Monday, May 16, 2016

Concrete panels arriving in South King County

By Tom Pearce

Driving between Tukwila and Federal Way you may notice that new concrete panels are appearing overnight, as if by magic, at several locations.
Once the concrete panel is removed, the subsurface is prepared.

It’s not the work of elves – it’s part of our southbound I-5 South 320th Street to Duwamish River Bridge pavement rehabilitation project that started about six weeks ago. Sunday through Thursday nights, our contractor crews have been replacing broken concrete panels. The crews are also repaving some asphalt sections and have started grinding areas that are still in good shape, except for ruts from 50 years of carrying cars and trucks.

Replacing panels
Starting at 8 p.m. most weeknights when traffic starts to diminish, crews begin to close lanes on southbound I-5 so they can replace a few of the more than 230 broken panels between the Duwamish River and Federal Way.

Crews place a liner before the new panel is poured.
Panel replacement requires a few basic steps:
  • Cut the panels up with a concrete saw.
  • Remove the pieces of the panel.
  • Prepare the hole for the new concrete.
  • Pour the quick setting concrete.
  • Reopen the interstate by 5 a.m.

Once the new panel is poured, it needs time to cure before traffic can drive on it.

Crews will replace three to six panels in a night, depending on where they’re located. Typically the panels are cut a night or two before they are removed to save time. Once the crews begin to take out the panel, they’ve got to get that hole filled in with new concrete in time for morning traffic, so you can see they have to work quickly and efficiently.
Once the new panel is poured, it needs time to cure
before traffic can drive on it.

Recently our contractor crews also started to grind lanes in the Des Moines area to remove ruts created by 50 years of traffic. Grinding out the ruts and small cracks will keep water from pooling, providing better traction.

Grinding is a noisy process because they’re grinding up concrete, and there’s no quiet way to do that. If you’ve ever worked with wood and used a power planer, that’s exactly what we’re doing to I-5. Of course, our contractor’s grinders are much bigger – they mill a thin layer of concrete about four feet wide, moving at about 10 feet a minute. Sometimes it needs to make two passes over an area to smooth it out.

Throughout this project our contractor will grind much of I-5 between the Duwamish River and Federal Way.
Crews are using a grinding machine like this on the
pavement in South King County.

Asphalt repaving
The I-5 overpass above South 336th Street is paved with asphalt, as are several ramps in this project area. In addition to rehabbing the concrete, we need to repave the asphalt sections. This means grinding out about two inches of asphalt and repaving those areas. We’ve already ground out the South 336th Street overpass and we’ll be putting down new asphalt next month. Grinding and repaving the ramps also will be done this summer.

Replacing concrete panels, grinding concrete and repaving asphalt sections are only some of the work we’re doing to rehabilitate southbound I-5 from the Duwamish River to Federal Way. This summer we will repave a 2.7-mile section of southbound I-5 using a process called crack-and-seat. What’s that? We’ll tell you about that process, and what it means for southbound I-5 traffic, later this month. Stay tuned!