Tuesday, October 12, 2021

Revive I-5 closures turn to the northbound interstate

Update: Oct. 14
Work on the northbound I-5 collector/distributor in Seattle has been postponed due to rain in the forecast. The work is rescheduled for 11 p.m. Monday, Oct. 18 to 5 a.m. Tuesday, Oct. 19, and 11 p.m. Tuesday, Oct. 19, to 5 a.m. Wednesday, Oct. 20. The same ramp closures listed below will be in effect.

By Tom Pearce

We've been working nights on Seattle's northbound Revive I-5 project between Seneca Street and SR 520 since early summer, but that project is about to become a whole lot more visible.

This weekend – weather permitting – we're going to close the northbound I-5 collector/distributor overnight to prepare for a lot of work to improve mobility on the northbound interstate. We will close the northbound C/D:

  • 11 p.m. Saturday, Oct. 16, to 5 a.m. Sunday, Oct 17
  • 11 p.m. Sunday, Oct. 17, to 5 a.m. Monday, Oct. 18

This means ramp closures as well, including:

  • Both directions of I-90 to northbound I-5
  • The northbound I-5 off-ramps to James and Madison streets
  • The Dearborn on-ramp to northbound I-5 (through the C/D) will close from 9 p.m. to 8 a.m. Saturday and Sunday nights

So far with this project, it's been all night work and we've had at least one lane open on I-5's mainline. The next part of work on mainline I-5 requires nighttime full closures with all traffic shifted through the C/D. Restriping the C/D gives us two northbound lanes for travelers when the I-5 mainline is closed. When the mainline is open during the day, we'll have the current configuration of one lane from the C/D to the mainline.

With an exit-only lane to Seneca, northbound I-5 in Seattle narrows to two lanes. Single-lane on-ramps from the collector/distributor and Cherry Street add lanes, but the Seneca bottleneck
is one of the worst in the state.

Improving mobility on northbound I-5
OK, so that's what we're doing this weekend, but in the big picture, why? Currently northbound I-5 has an exit-only lane to Seneca Street, which reduces the interstate to just two lanes in downtown Seattle. Between now and fall 2022, we're going to move some barrier along the northbound I-5 mainline north of Seneca Street. By changing the Seneca exit-only lane into a through lane and restriping, we'll have enough room to create three through lanes in the mainline. This should help reduce northbound congestion.

The current lane configuration has only two through lanes on the I-5 mainline and one lane from the collector/distributor to northbound I-5. When work is complete, here’s what the lanes will look like. These maps are not to scale.

In addition to three through lanes on the mainline, this project will create two metered on-ramp lanes from the northbound C/D to I-5. It also will add an auxiliary lane for the ramp from Cherry Street to northbound I-5. The auxiliary lane will only be open during peak traffic times.

Other northbound closures
Finally, this project will require a handful of overnight full closures of northbound I-5 between 12:01 and 4 a.m. We're going to replace a number of the posts and crossbars that hold signs over the freeway and we can't do that while there's traffic below. We'll announce these closures well in advance.

If you're going to Snohomish County while we're doing this work, you'll want to consider using I-90 to I-405 before heading north. You can also use SR 99, just remember there's a toll to use the tunnel. The other detours will be through Seattle on city streets.

This project is one of dozens we are doing to Revive I-5. All these projects will take about a decade to complete, but when we're finished, I-5 should be in good shape for many years to come. Thanks for your patience.