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Viaduct inspection reveals new and widening cracks

Washington State Department of Transportation will close the viaduct on March 22, to take a closer look at damage near Seneca and Spring streets.
Cracks in the viaduct, but don't panic yet.

Cracks in the viaduct, but don't panic yet. Credit: joeszilagyi/Flickr

During a recent inspection of the Alaskan Way Viaduct, Washington State Department of Transportation engineers found that new cracks had formed and existing cracks had widened on the 61-year-old overpass.

The cracks, near Seneca Street and Spring Street, were discovered on March 1. WSDOT will close the double-decked bridge for one day on Saturday, March 22 to conduct further inspections and tests and to install equipment to monitor the size of the cracks.

“They're really small hairline cracks,” said WSDOT spokesperson Travis Phelps. “When I say widen I don't mean big gaping holes you can put your hand in. The viaduct is safe or we wouldn't have reopened it after inspection.”

Since the 2001 Nisqually earthquake, WSDOT has observed similar cracks on other segments of the viaduct. During the next inspection, Phelps said, engineers will try to determine whether a spot repair will keep the bridge sound, or if more “robust improvements” are required. The department could inject an epoxy into the cracks to prevent them from spreading or widening.

One of the tests that engineers will conduct during the closure will involve driving a truck loaded with gravel over the cracked areas to see how the structure reacts. WSDOT has said that it is unlikely the cracks are related to construction work on the Highway 99 Tunnel. The machine digging the tunnel is currently stopped, awaiting repairs, a little less than a half mile from Spring Street.

The structure has hundreds of cracks that are millimeters in width, Matt Preedy, deputy program administrator for the Alaskan Way Viaduct Replacement Project, said during a recent press conference. The cracks are mapped, and monitored with gauges and photographs. To strengthen other damaged sections of the viaduct, WSDOT has wrapped portions of the structure with carbon fiber.

If too much cracking takes place on the viaduct’s concrete, weight could be transferred to the structure’s steel, causing it to lose strength. The most sensitive section of the viaduct, said Preedy, is between S. Main Street and Columbia Street. “It’s safe for everyday use,” he said. “If we have a big earthquake, that’s the one thing that can take the bridge out of service.”

The Highway 99 Tunnel is designed to replace the viaduct. The new stretch of underground roadway was scheduled to open around December 2015. But an expert panel recently estimated that repairs to the boring machine digging the tunnel would delay the project's completion until summer or fall of 2016.

Bill Lucia writes about Seattle City Hall and politics for Crosscut. He can be reached at bill.lucia@crosscut.com and you can follow him on Twitter @bill_lucia.


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Comments:

Posted Mon, Mar 10, 3:56 p.m. Inappropriate

While spinmeister Phelps is the best in the business, it cannot go unnoticed that part of the pre-work here is removing the IVY.

I previously noticed, why have they not removed the ivy previously?

It is highly invasive to whatever it is growing on for support, and will even infiltrate Kryptonite!

Lordy, if the ivy is where the big 1/16th inch crack is, don't need a high priced engineer or expert panel to identify at least part of the problem.

The Geezer has thus opined.

Geezer

Posted Mon, Mar 10, 8:17 p.m. Inappropriate

Well also, Geezer, they have just removed part of the bone structure supporting that thing...the mammoth is still under there, but is falling apart at the seams! Tinkering with the sides of the Puget Sound is a scarey proposition!

sgh

Posted Tue, Mar 11, 8:32 a.m. Inappropriate

WSDOT PLANNED OBSOLESCENSE! Since the 70's. THE BIG LIE!
206.669.5048

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