520@50: When Machines Appeared in the Arboretum Wetlands

Dredging the shoreline near Foster Island in preparation for SR 520. Image: PEMCO Webster & Stevens Collection, MOHAI

The 520 bridge turns 50 next year which marks the end of its serviceable life. In recent days, impressive looking cranes and barges have appeared out on Lake Washington to start construction for the replacement highway. So what kind of machines were used to build 520 in the early 1960s?

This image shows a floating crane dredging the west side of Foster Island in the Arboretum, just where 520 stands today. The lakeshore in this area was a vast wetland exposed to the sky when Lake Washington was lowered in 1916. But building a modern highway through wetlands proved to be difficult. Construction trucks can’t drive through muck and barges can’t float in muddy shallows. So the area was dredged into the “lagoons” we see today.

In the foreground, trees and vegetation are removed to make the dredging work easier. The crane’s bucket “eats” the shoreline to the left and puts the spoils on the second barge to the right. There is a worker standing next to the bucket giving the crane a sense of scale. In the distance, the Montlake Bridge is on the far right and Capitol Hill rises to the far left.

6 thoughts on “520@50: When Machines Appeared in the Arboretum Wetlands

  1. thanks for the dredging history — pretty interesting…you always assume things are “natural” when you see them.

    • Agree, it looks so different now. Land was created by the 520 construction that I had assumed was always there.

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