Tuesday, March 24, 2015

Don’t let closures on SR 99 and I-90 detour your weekend plans

By Annie Johnson

Between games, festivals, concerts and recreation, there’s always a lot going on in the Puget Sound area. There’s also a lot of roadwork that has to get done. It’s a challenging balancing act to get as much work in while creating the least amount of traffic disruption. And so when we can, we look for gaps that accomplish those two goals.

Even with these gaps, there’s no “good” time to close parts of the highway.

Work on SR 99 and I-90 is expected to cause congestion starting Friday evening, March 27 until Monday morning, March 30. The Alaskan Way Viaduct will be closed Saturday and Sunday during the day for its semi-annual inspection. Crews will also be working on SR 99 north of the Battery Street Tunnel and on westbound I-90 in the Mount Baker and Mercer Island tunnels from Friday night to Monday morning. That’s a lot of vital work packed into a short amount of time. We need to get these closures out of the way before our busy summer event and construction season heats up.

It doesn’t take a traffic engineer to know that when we close one stretch of highway, traffic goes other places. It’s also clear that closing lanes in the same direction on north/south or east/west routes at the same time would be a bad thing. When it’s possible we look at combining work to avoid spreading out the closures over multiple weekends. It’s kind of like putting together pieces of a puzzle.

Looking at this weekend’s closures, we know that closing SR 99 leads to more traffic on I-5 so we wouldn’t want to add to that additional traffic by also detouring eastbound I-90 to the express lanes for the weekend. The eastbound I-90 detour can create backups on I-5 since we only have about a mile to funnel traffic down from four lanes to one as it enters the express lanes. However, if we do the same detour to the I-90 express lanes westbound we avoid impacting I-5. And with more than two miles to get folks in the express lanes we have less of an impact on I-405.

Don’t get me wrong, we still expect to see heavier than normal weekend traffic around the region, particularly on alternate routes like I-5, I-405 and SR 520. People headed to Emerald City Comicon at the Washington State Convention Center, the Professional Bull Riders event at KeyArena and Taste Washington! at the CenturyLink Field Event Center will want to leave as early as they can so they don’t miss out on the fun. After all, when we close lanes, all that traffic has to go somewhere. We greatly appreciate your patience during this time.

So what exactly are our crews doing during these closures?

Well, on SR 99 our bridge inspection crews will be conducting their semi-annual inspection of the Alaskan Way Viaduct. During the closure, crews get up close and personal with the viaduct to measure existing cracks and look for new ones, check for movement of the viaduct structure, and closely examine the viaduct’s foundations.

WSDOT bridge inspectors use Under Bridge Inspection Trucks (U-BITS)
to inspect the viaduct. This special equipment allows them to
see the bridge from all angles.
It’s pretty common for us to extend the closure boundaries during viaduct inspection weekends. This lets us and other agencies complete additional work with minimal added inconvenience to drivers. For instance, this weekend our contractor crews will complete important utility work just north of the Battery Street Tunnel while Seattle Department of Transportation contractor crews install large sign posts for future use. A bit further up the road, Seattle Public Utilities crews will do street restoration and drainage repairs.

Meanwhile, over on westbound I-90, contractor crews will be working inside of the Mount Baker and Mercer Island tunnels as part of a project to add all-day carpool lanes to I-90. In order to squeeze a fourth lane across I-90, from where the carpool lanes end now on Mercer Island to Seattle, we have to  upgrade our fire detection systems, fire sprinklers and hydrants, cameras and other items that help us keep drivers safe in the event of a fire or other incident inside the tunnels. Getting all that done will take a while but doing it during weekend closures maximizes the amount of time crews have to do their work while keeping drivers and workers safe. If we did the work with just nighttime closures it would significantly extend the amount of time needed for the project. As it is, this is the second of up to 30 directional weekend-long closures between now and mid-2017.

Crews work on the fire detection system inside the eastbound Mount Baker
Tunnel during an earlier weekend closure.
What can you do to help keep traffic moving during this weekend’s work? The most important thing is to know before you go. Check our Seattle traffic website, call 5-1-1 or check the WSDOT app for real-time travel information. Definitely plan ahead for congestion and add plenty of extra time to get where you need to go. If you can, consider using transit, delaying your trip, or traveling outside of times when we typically see higher traffic volumes (on weekends that’s usually between 10 a.m. and 8 p.m.). Also, expect congestion on alternate routes like I-405, I-5 and SR 520 as well as local streets.

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