San Francisco high-rise sinking, tilting

[TheRifleman]

Anybody see this in Yahoo today?

http://www.foxnews.com/us/2016/08/01/swanky-san-francisco-high-rise-sinking-tilting.html

"The 58-story Millennium Tower, located at 301 Mission Street just south of the city's financial district, was completed in 2008 and has sunk 16 inches and shifted 2 inches to the northwest since opening"

I wonder what the average is for a building to sink in over 20 to 30 years?

 

[bigpicture7]

Depends on a number of factors, including trade-offs in foundation type, etc, but, as some of the articles on SF's MT have discussed, the developer expected the 58-story building to sink 6-inches over it's lifetime. That's substantially different from 16 inches in 8 years!

BTW, we are now discussing this on 3 separate threads (myself to blame as well for assuming it was of interest but not sure where to post). Appreciate any guidance from the Mod's as to where we should chat about this...

 

[statler]

Right here is perfect.

This is horrifying, by the way.

I guess I accept the assessment that the residents aren't in danger but the idea of putting piling on sand (which liquefies during an earthquake) seems insane to me.

 

[TheRifleman]

What about the Backbay in Boston:
PRU and Hancock must have sunk a certain amount over the last 50 years.
I'm curious if they have been taken measurements.

 

[statler]

Only thing I could find on a quick search:

Back Bay structures such as the Hancock Tower drive steel pilings right down into the bedrock 30 or more feet below the ground-water line, anchoring the building in stone.

 

[Arenacale]

I seem to remember this building on the Channel - https://goo.gl/maps/e9TX6arhDmm - being referred to as a "sinking" building as a kid. I don't know if it was actually sinking or it was my parents making fun of the covered walkway along the water, but does anyone know anything about that?

 

[bigpicture7]

A summary of the types of factors that come into play, for those who are interested.

(scroll down to the sections on foundation types, piles, etc.)

Time for some underpinning?

 

[TheRifleman]

http://sf.curbed.com/2016/8/1/12341914/millennium-tower-sinking

Could they have built this on a SINK HOLE?
http://www.sfgate.com/bayarea/article/SF-s-landmark-tower-for-rich-and-famous-is-8920197.php

I will say this (This is going to be an interesting situation concerning how this plays out for Investors/Lenders/Insurance Company/Developer/Tenants/City

 

[bigpicture7]

I will say this (This is going to be an interesting situation concerning how this plays out for Investors/Lenders/Insurance Company/Developer/Tenants/City

I am willing to bet that they are going to spend the $75million it would take to underpin this. I almost guarantee it. Because if they don't, they'll spend at least as much on drawn out legal expenses/etc.

 

[Brad Plaid]

I seem to remember this building on the Channel - https://goo.gl/maps/e9TX6arhDmm - being referred to as a "sinking" building as a kid. I don't know if it was actually sinking or it was my parents making fun of the covered walkway along the water, but does anyone know anything about that?

It was 303 Congress, only 12 years old demolished because of concrete pile failure.
http://www.sgh.com/projects/303-congress-street

 

[TheRifleman]

I am willing to bet that they are going to spend the $75million it would take to underpin this. I almost guarantee it. Because if they don't, they'll spend at least as much on drawn out legal expenses/etc.

This would be the smart thing to do.
Rally up the tenants and say we will do what we need to do to make sure this building is settled.
Just FIX the entire development and be accountable now.

Because in the end it will all go to the lawyers and your creditability might be shot.

 

[Scalziand]

I seem to remember this building on the Channel - https://goo.gl/maps/e9TX6arhDmm - being referred to as a "sinking" building as a kid. I don't know if it was actually sinking or it was my parents making fun of the covered walkway along the water, but does anyone know anything about that?

When I took a walking tour of bridges in the area, the guide mentioned that building, said that there was some kind of reaction between the concrete pilings and the seawater that rotted the piles.


BTW, I note that this SF tower is a Millennium tower. It's not the same Millennium in Boston, is it?

 

[datadyne007]

When I took a walking tour of bridges in the area, the guide mentioned that building, said that there was some kind of reaction between the concrete pilings and the seawater that rotted the piles.


BTW, I note that this SF tower is a Millennium tower. It's not the same Millennium in Boston, is it?

It is.

 

[CSTH]

I will have a hard time believing it's actually 16 inches until someone finds me a photo of where the front door meets the sidewalk.

 

[bolehboleh]

Sooooo....

Did they use "cost cutting measures" to build the Millennium in Boston?

 

[Arlington]

I will have a hard time believing it's actually 16 inches until someone finds me a photo of where the front door meets the sidewalk.

I suspect that the building's foundations extend out well under the sidewalk for things like parking and utility vaults, so at least an apron of, say the first 8' of the sidewalk is likely sitting on top of those foundations and sinking along with everything else.

Can you see a difference here in 2009 streetview:
https://goo.gl/maps/ePGXkrev3JS2

or 2011 streetview
https://goo.gl/maps/aKQYN3gmnUD2

I say that in the 2009 & 2011 views, the sidewalk appears crowned, or at least to be above the level of the street, whereas in 2016 the sidewalk and parking area appear flush or even depressed relative to the street.


Versus 2016 streetview:
https://goo.gl/maps/3wCiNu2DYTF2

 

[datadyne007]

I suspect that the building's foundations extend out well under the sidewalk for things like parking and utility vaults, so at least an apron of, say the first 8' of the sidewalk is likely sinking along with everything else.

Can you see a difference here in 2009 streetview:
https://goo.gl/maps/ePGXkrev3JS2

or 2011 streetview
https://goo.gl/maps/aKQYN3gmnUD2

I say that in the 2009 & 2011 views, the sidewalk appears crowned, or at least to be above the level of the street, whereas in 2016 the sidewalk and parking area appear flush or even depressed relative to the street.


Versus 2016 streetview:
https://goo.gl/maps/3wCiNu2DYTF2

Thanks for this observation! Appears that yes, it's taking the sidewalk down with it.

 

[CSTH]

Wow thanks.

And it really is right next to the Transbay terminal, maybe they're onto something by blaming it on the tunneling.

 

[bigpicture7]

Yes, thanks for finding this evidence.

There's no way the residents would make this up - it is not in their advantage to do so, as pointing out one's tower is sinking/leaning can only harm one's property value. In fact, at least in the timeframe in close proximity to this announcement, there is basically no resale market for SF MT condos until this is resolved. Residents simply want swift action to put this to bed.

 

[Arlington]

...And it really is right next to the Transbay terminal, maybe they're onto something by blaming it on the tunneling.

I think the Transbay authority (TJPA) makes a pretty good case, as quoted in the Curbed article, that it wasn't their fault:

When Millennium Partners started construction of the Tower in 2006, they knew that the TJPA intended to excavate adjacent to their building. Nonetheless, Millennium elected short piles that did not reach bedrock. The engineers who designed the foundation for the Millennium Tower predicted that the Tower would settle vertically a maximum of six inches over the life of the building. By the time the TJPA started work on its project in 2010, the Millennium Tower had already settled ten inches – four more inches than Millennium’s engineers predicted over the life of the building. The building has continued to settle vertically, now 16 inches, even after the TJPA completed the excavation for the Transit Center. A foundation of piles down to bedrock would have prevented.

(bolding mine)

While not a slam dunk, the TJPA also points out that the Millennium tower is skinking faster on the Northwest side--the side farthest from the Transbay site. Site map Image from the SF Chronicle article: