Friday, July 22, 2016

Heading out: History in motion as old SR 520 floating bridge pontoons set sail

By Haylee Morse-Miller

We're waving a fond farewell to the old SR 520 floating bridge after 53 years of stalwart service.

Vulnerable to wind and waves, the old bridge is now a relic, replaced by a bigger, stronger and safer floating highway. Our next step: take apart and remove the old span from Lake Washington, a process that will continue through the end of the year.

Pontoon E from the old SR 520 bridge floats through the Lake Washington Ship Canal on its way to the locks.

One of the most exciting parts of this process happened Wednesday, July 20, when we towed the first of 31 old floating bridge pontoons from Lake Washington and through the Hiram M. Chittenden Locks in Ballard on its way to new endeavors. Powerful tugboats guided the massive floating piece of concrete along Seattle's waterways.

Like most of the old bridge's 30 other pontoons, Pontoon E is 360 feet long and weighs about 4,725 tons– the equivalent of around 500 adult Orca whales. Towing these enormous boxes of concrete from Lake Washington is a major step in the old floating bridge decommissioning process.

Pontoon E as it passes through the Hiram M. Chittenden Locks in Ballard July 20. The old floating bridge
pontoons are following the same route as the new floating bridge pontoons, but in reverse.

That process is moving along. We removed both the east and west high-rise trusses from Lake Washington in June. In preparation for removing their columns, girders and other concrete superstructures before they are floated out, we also separated four pontoons from the west end (A through D) of the old structure.

What's going to happen to the old bridge?
All 31 massive pontoons make up approximately 75 percent of the old bridge's mass. We will dismantle the old floating bridge's remaining components onsite, then haul them away to concrete-recycling facilities. We'll process most of these materials for reuse on other paving projects throughout the region. So while the old SR 520 bridge will soon be gone, the traveling public will benefit from its recycled components for years to come.

Once traffic shifted onto the new floating bridge, WSDOT' contractor on the project—Kiewit/General/Manson, A Joint Venture (KGM)—took ownership of the old bridge. They now have responsibility for decommissioning the old bridge, including removing the old pontoons from the lake.

We've sold all 31 pontoons to TrueNorth Operations Group, which in the past has resold old pontoons for use as wharfs, docks, storage facilities and artificial reefs. Although we don't know the final destination of the pontoons, we know they will be put to good use wherever they end up in the world.

Want to see the next float out?
If you missed this float out, check out our Facebook Live video report as Pontoon E enters the locks. You can also follow the movement of the 30 other pontoons, which will be floated out of Lake Washington in coming weeks, by following SR 520 on Twitter. If you are interested in watching in person, check out our graphic of suggested viewing locations and join us in commemorating the end of an era.

Wednesday, July 20, 2016

It takes time to do the job right

By Tom Pearce

Remember in the movie "Cars" when Lightning McQueen was sentenced to repaving a section of highway before he could leave Radiator Springs? He races through the work and yeah, technically the road's paved, but it's a horrible mess. He ends up having to repave it, and learns his lesson.

That's something we want to avoid, but that's also why we have weekend-long lane reductions for our #SouthKingSlowdown project. In order to do this project right, we need full weekends and not just overnight closures.

We'll have lane reductions for a total of five weekends on southbound I-5 this summer: three this month to repave 2.7 miles in SeaTac and Des Moines and two in August to replace four expansion joints on the southbound I-5 Duwamish River Bridge.

We've talked a lot about what it takes to replace expansion joints, so you probably understand that. The bigger joints simply can't be done overnight. It takes a weekend.

But paving? Does it really take a whole weekend? In this case, yes. If you're just putting asphalt over asphalt, that can be done with overnight lane reductions. Just do some grinding, then pave.

When you're putting asphalt on top of concrete, it's a whole different story.

The section of I-5 in SeaTac and Des Moines is made of 12-foot by 15-foot concrete panels. These panels are more than 50 years old, and more than 500 are broken and need to be replaced. It'd take a couple of years to replace those during overnight lane reductions. Eventually, they'll all break and need to be replaced.

We studied the best way to repair this section and determined it would be more cost-efficient to repave it with asphalt. To do this, during weekend lane reductions our contractor crews are taking out a football-field length of concrete panels at each end of the work zone and replacing them with asphalt. This creates a smooth transition from concrete to asphalt and back again.

Once the concrete panels are removed, a roller compacts the soil on
the transition before that section is paved with asphalt.

As for the rest, you can't just put asphalt on old concrete. Old concrete panels move. It's slight, but if you put asphalt on top of those panels, they'll continue to move and crack the asphalt. So before we put down the asphalt, we're using a process called "crack and seat." Our contractor is using a machine to crack the concrete. After a 35,000-pound roller compresses, or "seats" it, we can put asphalt on top of it.

The video below is of a machine that drops a six-ton blade onto the concrete panels, cracking them. A 35,000-pound roller then compresses the roadway to create a stable base for asphalt paving.

Asphalt paving is time-consuming. We need eight inches of asphalt here, enough to support the more than 100,000 vehicles that use it each day, and it has to be paved in layers. Each layer needed to be compressed by a heavy roller for strength, then it has to cool for 30 to 60 minutes. Then we repeat the process a couple of times.

For now, we have just the first layer on the right side of the interstate. That's OK for a couple of weeks, but for the best final product, the rest of the layers need to be paved soon. Spreading out that paving over a couple months of nighttime lane reductions could diminish its durability. With the weekend lane reductions, in a couple of weeks we'll have repaved this 2.7-mile section of I-5 the right way.

We know that closing lanes on a summer weekend is tough but this is vital work that needs to happen when we have predictably dry weather, and so we appreciate your patience, understanding and cooperation. And as Lightning McQueen learned, taking the time to do the job right the first time is the only way to go.

Tuesday, July 19, 2016

#405ETL: A lot can happen in nine months

By Jennifer Rash

We all know a lot can happen in nine months, including over 11 million vehicles traveling in the I-405 express toll lanes. What's more, tolls collected from those trips will help fund new I-405 capacity sooner than we thought.

Here are some other nine-month trends:
  1. More vehicles are moving through the express toll lanes than ever before. Our numbers from the spring show the express toll lanes are now carrying more vehicles on weekdays from 5 a.m. – 7 p.m. than they did in the winter operating 24/7. We're also seeing that when people choose to drive in the express toll lanes, it frees up space in the regular lanes.
  2. Travel time savings are up, even in the regular lanes. All lanes of I-405 are moving more vehicles at faster speeds than last year, though the express toll lanes are providing 40 percent faster trips than the general purpose lanes. The exception? Northbound general purpose lanes between SR 522 and I-5, where travel times are three minutes slower than they were last year. We have plans to fix this bottleneck using hard shoulder running (more on that later).
  3. As demand increases, so does the average toll rate. The nine month average is $1.61—up from $1.26 during the initial three months of operations. More drivers are using the lanes, which mean higher rates, especially north of SR 522 where express toll lane capacity is limited to a single lane. However, the most common toll rate during peak hours this spring was still just 75 cents.

  4. We're hitting the $10 max toll more often. Toll rates adjust to keep the express toll lane flowing at 45 miles per hour 90 percent of the time, taking into account volumes in the express toll lanes and the regular lanes. We're seeing frequent $10 maximum tolls at access points between Bothell and Lynnwood, where demand is high and capacity reduces from five lanes to three lanes, creating a bottleneck.

    While we're meeting our 45 mph 90 percent of the time goal, we see speeds drop below 45 mph when drivers enter the express toll lane when it's already at capacity. However, even when the express toll lanes are operating at slower speeds, they are still typically faster than the regular lanes.

  5. Express toll lane revenue is much higher than forecasted. With more drivers choosing the express toll lanes than we predicted, our revenue numbers are nearly three times the original forecast from 2012. There are some key reasons why our original forecast was so off, namely WSDOT is one of the first agencies in the nation to implement lanes that offer both electronic and pay-by-mail options for travelers, offering drivers an option to use the express toll lanes without a pass. In addition, the economy rebounded quicker than expected – creating new jobs and increasing traffic.

    The increased revenue is good news for drivers because besides covering our operations and maintenance costs, we're working with the legislature to fund our first reinvestment of your toll dollars in the corridor. The first project that could receive express toll lane funding next year is the Northbound Hard Shoulder Running from SR 527 to I-5 Project. Through this project, we will add additional capacity during the northbound evening peak commute period by opening the northbound shoulder to general purpose traffic.

We'll have more details on this project in an upcoming post.

Monday, July 18, 2016

How a new interchange reduces backups and improves travel times in east Vancouver

By Tamara Greenwell

Does this sound familiar? You're driving down Interstate 205 in Vancouver and traffic near the Mill Plain off-ramp is backed up onto the freeway. Or how about this? You're merging onto I-205 to head north from Mill Plain Boulevard… and because of the backup you don't know if you should speed up or slam on your brakes to enter the freeway.


These are things we know are a problem, but these will soon be a distant memory. Why? Because after 329 days of construction, a new interchange connecting I-205 to Northeast 18th Street will open this week and help make things better.

Really, how?
The I-205 and Mill Plain Boulevard interchange is the busiest in Clark County, with more than 100,000 vehicles using this stretch of interstate daily. If you drive through this area, you'll notice there isn't an on- or off-ramp for three miles between Mill Plain Boulevard and State Route 500. When the new Northeast 18th Street ramps open this Wednesday, that distance will be cut in half.

What's it look like?
New I-205 northbound off-ramp to Northeast 18th Street
You'll have a new access point into east Vancouver, which means less vehicles using Mill Plain Boulevard and SR 500.

New I-205 southbound on-ramp from Northeast 18th Street via a roundabout
For the first time ever, you'll be able to get onto southbound I-205 from Northeast 18th Street. We built a roundabout at the intersection, so you won't have to wait through a light to get onto the highway. The roundabout also keeps local traffic moving through the area.

New southbound I-205 off-ramp to Southeast Mill Plain Boulevard
The longer separated off-ramp takes traffic off the interstate sooner and reduces backups onto the mainline. Slowdowns and collisions often occur near merge areas. By separating the on- and off-ramps there's more distance for drivers to merge or exit, without crossing paths with traffic doing the opposite, which means fewer crashes.

New northbound I-205 on-ramp from Southeast Mill Plain Boulevard
The extended on-ramp gives you more distance to merge onto the interstate, which means more time to accelerate to the speed of traffic.   The end result is an interchange that'll give you a smoother ride with improved travel times and safety. While the on- and off-ramps open this week, additional work to finalize the project, including landscaping, is expected to continue through the end of this year.

Pretend you have X-ray vision – then, we’ll help you picture a buried bridge

By Kris Olsen

One of Superman's powers is X-ray vision. While there's only one Superman, we want you to imagine you have that same power and peer into the earth with us so you can see an unusual culvert replacement project in Woodinville.

Little Bear Creek, and the culvert that will be replaced in part by building a buried bridge.

Typical culvert replacement approach
Usually, replacing a culvert involves closing a road, digging up the existing culvert and installing a new one. But Little Bear Creek is 30 feet below SR 202/131st Avenue Northeast. The typical approach doesn't work here. That's because we'd need to close the road for about a month and dig up a huge amount of dirt to safely reach, remove and replace the culvert. A month-long closure of the main entrance to Woodinville is neither practical nor something we wanted to put Woodinville drivers, businesses and residents through.

Crews will break through this large concrete wall in order to build a buried bridge as part of a culvert replacement project.

An unusual solution
So our engineers devised another plan: build a bridge underground and then excavate underneath it to reveal the belly of the bridge and a bigger space for Little Bear Creek to pass under the road.

But no matter what words we use to describe how we're going to build a bridge underground, it's still hard to visualize. So, we're going to show you. You just have to picture yourself in waterproof boots, standing in Little Bear Creek, and that you have X-ray vision that allows you to see through a concrete wall and into the earth. Scroll through the building a buried bridge graphic (pdf 3.44 mb) we've created to see how we'll build the bridge.

What the buried bridge at Little Bear Creek will look like.

Work starts Monday
Contractors will start drilling through the top of SR 202/131st to start building the bridge the night of Monday, July 18. We'd recruit Superman, but as far as we know, he doesn't have the power to drill holes into the earth, so we'll have to rely on good ol' fashioned heavy equipment for it.