by Mike Allende

Concrete sealing part of the new expansion joint

The concrete needs about 12 hours to cure but workers will be monitoring it this afternoon. The concrete needs to reach a strength of 2,500 psi (pounds per square inch) for traffic to go over it. Whenever that happens, we’ll be switching the work zone to the other side of the highway to work on the other half of the joints. That is scheduled to happen around 9 p.m. Monday morning drivers will see traffic moving through the work zone in the Phase 2 configuration.

Phase 2 - Monday - Friday morning

By Mike Allende

By now, hopefully you’ve heard that westbound Interstate 90 will be reduced to one lane at Bellevue Way Southeast from 9:30 p.m. Friday, July 18 until 5 a.m. Friday, July 25. That’s 24-hours-a-day for a week, and yes, it’s going to be messy.

During that time, contractor crews are going to be replacing two huge, old expansion joints embedded deep in the roadway near Mercer Island. They’re 33-years-old and despite repairs over the years, they are at the end of their useful life.

We don’t make decisions to do these kind of closures lightly, and a lot of thought and discussion went into it. There’s never a good time to close lanes on major highways. In the end, doing a few weekend closures like we did for our I-5 expansion joint replacement just wouldn’t work this time.

Construction details
These expansion joints are massive, much bigger than those on I-5. Each of the 33-year-old joints are 92-feet long and weigh almost 29 tons. They’re embedded into 11-inch-thick concrete. Chipping out the concrete, replacing the joints, pouring new concrete and letting that concrete cure for a minimum of 12 hours would take longer than a typical weekend-long closure allows. Once in place, between 24 – 30 hours of welding is needed to connect both sides of the new joints.

Keeping traffic moving
No two-ways about this, we’re going to need your help. Knowing what to expect and staying informed is something everyone can do. For an idea of what this closure will look like, we put together this animation showing what is closed and how cars will move through the closure.

As the animation shows, besides the three lanes of I-90, we’ll also have some ramp closures. Take a look and get an idea of how to move through the closure if you end up having to go that way.

Stage 1

Stage 2

If you don’t plan ahead, your typical commute could last an hour or more. The best advice is to avoid using westbound I-90 during the closure. With a big Sounders match and the Mariners in town, along with work and other trips, we know that’s not easy. Taking an alternate route will help, but still add extra time to your trip because other routes will be affected with folks doing the same thing. If you can telework, or even take a vacation, this would be the week to do it.

When we had two lanes closed on westbound I-90 floating bridge in July 2009, we saw up to 7-mile backups, but we had the express lanes to help. On this closure we do not. Congestion could be much worse this time around.

To keep delays from really getting horrible, we need at least 60 percent of drivers to adjust their plans. We recognize that’s a lot to ask, but every person who can change their plans helps.

The graph below shows that normal peak travel times on westbound I-90 in the closure area are up to 15 minutes in the morning, up to 30 in the afternoon. If we get a 60 percent diversion during the closure, we still expect morning travel times to be 45 minutes to 1 hour, and a little longer in the afternoon. So if there's any way for to you avoid the area that week, do it.


We wouldn’t do this closure if we didn’t have to but it’s vital to maintaining our infrastructure and avoiding emergency closures that would lead to having to replace the expansion joints anyway.

Tolls on SR 520
Folks have asked us about tolls on SR 520 during construction on I-90. SR 520 is just one route from the Eastside to Seattle. The Transportation Commission sets toll rates and exemptions and there are none for this project or other construction closures. Drivers can set up a short-term account and can save $.50 on the pay-by-mail toll rate.

Aging infrastructure
This is a safety and mobility issue. We’ve had several temporary fixes over the years, and these expansion joints simply need to be replaced before they break.  If we do nothing, this could happen during a busy commute and tie up traffic for a long time. Vehicles could be damaged and lanes of traffic closed for an indefinite amount of time. As you can imagine, you can’t just go to the store to buy a replacement expansion joint. These are custom made for the bridge, and it takes between six to nine months to fabricate.

New expansion joints to be installed

It’s not going to be easy, but hopefully with some planning and adjustments, many of you may be able to avoid the congestion that inevitably happens with a major closure like this. With many of our roads being 30 to 60 years old, this is a step we need to take to ensure they can meet the demands of day to day traffic.

Learn more about the I-90 closure on the project website.