Did you know that each of the 58 anchors that hold the

Did you know that each of the 58 anchors that hold the floating 520 Bridge “can weigh as much as 10 male African elephants”? Neither did I until I read today’s piece in Popular Mechanics. The engineering mag profiled Seattle’s floating bridge–the longest in the world–focusing on the redesign that will, when completed in 2014, make it longer, wider, taller and generally more awesome. A sample:Here are the basics of a floating bridge: Crews build watertight concrete pontoons connected end-to-end, and then place the roadway on top (there are also supplementary stability pontoons off to the side). The weight of the water displaced by the pontoons is equal to the weight of the structure and vehicles, allowing the bridge to float. Once the pontoons are in the water, crews will drop 58 anchors, made of reinforced concrete and attached to the pontoons via steel cables nearly 3 inches thick. A typical anchor can weigh as much as 10 male African elephants; they will sink into the loose material on the bottom of the lake to hold the pontoons in place. At each end of the bridge, the anchors will be drilled directly into the ground. Altogether, this system keeps the roadway from swaying.As one might expect, building the world’s largest floating bridge is a complicated affair. Concrete pontoons can crack, underwater support structures can erode, waves can crash over the side.But with a 200-foot-plus deep lake, building the bridge in any kind of conventional way just won’t work. All this, of course, is known to most locals here in Seattle.But PopMech, as it’s so famous for doing, manages to illuminate many of the most interesting details about the redesign. For example:–77 concrete pontoons will support the new bridge, each about 360 feet long, 75 feet wide and as heavy as 23 Boeing 747s.–It took $2.8 million worth of testing to come up with the salt-water-resistant fly ash and microsilicia concrete mixture that is used on the bridge.–The new bridge will be raised seven feet higher from the water’s surface than it is now, making able to stay open during wind storms up to 92 MPH. The whole thing is fascinating and I can’t wait to see the Discovery Channel’s inevitable Build It Bigger episode about the bridge.

Talk to us

Please share your story tips by emailing editor@seattleweekly.com.

More in News & Comment

King County approves emergency grant after U.S. Supreme Court overturns Roe v. Wade

Washington is expecting an influx of people seeking abortions from out of state.

Fedor Osipov, 15, flips into Steel Lake in Federal Way during last year's heatwave on June 28, 2021. Olivia Sullivan/Sound Publishing
Heatwave expected to hit King County

Temperatures will likely reach 90 degrees Fahrenheit on Sunday, June 26, and Monday, June 27.

Judged by XII: A King County Local Dive podcast. The hands shown here belong to Auburn Police Officer Jeffrey Nelson, who has been charged with homicide in the 2019 death of Jesse Sarey.
JUDGED BY XII: Examining Auburn police officer’s grim tattoos

Episode 5 in special podcast series that explores Jeffrey Nelson’s role in the death of Jesse Sarey.

Des Moines Police arrest murder suspect in Kent | Update

Medical examiner identifies body found June 20 in Duwamish River

Photo courtesy of King County.
Officials urge caution when swimming this summer

Cold spring temperatures and larger than normal snowpack have created dangerous conditions

File photo
Fireworks ban takes effect this year in unincorporated King County

The new law does not extend to cities, which each have their own regulations around fireworks.

A semiautomatic handgun with a safety cable lock that prevents loading ammunition. (Sound Publishing file photo)
Large-capacity ammo magazine sales ban starts soon in Washington

Starting July 1, a 10-round capacity becomes the limit for sales. Meanwhile, “there is a rush on magazine purchasing.”

At Dash Point on June 16, 2022. Henry Stewart-Wood/Sound Publishing
All that the tides reveal: Puget Sound’s hidden intertidal world

Exploring King County beaches during the lowest tide in the last 13 years.

Most Read