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February 19, 2019

It's official: First pieces of viaduct crumble away

Photo by Benjamin Minnick [enlarge]
The first part of the viaduct to come down was the north concrete guardrail of the Columbia Street on-ramp.

Crews from Kiewit Infrastructure West and subcontractor Ferma on Friday began removing the first pieces of the Alaskan Way Viaduct: the north concrete guardrail of the Columbia Street on-ramp.

Ferma used an excavator equipped with an impact hammer to do the work. Another piece of equipment adjacent to the ramp raised a fabric curtain near the hammer to protect nearby businesses, including Mae Phim Thai restaurant at 94 Columbia St.

Crews have a big task ahead of them over the next six months. Here's what the Washington State Department of Transportation said the job will entail:

• 1.4 miles of roadway will be removed

• 400 columns will be removed

• 61,000 cubic yards of concrete will be removed weighing about 122,000 tons

Crews are working at three locations to start: Columbia Street; near the Battery Street Tunnel; and just north of the Seattle Aquarium.

A Volvo excavator equipped with a processing claw was moved in Thursday adjacent to the Columbia ramp. Up north, near the aquarium, a much larger excavator with much bigger claw was also moved into place last week.

WSDOT says the viaduct is a series of bridges, which allows crews to remove one section without affecting other sections.

Here's how WSDOT describes the work sequence:

1. Fence a work area and complete staging.

2. Use impact hammers to remove the roadway deck.

3. Remove the girders and columns that support the deck using large hydraulic munchers.

4. Remove lower decks following the same process.

5. Remove foundations, in some places to 5 feet below grade, and restore the site.

In places where buildings are close by, crews will sawcut pieces of the viaduct and lift them away with cranes.

The entire viaduct — from South Dearborn Street to the south end of the Battery Street Tunnel — is expected to be down in six months. The section along the central waterfront should be finished by June.

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