Monday, September 20, 2021

Crews work to get in a few more weekends of work on southbound I-5 as fall looms

Update: Sept. 24
Because of rain in the forecast for Sunday, this work is postponed. We will try again next weekend.

By Tom Pearce

As this past weekend shows, the end of our major construction season is nearing as the fall weather begins to assert itself. A lot of the work we do uses materials that don't do well in wet or cold conditions. Hopefully we'll still get a few good weekends, starting with this coming one.

We plan to close several lanes and ramps on southbound I-5 between downtown Seattle and Spokane Street to replace the right side of four expansion joints as part of our Revive I-5 work. Here are the details:

8 p.m. Friday, Sept. 24 to 5 a.m. Monday, Sept. 27

  • Two left lanes of mainline I-5 will remain open.
  • People will be able to use the collector/distributor to reach off-ramps at Dearborn, I-90, Fourth Avenue South/Edgar Martinez Drive and Airport Way. All C/D traffic will have to exit before or at Airport Way.
  • The following on-ramps to southbound I-5 will be closed:
    • Spring Street
    • The collector/distributor
    • Both directions of I-90
  • Off-ramps to Forest Street and Columbia Way/Spokane Street will be closed.
Drivers will be able to go into the collector/distributor Sept. 25-26 but they’ll nee to use an exit to SODO or I-90. The off-ramps to Forest Street, Columbia Way and Spokane Street will also be closed.

We also plan lane reductions Friday night, Oct. 1, to early Monday morning, Oct. 4. With that closure, we'll again funnel all traffic through the collector/distributor so we can replace the left side of several expansion joints. While the I-90 ramps to southbound I-5 will be closed most of the weekend, we will open them for a couple hours after the Sounders and Mariners games to give many people their usual route out of the stadium district.

Why weather matters
This past weekend our contractor, C.A. Carey, postponed our Revive I-5 work southbound between I-90 and Spokane Street because of rain in the forecast. For this project we are using polyester concrete, which uses a polyester resin binder with sand and aggregate rock to create a more durable driving surface.

We've already paved 1¼ miles of southbound I-5, but when we install each of the 40 new expansion joints on this section of I-5 we will use the polyester concrete to hold the new joints in place.

When we worked during the June heatwave, we had to wait for the existing road surface
to cool before paving with the new polyester concrete.

While polyester concrete is more durable, it's also more weather-sensitive than regular concrete, which can handle cooler temperatures and even a little rain. With polyester concrete, if there is any moisture – even from dew – the concrete may not cure properly. Also, temperatures need to be between 50 and 100 degrees. That was a factor when we paved during the June heat wave. Our contractor had to wait until late into the evening for the surface to cool before they could pave.

About those bumps on southbound I-5...
Anyone who has driven southbound I-5 between I-90 and Spokane Street in the past couple months knows there are bumps at each expansion joint where we repaved the freeway. The old joints are typically an inch or so below the new road surface. As we replace the joints, our contractor is making the new ones more level with the new roadway.

Looking across I-5 from ground level, a 4:1 grading at each expansion joint will lessen the bump.

We did the paving first because it's easier to match the new joint height to the new pavement than vice versa. Piecemealing this process – doing a little paving here and replacing a few joints there – would have greatly increased costs and the time needed to complete this work.

The contractor is now working to lessen these bumps. They are grinding a 4:1 bevel on both sides of each joint. That means for each inch of drop, they shave the surrounding concrete at an angle back four inches, creating a little ramp. There still may be a bump, but it won't be as sudden.

It's going to take until fall 2022 to complete all of this work, but in the end you'll have a smoother ride through this section of I-5. This is just one of many projects we're doing in the next decade to Revive I-5.