Closures part of big widening of freeway

Travel on southbound Interstate 405 through Renton next weekend will slow considerably as the state moves traffic to a new bridge over Oakesdale Avenue Southwest, part of a state project to widen the freeway.

That’s a pretty small inconvenience compared to the complete closure of southbound I-405 for three weekends through Bellevue, also starting next weekend.

State transportation officials have this message: Plan to avoid those stretches of freeway by taking alternate routes, especially through Bellevue.

The state is closing southbound 405 in Bellevue in order to remove the Wilburton Tunnel, a key part of widening the freeway north from Renton.

The goal of the $163 million, I-405 project in Renton is to relieve what commuters have known for years.

“That section on I-405 is the most congested section of freeway in the state,” said Stacey Trussler, the I-405 project deputy director for the Washington state Department of Transportation.

Unlike Bellevue, southbound I-405 through Renton from State Route 167 to Interstate 405 won’t close completely. The idea is to transition three lanes of southbound traffic – one lane at a time – to the new bridge, Friday (Aug. 8) starting at 10 p.m., Saturday (Aug. 9) starting at 10 a.m. and Sunday (Aug. 10) starting at noon.

The three lanes also include a new one; the state also will add a new lane for northbound traffic on the freeway.

The work also will require closures of the onramp to southbound I-405 from the Rainier Avenue/State Route 167 intersection at Grady Way.

It’s expected that Grady Way and Lind Avenue will get additional traffic next weekend as motorists avoid the freeway.

Next summer, the northbound traffic will go through a similar routine as vehicles are routed to the rest of the new bridge, which will be built without disrupting traffic.

According to Trussler, the state chose next weekend to switch traffic in Renton because it’s hoped the southbound freeway closure in Bellevue will help reduce traffic volumes.

Also, typically about half the traffic southbound on I-405 from Bellevue diverts to SR 167, while the rest stays on I-405 to I-5, according to Trussler.

So, it’s likely that some motorists traveling on I-405 next weekend will go through both construction zones.

The state didn’t model how long delays might last through Renton because the freeway won’t close completely, Trussler said. However, motorists should plan for extra travel time because there will be delays, she said.

In Bellevue, the complete southbound closure of I-405 will require more planning by travelers.

For travelers coming from as far north as Snohomish County, the state suggests avoiding

I-405 altogether and instead taking I-5 south. That would remove about a third of the vehicles that typically would have continued on as far as the Wilburton Tunnel.

The state expects more congestion on I-5, as I-405 is often used as a bypass for I-5; the express lanes will open for southbound traffic to help ease the load, according to Trussler.

Travelers also can divert from I-405 and take State Route 520 across the lake to I-5. That should remove about half the traffic from I-405, according to Trussler. The state is hoping the other 20 percent “will stay home,” she said.

However, the state is still expecting about 15 percent of the normal traffic load will make it to Southeast Eighth Street south of downtown Bellevue, the last point to exit the freeway before the Wilburton Tunnel.

Those familiar with city streets in Bellevue can use other alternate routes that parallel along I-405, eventually hooking up with Interstate 90.

The state estimates that a trip southbound on I-405 would take an additional two hours. The backup caused by motorists exiting I-405 at SR 520 alone could add about 45 minutes to the trip. The other chokepoint would be at Southeast Eighth Street, although the delay there should last only about 10 minutes.

The Saturday peak commute time is 10 a.m. to 7 p.m. Typically, about 94,000 vehicles travel southbound on I-405 on a Saturday and about 77,000 on a Sunday. The traffic volume on a weekday is about 101,000 vehicles.

The 360-foot-long Wilburton Tunnel isn’t visible to northbound traffic on I-405, so it’s not expected motorists will slow to look at the work which would cause a backup, Trussler said.

The Wilburton Tunnel, built in 1972, carried the Burlington Northern Santa Fe Railroad tracks over I-405. That line was severed near the tunnel as part of the multimillion project to widen I-405. The project contractor, Atkinson Construction, will use a wrecking ball to demolish the bridge. It also ordered bigger equipment to crunch the bridge into smaller pieces for easier removal, Trussler said.

The new freeway configuration will reduce congestion, increase capacity and provide for safer mergers approaching the I-90/I-405 interchange, according to state officials.

Following the demolition of the tunnel, a new southbound bridge over I-90 will be open to traffic by Thanksgiving 2008 and an auxiliary lane will open on northbound I-405 from 112th Avenue Southeast to I-90. The traveling public will see relief this fall, said Trussler.

I-405 lane closures through Bellevue

The southbound lanes of Interstate 405 will close at the following times in Bellevue:

• 11 p.m., Friday, Aug. 8 to 5 a.m., Monday, Aug. 11

• 11 p.m., Friday, Aug. 15 to 5 a.m., Monday, Aug. 18

• 11 p.m., Friday, Aug. 22 to 5 a.m., Monday, Aug. 25