Wednesday, July 14, 2021

Buckle up: Construction starts this summer on the SR 520/I-5 Express Lanes Connection Project

By Amanda Christopher

Despite all the negative effects of the COVID-19 pandemic, our largest county, King, still added 34,000 new residents in 2020. By 2050, the central Puget Sound region is predicted to add 1.8 million more people and another 1.2 million jobs, according to the Puget Sound Regional Council's VISION 2050 report.

The region's population and employment boom has been especially pronounced in Seattle's South Lake Union neighborhood. At the same time, the Eastside's technology-driven cities continue to grow steadily. This ongoing growth underscores the importance of a safe, reliable transit/HOV link between Seattle and the Eastside via State Route 520.

To that end, we're beginning construction of a new project this summer in Seattle – the SR 520/I-5 Express Lanes Connection Project. This project will connect SR 520's new transit/HOV system to the I-5 express lanes, creating a direct bus and carpool connection between the Eastside, South Lake Union and downtown Seattle.

The work is part of our overall "Rest of the West" program – a series of safety and mobility enhancements along the SR 520 corridor in Seattle. Construction on the SR 520/I-5 Connection project is slated to begin soon and take about three years to complete. The Legislature's 2015 Connecting Washington transportation legislation provides the project's funding.

This project will deliver several key benefits to improve travel speed and reliability:
  1. A new ramp between SR 520 and the I-5 express lanes for buses and carpools.
  2. A new, reversible transit/HOV lane along the I-5 express lanes, running between I-5's interchanges with SR 520 and Mercer Street. (Traffic moves southbound in these lanes during the weekday morning commute, and northbound during the afternoon/evening commute.)
  3. A reconfigured Mercer Street on-/off-ramp to and from the I-5 express lanes for buses and carpools.
A look at the key features of the I-5/SR 520 connections project

Building for the future

Although the COVID-19 pandemic caused a significant decrease in traffic volumes and transit ridership throughout the state – including on SR 520 and I-5 – we're building for the future. The improvements from this project will serve the region for at least the next 75 years as our population and economy continue to grow. Already we're beginning to see traffic and transit volumes rebound as businesses reopen and workers begin returning to the office.

Overall, the $4.5 billion SR 520 Program is reconstructing the highway from I-405 in Bellevue to I-5 in Seattle. When our remaining SR 520 improvements in Seattle are complete, we expect about a 30-minute reduction in peak-period travel time for buses and carpools between the Eastside and South Lake Union. We also expect to see an increase in additional daily transit trips/riders. We're working closely with our transit agency partners at Sound Transit and King County Metro, as well as the city of Seattle, to confirm future bus service and routes on the highway and into South Lake Union.

A couple other important notes:
  • The new direct-access ramp and reversible express lane initially will open to buses only; carpools won't be able to use the new ramp until the completion of the Portage Bay Bridge and Roanoke Lid Project. This phased approach will help provide safer merges for buses while the Portage Bay Bridge replacement is under construction.
  • While the SR 520/I-5 connection will improve travel for buses and carpools, this project does not address the "Mercer Weave" for motorists crossing several general-purpose lanes of traffic when merging from SR 520 onto southbound I-5 and then exiting at Mercer Street.
    • Untangling the "Mercer Weave" would require a separate, legislatively directed I-5 project in the future that is not currently planned or funded.
An aerial view of the SR 520/I-5 interchange looking southwest toward Lake Union and downtown Seattle. The future SR 520/I-5 express lanes ramp's location is in orange

What to expect during construction
As with any major construction project, while we're excited for the end result, we know the work will present some challenges and trade-offs for the community. Nearby neighbors may experience increased noise, truck traffic and nighttime lighting. And travelers may see delays, detours and temporary road closures as crews work to safely and quickly build this new connection.

Because this project is taking place right in the middle of two major highways – I-5 and SR 520 – much of the work must occur at night. This is for a few key reasons:
  • Working at night with less traffic will provide a safer work environment both for the contractor and for the traveling public.
  • Night work will avoid disruptions to daytime traffic on SR 520 and I-5, two vital routes for weekday commuters.
  • Working at night allows us to shorten the overall project duration, which reduces the length of time we're affecting the surrounding communities and reduces construction costs to taxpayers.
We recognize that working at night can be especially disruptive for neighborhoods closest to the work zone. As part of this project, we were granted a project-long nighttime noise variance from the city of Seattle. The variance lays out specific measures our contractor must and will take to mitigate effects on nearby residents, including advanced notice of noisy work, limiting impact work (such as jackhammering and pile driving) at night, and other adjustments such as not using compression brakes or letting equipment idle. You can read more about the variance by visiting the Seattle Services Portal, project number 6733975-NV.

In addition to this noise variance, we developed a Community Construction Management Plan that details the actions our contractor crews will follow to limit the effects of construction on nearby neighbors and travelers. This is a living document that can be updated periodically based on community feedback.
The SR 520/I-5 project will add a new connection between two of the Puget Sound area's busiest highways.

In addition to noise and other effects such as dust and added lighting, we know that a major project like this will bring delays and highway closures for drivers in the area. This may include temporary off-ramp detours, closing the I-5 express lanes earlier in the evening, and opening the express lanes later in the morning. As with any major traffic effect, we'll be sure to communicate these closures in advance so drivers can make alternate plans.

Staying informed
There are a number of ways to stay informed during SR 520 construction:
  • Call our 24-hour construction hotline (206-316-2559) with pressing questions or concerns.
  • Email SR 520 staff with your questions about the project or construction activities.
  • Visit the SR 520 Construction Corner for the most up-to-date information on closures and construction effects.
  • Visit the SR 520/I-5 Express Lanes Connection Project website to find general project information.
  • Follow us on Twitter @wsdot_520 to get key news and updates about the SR 520 program.
  • Get weekly updates via email by visiting our email updates page, enter your email address, and under "Construction Reports" select "SR 520 Rest of the West News"