Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Millennium Tower is tilting, sinking

sf.curbed.com

Post reply on HN
Print view View original

101–110 of 187 posts

Re: Millennium Tower is tilting, sinking

#101

Post by whyenot »

wahern wrote: post #29
WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

I live in the Outer Richmond district of San Francisco, which was built on sand dunes. Most houses in my neighborhood were built in the 1920s and 1930s, +/- a decade. I was told by a contractor that it's extremely common for houses to have shifted considerably, sometimes by several feet. Mine certainly has, though not nearly that bad. Most of the houses are built on concrete foundation walls that go about 3 feet into…

I lived in SF's Inner Sunset for several years. When the old DeYoung museum was demolished and all the landscaping scraped away, the "soil" underneath was pure sand.

I noticed the same thing at my home a few blocks away -- the city had to dig a trench in the street and after they got down a few feet, there was no soil, just beautiful beach sand. A little disconcerting with SF's earthquake history.

Re: Millennium Tower is tilting, sinking

#102

Post by ams6110 »

Reminds me a bit of the CitiCorp Center fiasco.

http://failures.wikispaces.com/Citicorp+Center

Not only did the architect miscalculate the worst-case wind load on the building but the builder substituted cheaper bolted steel connections for the originally-specified fully welded connections.

The problem was remediated by heavily reinforcing the connections of the diagonal steel braces in the frame of the building, but until it was done there was a very real chance of the building blowing over.

Re: Millennium Tower is tilting, sinking

#103

Post by WalterBright »

jondiggsit wrote: post #79
WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

I, for one, would rather be building on sand rather than clay. Clay is an absolutely terrible substrate for construction. Not to mention it does not drain. Hills don't become saturated with water... the water tends to flow to ze bottom of ze hill, where it will saturate things. I'd be curious to know what exactly you are draining into... drywells and clay are not friends. - High-end residential builder here

It drains into the storm drains, and the pipes carry that off to wherever they go :-) which is the waterways. I know that because the code people had me build a grass swale to filter the runoff from the driveway before it entered the drain.

Some other homes on the hill had to be built on pilings because they were in an area which was loose dirt that had eroded away from higher up.

I'm not sure if 'clay' is the right word, I don't know much about geology, but the geologist definitely said compacted "glacial till" which he said was ideal.

Haven't had any settling problems so far despite an earthquake and lots of rain.

I passed on another lot where the geologist said the whole hill was going to slide away at some point. The seller didn't want to hear that.

Re: Millennium Tower is tilting, sinking

#104

Post by honkhonkpants »

spikels wrote: post #97
honkhonkpants wrote: post #47

Earlier quoted context omitted.

How did it get approved? The developer's lobbyist and PR rep is former mayor Brown's spokesman and personal friend, and at the time the current mayor was Newsom, a product of Brown's machine. Newsom was a bit of a crook in the area of real estate, having some self-dealing while he was on the board of supervisors and making sure all of his friends' problems got cleared. The same lobbyist also represents the Warriors i…

Nobody in SFgov is qualified to review the design of a skyscraper's foundation. That is why everyone involved in the project (city building inspectors, investors, lenders, etc) relie on expert engineering firms. Any firm making a mistake of this magnitude - if it is an engineering error - will be out of business and there insurers writing big checks. While I agree Brown/Newsome/SFGov is shady but I highly doubt they…

Sure. I was only pointing out that there was no possibility of this project being blocked on any grounds.

Re: Millennium Tower is tilting, sinking

#105

Post by 205guy »

vonmoltke wrote: post #96
omegaworks wrote: post #93

Earlier quoted context omitted.

...And allowing them to pass on 100% of the cost to their renters.

So, you think landlords should operate at a loss for the benefit of their tenants?

So you think that capital investments (in this case property) should have zero risk, in other words guaranteed returns?

Re: Millennium Tower is tilting, sinking

#106

Post by danieltillett »

WalterBright wrote: post #36
danieltillett wrote: post #24

Earlier quoted context omitted.

Or there is a lot of wind from a prevailing direction :) The other thing to look at is fence posts if they are old.

I've seen fields of trees that have been clearly bent by the wind, they look different than ones from shifting ground. For one thing, there tend to be more branches on the downwind side.

Yes this is true.

One other thing to look at is fence lines. If you line up a old fence line by eye and look down the line you can see quite small ground shifts. If you do use this make sure you crosscheck with other fences close by to make sure that any deviations are not just due to incompetent fencing.

Re: Millennium Tower is tilting, sinking

#107

Post by CrossWired »

Animats wrote: post #19

From the article: "To cut costs, Millennium did not drill piles to bedrock." I'm amazed that a building of that height would be built on a slab with friction piles in the mudflat fill zone of the SF bay. How did they get a building permit for that? 16 inches of sinkage in 8 years is huge. Building sinkage isn't all that unusual, but not for skyscrapers. There was a time when skyscrapers were only built on competent r…

Years ago I was working for the final company to own the project for Trump Tower Tampa. The reason it didn't get built? It was to be built right next to the river. After the initial site survey the geologist weren't comfortable with the original shoring design, thus they drilled more, and still weren't comfortable. Somewhere along the line the rights to the project were sold off and the incredibly small company I worked for ended up with the rights to the project, which was eventually scrapped. Had the housing boom continued for much longer, I'm afraid it likely would have been built.

Re: Millennium Tower is tilting, sinking

#108

Post by 2muchcoffeeman »

wahern wrote: post #29
WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

I live in the Outer Richmond district of San Francisco, which was built on sand dunes. Most houses in my neighborhood were built in the 1920s and 1930s, +/- a decade. I was told by a contractor that it's extremely common for houses to have shifted considerably, sometimes by several feet. Mine certainly has, though not nearly that bad. Most of the houses are built on concrete foundation walls that go about 3 feet into…

How do you plan plumbing and electricity for houses moving several feet?

Re: Millennium Tower is tilting, sinking

#109

Post by Finnucane »

jghn wrote: post #99
Finnucane wrote: post #31

Earlier quoted context omitted.

Most of our big coastal cities are like that. Boston is about twice as big as it was in colonial times; all of the Back Bay is landfill. A lot of Cambridge is landfill. And yes, most of the taller buildings cluster around the more solid bedrock areas closer to downtown. But the engineering principles needed here aren't unknown--cities like Las Vegas and New Orleans have modern buildings that are much taller than were…

As a kid I always wondered why so many of the taller buildings clustered up near DTX and then down that little strip down Boylston. As I got a bit earlier and learned what Boston originally looked like, it all made sense.

Of course, all of this landfill area is going to be the first to go back into the sea when the water rises. I figure our house is going to be riverfront property some day.
Post reply on HN