5 Things Lurking Underwater

We previously posted about things you didn’t know were under your feet. Now we’re posting about things you may not know are underwater. Hart Crowser staff have been involved with projects with the following submerged items:

  • Logs and wood waste. This isn’t that surprising, given Seattle’s logging industry history. See this KOMO news broadcast for video of dredging operations at the Northlake Shipyard.
  • Fifty (give or take) cars. Used to shore up an underwater slope (not currently the recommended practice).
  • Cement kiln dust. Left over from cement manufacturing, used as fill.
  • Asarco slag. From a former smelter. Also used as fill.
  • Abandoned or lost nets and crab pots. These are dangerous to people and marine animals. Read about the Derelict Fishing Gear Removal Project on the Washington Department of Fish and Wildlife website.
  • Just about anything else you can think of. Old boots, kitchen sinks, staplers, century-old bottles, outboard motors. You name it, you’ll probably find it in the water near the shore.

What have you found underwater?


505 First1

Bathtubs and Floating Buildings

You wouldn’t think that a building built on solid ground would be in danger of floating upwards. In fact, building where the water table is close to the surface can make this a concern. Dewatering the soil can keep floating buildings from being a problem, but some areas can’t be dewatered.

Here’s one example. Back when Seattle was just a pioneer town, the 505 First Avenue Building property was part of the waterfront. It had a wharf on pilings for timber mill-related businesses.  In the late 1880s and early 1890s, the area was filled in with, among other things, sawdust and wood debris from sawmills, wood planks and pilings, ship ballast, and burn debris from the Great Seattle Fire of 1889. This all meant that the soil where Starbucks now wanted to put up an office building was very soft and contained wood debris, abandoned timber piling foundations, and many other obstructions.

For this and other reasons, engineers couldn’t pump out the groundwater during or after construction. The four-level deep excavation had to be water-tight (think bathtub, but with the water on the outside). And this could lead to “an unbalanced hydrostatic uplift force in excess of the building weight acting on the foundation.” In other words, the seven-story building would float upwards.

How do you restrain such a building? In this case, engineers tied it down with 360 micropiles below the five-foot thick structural mat foundation.

Husky Stadium

Husky Stadium Metamorphosis

Husky Stadium under construction at the University of Washington

Why is time lapse construction photography so intriguing? Is it the magical aspect of a building seeming to grow by itself, like a plant? Is it the wonder of seeing the sheer scale of the work required to complete a project? Or is it that we live in a fast world, so we prefer fast results?

Whatever your reason, you’ll enjoy these OxBlue time lapse shots of the Husky Stadium construction underway in Seattle, Washington. Construction will be complete before the first home game this fall. Of the six viewpoints, Husky Stadium Camera #3 is the most satisfying, with fewer camera shifts and a seemingly smoother transformation.