




I camped overnight at the Island County Fairgrounds in Langley.



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I camped overnight at the Island County Fairgrounds in Langley.
Approaching the Fremont Bridge.
...and under the bridge we go!
Mark in the drivers seat with the Fremont and Aurora Bridges in the background.
Along the ship canal.
I always find one of the best parts of staying at a hostel to be the people I meet. Since every everyone is using the same kitchen, dining space, and living room/lounge there are lots of chances to get to know each other.
The underground station, which is nearly eighty feet deep, is built using a braced slurry wall process to dig the hole. To build a slurry wall a series of 4'x12' shafts are dug into the ground around the full perimeter of the station-- about 70ft by 400ft. As each hole is being excavated, with a mechanical excavator, it is filled with a slurry of bentonite clay and water to keep the hole from collapsing. After reaching it's full depth, nearly 100 ft in this case, the hole is filled with concrete from the bottom up through a tremie pipe. As the hole fills with concrete the slurry mixture is pumped out and saved for reuse. When the hole is full of concrete a cage of steel reinforcing is dropped in.
When the slurry walls are in place around the full perimeter of the station the dirt in the center can start to be excavated. As the dirt is excavated a series of braces, each about 65ft long and weighing nearly 30 tons, are installed to support the slurry walls. My part has been to design the temporary bracing system that will support the two walls during excavation and prior to placement of the permanent concrete floors.
You can see a section through the station here:
UW station section view
Find out more about slurry walls at:
Wikipedia article on slurry walls