
Millennium Tower is tilting, sinking - lelf
http://sf.curbed.com/2016/8/1/12341914/millennium-tower-sinking
======
WalterBright
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 hard it could not be dug with hand tools.)

I did have a scare because a spring appeared on the edge of the property, as
underground water is indicative of slide risk. Fortunately, it turned out to
be a leak in the water main!

I still made sure the hard surfaces all drained into the storm drain, so that
the hill wouldn't become saturated with water.

I can't conceive of building a 58 story building on sand in an earthquake
zone. Reminds me of that Monty Python quote:

"When I first came here, this was all swamp. Everyone said I was daft to build
a castle on a swamp, but I built in all the same, just to show them. It sank
into the swamp. So I built a second one. That sank into the swamp. So I built
a third. That burned down, fell over, then sank into the swamp. But the fourth
one stayed up. And that's what you're going to get, Lad, the strongest castle
in all of England."

~~~
wahern
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 the sand. Despite being unreinforced and using water-permeable cement,
they've seemed to hold up reasonably well. It's usually the whole house that
shifts and racks. Yet looking from the street you wouldn't expect that because
all the houses abut each other, with only a few inches or none of space in-
between. (Perhaps this has mitigated the problem somewhat, though.)

Despite being built entirely on giant sand dunes, the Richmond district is
only "moderately" prone to liquefaction. And there wasn't much notable damage
during the 1989 earthquake, AFAIK. I think (though cannot confirm) that
similar foundation techniques were used as far back as 1905 and earlier, in
the Richmond, Sunset, and elsewhere, and judging by their survival and
continued use of the foundation techniques I'm not particularly worried.
(While widespread building in the western half of the city didn't begin in
earnest until about 1910'ish, there are hundreds of buildings many decades
older randomly distributed, especially closer to the beaches.)

The bigger problem is that almost all houses in the western half of the city
were built with so-called soft stories as the first floor--basically a giant
open space supported almost entirely by the external walls. Interestingly,
AFAIK this design came before the widespread introduction of cars. These days
nearly all houses use that space as a garage, but I believe they were built as
unfinished first floors intended to be finished as desired--e.g. workshop,
additional family rooms, in-law apartments, etc--while keeping the initial
purchase price low.

~~~
2muchcoffeeman
How do you plan plumbing and electricity for houses moving several feet?

~~~
ptaipale
If it's the earth below houses also moving, then the problems in plumbing and
electricity do not appear at the house; they appear at the cross section of
the moving and non-moving earth masses, and are typically the responsibility
of utility provider.

------
Animats
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 rock, like NYC's. Now
they're being built on much more iffy soils. Singapore and some other coastal
Asian cities are doing a lot of this.

SF used to be smaller. The outer half mile or so on the bay side is fill.
There are buried shipwrecks all through that area.[1]

[1] [https://medium.com/the-secret-history-of-america/from-
starbo...](https://medium.com/the-secret-history-of-america/from-starboard-to-
shot-glass-941b8a863c69#.8r2p8rewz)

~~~
Finnucane
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
thought possible in earlier times. If the developers didn't do it right
because it was expensive, then it is on them.

~~~
was_boring
To add on, Chicago and New Orleans are both built on swamps, and the outer
edges of New York are filled in -- making land for cities isn't the issue with
the tower.

~~~
Animats
The tallest buildings in Chicago have foundations drilled down to bedrock. The
Sears Tower (now Willits Tower) is built on bedrock. The Trump Tower [1] has
pilings down to bedrock. The John Hancock building has foundations down to
bedrock, even though they had to go down almost 200 feet.[2]

How unusual is 83 floors in earthquake country without foundations down to
bedrock?

[1]
[http://faculty.arch.tamu.edu/media/cms_page_media/4433/trump...](http://faculty.arch.tamu.edu/media/cms_page_media/4433/trumptowechicago.pdf)
[2]
[http://khan.princeton.edu/khanHancock.html](http://khan.princeton.edu/khanHancock.html)

------
ams6110
Reminds me a bit of the CitiCorp Center fiasco.

[http://failures.wikispaces.com/Citicorp+Center](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.

~~~
clintonb
99% Invisible has a story on that building, and how the issue was discovered:
[http://99percentinvisible.org/episode/structural-
integrity/](http://99percentinvisible.org/episode/structural-integrity/).

------
wallflower
In contrast, the Salesforce tower under construction at 415 Mission Street is
built on piles that connect to bedrock.

> In a big earthquake, the ground is actually trying to slip sideways
> underneath the building. “You need something to keep you from changing
> addresses,” says Joseph. Those somethings are called piles, in essence
> underground stilts connecting the building with the bedrock. In the lowlands
> of San Francisco’s Financial District, bedrock is 300 below street level.
> “We have 42 piles that go all the way down and are socketed 15 to 25 foot
> deep into the rock,” says Tymoff.

[http://www.wired.com/2015/11/it-took-18-hours-to-pour-san-
fr...](http://www.wired.com/2015/11/it-took-18-hours-to-pour-san-franciscos-
biggest-ever-concrete-foundation/)

And this was part of the proposal from the very beginning.

> The Transit Tower would have a concrete slab foundation supported by driven
> piles anticipated to be founded on bedrock more than 200 feet below grade.
> The tower’s structural system is anticipated to employ the concept of
> “megacolumns,” which are very large structural columns several feet in
> width. The concentrated load supported by these megacolumns would be
> sustained by large diameter piles approximately 10 feet in diameter, with
> additional piles driven to support the building’s foundation slab.

[http://sfrecpark.org/wp-
content/uploads/00_FEIR_Draft-1_12-0...](http://sfrecpark.org/wp-
content/uploads/00_FEIR_Draft-1_12-0629_CD_reduced.pdf)

------
qq66
16 inches over 8 years is absolutely insane. That's the Usain Bolt of a
sinking building.

~~~
torgoguys
And the article mentions it was 10 inches in only (it's first) 2 years after
completion!

~~~
matthewowen
Good news, the sinking is slowing!

:/

~~~
PhasmaFelis
If the pilings go down 80 feet, and bedrock is at 200 feet, then worst case
you'll still have 46 usable stories!

------
dsfyu404ed
FWIW building on sand isn't all that bad if you design the building expecting
it to be on sand. The Nazis build AA defenses on sand because a concrete
building that's sandwiched between the recoil of small artillery and bedrock
won't be around very long. The sand acts like a damper. It's harder to break a
cinder block with a hammer if the block is sitting on a pile of sand than if
it's on a paved surface and you can apply the same principal at scale if
you've got the resources to do all the prerequisite work.

It's not that exotic of a design when you consider that the ground under
California tends to move around. Too bad it doesn't look like this building
was meant to support itself atop a less than solid underlayment. Too bad for
the developers.\s If they have to take corrective action they only get a crazy
profit margin instead of an insane one. Should have done it right the first
time.

------
djsumdog
The article doesn't talk about the how this practically affects the entrances
to the building. Do the doors have to be adjusted for such a drastic sinkage,
or are buildings somehow designed so this isn't noticeable to the public?

~~~
VonGuard
Seems to imply they had to do something to the entrances, but not what. Maybe
there are little ramps added every year? I'm gonna go look now.

~~~
jonah
Please take some pictures and share them with us.

Another article I read said they have needed to make adjustments to the first
floor interface but didn't say what they were.

------
pnevares
A fair warning that sinking doesn't just happen to towers:
[http://science.time.com/2012/05/21/soaring-to-sinking-how-
bu...](http://science.time.com/2012/05/21/soaring-to-sinking-how-building-up-
is-bringing-shanghai-down/)

------
philip1209
"To cut costs, Millennium did not drill piles to bedrock."

What are the implications for earthquake safety?

~~~
capkutay
Because Millennium is on reclaimed land, they cannot determine whether or not
they have drilled into bedrock. They drill into what's called the 'point of
refusal'; a point where they can no longer drill deeper. Whether this is
bedrock or even stable soil is somewhat vague.

~~~
spikels
Almost nothing in this comment is accurate:

\- You CAN determine the type of rock you are drilling through as well as it's
relevant characteristics. Pieces of the material are brought to the surface
with the drilling mud and instruments are put down the hole.

\- Builders DO NOT just stop drilling when their drill won't drill no further.
(This made me laugh!) There is testing, design, design review, more testing
during construction, more design review and perhaps modification based on
conditions. If a particular drill could not drill to design depth, they would
likely change the bit or drill.

\- While there will always be some uncertainty, engineers require more than a
vague understanding of soil conditions to design the foundation of a building
like this. Any remaining uncertainty should be taken into account in the
design.

~~~
capkutay
Maybe I have a poor definition of 'point of refusal', but this is the term
developers use. Most developers in SF don't tell you whether they drilled down
to bedrock or not.

~~~
duaneb
It's a real term. This is not how the pile depth is decided but a maximum
depth.

------
andylang_
to quote Stewart Lee: "as a piece of architecture, that is abysmal. But as an
extremely heavy-handed satire of exactly where we're going wrong, superb."

------
shirro
Surely the first rule of building large buildings in earthquake zones has to
be solid foundations. Isn't liquefaction a concern?

------
jpeg_hero
I heard that there is already a $100m+ compensation fund in place for owners
who agree not to sue. Any other information?

~~~
erdevs
If this is true, then it's a big tacit admission of guilt, or the expectation
if being found liable, at least. Where did you hear?

------
Johnny555
Probably the residents have a lot of books, and the architect forgot to
account for the weight of the books.

[http://www.snopes.com/college/halls/sinking.asp](http://www.snopes.com/college/halls/sinking.asp)

------
helmett
...2 inches for such a tall building is such tiny angle

If it sinks does this mean the first floor is slightly below the street level
..it probably means that the areas around the door and where the concete meets
the street are cracked

~~~
carleverett
I was wondering the same thing, but Google street view (taken in 2014) doesn't
show any evidence of such a big dip. How is that possible?? The only thing I
can think of is that it's more of a "sag," where the middle has sunk 18" but
the edges haven't moved much, but I'm not really satisfied with that theory.

[https://www.google.com/maps/place/Millennium+Tower+San+Franc...](https://www.google.com/maps/place/Millennium+Tower+San+Francisco/@37.7901875,-122.3962408,3a,90y,237.99h,64.97t/data=!3m8!1e1!3m6!1s-35rB20DzRME%2FU7BvmBlYzUI%2FAAAAAAAAKgs%2FidvFTvbnBG4BG0iCULQUc1scg2DlGAkaw!2e4!3e11!6s%2F%2Flh5.googleusercontent.com%2F-35rB20DzRME%2FU7BvmBlYzUI%2FAAAAAAAAKgs%2FidvFTvbnBG4BG0iCULQUc1scg2DlGAkaw%2Fw203-h101-n-k-
no%2F!7i11884!8i5942!4m5!3m4!1s0x0:0x9fe15ebd4a8300d8!8m2!3d37.7905058!4d-122.3961611!6m1!1e1)

~~~
dpark
It's extremely unlikely that the building is sinking and the surrounding area
is stable. More likely the building is pulling the entire area down, so it's
probably hard to detect as a pedestrian.

~~~
Naritai
A commenter upstream reports seeing the sidewalk being repaired multiple times
throughout the last 10 years as well.

------
jordanlev
> _While the Millennium Tower’s sinkage into the earth is reportedly not a
> safety issue for residents, it does pose a problem for investors._

This is confusing to me -- if it's not a safety issue, then why is it a
problem?

~~~
PhasmaFelis
The Leaning Tower of Pisa, for example, has stood without toppling for many
centuries, but it's not a place you'd want to _live_ in.

I also suspect that people with the kind of money they're looking for are not
going to accept "don't worry, we checked and it's definitely 100% safe!"

------
RGamma
This brings me back to a question I have frequently asked myself: What do you
do with unsafe or old skyscrapers? How would you raze such a thing? What if it
falls over, breaks apart or breaks in on itself (9/11 gives an idea)?

To a layman (with slight acrophobia) skyscrapers seem pretty fragile, and I'd
much rather have them built into the ground than towards the sky, but
obviously they're holding up in general and I'm interested to see what happens
with this one: Hope that it stops tilting or sinking? Raze it before anything
bad happens?

~~~
ChoGGi
Slowly?
[https://www.youtube.com/watch?v=jwf9LoS9Xt8](https://www.youtube.com/watch?v=jwf9LoS9Xt8)

~~~
TheSpiceIsLife
Wonderful! Thanks for sharing that. I work in the steel construction industry,
we put buildings up all day every day, so watching them come down always
interests me.

------
sharpercoder
I wonder what effect a medium to heavy earthquake would have on this
building's foundation.

~~~
erdevs
Probably not good. According to this and other articles, the building's
concrete slab foundation sits roughly 80 ft below street level upon sand,
while bedrock lies 200 ft down. That means there is 120 ft of sand, possibly
susceptible to liquefaction, between the buildings foundation and solid
bedrock. That sounds bad enough. But now imagine the building is tipping over
slightly. The already potentially worrisome problem compounds dramatically.

~~~
clock_tower
How much would it have cost to dig down to bedrock, and pour a concrete
foundation from the bedrock up to surface level?

Between the amount of sand to be moved and the amount of concrete to be
poured, it sounds like an enormous fortune; I guess that the relevant
questions are whether the market could bear it and whether it would be cheaper
than the rapidly-developing lawsuits. It may be that the building didn't make
economic sense in the first place, if it couldn't be built both safely and
profitably -- which has unpleasant implications for the SF housing crunch...

~~~
WalterBright
The real problem with digging down to bedrock is destablizing the building.
Though there may be enough redundancy in the pilings to do it one at a time.

~~~
vonmoltke
I think the question was why the builders didn't do it in the first place.

~~~
jonah
You dig down 200 feet to the bedrock, pour a foundation, and then pour pilings
up to the surface to put the building on.

------
rwallace
"it's not steel-framed and instead uses a concrete design"

I thought concrete buildings without steel frames came down instantly in
earthquakes. What am I missing?

~~~
pja
_I thought concrete buildings without steel frames came down instantly in
earthquakes. What am I missing?_

Concrete buildings without sufficient bracing at the corners where supporting
beams meet floors fail pretty much instantly in earthquakes for sure, but if
you put bracing supports in at the corners then that makes them much, much
stronger. You’re probably thinking that concrete buildings just collapse from
your experience of post-earthquake film footage from countries with poor
governance where building firms can cheap out on the construction (lets save
15% of our material costs by skipping the bracing!) and their buildings
inevitably collapse when the next earthquake comes along.

------
walrus01
Reminds me of this:

[https://en.m.wikipedia.org/wiki/Ocean_Tower](https://en.m.wikipedia.org/wiki/Ocean_Tower)

~~~
jobigoud
Hmm, they imploded it after discovering it had sunken 14 inches. Millennium
Tower has sunken 16 inches…

~~~
duaneb
I figure it was due to the cracked supports.

------
SeanDav
> _" The Millennium’s engineers anchored the building over a thick concrete
> slab with piles driven roughly 80 feet into dense sand. "To cut costs,
> Millennium did not drill piles to bedrock,"... _

They built a skyscraper, on sand, in an earthquake zone!!! What the heck were
they thinking?

Consider me completely unsurprised that the building is sinking and tilting.

~~~
raverbashing
> They built a skyscraper, on sand, in an earthquake zone!!! What the heck
> were they thinking?

My guess is that they were thinking of something that starts with "pro" and
ends with "fit"

I mean, Tokyo is earthquake zone, but it's not unsupported sandy soil

------
cheeze
What is the risk? Does this make the building more dangerous because it's in
an earthquake-prone area? Obviously this doesn't sound good, but the article
mentions that there is no threat to safety of occupants. Is it merely
aesthetic?

~~~
Artlav
Uneven sinking is not good - doors/windows won't close, walls would crack, and
so on. It does not take much to seize things, however buildings are usually
designed to take a little of it. The rate at which it's sinking is the
alarming part.

But i would be mostly alarmed about earthquakes - the thing sits on sand.
Proverbial or not, that would make it very susceptible to soil liquification.

Imagine a stick with a weight on top of it. On solid ground it stands still.
But if the ground was to turn into a liquid, the stick would tilt and sink
rapidly. If the soil were to liquify for a second, it would end up at an angle
half-sunk. And a building can't tolerate side loads, so it won't stay at an
angle - it would collapse down.

~~~
aidenn0
When I read that it was built on fill, liquification was my first thought.
Doesn't SF have limits to building sizes in liquification zones?

------
trhway
a nearby tower under construction - Fremont 181 - has been drilled 260 feet
into the ground, well reaching the bedrock.

[http://sf.curbed.com/2016/8/1/12343776/sinking-millennium-
to...](http://sf.curbed.com/2016/8/1/12343776/sinking-millennium-tower)

------
arxpoetica
The wise man built his house upon the rock...

------
tomc1985
Wouldn't 16 inches warp the surrounding pavement and street? I imagine there'd
be a large dip.

------
Overtonwindow
Makes me a little thankful (for once) that my Georgia home is built on a hill
of dense, unyielding clay.

~~~
blantonl
Dense clay might be unyielding, but depending on the plasticity of that clay
you could be facing serious issues with heaving when the soil gets extremely
moist.

------
skeletonjelly
Would be interested to see a video of water being poured onto a flat surface
inside this building

------
davidw
Perhaps they can turn it into a tourist attraction. It has worked out well for
Pisa.

------
SagelyGuru
Surely, the tilting is the biggest worry. Anybody care to estimate how many
more inches can this tall building tilt before the lateral stresses lead to
its collapse?

~~~
huuu
I think you would be amazed how far it could tilt before it collapses.

For example the Tower of Pisa (55m height) is leaning much worse: almost 4
meters.

[https://en.wikipedia.org/wiki/List_of_leaning_towers](https://en.wikipedia.org/wiki/List_of_leaning_towers)

------
Nuffinatall
Pretty sure they need to safely dismantle this building and try again.

In non-earthquake prone areas, it might make sense to jack it up and what not,
but not in SF.

~~~
dpark
There is no scenario in which a 350 million dollar skyscraper deemed "not a
safety issue for residents" will be torn down so they can "try again". They'll
find a way to stabilize it and that will be that. No one is going to tear down
nearly half a billion dollars worth of skyscraper if there's any chance of
salvaging it.

~~~
nostromo
It's not without precedent.

In Seattle a cost-cutting method was used to build a 25-story downtown
apartment building in 2001.

In 2010 it was found to be flawed and unfixable, and so it was dismantled.

And now there's a new building being built on the site.

[http://www.seattletimes.com/seattle-news/9-year-old-
belltown...](http://www.seattletimes.com/seattle-news/9-year-old-belltown-
high-rise-too-flawed-to-fix/)

~~~
dpark
Key there is it was deemed unfixable. $350 MM can do a lot of fixing.

Edit: To be clear, I'm not denying the entire possibility. It's just
_extremely_ unlikely, especially given that the tower is currently deemed
safe.

~~~
spikels
Plus if it turns out to have been caused by the Trans Bay Terminal, they have
very deep pockets (they supposedly spent $58 million on a buttress to protect
the Millineum Tower). As does the developer, Millennium Partners and the
engineering from firm's insurance companies.

This will get fixed. There will just have to be a big fight to see who has to
pay.

------
spikels
Lots of misinformation in this thread. Would be great to hear from a
professional.

~~~
vonmoltke
What here is misinformation?

~~~
spikels
A few examples:

\- Foundations of tall building must go to bedrock - not true.

\- Large buildings settling is unusual - not true.

\- Earthquake safety has been compromised in this case - not true.

The structural engineering of tall buildings is complex. Multiple large
engineering firms were involved in the design and construction of this
building.

Curbed (owned by Vox BTW) took the SF Cronicle article and cut out the more
reasonable paragraphs (such as that same Stanford they quoted saying he
"doesn’t consider the sink or tilt a safety issue".).. And of course the Chron
article already probably skewed it to make it more exciting.

I always shake my head when I read article on a subject that I happen to be be
an expert. I'm sure experts in the engineering of these sorts of projects
could teach us alot about this situation.

~~~
erdevs
It seems that you need to read more carefully and perhaps with more
generosity.

> A few examples: \- Foundations of tall building must go to bedrock - not
> true.

I see few if any comments here asserting, let alone asserting without
qualification, that buildings _must_ be built to bedrock. Further, heeding
your own advice that expertise should be bidden, note that the apparently
expert sources in the article said themselves that not building to bedrock
_can_ be a problem.

I see people here noting and reflecting that expert opinion. Few if anyone
going beyond it. And you're not reading the source material carefully enough
if you miss the take that not building to bedrock can carry some risk.

> \- Large buildings settling is unusual - not true.

Again, I see no one or very few people here saying this. Of course buildings
settle over time. And here in this thread, contrary to your blithe and
dismissive assertion, we even have people pointing out that settling happens
not just in towers but in buildings of most any kind.

Note as well, again, that the very experts you appeal to say that this tower's
settling is both comparatively fast and that its magnitude is unexpected.
These are the experts talking, so you come off as hypocritical at best here.
The nature and particulars of the settling in this particular case appears
noteworthy and to be a reasonable cause for concern.

> \- Earthquake safety has been compromised in this case - not true.

Ahh... so, now you are the expert and capable of refuting this possibility so
entirely-- upon merely a cursory examination of second- or third-hand
information, rather than a primary analysis, no less-- that it is somehow
faulty for people to question whether this might have an impact on earthquake
safety? My, my; odd that you called for caution in drawing conclusions until
experts had weighed in, then turned around and flatly conclude that which I
doubt even experts would leave completely unqualified, and certainly not
universally and unanimously so.

The comments here so far are not much of the chicken-little or even rabble-
rousing type. Try being more respectful toward your fellow community members.

~~~
karma_vaccum123
you should instead be grateful for a curt correction to the unending stream of
faux-expertise and hand-waving that HN has become

I only ever bother with the comments section anymore if only to watch the
cringe-inducing attempts at "insight" by the same dozen or so users...

~~~
erdevs
What "correction" was there, exactly? I replied to an over-generalization and
misstatement. What exactly do you see being _actually_ corrected?

------
3327
OUch. Big write down to the yuppies who bot into this glass brogrammer tower.

------
chiefalchemist
"the building is located on unstable mud-fill, just off the bay’s original
shoreline."

Nuff said.

