  

Our neighborhood must have input on construction sequencing. The City street use permit and the construction contractor management plan will include public comment periods.


Project Shoreline Permit  - WSDOT will apply for a new Seattle shoreline permit likely in early 2021. It is needed for the SR 520 Portage Bay Bridge replacement.  The Shoreline Permit includes a neighborhood resident comment period.  This permit can require shoreline trail and habitat mitigation.  This may be our last opportunity to propose enhancements that would be funded by WSDOT.  

For the past 8 years, grant funding and extensive volunteer efforts have removed harmful invasive plant and animal species, have provided trail access and reestablished native habitat. These extensive work activities have been completed along the playfield shoreline and at the unused west end of the park property.  Additionally, the kayak launch site has been improved. 


Some of our neighbors have developed a detailed proposal to further enhance trail access and shoreline habitat.  WSDOT and the City provided similar mitigation measures at Magnuson Park, Arboretum and a new park at the UW South Campus shoreline on North Portage Bay.  The City can require that WSDOT fund this plan as part of its approval of WSDOT’s shoreline permit application.  Extensive public support before and during next year’s shoreline permit comment period will help ensure implementation.  Trail access improvements identified to date include:

  • A stairway from Boyer Ave. to the Delmar lid. 

  • A Boyer Ave. overlook that may include shoreline access at the west end of the bridge. 

  • An Everett Ave. street-end improvement. 

  • A pedestrian connection to Boyer Ave. from the west end of Montlake Playfield property.  

  • A park shoreline trail connection from West Montlake Park to the Bill Dawson trail and the Montlake Playfield.

  • This trail development will link the Montlake Park/Playfield area to the Delmar Lid, the Ship Canal trail, the Arboretum, Interlaken Parkway and Boren Park.  It will also provide improved access to transit at 10th and Roanoke.  This would both improve shoreline access and provide additional shoreline habitat enhancement.


Habitat Improvement of South Portage Bay - Below is a current list of habitat related activities. Additional fish, waterfowl, wildlife and habitat enhancements can be proposed. 

  • The Woodland Park Zoo is facilitating a volunteer survey for amphibian eggs in Portage Bay (on hold due to COVID-19).

  • Beavers Northwest has reviewed beaver activity in the Bay and is working with neighbors to document beaver impact on Bay ecology. 

  • Bird use of the South Portage Bay shore is being documented. 


The King County Weed Board has a grant from the WA State Dept. of Ecology to treat non-native lily pads and shoreline invasive weeds in South Portage Bay.  Non-native, invasive lily pads have a devastating effect on fisheries, water quality, sedimentation and recreational boating.


Stormwater and Portage Bay Water Quality Construction impact uncertainty contributes to a public perception of the bay as an acceptable dumping ground for polluted stormwater.  This can create a hopeless attitude toward fisheries and aquatic habitat restoration.  The following issues can be included in public comments during the Shoreline permit comment period. 


  • SR 520 direct discharge of untreated runoff should be stopped. While stormwater treatment will be included in the bridge replacement, funding uncertainty and the long construction period suggest that low-cost temporary treatment should be retrofitted now. This approach has been implemented for the Aurora Bridge.

  • South Portage Bay has become shallower by 4 feet, with polluted sediment from untreated runoff from the bridge. WSDOT considers that the cost of cleaning up the bay sediment is at an unfeasible level. Since the bridge was exempt from providing treatment when built, WSDOT has the position that they have no legal requirement to do so.  The Army Corps of Engineers has granted WSDOT a permit to dump column replacement related debris.

  • Much of the runoff discharged to South Portage Bay runs in creeks flowing through Interlaken Park.  Additionally, a proposed combined sewer overflow 11-million-gallon underground storage tank will take 2.5 years to complete.  It will be located in the general playfield area east of the recreation center. The Montlake CC has asked (1) King County Public Works to barge the excess soil through Portage Bay and (2) the tank be completed during bridge construction. 


If any of these issues concern you, please indicate your interest by completing the survey linked below.

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