OMG!!!!!!
Referring to both links above.
I had no idea that the real numbers were anywhere near this big.
Any idea of the cause?
Quite a mess!
http://www.nytimes.com/2014/12/10/us/in-seattle-a-sinking-feeling-about-a-troubled-tunnel.html?_r=0
Our area appears to have a non-uniform subsidence rate that varies between 1-3 mm/year or 4-12" a century.
Thank you for this as I will be passing it along to some of the folks designing the sewers in the area. Big pipes are often laid flat and if one end drops at 12" and the other at 4" we may find some sewers flowing the wrong way.
> Any idea of the cause?
Note that the shaft is across the street from the Puget Sound. And that whole area of waterfront Seattle is built on reclaimed land. It was originally a tidal flat.
Monitoring the Surface
Just out of curiosity do you know how they are monitoring the surface? What surveying methods are they using to determine the amount of settlement?
Monitoring the Surface
Not specifically, but I proposed on a similar project in Portland a few years ago. It was to involve regular differential levelling of surface benchmarks established cross section style along the alignment route. Frequency of the monitoring was increased in the immediate area of the active boring work.
