Thursday, April 15, 2021

The return of Revive I-5 means lots of work in Seattle this summer

By Tom Pearce

Revive I-5 in Seattle is back this year. After a summer off in 2020, we have two big rehabilitation projects – one northbound and one southbound – to help preserve our region's main travel artery. Each project will take about a year and a half to complete.

The northbound project will improve traffic flow between Seneca Street and the Washington State Convention Center. The southbound project will replace a lot of expansion joints and resurface a section between I-90 and Spokane Street. Here's how we're going to do it.

Northbound I-5
In early May our contractor, MidMountain Construction, will start work to alleviate a pinch point on northbound I-5. Currently, the exit-only lane for Seneca Street reduces the freeway from three lanes to two. 

When complete, we'll eliminate the exit-only requirement at Seneca and have three through lanes
The current lane configuration on I-5 near Seneca Street (above)
compared to the lanes when work is complete (below).
These animations are not to scale.

To make this work, we'll widen I-5 slightly for about 1,500 feet and shift the lanes to the right a little. This will reduce merges and help traffic move through the area more smoothly.

Another thing we're doing to help improve traffic in this same area is adding a second lane to the I-90 collector/distributor on-ramp to northbound I-5 and install ramp meters for both lanes. This will increase capacity in the C/D and help smooth the flow of vehicles onto I-5. We'll also add a ramp meter to the Cherry Street on-ramp.

The third portion of this project will install an Active Traffic and Demand Management system, which allows us to adjust for speed limits based on the amount of traffic and warn of lane closures. This is the same system we have on northbound I-5 between Boeing Field and I-90. 

Installing ATDM will have the biggest effect on traffic during construction. While all the work is being done at night, when we're installing the ATDM over the freeway, we need to have about 10 to 12 full closures of the northbound lanes of I-5 between midnight and 4 a.m. This means detours via city streets, or for through traffic and trucks via I-405 or SR 99.

All of these improvements will help keep traffic moving through downtown Seattle, but there is only so much space for vehicles on I-5. There will still be times when drivers experience congestion. 

Southbound I-5
In late May, our contractor crews from CA Carey will begin work to resurface about 1.2 miles of the southbound freeway between I-90 and Spokane Street as well as replace 23 expansion joints. If you remember similar Revive I-5 projects from the past, you know what this means – weekend lane reductions. 
Reducing northbound I-5 to two lanes lets us repave large sections of the freeway south of Seattle, similar to the work we did on northbound I-5 in 2019.

This project is a doozy – it will require 16 weekends of lane reductions on southbound I-5. This is a big reason we're spreading it out over two years. Between the weather and major events in the city such as Seafair, pro sports and concerts, it would be extremely difficult to do all of this in a single year. We're still working with our contractor to schedule this year's weekend work; as soon as we know, we'll share it through social and traditional media.

In the meantime, start thinking about alternatives – taking I-405 or SR 99, adjusting your travel schedule to avoid the area between 8 a.m. and 8 p.m., or using buses or light rail to get around.

The big picture
I-5 in the Seattle area was built in the 1960s. The original designers expected it to last about 25 years before needing major rehabilitation, but it held up for more than 50 years and now these projects are necessary. 

This year's work represents just two of dozens of Revive I-5 projects we have planned for King County in the coming decade. Some projects are in the draft design phase while others are not funded at this time. These projects include pavement repair, improvements to reduce damage to I-5 in the event of a major earthquake, expansion joint replacement like we are doing this summer and bridge work.

It's a big task and we're going to need your help to be successful. As these projects come up, please plan ahead when you need to travel. We're out there in the traffic too, so we know it can be a challenge. We appreciate your patience!