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SF tower settlement
15

SF tower settlement

RE: SF tower settlement

That has got to be a "worst nightmare" scenario starting up.

I sure wouldn't want to be in a building like that during the soon-to-happen next Big One.

Keith Cress
kcress - http://www.flaminsystems.com

RE: SF tower settlement

Good thing it's not too tall... only 58 stories... Settled 16" so far and tilted 2". Constructed on mud fill with a slab foundations supported on piles into dense sand.

Max condo value is $10M...

I don't know if the sand is saturated, but, there could also be problems during a seismic event...

Dik

RE: SF tower settlement

Well, this will be quite the case study on foundation improvements assuming they don't just demo it and start over.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com

RE: SF tower settlement

For those that don't want to sign up as a member of the SF chronicle. Here's a fox "news" article posted by Tigerguy in the foundation forum

Link

RE: SF tower settlement

Quote (Article)

The HOA added that it is exploring its legal option and could pursue damages from several parties, including the developer, the original design professionals, the original contractors and the Transbay Joint Powers Authority.

Trouble in paradise that's for sure.

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RE: SF tower settlement

2
I worked on the BART station construction one block away on Market. During lunch, a group of Archeologists would poke around the excavation and found all the stuff that was dumped from ships moored in the Bay before this area was filled. Lots of those clay pots, apparently used to ship rice, and many small bottles, some still sealed and full. Also met my wife there.

But I had nothing to do with this settlement.

RE: SF tower settlement

Quote (Article)

The transit authority also said the high-rise is made of concrete rather than steel, "resulting in a very heavy building. This heavy structure rests on layers of soft, compressible soil. The foundation of the Tower, however, consists only of a concrete slab supported by short piles that fail to reach the bedrock below. That foundation is inadequate to prevent settlement of a building with the weight of the Tower."

That's a pretty strong statement for the transit authority to make...

Time to grab some popcorn.

RE: SF tower settlement

Various places in that part of the city is soft landfill; they used to find ships and whatnot when digging foundations for various buildings. Near as I can tell, that particular high rise is sitting on what used to be Yerba Buena Cove:
http://www.davidrumsey.com/luna/servlet/detail/RUM...

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: SF tower settlement

"and has sunk 16 inches and shifted 2 inches to the northwest since opening"- That's from the Fox news article, doesn't say it tilted, but moved sideways?
I suspect a lot of lawyers will make a lot of money out of this and that's about the only positive aspect all the way around.

RE: SF tower settlement

Quote (JStephen)

I suspect a lot of lawyers will make a lot of money out of this and that's about the only positive aspect all the way around

I guess if you consider such a thing a positive... upsidedown

RE: SF tower settlement

Been reading about the engineers and such involved with Flint.
I was a concrete inspector on the BART Lower Market Street Station. I inspected the concrete used in the slurry walls on the south side of Market, 720 feet away from 301 Mission. As I mentioned, I met my wife here. Suppose I was watching her instead of the concrete pour. And as a result, after 45 years of seepage from bad concrete, the millenials had their building damaged?

RE: SF tower settlement

Quote (BUGGAR)

Been reading about the engineers and such involved with Flint.
I was a concrete inspector on the BART Lower Market Street Station. I inspected the concrete used in the slurry walls on the south side of Market, 720 feet away from 301 Mission. As I mentioned, I met my wife here. Suppose I was watching her instead of the concrete pour. And as a result, after 45 years of seepage from bad concrete, the millenials had their building damaged?

Well, in your case, let's hope the statute of limitations for arousal-induced negligence has expired.

RE: SF tower settlement

Likely tilting because of all the compressing beer cans tossed in the hole by BUGGAR and his cohorts. wink

Keith Cress
kcress - http://www.flaminsystems.com

RE: SF tower settlement

My guess is that the legal settlement may take longer than the ongoing foundation settlement...

RE: SF tower settlement

"Founded on piles bearing on dense sand". There was a drainage system built to collect leakage from the slurry walls around the Lower Market Street Station. What if these dense (previously) sands have been draining through the slurry walls and into the Market Street Station dewatering system and no one knows this?

I'm not really trying for some witness per diem, honest.

RE: SF tower settlement

It will have to tilt a lot more than 2 inches before it becomes a major tourist attraction. It will be some time yet before the Italians become concerned about losing tourist dollars to SF.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: SF tower settlement

The Transbay Transit Center is 90% over budget and considering a special tax on the properties, including 301 Mission, to pay for the bail out. This is just for Phase I of the Project. Funding for Phase II has not been identified. Phase III??

Excavation is just like BART - cut and cover using soldier piles and concrete slurry walls. Big HSS struts supporting walls during excavation. The excavation is bigger than Lower Market. I presume the walls are structural like on BART, a first at the time. I also read that they consider the Lower Market Street Bart Station to be obsolete. Hey, I just built that thing! The concrete is just reaching its prime.

RE: SF tower settlement

A new icon to advertise for tourists for the local money mongerers - The Leaning Tower of San Francisco - And Vegas can take bets as to when it will fall too.

Many investment opportunities here...

Mike McCann, PE, SE (WA)


RE: SF tower settlement

Imagine having property on the now "underside" of that building. <shudder>

Keith Cress
kcress - http://www.flaminsystems.com

RE: SF tower settlement

Obviously someone needs to do pushover analysis if it is leaning left.

Mike McCann, PE, SE (WA)


RE: SF tower settlement

Leaning left from one side; leaning right from the other side. winky smile

RE: SF tower settlement

Ah ha, so the building didn't follow the notes on the drawing, not the engineer's fault!

RE: SF tower settlement

It goes to show we don't need to be so darn conservative when designing foundations. I'd bet this one well stand well beyond the lives of all the members here and with full occupancy.

RE: SF tower settlement

Geez Dan, don't make everyone play the clickclick game, just post the dang picture directly!

Keith Cress
kcress - http://www.flaminsystems.com

RE: SF tower settlement

Any suggestion on how to prevent the building from sinking and tilting? Would it be possible to jack up columns like in Kansai airport terminal?

RE: SF tower settlement

Why jack it up? Do like in Mexico City. Just install new entry ways in the second floor so that no one is trapped inside when current doors won't open due to earth there. Should cost less.

RE: SF tower settlement

So, in 45 years or so, it will be 57 stories high!

STF

RE: SF tower settlement

Unfortunately, they will have to lower the rent on the bottom story.

Seems like there will be a LOT of plumbing and electrical issues here too, not just structural.

Mike McCann, PE, SE (WA)


RE: SF tower settlement

Rather than make fun of the situation I am more interested in finding out what led to the mistake so that others may not make the same. This is a serious situation I am sure not one of us would want to be in. Any leads on this?

RE: SF tower settlement

I know next-to-nothing about civil/geotech, but is grouting an option on something this big to at least stabilize and stop further sinking? Wow, what a nightmare. I'd hate to think what a seismic event would do this site.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: SF tower settlement

Somewhat of a side note, but...

Could the right "seismic event" cause liquifaction of the underlying sand and cause a rapid decline in building stability, or are the underlying ground specifics not appropriate for such a reaction?

Dan - Owner
http://www.Hi-TecDesigns.com

RE: SF tower settlement

Quote:

Rather than make fun of the situation I am more interested in finding out what led to the mistake...

It doesn't have to be either/or. We all take it very seriously I'm sure. Especially the structural engineers among us.

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RE: SF tower settlement

Could it be that the higher ups wanted to cut cost, opting for foundation slab with piles not going all the way down to bed rock and the structural engineers come up with calculation based on ideal case to justify decision without sufficient core bore data?

RE: SF tower settlement

(OP)
lillliput,

Suffice it to say that there are a lot of possibilities. You won't find any definite answers here, and as discussed above, this will take years to resolve, if ever.

RE: SF tower settlement

OK so we joked a little. However, does anyone have any CORRECT history of construction as well as an on-going record of measurements? Can we learn from any mistakes? Maybe.

RE: SF tower settlement

What makes you think I was joking?

Mike McCann, PE, SE (WA)


RE: SF tower settlement

there is no negligence by running piles to dense sand rather than bedrock. If each pile can develop the capacity it needs in the dense sand, where's the problem? There is a problem designing for some capacity and not documenting that the installed pile developed that capacity. There is also a problem not knowing the performance details of the piles. I mean if the piles remain good against failure, but they required 16 inches of settlement to develop their full capacity, that's a serviceability problem.

I can't believe 16 inches of settlement! I mean are the water/sewer connections failed?

f-d

ípapß gordo ainÆt no madre flaca!

RE: SF tower settlement

(OP)
Why do you question the 16" settlement quoted, fattdad? I would think if this was not factful, there would have been a denial by now.

Yes, the service connections would present big problems, as would probably a lot of other relationships with the surrounding ground level surfaces.

In a situation like this, servioeability/settlement failure is overriding, and strength is of less importance. Too much settlement can indeed be evidence of negligence. That remains to be determined in this case.

RE: SF tower settlement

I wonder if the parking garage entrance is near the maximum settlement area. It would make the perfect home for Evel Knievel.

RE: SF tower settlement

To say nothing of raising havoc, in one fashion or another, with the handicap accessibility.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: SF tower settlement


Quote (MacGyverS2000 (Electrical))


9 Aug 16 16:59
Somewhat of a side note, but...

Could the right "seismic event" cause liquifaction of the underlying sand and cause a rapid decline in building stability, or are the underlying ground specifics not appropriate for such a reaction?

In just the last moderate SFO earthquake in 1989, Mission District buildings on fill dirt in the bay DID collapse and sink into the ground just for that cause. Saw videos of the entire first floor below ground.

RE: SF tower settlement

I don't question the settlement at all! I was just saying the dense sand could be safe for foundation support (i.e., strong enough), but some other layer may settle. So, how did the original design consider settlement if the foundation bears on soil rather than rock? Were the soil layers and their properties estimated (I'd doubt it)? So, it'd be likely that somebody studied the strength and compressibility of the dense sand, the soil above (mud?) and the soil/rock below. I just could not claim because the foundation did not go to rock there was some negligence.

Sorry to confuse. . .

f-d

ípapß gordo ainÆt no madre flaca!

RE: SF tower settlement

Just a stir-the-pot article, no real news:
http://www.pressdemocrat.com/home/6370566-186/lean...

My favorite line,
"said Dodson, an attorney who has helped organize homeowners lawsuits. 'I can tell you that satellite data is way more accurate that digging in the dirt.'" Translation: We don't need no stinkin' surveyors, we got Google maps!"

RE: SF tower settlement

Heck of a project for "Slabjack".

Mike McCann, PE, SE (WA)


RE: SF tower settlement

Dodson is going to be in for a few big surprises over the coming years.

RE: SF tower settlement

This is the perfect storm:
  • Condominium
  • Flaws that might be huge or not.
  • Extremely rich entitled tenants.
Many lawyers are going to get very rich.

RE: SF tower settlement

boo1 - that is a good article and fairly described all the challenges, both engineering-wise and in terms of the legal issues.

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RE: SF tower settlement

great... and I'd be somewhat concerned about the hairline cracks in the basement...

Dik

RE: SF tower settlement

(OP)
Thick hairs, those.

RE: SF tower settlement

LionelHutz:

Yes

Dik

RE: SF tower settlement

So if this issue was settled out of court, would it be a settlement on the settlement?

RE: SF tower settlement

I was thinking, micropiles to rock and secured in the slab foundation. Would the poor soil offer enough restraint to preclude buckling. Lets try to think of some remediation.

Dik

RE: SF tower settlement

IR, perhaps we should come at this from a different angle rather than straight on? I'm leaning towards a simple solution.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: SF tower settlement

curious. has anyone heard who the geotech firm was on this? i know DeSimone was structural but haven't seen any reference to the geotech. FYI... they have a new geotech in now who was not related with the original construction.

RE: SF tower settlement

That settles it.
I will only read this thread for shear amusement from now on.

STF

RE: SF tower settlement

Quote (garthsoilsguy2)

curious. has anyone heard who the geotech firm was on this?

Treadwell & Rollo, now part of Langan Engineering. ENR link re aquisition and Langan Engineering website.

Quote (garthsoilsguy2)

i know DeSimone was structural...

Sadly, Vincent DeSimone (founder of DeSimone Consulting Engineers) passed away in November, 2016. Memoriam

RE: SF tower settlement

This one only settled 14 inches before it was "dealt with."

RE: SF tower settlement

A structural engineer did a review of the building design, but only the building, not the foundation.
I kind of sympathize with the guy, no one welcomes you reviewing scope beyond your contract.

RE: SF tower settlement

Just curious here - it says that the tower has sunk 16" - that is "significant".
But the lean is 2".

For a 645 ft. (196.6m) tall building the ACI 117 tolerances (for construction) would be on the order of 3" to 6" depending on the direction of the measurement.

So a 2" "lean" here doesn't sound too bad.

For typical wind load deflections, a tall building like this might lean L/500 = 15 inches.

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RE: SF tower settlement

Quote (JedClampett)

A structural engineer did a review of the building design, but only the building, not the foundation.
I kind of sympathize with the guy, no one welcomes you reviewing scope beyond your contract.

And non-other than Prof Jack Moehle of UC Berkeley:

Quote (Curbed SF)

“The interest was to do an internal review to ensure that the structural system selected was suitable,” Moehle told city lawmakers at Thursday’s hearing. “[So] that if there was a formal peer review for the city later that most questions would be dealt with already.”

RE: SF tower settlement

And this from 2004 about 80 Natoma SF proposed 50-story tower that was NOT constructed Link:

Quote (Bizjournals)

A 50-story building is heavy. If constructed, the 80 Natoma Building would impose 13,000 pounds per square foot on the soil below it. Moreover, if the developer went ahead with his plan to use short (70-foot) piles to support the building, the bottom of his piles would lie just above a 90-foot layer of compressible clay. Geotechnical experts concluded that imposing such loads through the piles to the clay would cause the clay to deform and the building to settle several inches. Unless the developer were to extend his piles another 100 feet or so to bedrock, there is no getting around this.

RE: SF tower settlement

Link to C & C of SF video testimony of Prof Jack Moehle dated 2/2/17 - all 2.5 hours! Link

RE: SF tower settlement

(OP)
I had the same thought, Keith. But I'm not betting.

RE: SF tower settlement

From Curbed, "Moehle says he inspected the high-rise’s design from top to bottom—but no lower than the bottom. A geotechnical review—i.e., an assessment of the condition of the soil under the building site—wasn’t part of the process, because no one ever hired a geotechnical engineer."

Even as a rookie, if I had been asked to provide an engineering report for a building with substantial subsidence, I would have raised a bit of a flag about having a geotechnical report included with the overall report (and that is not hindsight being 20/20). Because subsidence was a key issue, this would be a significant part of the engineering report.

Dik

RE: SF tower settlement

Quote (Cubed SF and dik)

...because no one ever hired a geotechnical engineer.

A somewhat misleading quote on behalf of Cubed SF, IMO. A geotech engineer was NOT hired as part of the internal peer-review (which was primarily initiated to look at the structural framing system pertaining to seismic), however the project did have a geotech engineer - namely, Treadwell & Rollo, as part of the project design team.

RE: SF tower settlement

Unless Cubed is misquoting Moehle, with the problems encountered, a 'new' independent geotech firm should have been retained to make the report complete and to address any concerns.

Dik

RE: SF tower settlement

It makes me curious who recommended what. On much smaller projects it is very common to have a geotechnical report that says "You can do it this way, and may have this problem or you can spend more and do it this other way and have less problem", etc. There's quite often a calculated risk involved, and the geotechnical reports I've seen more often reported both options with pros and cons, or went the more conservative route if there was any doubt.

RE: SF tower settlement

If you listen to the testimony of Moehle [Link] City and County of SF Supervisor Aaron Peskin asks Moehle why he did not stamp/seal his internal peer-review report, and also why was he was not an SE.

There was some interesting background information given on the 80 Natoma project in the testimony, which underwent peer-review about the same time as the Millennium Tower project (mid-late 2004).

RE: SF tower settlement

Ingenuity:
Good link, and a bit long. It explains why the documents weren't sealed and that the prof wasn't a registered SE. In some jurisdictions, a professional can be held to the same standard if the documents are not sealed. I have to review it again; it appeared that the politician stated that the foundation peer review had been undertaken by the prof and this went unchallenged(53 minutes into the hearing). It appeared that the whole purpose of the dialogue was to distance the city from the problem.

Dik

RE: SF tower settlement

would appreciate if anyone can provide some information on the ground profile below pile toe, especially clay thickness/depth.

RE: SF tower settlement

from one of the links, "Moehle wrote that "On the basis of my review, it is my opinion that the foundation design is compliant with the principles and requirements of the building code, and that a foundation permit can be issued for this project." The statement is a little confusing because Moehle clearly recuses himself from having any involvement with the foundation. If his statement is correct, he is stating that the foundation is... and, that a foundation permit should be issued.

Dik

RE: SF tower settlement

Current articles indicate it has tilted 12" and not 2"...

Dik

RE: SF tower settlement

Quote (dik)

Current articles indicate it has tilted 12" and not 2"...

dik: What is your article source for this 'revised' tilt, and what is the magnitude of the 'revised' vertical settlement?

RE: SF tower settlement

The one lawsuit indicated the 12" tilt and there was this news article:

SAN FRANCISCO (KRON) — It has become known as San Francisco’s sinking tower, and attorneys representing those who live in the Millennium Tower are seeking more than $200 million from those they say are responsible for the building sinking and tilting.

The tower is sinking 16 inches and tilting 12 inches at the penthouse level, attorneys said.

Most of the other articles indicate 2" still and are dated a year ago; it is not known what actual measurements have been taken.

Dik

RE: SF tower settlement

Flexural cracking in concrete is very bad. Since concrete has a low tensile strength, reinforcing steel (rebar) is added to increase its ability to carry loads that would otherwise cause it to crack & lose its load carrying ability. Flexural cracking in concrete can lead to bond loss to reinforcement. Considering this is happening at the base of the structure, it is not a good situation. Gluing it back together with a structural epoxy is very slow & expensive. The cracks seen at the surface do not fully represent what might be going on inside the concrete. Fleural cracks can fold back on themselves, creating an interwoven network of cracks that are difficult to penetrate using standard gravity hydraulic injection techniques and require a very low viscosity epoxy with a long working time & exceptional patience & experience by the technicians.

RE: SF tower settlement

Any problem left ignored long enough will stop being a problem. Sometimes the cessation of one problem causes the start of another, but that's for others to deal with.

I am reminded that the lowest accessible levels in Venice, Italy were at one time second and third floors.

RE: SF tower settlement

See linked article. It seems like the this was the solution all the time, but it sure won't be easy.

RE: SF tower settlement

Without going to bedrock, I'd be really concerned with liquifaction of the supporting soil.

Dik

RE: SF tower settlement

(OP)
Piling to rock is good, but I wonder about their numbers. They are talking about 100 bored piles, each 10" to 12" in diameter. To me, that doesn't sound like the capacity to jack up that building.

RE: SF tower settlement

It's OK Hokie... They did the sums on it, just like the original foundation...

Dik

RE: SF tower settlement

LERA certainly knows tilting buildings Link
And DeSimone Consulting Engineers can give their project it's own twist on things. Link

Tubex Grout Injected Piling is probably what they are thinking.
Link
Link

RE: SF tower settlement

Epoxybot: With extreme settlement, the building with a twist, just screws itself into the ground.

Dik

RE: SF tower settlement

From the news,
"Millennium Tower, the tony but troubled downtown high-rise that made international headlines last year when the secret got out that it’s slowly sinking and tilting, returned to its customary place in the news late Tuesday when NBC Bay Area revealed that the building “has tilted two and half more inches in just the first half of this year, according to new monitoring data.”

Says the affiliate:

The data, compiled by the ARUP engineering firm brought in by officials of the nextdoor Transbay transit terminal project, suggest the structure is tilting twice as fast as it had been in earlier ARUP data.

It is now listing at least 14 inches toward the massive Salesforce building going up nearby on Mission Street. The data also show the building has sunk close to 17 inches at its low point, settling about an inch since the problem emerged last year.

Supervisor Aaron Peskin, who has conducted a series of City Hall inquisitions trying to figure out who dropped the ball on the building’s design, took to Twitter to voice his exasperation.

“Accelerated sinking continues,” tweeted Peskin, then sarcastically referenced Mayor Ed Lee’s efforts last year to reassure U.S. Senator and former Mayor of San Francisco Dianne Feinstein that the city could manage the building’s woes.

In comments to NBC Peskin compared his hearings (which he vowed to continue) as “yelling into the wind.”"

Link: https://sf.curbed.com/2017/7/19/15998338/millenniu...

RE: SF tower settlement

Clearly the Salesforce building should be modified to take the load then a 'skyway' needs to be built between them.

Keith Cress
kcress - http://www.flaminsystems.com

RE: SF tower settlement

They should have just built it with the flammable cladding. It'd be that much lighter, then when it burned, nobody would care if it was sinking or not- in fact, the more the better in that case.

RE: SF tower settlement

Here is a link to a cross section of the soil conditions commissioned by Transbay Joint Powers Authority TJPA for the neighboring Transbay Center. Link TJPA are a greater bay area, regional authority, so you can imagine the other parties would love for the Transbay Center to be partly/mostly to blame for the Towers settlement & tilt. Considering the circulation of water in & out of SF Bay, the ground section should largely be indicative of what lies beneath the Millennium Tower project. The Tower takes up the block between Fremont St. & Beale St. Horizontally flip the building section below, to overlay the soil cross section in the above link to get an idea what is going on.


The parking garage basement of the Mid-Rise Tower was a 75 foot deep excavation. The garage foundation looks to be sitting on a lens of clay while the Tower foundation is on sand. The High Rise sits on 950 - 60 to 80 foot piles with a 10ft thick pile cap with a 35ft to 50ft deep excavation. Unknown is if the length of the piles is quoted as from original ground, top of the pile cap or from excavation grade.

Here is a link to a paper on the structural design of the tower. It doesn't mention the extensive use of GFRP. Link You can see the GFRP in the connection of the Steel Link Beam; here Link & again here Link

This link from CRSI gives some good details about the overall project. Link The first photo on the page gives a good idea of the concentration of piles under the tower. The 4th photo in the series is the podium/mid-rise basement/parking garage. The basement/parking garage photo is from around Summer 2007 and by this stage the very heavy Tower was topping out. The basement used an integral waterproofing admixture, so there isn't anything to stop water once the cracks grow too large. Here's my best 'eye-ball gestimate' of where the 10ft thick pile cap is in relation to the garage excavation. Since the building is leaning away from the garage, you have to wonder if this is when the tilting started. The tower foundation is supposed to be designed for 14kpsf. Wouldn't this be a vulnerable time for the tower to take on a slip circle tilt? If 7ft diameter concrete piles 200ft deep & anchored in bedrock on the South side of the property aren't preventing a Northern tilt, then how is a 75ft deep concrete box on the East side of the property, possibly built on top of a clay lens, suppose to prevent the building from tipping to the West?



The Tower was completed in 2009 and the Transbay Authority, TJPA began excavating next to the Tower in 2011. Before doing so & exclusive to the Millennium Tower/TJPA property line, TJPA took the preventative measure of drilling 181 7-foot diameter overlapping concrete piles all the way to bedrock at a cost of $58 million. Link The Transbay Center excavation is 65ft deep and runs 4 blocks, including along the South side of the Millennium property, with both the Transbay excavation & Millennium Tower project ending at Beale St. Link According to Millennium Tower's attorney (HOA?), the Transbay site has dewatered 5 million gallons/month for most of its duration & the water table has dropped 20 feet. As the TJPA states, their hole in the ground is the size of 120 3 meter deep Olympic sized swimming pools. Then again thier dewatering is enough to fill over 79 of those pools to date. Still, the HOA at Millennium Tower should be worried when the TJPA finally stops dewatering because those cracks in their basement garage are going to be fountains when the water table is recharged. If the dewatering is affecting the clay maybe the Tower will rise back up when TJPA stops dewatering? bigsmile

The tower had sunk 12 of its 16 inches before the Transbay Center excavated next to the building. Refutation from the TJPA: Link As TJPA sees it, the Tower is just too heavy & sinking into the mud. They are probably right. The Old Bay Mud may be behaving like a pseudo-plastic and yielding gradually, while the garage sits on a (fulcrum) lens of another clay deposit and the pile cap of the tower is squishing the water out of a sand pile.

Maybe I don't understand well enough the nomenclature of Geotechnical Engineering but when I started looking for information on the possibility that disturbed hence less consolidated clay might not produce an elastic response but instead display a prolonged visco-elastic or thixotropic phase; there was very little research. Just bits here and there that the phenomenon does exist in some clay and was noted after the Kobe Quake. That might suggest that resistance piles driven through sand in to dense clay might not be as resistant as planned and that after an earthquake when the clay has experienced liquefaction could, under sufficient load, remain unstable. There is a fair amount of information about clay behavior and high initial shear resistance with some elastic recovery as high as 99% but not all clay has this recovery shear strength. Include the high initial shear resistance with a dramatic loss of shear strength and lesser resistance on recovery & the recovery stage starts looking more and more like thixotropic/visco-elastic behavior and that means deformation under load/creep.

Considering that the City of San Francisco has prior experience with the soils in the area, BART & Muni tunnels & underground stations AND both the City & the Developer knew in advance that the Transbay Center was going to be built, why the developer & why the City didn't determine to build a tower that could stand all on its own is hard to fathom. Seems TJPA was the only party think holistically and to act with anticipation or practice any preventative measures. If I was TJPA, I'd tell the HOA, the Developers & the City of San Francisco that when they have all each spent $58 million, then the TJPA will be willing to discuss what part TJPA will thereafter play. Link

RE: SF tower settlement

Thanks epoxybot...great post. "The first photo on the page gives a good idea of the concentration of piles under the tower. The 4th photo"... they don't mention the type of teaspoon used to place the concrete in photos 3 and 6...

I'm not a highrise expert, only done 30 storeys, but, looking at the soil profile... I wouldn't like to construct anything tall or heavy in that stuff... there may have been a really good reason that everyone else went to bedrock. Also, only done a little seismic stuff and I have no idea of how a building, founded in that 'stuff' would behave during a seismic event...

There are more clever people out there than I would have imagined.

Looks like they terminated the piling before they hit the 'Old Bay Clay'...

Dik

RE: SF tower settlement

As condo owners, are they responsible for maintenance costs? (part of condo fees?) as registered owners... even if they walk away...

Dik

RE: SF tower settlement

dik

One of the arguments that Millennium Partners has issued regarding their liability is that the residents of Millennium Tower, in effect OWN the tower & the tower's problems.

RE: SF tower settlement

I've said it before, and maybe even on this thread. Condominium projects are litigation magnets. And this one is the perfect storm.
  • Condominium. Check
  • Extremely wealthy owners. Check
  • A good portion of them are probably lawyers. Check
  • Owners heavily inve$ted in the project. Double Check
  • And real damages. Check
.

This one will be in the news and courts for many years. There will be quadruple digit replies to this thread before it goes away.

RE: SF tower settlement

Jed... you'd think with all the lawyers that they would be able to 'plot a course' to wind this up... surprised the SEAOC wasn't a little more proactive. I guess no one wants to say anything for fear of it coming back to bite them... Read the ARUP report and thought it was very technical and very well done. A real concern is how this building might lay down in a serious seismic event... and, maybe FEMA will pick up the insurance tab...

Dik

RE: SF tower settlement

Would it be cheaper for everyone to put in re-leveled floors than fix the building? My old house had issues with a door not closing correctly because the ground was shifting. A contractor wanted to fix the foundation, I just adjusted the door hinge.

RE: SF tower settlement

The expectation is that re-leveling will soon be 90 degrees after the building lays down. Not only is the tilt increasing, the tilt rate is increasing. This is not a situation that ends well. Has anyone make a graph of the two factors or has the data been too poorly collected to make a useful prediction?

RE: SF tower settlement

I wonder at what point 90 degrees looks imminent and they begin to de-construct the tower to prevent it...

Dan - Owner
http://www.Hi-TecDesigns.com

RE: SF tower settlement

When do you start bailing your corporation out of the neighboring buildings?

Keith Cress
kcress - http://www.flaminsystems.com

RE: SF tower settlement

... or at least those in the direction of tilt <G>. Is there a site that has a running record of the settlement and tilt and rates of these? You'd think someone would be monitoring this.

Dik

RE: SF tower settlement

Quote (3DDave)

Has anyone make a graph of the two factors or has the data been too poorly collected to make a useful prediction?

Here is a settlement timeline over a period of near 10 years from this source: Link



For combined tilt-settlment data I think ARUP have data dating back to 2009.

RE: SF tower settlement

According to one observation by a geotechnical engineer, sorry I didn't save the link, one problem is that the Transbay Authority, TJPA did too good of a job with their secant pile wall. The wall does too good of a job of resisting earth movement and without similar resistant walls on the North & West sides of the Tower, North & West is where the ground is shifting.
The Transbay Authority didn't just build a wall, they heavily buttressed the wall. This is why Millennium Partners & Millennium residents focus on dewatering, because the wall works. Millennium residents also accuse the Transbay Authority of attempting to hide the shifting but it may be that the TJPA was unaware of the preexisting condition of the Tower's accelerated settlement when they entered into an easement contract with Millennium Partners and were alarmed at what they were seeing from early monitoring results. My guess is TJPA approached Millennium Partners and Millennium Partners wanted to keep the situation private.

RE: SF tower settlement

2
Perhaps the original plan was the tower would be on bedrock by slowly lowering itself thorough the muck, but the asymmetry introduced by the new construction has upset that plan.

What is very surprising is the effect the execution of the easement agreement had on the settling rate.

RE: SF tower settlement

Dave... nearly spilled my coffee...

Dik

RE: SF tower settlement

Another concern is that earthquake can cause liquefaction of the soil which would be catastrophic because the piles do not go all the way to bedrock.

RE: SF tower settlement

Correction: In my post on 25 Aug 17 01:44, I alluded to GFRP rebar in photos for the Millennium Tower reinforcement but after more searching it now seems that Baugrid is produced using smooth steel bar. The smoothness of the bar & the color of the surface corrosion on the bars led me to believe I was seeing GFRP.

Attached is a copy of the July 2017, City of San Francisco Safety Review of the Millennium Tower Link

The report is the City of San Francisco's interpretation of the 2016 Structural Review with requested follow up analysis performed by Simpson Gumpertz & Heger on behalf of Millennium Partners and is seen by some as a walk back from SGH's 2014 review that concluded 8 of the Outrigger Columns (upper floors) would be over stressed during an earthquake. The 2014 report was seen by some engineers as a sign the building could be "Red Tagged" after a major quake. Link In the City's July 2017 review the focus is on the Outrigger Coupling Beams.

The City of San Francisco vis-a-vis the SF Dept. of Building Inspection, SFDBI has two strikes against it in this affair.
Firstly, the City had previously halted work on a project of almost identical design, 50+ story, concrete building with friction piles (geo-tech by Treadwell & Rollo) at 80 Natoma, citing 'new information' that it was too heavy and sink too much. 80 Natoma was a property directly over the favored path of the CalTrain underground extension to the planned Transbay Center transportation hub. If the tower was built it would be impossible to come back later and tunnel under such a heavy building resting on friction piles. The developer refused to sink piles to bedrock citing delays would compromise project funding. The site was eventually purchased via Eminent Domain for between $58 & $90 million. More than a little speculation circulated that the whole project was always a shakedown.
Secondly, the City's failure to look into the accelerated sinking of Millennium Tower, AFTER they had initiated inquiry & subsequently approved the structure for occupation (sale of condos).

The City of San Francisco & Millennium Partners have a common interest in dissociating themselves from blame. Both Millenium Partners & SFDBI claim there was no requirement for the developer or the Peer Review panel to consider the Transbay Project next door. Link That seems to be in conflict with the Mission Street Development LLC (Millennium Partners) 301 Mission Street - Environmental Impact Report that cited the adjacent proposed Transbay Center project Link and SFDBI's actions at 80 Natoma.

RE: SF tower settlement

All is well... at this time. From the report, "To an extent consistent with the scope of our review, our professional opinion is that the foundation settlement experienced by the Tower has not appreciatively affected the safety of the building at this time."

Sounds great, and at an inch per year, who knows... settled 18" so far.

Dik

RE: SF tower settlement

Quote (report)

Further, the review is
limited to evaluation of the current condition of the Tower and does not address the effects of
future settlement or other changes that may occur to the Tower in the future.

All was well July 28th; July 29th is out of scope. Does the report contain any useful information?

RE: SF tower settlement

stevenal... nothing of substance... nothing to give you a warm fuzzy feeling...

Dik

RE: SF tower settlement

That ought to increase the value of those condos.

RE: SF tower settlement

Description of the shoring work for the Millennium Tower & adjacent 5 level parking structure basement. Webcor Builders: The garage is an internally braced soil cement slurry wall system with soldier piles 5’ OC and the High Rise foundation is a soil cement slurry wall system with soldier piles 5’ OC with a few rakers and the balance of the hole supported with a single row of tiebacks. Both of these perimeter wall systems are augured 3’ diameter overlapping holes creating a continuous wall.

Early into the pile driving - Photo (A): Link
Looks like pile driving started in the Northwest corner of the lot: Photo (B): Link
Pile driving complete Photo (C): Link
ARUP's illustration of the relationship of the Transbay Center excavation & Millennium Tower Photo (D): Link
Photo of full excavation next to Millennium Tower - Link

In photo (B) note the high concentration of soldier piles on the left side of the photo. In photo (C) the soldier pile are capped with a steel beam & rakers tie to a stepped perimeter wall. What is different about this section of the shoring?

In this Old Tranbay Terminal demolition phase photo you can see that ground water is somewhere around 7 to 12 feet below grade. Millennium Tower is to the right in the photo. The area was used for staging for most of the Transbay Center project. Soil stabilizing fabric was laid & a waste slab poured.


RE: SF tower settlement

On Tuesday, October 3rd, 2017, UC Berkeley professor, Abolhassan ASTANEH-ASL, gave an Ethics Seminar: "Did the Unethical Conduct of Engineers and Academics Contribute to the Tilting and Sinking of the Millennium Tower?"

The seminar was a live webcast, however it was recorded and is available for public viewing here:

https://drive.google.com/file/d/0B6Cv_TTKSlYiMWdZS...

I have yet to view the presentation.

RE: SF tower settlement

Really good article... I don't envy the position Abolhassan has taken... but, I think he's correct. At Harvard, he'd have been turfed.

Dik

RE: SF tower settlement

(OP)
Maybe there is some validity in some of his opinions, but he is a blowhard. Although he promised to limit his discussion of the WTC, he spent more than half the time talking about it. Then his only conclusion about the Millennium Tower was that the piles are too short. We all know that already. Ethics? He stated he doesn't know about geotechnical issues, but then proceeds to comment on the piling.

Maybe it is just his accent, but some of his terminology is not that of a structural engineer.

He speaks about conflict of interest. I think at this point, anybody from UC Berkeley is conflicted.

RE: SF tower settlement

Blowhard or diehard or whatever, he raises some very good points for both the WTC and Millenium... call him Don Quixote... He likely feels 'slighted' and the presentation was his vindication. I've never seen a 'flat plate' with an 11" slab... contributes to the mass and rate of settlement...

With the WTC, there was an excellent thread on Eng-tips that disappeared... don't know if the webmeister was asked to remove it and 'turn it over' or what... it was just gone. A lot of what was discussed on the presentation was there... I didn't realise that a permit was not required and that stuff was 'approved on the fly' by those with a vested interest.

I'm not a geotekkie, and unlike Moehle, I would not have signed off on the foundations... The foundations would have been my first concern. My first posting on this thread ended with, "I don't know if the sand is saturated, but, there could also be problems during a seismic event..." and, is still a concern, and very likely the mode of failure, and, maybe after the first floor is at grade. I'm surprised that the SEAOC has not done a study... if a potential life safety issue, then they are 'obligated' to look into it...

Dik

RE: SF tower settlement

(OP)
11", and thicker, flat plates are common in my environment. That's what our builders and developers want. Simple, it is. He called it a flat slab, one example of my reference to terminology.

He said more than once that there was "no structure" in the WTC, and no columns. Rubbish. And I would take the "no permit" thing with a grain of salt.

Anyone with that many pictures of "my projects", bridges and buildings, is a horn blower.

RE: SF tower settlement

A flat slab in these environs is one with drop panels or slab bands or a mix...

As to codes... I don't know, except, that I have never heard a prior reference to design requirements, and never considered that there were no permits if that's the case.

Whatever the issues, there are/were serious oversights made with both structures... not common, in these environs, to design for 747 767 loading... I thought and still do that using trusses from a core to an outside 'tube' structure was a neat way to do tall buildings... Light weight and using the outside 'skin', about as stiff as you could make it.

Dik

RE: SF tower settlement

(OP)
Yes, that is my definition as well. I think the floors of Millennium are flat plates, but he called them flat slabs. I saw a report this morning about the Mexico City earthquake, where some California engineer reckons that flat slabs should be outlawed in seismic areas. I would agree, if there are not cores or shear walls, but the statement was misleading.

Disagree about the trusses, if you mean bar joists. They didn't adequately connect the exterior tube to the core, and that is a big reason for the collapse.

RE: SF tower settlement

They can be adequately connected... bar joists may be the correct term (more likely) depending on how they are fabbed... My only reservation about bar joists is that they have a large surface area for fire resistance protection... on impact (like a plane), the fire proofing can be 'knocked off' leaving little or no protection. Prior to the 'attack' I thought the approach was real 'neat'. I still think it can be workable... my tallest building is less than 1/4 the number of storeys of the WTC... and, not what I would call a tall building...

Dik

RE: SF tower settlement

Hell hath no fury like a woman professor scorned

RE: SF tower settlement

Hokie66:
"where some California engineer reckons that flat slabs should be outlawed in seismic areas. I would agree" Can you elaborate? I would think that the reduction in mass would be beneficial.

Diiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiik

RE: SF tower settlement

(OP)
I think the issue is the use of flat plates supported only by columns, with no other lateral system. But just to say flat slabs should be outlawed is ridiculoua. The old flat slab has a place in our tool kit.

RE: SF tower settlement

This is diverging the discussion a bit.. but this dude's assertion is that WTC building failures were due to unethical or, at best, ethically ambiguous behavior by its engineers? Really?

RE: SF tower settlement

jgKRI: The part I got from his presentation was that there were some questionable decisions made with any peer review... and, if his information is correct, then I concur with some of his criticisms.

Dik

RE: SF tower settlement

Sorry I got carried away...,
Professors, particularly at upper crust universities blow the horn loudly because it is a pretty cut throat environment despite their use of reserved social graces. If you are not publishing, consulting, designing or patenting, then you had better be stealing the ideas of you grad students or you are not going to stick around long. Unless of course you have a visiting professor gig and then you can go on sabbatical out of the country, while the students pay tuition for your salary & the house the University paid for, which sits vacant for a year - (This really happens).

Seems professor, Abolhassan ASTANEH was hired for about a week by some of the condo owners, before he made this presentation. It really doesn't matter if the professor can generate ground motion modeling to prove that the building is not as safe as De Simone designed and SG&H have asserted. It is safe according to the design criteria supplied by the 1997 UBC and made law at State, County & City levels and was in effect when the permit was issued. Prof. Jack Moehle is not the Engineer of Record so his PEER review is just that, a review, not a absolute declaration. Still he is talking out of both sides of his mouth. The STRUCTURAL ENGINEERS ASSOCIATION OF NORTHERN CALIFORNIA 2015 SEAONC "Guidelines for the Use of Geotechnical Reports" Link , both supports his initially stated position regarding his qualification, "that he looked no further than the tower foundation" & it doesn't. I think he is one of many, who were very excited at building a tall "poured-in-place concrete" building in SF Downtown. You gotta have something to blow the horn about at UC Berkeley. While SFDBI / SEAONC /PEER were working on the Tall Building Initiative & SFDBI AB-032 before the Millennium Tower, they look to have redoubled their efforts since and were possibly racing to close the door after the horse had already left the barn, as in, before the sinking became public.

I feel for the condo owners, they may have hired good litigation attorneys but they are lost when it comes to making relevant arguments concerning the defects of the tower and their attorneys don't seem to know what is a good plan of attack either. The design requirement for a maximum considered earthquake is that the building not fall down and people are able to safely exit the building. It could subsequently be red-tagged but as long as it protected life & limb, then mission accomplished. So coming up with ground motion simulations that are not embodied in the UBC are irrelevant. It is not the Structural or Seismic or Wind design of the BUILDING, that needs scrutiny, it is not the building at all. It is the shoring & bracing, the group depth of the pilings, the effect of the pressure bulb from the pile group on the soil beneath & around the piles, the method the piles were driven & order of placement, if the sides of the foundation were included in the resistance calculations, the soil characterization used in the geotechnical reports, the geotechnical calculations and which UBC piling loading criteria was chosen, the excavation & dewatering of the parking structure/basement, the sequence of building a heavy tower and then starting to dig a very deep excavation immediately adjacent to the tower when the foundation was already exhibiting rapid settlement even before they began the excavating. Maybe they should have started with the parking structure basement & later the tower. Too much deflection of the West podium basement shoring wall would have been bad for friction/resistance bearing piles, the same for too much dewatering. These are all the vulnerabilities that relate to the sinking & tilting. These 2 photos, taken on the same day 8/19/2007, give an idea as to the dichotomy of the tower and adjacent basement structure's progress. By this time the tower had settled 3 inches. I think there were 23 floors on the tower when the podium basement excavation began.





Treadwell & Rollo only gave a 50/50 endorsement of their own settlement predictions. With a confidence level like that, how is any foundation consider NOT a performance design, regardless of UBC design criteria? You really have to wonder if SFDBI is out of it's depth and just looking for a CYA engineer's stamp when it comes to shoring, piling & foundations. They don't seem to have in place the same internal structure for foundation review that large cities on the East Coast have in place.

Clearly prudence was exercised concerning the effect of weight of the building and ground pressure on the adjacent basement shoring by the General Contractor, Webcor Builders. Before they began excavation of the parking structure basement they bolted heavy steel strongbacks to the footing of Millennium Tower & then welded them to the solider pile/CDSM shoring to support the upper reach of the Westward diaphragm wall. It does appear that they used used tie-backs lower down on the shoring wall. Blue Dots in photo: Link The piling contractor augured each pile 40 feet from a working elevation of about 10 to 15 feet below grade, so there wasn't a lot of upper pile confinement generated from the pile driving. Since it appears that pile driving started on the North side of the foundation, this would be where the piles with the least confinement & lesser capacity would be located. It just seems that with less skin friction due to auguring that the potential for shorter piles to heave is greater once remaining and/or deeper piles are driven & reach the deeper soil that was undisturbed by the augur. The piles range from 61 feet to 90 feet according to SFDBI Raymond Lui. So perhaps only around 20 to 50 feet of that is below the mat foundation. If you look at the cross section illustration De Simone used for a SEAONC presentation of the project, the scale of the piles beneath the tower is more on the order of 150 feet deep, when they should be just a bit deeper than the podium basement foundation.

The 2003 Final Environmental Impact Report, Page 247 Link included an acknowledgment that dewatering was a concern on this project for which the the City of SF was empowered to enforce a requirement for ground settlement monitoring, special inspections & even a halt to the work if settlement was beyond anticipated values. So when the SFDBI testified that they had no way to compel the developer to include a geotechnical engineer to be part of the PEER review, they are not being completely honest. The dewatering/ground settlement monitoring - special inspections could have compelled the developer. It seems SFDBI passed on this Special Inspection, otherwise they would have (?should have?) known a month after the tower foundation was poured that the structure was on the move and long before the podium basement excavation commenced. To later sign off on an occupancy permit, having failed to implement a monitoring scheme or failing to "INSPECT" the special inspectors reporting is just seems like double negligence. Perhaps too much myopia from staring at plans all day?

SFDBI is also not being truthful when they say they had no cause to consider the Transbay Center project during plan review. It was acknowledged in the 301 Mission Street EIR, page 159 Link and the final design was a hybrid of Alternative E-1 of the EIR, which itself was the result of conversations the developer's design team had had with the TJPA about the Transbays Center, over an anticipated 5 foot encroachment on to the southern Millennium project property line. Why even have an EIR if the Building Dept. Plan Review section isn't going to use it to carry forth the City's expectations? The global lack of recollection by the SFDBI is also questionable. There is a close knit Major Projects Permits/Plan Review unit to handle tall buildings. According to SFDBI Quarterly & Annual Reports there were then only 3 to 4 tall building under construction & about 7 in various stages of plan review. Finally, SFDBI has an internal peer panel "Permit Coordination Division", to assess the department's own compliance of permits. SFDBI 2004-2005 Annual Report, page 39 Link

At the time of the 2003 Final EIR the tower was likely a steel frame structure and the building elevation cross-section showed 3 floors of parking under the tower & 3 under the podium. Page 157 Link So the tower foundation & the podium foundation were both of equal depth but neither as deep as the 5 floors of parking now under the podium. So this much deeper excavation should have spurred the SFDBI to be more attentive to dewatering & the tower foundation. Steel tripled in price over a years time and then too SF was desperate to keep major developments within the Transbay redevelopment area on track. They needed kick-starter projects to generate developer interest for the later sale of Transbay properties to fund the Transbay Center. Include that during testimony on 80 Natoma the SFDBI somewhat bemoaned the lengthy PEER review process of performance designed buildings before the SF Building Inspection Commission and the stage was set for another 80 Natoma-like concrete high-rise but of a prescriptive design, that would sail through the Plan Review dept with a degree of deference. You even have to consider that some bias may have occurred, at the excitement & prowess over the daring feat of building a tall "concrete" tower in earthquake country. The real failure is that, search as I might, I can't find that SFDBI has even one geotechnical engineer on SFDBI permanent staff. Seems they are only hired on PEER review panels or short term contracts. It also seems like any time pointed questions about SFDBI & geotechnial reviews are asked, they habitually give indirect answers that never touch upon the gist of the question. The SFDBI responses in the minutes of this August 30, 2004 Building Inspection Commission meeting regarding 80 Natoma are practically boilerplate in resemblance to their ambiguity over 301 Mission Street. Link All the while the Millennium Project is under permit review. SFDBI 2004-2005 Annual Report, Page 35 Link

This is where Jack Moehle really is not helping. When he told SF Supervisor Peskin that he was asked to right a project close out letter for 80 Natoma and that he was instructed to leave out the nature of the SFDBI Stop Work Order investigation over 80 Natoma regarding geotechnical reports that claimed the project would sink, certain things fell into place. Treadwell & Rollo had gotten in the last word, where they challenged the data used for opposing their own geotechnical report & the design. With no resolution to the reason for the Stop Work Order & a letter from the developer's design team reporting the property under purchase & the 800 Natoma project abandoned, there wasn't any precedent for the SFDBI to apply prior work as a measure of discrimination. While Jack Moehle may not recall off the top of his head, what discussions took place regarding the desired composition of the letter or who participated in the selective content, I'd be surprised if he doesn't have it all in one of many black & white marbled composition books filling a number of drawers of one of his filing cabinets. This is where the real ethics questions begin and they all point to the City of San Francisco, the Developer, the design team & the PEER Review panel, TJPA is way off in the distance. Although it would be interesting to see ARUP's projected dewatering gradient map for the surrounding area. The attorney for the larger body of condo owners going after TJPA loves to scream bloody murder about TJPA dewatering but the siltation tanks he harps about on the TJPA site south of the Millennium property were for the entire TJPA dig. There is an 8 inch diameter "common" pipe running atop the TJPA shoring the entire length of the project feeding those tanks. They don't represent the West excavation dewatering by TJPA at all. It was the last dig and the tanks were removed/moved.

So far SF Supervisor Peskin has wasted a year on Structural Safety when the building code already gives assurances that in it's current state the tower is still well within design & safe. When SG&H reports on the structural integrity of the pilings & foundation, they are speaking of the seismic safety performance. The report has nothing to do with dispelling the fact that in the tower's "semi-static" state of rest on the ground, it is sinking & tilting. That is beyond the scope of their report. It is time for the Structural guys to step aside & have the Geotech guys do their song & dance. Seems like it is the developer, Millennium Partners that wants to keep everyone focused on the building instead of what is under it. Same as during the permitting. Typical realtor behavior, "don't look at the crack over the doorway, look at these new countertops & tile". Millennium Partners seems to keep pushing the "Building is Safe" message to perhaps escape the grasp of the California Real Estate Disclosure Law, which the condo owners need to push, as akin to the "Calif Automobile Lemon Law" (Song-Beverly Consumer Warranty Act). The fact is that Millennium Partners was selling something "as New" that was in fact highly likely to need remedial work performed to such an extent that the building is a Lemon. The question is whether SFDBI's issuance of an occupancy permit endorses the "as New" representation & nullifies the real estate disclosure law. The only thing that is certain is that SFDBI is too busy demonstrating the complexity of their bureaucratic cognitive dissonance to know one way or the other.

RE: SF tower settlement

You didn't get carried away... to paraphrase your effort, "It's a mess and no one is moving forward at fixing it." I guess it's a problem with self-regulating agencies, that unless someone files a complaint, they have no reason to undertake an investigation of their own. Thanks for the excellent 'write up'.

Dik

RE: SF tower settlement

(OP)
Great post, epoxybot. If only some of those professors at UC Berkeley had the same ability to sort through the chaff and get to the real issues.

I suppose the City has its hands full protecting criminal immigrants, and doesn't have time for mundane issues like buildings tilting.

RE: SF tower settlement

If these people still live here,in San Francisco, the tenets on this highrise should be able to manage.

RE: SF tower settlement

San Franciscans have reason not to have a lot of confidence in their building officials. The owner of this property & the manager of the company doing the work was a former President of the SF Building Inspection Commission & the EOR was also a former BIC President.

MAYOR NEWSOM AND SUPERVISOR PESKIN ANNOUNCE APPOINTMENTS TO DEPARTMENT OF BUILDING INSPECTION COMMISSION
Link

S.F. home in Twin Peaks collapses during disputed expansion
http://www.sfgate.com/bayarea/article/S-F-home-in-...

Link

Investigation and Mitigation Report on Incident Occurring at 125 CROWN TERRACE
http://sfdbi.org/sites/default/files/125%20Crown%2...



RE: SF tower settlement

So here Link is a Press Release from the Office of the City Administrator for San Francisco. The press release lists the members of Mayor Lee's "301 Mission Seismic Safety Study Committee", to some extent the committee was formed at the suggestion of Sen. Dianne Feinstein. The 301 Mission Seismic Safety Study Committee is the group that selected the "Expert Panel" to review the 301 Mission Seismic Safety Structural Evaluation performed by Ron Hamburger of Simpson Gumpertz & Heger. Working at the behest of Mayor Ed Lee are, City Administrator Naomi Kelly, an attorney - Department of Building Inspection, Director Tom Hui - Executive Director of the Department of Emergency Management, Anne Kronenberg, and San Francisco Public Utilities Commission Assistant General Manager of Infrastructure, Kathy How. The reason the Executive Director of the San Francisco Public Utilities Commission isn't on the Committee is probably because he is the husband of City Administrator Naomi Kelly.

The "Expert Panel" is in many respects a Mulligan, a do-over, if you will for a full 3 member PEER review of the structural integrity of 301 Mission St. One would expect that, the City of San Francisco being under the microscope would steer well clear of even a hint of Conflict of Interest. More especially, those who formed the Expert Panel but you will have to decide for yourself. What caught my eye after having looked at many documents was panelist: Craig Shields, President at Rockridge Geotechnical. Craig Shields, opened shop in 2006 after leaving TREADWELL & ROLLO where he had worked since 1989, virtually from T&R's inception. Before that he worked with Frank Rollo Sr. at Harding Lawson Associates. Link

You really have to wonder what Mayor Ed Lee was thinking.

RE: SF tower settlement

epoxybot... is prostitution legal in California? Just curious... I read through the letter, it was crafted a couple of months back... and it doesn't appear that there is an independent geotechnical consultant in the cluster (or whatever you call a bunch of ladies of the night... a flock, perhaps <G>)... My biggest concern with the project is how it would behave during a significant seismic event based on the founding soils. I guess, time will tell... California is due for a good one...

Just read the last link... there was a geotekkie, but not an independent one... and part of the party...

Dik

RE: SF tower settlement

I have no idea if it matters or not but the SF Millennium Tower not only sits on top of the old historical Yerba Buena Cove shoreline but it is perched on the edge of stream bed. This Link early illustration of Yerba Buena Cove suggests there was a creek flowing into the southerly end of the cove and this bedrock elevation map Link from the "Final report, geotechnical site investigation : CalTrain S.F. downtown station relocation EIS/EIR project" Link would seem to confirm that the stream/creek flowed along the northern property line. It's possible the lower part of Mission Street was the creek bed and was used as a trash ditch by early settlers. Here is a larger version of the idealized ground profile from an earlier post & the plot for the bore holes. Link Link
Does the geotextile seen in the photo I posted on Oct 2nd represent the tumbled shoreline of Yerba Buena Cove?

1840's San Francisco was a lumpy place of sand dunes.
If you are interested here is a video (1+ hrs) Link about how the dunes were moved about and how it affects buildings in SF.
Creeks would travel under the sand occasionally breaking the surface. If the early illustration is to be given any credence, the creek was capable of sufficient water volume to transport heavier sediment/sand far enough to create a sand bar at its mouth. Arguably, the creek is still there. This 1853 map Link seems to indicate that the location just opposite of the present day Millennium Tower was in a state of being filled in but in 1857 the site of the Millennium Tower was impounded. Link It seems San Francisco's early land speculators sometimes had problems filling in the marshes and parts of the bay. They would haul sand & build it up to elevation, send for the city's building official, only to come back the next day and see that all their work had subsided below the waterline.

Today, just across the other side of the Transbay Center is the 181 Fremont St. Tower. The geotechnical & foundation design are the work of ARUP and their reasoning for the foundation design recommendation is worth contemplating. Link The TJPA installed CDSM shoring that penetrated the Old Bay Clay by 10 to 20 feet. It was supposed to prevent a dramatic drop in the water table outside the excavation. When BART was built, they did things differently, recharging the ground outside their excavation to maintain the water table.

Finally, here is a link to all the SF Government Audit and Oversight Committee - Building Standards in Seismic Safety Zones hearings PLUS the records. Including the Oct. 18th testimony of De Simones Structural Engineer of Record, Derrick Roorda. Roorda came across as a decent guy but he was a bit gratuitous to Treadwell & Rollo on the rate of the buildings sinking. The actual SG&H 2017 report, and Treadwell Rollo's original geotechnical report, idealized ground profile & pile driving plot. Link Item 16. Comm Pkt 101817 - LARGE FILE is the sum of all the preceding item numbers and the contents list at the beginning of the pdf is conveniently hot-linked for browsing. De Simone provides a more detailed view of the settling rates but they also play politics ascribing the "commencement" of TJPA construction activity as playing a role when the only work being done was demoltion, site work, CDSM shore wall placement & the buttress wall. It would be a year later that actual excavation took place. Much like all the players who ignore the original settlement forecast and refer to the latter as though the original is a of no consequence. Coincidentally, Treadwell & Rollo were the on sight Environmental Soils firm working for TJPA while the shoring & buttress wall were being built.

During the SF Government Audit and Oversight Committee - Building Standards in Seismic Safety Zones hearings, Supervisor Aaron Peskin has asked almost every group of witnesses about some mythical letter from InSituTech. No one has indicated that they have any recollection of the letter. Unfortunately, it doesn't seem to be part of the records, to date. InSituTech was a small geotechnical consultancy in Orinda, CA, about 40 minutes from SF & run by D Michael Holloway, PhD. He went to work for Dan Brown Associates as a field consultant for the TJPA buttress wall. He has an interesting resume, you can view it on his LinkedIn profile. He has spent most of his career as a piling consultant in the field. Link It would be great to know what he may have observed & what he wrote to the DBI. Supervisor Peskin plans to hear testimony from former Treadwell & Rollo people. He mentioned Frank Rollo but it is Christopher A. Ridley of the present Rollo & Ridley who was the Millennium Tower Geotechnical Project Manager. Link I'd rather hear from D Michael Holloway. Records show the building weighs 220,000 kips, sadly Peskin did not ask what was included in that figure. After looking at the piling plot, the pile driving did start in the Northwest corner of the lot and between the plot & a photo from an earlier post, the piles concentrated around the core appear to be less than 3 pile dia. apart. Link

RE: SF tower settlement

"The geotechnical & foundation design are the work of ARUP and their reasoning for the foundation design recommendation is worth contemplating. Link"
In that link, I find a statement that:
"an equivalent top down load of 14,000 kips was applied by Loadtest."
Now, that makes me curious just how you go about doing that...

RE: SF tower settlement

JStephen (Mechanical)
"Using three 24-inch O-cells on a single plane, an equivalent top down load of 14,000 kips was applied by Loadtest."
Here is a link to the O-Cells Link
Here is Loadtest's write up of 181 Fremont. Link

RE: SF tower settlement

Okay, here's a "How they do it" paper: http://www.loadtest.com/media/Osterberg%20Method.p...
Short answer: They're putting a hydraulic cylinder at the bottom of the shaft and jacking using end bearing on the bottom versus skin friction on the sides to hold it in place. So it doesn't involve putting umpty thousand tons on top of the pile. Also, in one of those links, they did show a "load frame" that was presumably for that purpose, but it was 2,500 tons.

RE: SF tower settlement

Is there a correlation between the Shear Wave Velocity and the seismic sensitivity of a building site. For example, if there is a marked decrease in shear wave velocity does that mean the amplitude increases?

What is the significance in the shear wave velocity?

Dik

RE: SF tower settlement

epoxybot... when I see a pile of piles like those shown in the photo... the term cluster comes to mind... <G>

Dik

RE: SF tower settlement

dik (Structural)
Here is a basic explanation of seismic waves. There are two types, body waves & surface waves. Surface waves are slower, have greater amplitude, travel farther & destructive capacity. Link

When I was looking at the Dames & Moore idealized soil cross section Link , I wondered if the profile of the "Upper Sands with Clay Lenses" was the result of a past earthquake and that possibly the "Loose to Medium Dense Silty Clayey Sand" lens at bole hole F503 was a sand boil from the quake. The sand profile looks a great deal like a surface type, slow moving "Love Wave". So an earthquake wave trap in motion in the sand.

RE: SF tower settlement

Thanks... Dik

RE: SF tower settlement

Thanks for the article... a bit of a refresher on S, P, Love and Raleigh waves. On the one chart there appears to be fairly abrupt transitions with the Shear Wave Velocity and the various soil types. Do these transitions have an impact on the seismic design forces or are they just a feature of the soil properties/densities?

Dik

RE: SF tower settlement

Sorry Dik, that is beyond my accumulated knowledge.

RE: SF tower settlement

epoxybot: Same here... thanks. The original seismic reference was excellent... good work.

Dik

RE: SF tower settlement

CBS 60 Minutes will be doing a story on the Millennium Tower on Sunday, Nov. 5 at 7:30 p.m. ET and 7 p.m. PT Link

Preview: Jerry Dodson takes 60 Minutes for a stroll in the basement. Something the CBS 60 Minutes preview shows that the can't be observed in previous photos of the crack gauges, is a difference in plane from one side of the crack to the other.

RE: SF tower settlement

(OP)
Those buildings in Brasil are scary, as are lots in Europe. Amsterdam, Delft, Bologna are some of the best examples of cities with leaning buildings.

RE: SF tower settlement

I wonder if the city has a charter and that it may be a requirement that they look after items of this nature? Maybe they are in default of their charter?

Dik

RE: SF tower settlement

Yeah, saw the 60 Minutes story last night. One thing that jumped out at me was the claim that the settlement was due to the piles not going to bedrock. But if they had adequate capacity without going that deep.......why should they?

Scariest moment to me (in the 60 Minutes story): the attorney get together. So many of them, it takes (IIRC) 30 minutes to get down everyone's name.

RE: SF tower settlement

(OP)
WARose,
As in all other structural elements, the capacity of piles is not the full story. Serviceability, as in deflection and settlement, can't be ignored.

RE: SF tower settlement

Quote:

As in all other structural elements, the capacity of piles is not the full story. Serviceability, as in deflection and settlement, can't be ignored.

True. But I doubt the SE ignored that. In fact, they had a settlement estimate that the building was supposed to see over a 100 year period. (4" if memory serves.) To be sure they considered that level of P-Delta. (In the wind or seismic cases at least.)

Nobody is really owning up to it (as per the story on 60 Minutes).....but my gut instinct is the piles are in a strata that isn't what they anticipated.

RE: SF tower settlement

I thought the "60 Minutes" was pretty good, although I don't know what the point of the Danish guy on there was. He could tell from satellite images that the towers were settling? Or you could look in the buildings.
Way back in this thread, I linked to the Ocean Tower in South Padre Island, TX. The piles carried the load to compressible materials and they compressed. This is sounding more and more like that.

RE: SF tower settlement

(OP)
Jed, the major differences being that the Texas building had not been sold or occupied, and was not in the middle of a big city. So big difference in dollars. Same structural/geotechnical issue.

RE: SF tower settlement

If you want to take a close look at what SF Supervisor Peskin has accumulated you can download all 93mb here. Link

Here is an table of contents.

RE: SF tower settlement

There may be a fix in the works for San Francisco's very own "leaning tower."

Millennium Tower has sunk 17 inches and tilted 14 inches since its completion in 2008. Satellite images suggest the residential high-rise — home to more than 200 multimillion-dollar condos — will continue to sink two inches per year.

link: http://www.businessinsider.com/cost-to-fix-leaning...

RE: SF tower settlement

So now the curtain wall is presumed to be suffering from differential settlement. I watched an earlier video of the San Francisco Government Audit and Oversight Committee 10/28/2016 where Supervisor Peskin discussed with San Francisco Dept of Building Inspection (SFDBI), the differences in the two versions of the Simpson Gumpertz & Heger "301 Mission Seismic Evaluation" It seems the 2014 version which has not been made public, implied the mat foundation had already cracked from dishing. You can't see the cracks because they haven't migrated from the bottom of the mat to the surface YET. Simpson Gumpertz & Heger removed this line of inquiry from the more recent 2016 seismic report. I don't have the exact words but they divorce themselves from any comment regarding the health of the concrete foundation. Supervisor Peskin described the newer report as "Lawyered Up". The Director of SFDBI had written to Ron Hamberger at Simpson Gumpertz & Heger and asked for more detailed information about the dishing of the 10 foot mat. He was concerned that the greatest degree of dishing was under the northwest super-column at the edge of the foundation. The super-columns tie in to the outriggers off the shear walls in the core. The dishing migrates from the super-column back towards the north 3rd of the core. This was all in October of last year. If I had to guess, the curtain wall is starting to fail at about the northwest super-column. The curtain wall separation is compromising the Fire compartmentalization between units.

https://www.nbcbayarea.com/news/local/Gaps-in-Wall...

RE: SF tower settlement

This is a major building failure that will only get worse... needed a remedy a while back.

Dik

RE: SF tower settlement

"
San Francisco city building inspectors have issued a citation against a tilting 58-story residential tower for an apparent fire safety risk.

KNTV of San Jose reports the Department of Building Inspection issued the violation notice last month for the Millennium Tower after consultants found the tilting building was exacerbating gaps between the facade its concrete and steel core.

Experts say smoke and flames can shoot through such gaps, making it easier for a fire to jump to a higher floor.

The fire safety hazard warning was part of a December 2016 report commissioned by the Millennium Homeowners Association after a condo owner complained of a mysterious odour.

City officials issued the notice a week after the TV station reported on the warning."

Link: https://www.ctvnews.ca/world/leaning-tower-of-san-...

RE: SF tower settlement

Test Drilling Launched at the Sinking Millennium Tower Link

There has yet to be any disclosure by Millennium Partners, DeSimone, Treadwell & Rollo or Webcor Builders as to why the building is sinking & tilting. I have been through the information the SF Government Audit and Oversight Committee has on their site & I guarantee you that they are not being as forthcoming, as they could be. Even the SG&H 2017 "Supplement" commissioned by the SF Mayor's Office - 301 Mission Seismic Safety Committee is flawed. For starters the bore hole used to characterize all the piles isn't even under the tower. It is 25 feet to the east of the tower under the podium. Why not use any of the 5 bore holes that are under the tower? Other than that they pass through more clay and less sand at inappropriate elevations.

Spending millions of dollars on an exploratory remedial program when you have yet to fully examine the cause is imprudent. To what extent the HOA is being led down this road by Millennium Partners or other parties is a mystery. If it is a judge who is urging the homeowners to work towards a remedy at the expense of knowing all the facts, then that is unfortunate. I can guarantee you Millennium Partners, DeSimone or Treadwell & Rollo or Webcor Builders all know why the building is tilting & rotating.

SFDBI is no innocent party either. We have all seen the photos of the cracks & crack gauges in the basement. So on Tuesday February 9 2009 SFDBI's Deputy Director Raymond Lui writes to DeSimone regarding excessive Settlement of the Tower. On February 11 & 12 (Thurs & Fri) SFDBI Field Inspector for Major Projects, District 1: Yuang-Tam Chiu makes site verification inspections at 301 Mission. Yet SFDBI Tom Hui & Ron Tom have stated in testimony before the SF Government Audit and Oversight Committee that everything looked fine and no signs of settling were observed. But all the cracks were there! From 24 to 29 April 2009 ARUP installs 103 crack monitoring gauges in just the basement of Millennium Tower, only 79 Days since SFDBI's Ray Lui wrote Settlement Inquiry Letter. On 11 August & 19 August 2009 SFDBI Field Inspector Yuang-Tam Chiu does a Pre-Final & Final Inspection at 301 Mission. There are Crack Gauges! Crack Gauges Everywhere!. 156 days since the TOC was issued. 103 crack gauges are visible along the walls of the Tower Basement Level B-1. Mostly clustered on the North & South ends of the building. Not one request to see any surveyor data or reports. Final Inspection Approved.

If the Mat foundation is already cracked as Ron Hamburger at SG&H speculated in 2014, then where do they begin installing piles, since coring large diameter holes in the mat "could" make matters worse? The HOA should at least do some Pulse-Echo Testing of the foundation before they get too far into the piling scheme. Having to position & re-position equipment in a basement in order to satisfy a charted installation designed to prevent additional damage to the mat could greatly increase the time & expense. Has Millennium even told them that corrosion control is going to be needed long-term? The ground water is brackish. It isn't particularly expensive but it is a consequence of cracking in the foundation.

RE: SF tower settlement

5
Just to get started, the Millennium Tower is not built on top of fill that is at risk of liquefaction. The basement penetrates the fill.

It looks like The Millennium Tower HOA is moving forward with an objective to stabilized the Millennium Tower. LERA & Swinerton Builders are the team overseeing the work. Documents on file for 301 Mission at the SF Planning Dept. website show they will be coring possibly two penetrations through the 10 foot mat foundation at the north end of the tower, approx mid tower.

They will also be opening up the the wall of the parking structure at parking level 2, cutting two 3 ft by 3 ft openings, in order to determine if the tower has come to rest on the soldier piles of the CDSM shoring wall between the tower & the podium structure. In Treadwell & Rollo's 2005 Geotechnical Report, T&R had recommended that since the CDSM shoring wall was to be directly beneath the mat foundation, the shoring wall should be at least 12 inches below the mat, to avoid interference.

The tower may or may not be resting on the shoring wall. If it is, that will at least give engineers something to think about but if it is not, then they will have to consider the consequences and how much time they have before it does and matters become more critical. The soldier piles were about 1 foot higher than the CDSM shoring. In hindsight one would think the developer's team ought to have given thought to cutting the soldier piles down, since Treadwell & Rollo's second estimate for additional settlement of the tower was still a large number AND they knew or should have, well before the last level of the parking structure was poured, that shoring wall interference could be a factor. As soon as the last struts of the podium were removed the tower settlement accelerated. The building was sinking at 0.020 inches a day.



Apart from the Millennium Tower being, at one time, the tallest, heaviest building west of the Mississippi, it can possibly claim another first. I'm not really sure. Has there ever been another building to exploit an "Outrigger/Cellular Box Grade Beam"? Okay, it wasn't really intended to be an Outrigger/Cellular Box Grade Beam? It was supposed to be a 3 foot thick cantilever slab off the south end (Transbay terminal side) of the 10 ft thick mat that would fly over a 15H?x15Wx100L ft., PG&E utility vault but once the building started sinking there was going to come a point where the compacted back-fill would push back. You can see the vault in these two photos.





In the document package at the SF Gov website for the public hearing by the Government Audit and Oversight Committee, initiated by SF Supervisor Aaron Peskin, there is vague mention of the PG&E utility vault and the Millennium Partner's legal team geotechnical engineers, Sage Engineer's efforts to calculate the subgrade modulus of the soil beneath the vault. Later in the SG&H 2017 supplemental seismic report, it is less clear, stating Sage is working on providing the subgrade modulus for the "soil supported" cantilever slab at the south end of the mat foundation.

It would be easy for most people to be confused as to what is being discussed in either instance because the B1 basement of the tower was also constructed with an almost identical PG&E utility vault directly over the one that was buried beneath the former 129 Fremont St. before the properties on the block were merged into 301 Mission for the condo project. Sage Engineers & SG&H might want to consider 4.3 to 4.6 x 10-6 as a modulus. Not that I have any basis for suggesting a proximate soil subgrade modulus but I think that might be a reasonable approximation of the Young's Modulus of 5000 psi compressive strength concrete.

The subgrade modulus is indeed a tricky number. The shoring wall for the Transbay terminal is directly along the south (100 ft side) of the PG&E vault and is 90+ feet deep, followed by the buttress wall extended to bedrock, while the CDSM tower/podium shoring wall is 80 feet deep & directly at the east end of the vault, the north side of the vault has 10 to 15 feet of open soil (under a portion of the cantilever slab/B1 Basement) between the vault and the mat foundation and the mass of the soil enveloped by the piles below the mat. Then only portion not completely influenced by confinement is the west end facing Fremont St. here the shoring wall is no where near as deep, perhaps 35 to 40 feet SF Datum.

Using a round number of 100 pcf for the soil removed for the old vault and that of the new tower basement, the soil supporting the old PG&E vault is about 2.5 to 3 million pounds light of equilibrium. If one was looking for a reason why the building was tilting to the north..., a type 3 lever & fulcrum (correct me if I'm wrong) might have something to do with it. "Outrigger/Cellular Box Grade Beam"~®" any suggestions for a more elegant name?



Speaking of equilibrium, once the excavation for the tower basement was fully compensated by upper floors, the building was "by weight" perhaps only 3 stories tall when it started sinking.

One really has to wonder what is being done to resolve this issue since PG&E needs to show due diligence in defending their easement rights. When ARUP inspected the basement of Millennium Tower, they were not granted access to the new PG&E vault in the B1 basement. When one considers that half of the 103 crack monitors are positioned on this end of the building, where the 3 foot cantilever slab joins & prys away at the mat foundation, you have to wonder what the condition of the concrete inside of the vault looks like. There was some strange activity along the 301 Mission/TJPA property line back in March 2017. The underground work looks like it extends beyond the 5 ft TJPA/301 Mission easement but there doesn't seem to be a permit at SFPUC, SFDBI or SFDPW. I would hate to think the TJPA & Millennium were doing corrective work through back channels without the public knowing who is paying for what.



The screen wall in the photo approximately represents the limits of the 5 ft TJPA easement onto the 301 Mission property line.

Both DeSimone & SG&H have stated that the basement walls of the tower play no role in the seismic response of the tower and while this may be true, it still doesn't address the issue that the cracks in the basement walls of the tower are structural cracks and the walls of the basement are 15 foot high retaining walls. Unless all the service lines leading into the tower arrive above ground, it cannot be stated that the tower is prepared for a large earthquake. For a little perspective, if you assume that what is above the basement was just a 5 story wood frame condo building, then the condition of the basement walls would have resulted in this structure being yellow tagged after the Loma Prieta earthquake. So how did a really heavy 58 story building with a "Yellow Tag" grade basement get an occupancy permit? There are probably upwards of a thousand property owners that could attest to having to seek out an engineer and take corrective action for damage sustained equal to what can be seen in the basement of 301 Mission. Maybe San Francisco City Hall can get the world's first Office of Resiliency to explain.



If one takes a look at the pile driving record for the tower and maps it out in excel it really doesn't look too bad. There are vulnerabilities (soft piles) and the mat of the heavy tower does deflect where these piles are located but it is tough to conclude that these appear in sufficient numbers, in group to explain the westerly tilt. At least not without some precipitating cause. Treadwell & Rollo indicated in their letter responding to an inquiry by SFDBI's Raymond Lui, that the extended dewatering of the soil during excavation might explain the settlement, it seems that would be at least one possibility. Fremont St & Mission St both appear to have settled at some point proximate to the timeline of the project and Webcor Builders took out a SFDPW permit to reset manholes on Mission St in 2009 while closing up the project. The manholes on Mission St have been paved over & later reset at least once again since 2009.

What about the shoring walls of the tower? Do they contribute to the tilting? The shoring walls on Mission & Fremont are comparatively shallow, perhaps -35 to -40 feet deep from SF Datum(the base of the tower mat is -24 ft). The eastern shoring wall is sandwiched like a keel, between the tower & podium is between at 80 & 90 feet deep and backed up by the 57 ft deep x 5 level basement parking garage. Finally the south end of the tower doesn't have a shoring wall but does have a concrete bubble beneath it bobbing on Young Bay Mud.

In one of my early posts I pointed out the 40 or so, "strong-backs", for lack of a better name, that overlay the top of the soldier piles on the tower/podium shoring wall. I assumed they were tied to the tower mat foundation and welded to the soldier piles to provide additional cantilever support during early excavation. Later I realized they needed to float, in order for the building to be allowed to settle evenly. So were they floating or were they welded to the soldier piles? The tower was at 42 floors when the last of the cross bracing struts & strong-backs were removed. The lack of soil directly behind the upper tier of lagging caught my eye early on as well but I don't know how much to attach to this. Did the soil drop from the bottom of the mat foundation as a result of aggressive dewatering? The following photo is from end of May or early June 2007. The building had settled about 2 inches.



SFDBI when questioned by SF Supervisor Aaron Peskin about why they did not consider the impending Transbay Center project in their evaluation of the Millennium Tower foundation, responded that they only review what is within the property lines. This makes sense but in the case of 301 Mission, the very concise wording of the SF planning permit, right up to the last paragraph of the planning motion, called for the "Joimt Use" of the property. In essence the Transbay Center was figuratively 5 feet inside the 301 Mission project property line. "Joimt Use" is legal lingo commonly found in easement agreements. The easement agreement between Mission Street Development aka Millennium Tower & Transbay (TJPA) wasn't executed until after the tower was built but in 2002 when the TJPA was consolidating their options for the path of the Transbay Center rail alignment with the site of the old Transbay Terminal, there was a fair deal of back & forth between Mission Street Development, DeSimone, Handel Arch & Caltrans & the TJPA about alternatives & the 301 Mission Tower project, including some fairly detailed schematics. (It somewhat calls into question Myers Dev. argument that the TJPA was unresponsive to communicating in like fashion regarding 80 Natoma). Ultimately, the planning motion that approved the 301 Mission St. development was based on Mission Street Development's "PROJECT SPONSOR PREFERRED"(Alternate E-1) citing joint use & incorporating a 5 foot wide TJPA easement along the length of the southern 301 Mission property line.

SFDBI's response came with reference to California Civil Code 832 pointing to “Each Coterminous Owner is Entitled to Lateral & Subadjacent Support” as cause to disregard development on adjoining property when evaluating the merits of an individual project. One problem for SFDBI is that for more than 20 years the SF Planning Dept. has been issuing planning permits that call for areal groundwater & settlement monitoring, specifically citing the Special Inspections section of the building code. The 80 Natoma project specifically called out for a recommendation by the Geotechnical Engineer regarding groundwater & settlement monitoring as a "Condition". In the case of 301 Mission, Mission Street Development volunteered, stating they would follow the recommendations of presented in the Final Geotechincal Report for the 301 Mission project. Treadwell & Rollo had a long list of recommendations, including groundwater & settlement monitoring. I think it is fair to say that streets settling & PG&E utility vaults with buildings resting on top of them represent Environmental Impacts that SFDBI has failed to consider. Apparently because the street is beyond the property line, it is the City of San Francisco & taxpayers responsibility to provide "Lateral & Subadjacent Support".

Far from SFDBI finding safe harbor in citing CVC 832, they may have isolated themselves. As a Coterminous Owner, the Transbay Center was equally entitled to "Lateral & Subadjacent Support", perhaps more so because the 301 Mission St project, at least on paper does not receive clearance for an SFDBI building permit, vis-a-vis the SF planning motion approving the 301 Mission St development without the inclusion of the "PROJECT SPONSOR PREFERRED" & "Joint Use" stipulation. When you delve into the history of Lateral & Subadjacent Support, another phase pops up and that is "soil in its natural state". In the case of the Coterminous properties of 301 Mission & the Transbay Center, the natural state would historically be soil in a state of rest. The last time it might be said to have moved was 1989. But by virtue of the continued settlement problems at 301 Mission brought about by construction on the property, which precede the Transbay Center excavation, the soils of the 301 Mission street property cannot really be consider to be any longer at rest. One could actually look at the TJPA shoring wall and subsequent Buttress Wall as extraordinary remedial measures to protect the TJPA project from the instability of the ground of the adjoining property.

Essentially, the property at 301 Mission was like a car that hadn't moved since 1989, the tires deflated & having flat spots, the oil pan with sludge, the brakes possibly rusted a bit to the calipers or discs. Even a car that sits overnight is harder to push the next day than one that has just come to a complete stop. The Millennium team not only got the car rolling but when they all stopped to celebrate, it kept rolling. The TJPA just represents a gentle downward slope in the road. It all comes down to the coefficients of static and kinetic friction. It is far easier to push a car that is already rolling than to get the car rolling in the first place. Whatever minuscule portion of responsibility could be attributed to the TJPA excavation would require some very elaborate modelling.

Then again the Transbay excavation itself can only effect soil at a given distance from the excavation. The excavation was 60 feet deep. At 30 feet if you draw a 45 degree angle back up and towards the tower, it intersects the side of the 10 ft mat foundation. That is why Millennium bangs away at dewatering because the areal effects of dewatering can be larger. It is just that there was so little rain fall during the Transbay excavation, it may be difficult to point to groundwater gauges and blame the TJPA. 40% of downtown San Francisco's ground water comes from leaky sewer pipes. Welcome to the Golden State!

The Millennium residents cite the Non-disclosure Agreement between the TJPA & Millennium but the responsibility was Millennium's. For the TJPA to say anything that would diminish the value of the 301 Mission project would have been grounds for a lawsuit. It doesn't help that the attorneys representing the Transbay Joint Powers Authority were from the City of San Francisco Attorney's Office much to the objection of many at the TJPA. No doubt SFDBI was worried about being seen as a party that could damage the prospects for the tower project but they still had a responsibility to see the cracks in the basement structurally repaired before issuing a certificate of final completion. There is no way around the fact that the certificate was improperly issued.

In 2014 the City of SF replaced the sewer line in Fremont St, claiming it was old and had probably needed to be replaced for some time but in 2011 in preparation for the Transbay Center project, utility lines were run immediately adjacent to the sewer line and if it was in such a bad state, it would have been dealt with then. It is more likely that the sewer line was damaged by the rotation of the Millennium Tower. Here is an April 2014 on the Microsoft Map page suggesting rotation, more are found on Google Maps in Nov. 2014 & later. The curb in front of the bus stop on Fremont St was in a preliminary state of failure. Even for the curb to be in this condition in 2014 took at least a year or two for this degree of deterioration to manifest. It has progressively been snapping like a candy cane for the last 4 years. It begs the question, what do the people at the SFPUC & SFDPW know and how long have they known. Has anyone been hurt at this bus stop? Why has it gone untended for so long? The building appears to be plowing a 35 foot wall of fill and mud in front of it.

April 2014

Nov 2014

July 2015

Oct 2017


I'm sure there is more that I have left out since my last post but this is the bulk of what I've learned. In fairness to Millennium Partners, I do feel for them. In their preliminary EIR, they had plans to move forward with the project in 2002/2003, maybe they were hoping to open under a Luxury Hotel Brand, maybe the PG&E Land Office & utility vault was holding the project up. When the project was finally approved by the SF Planning Commission in July 2003, it still had a 4 story basement/parking garage beneath the tower. The Treadwell & Rollo soils investigation is almost entirely based on the data from 2001/2002 & a 4 level partially compensated mat foundation. In May 2004 Niaz A. Nazir Ph.D. - Managing Principal for DeSimone Consulting Engineers SF & Chief Engineer for 301 Mission Project passed away unexpectedly. Enter Derrick Rhoorda to take over for DeSimone. When you consider that Millennium Partners subsequently brought in Jack Moehle to make sure the project was up to snuff, you might begin to appreciate how Millennium Partners might feel like they did their best and are not happy about the outcome.

SFDBI really is the Reno 911 of Building Inspection Departments. If you have a weekend to burn, you won't be disappointed reading San Francisco news items about the scandals that permeate both SFDBI & the Planning Commission. I think what is perhaps the most stunning and overlooked part of the Millennium Tower debacle is that SFDBI does not have a Geotechnical Engineer or Civil Engineer to pass muster on Chapter 18 of the Building Code. They don't even have easily to find guidance or an Administrative Bulletin on their website concerning Geotechnical Requirements. There was an effort from 2001 to 2004 to craft a Geotechnical Administrative Bulletin but it died in the Structuaral Subcommittee of the Code Advisory Committee in the hands of Hanson Tom. He had been asked to invite Frank Rollo to address the Structural Subcommittee regarding a Geotechnical Administrative Bulletin. Did he make the invite? If I was an SF homeowner who paid a ridiculous sum for home in San Francisco & was required to higher a Geotechnical Engineer to put an addition on my home, only for SFDBI to ignore the work in the report I would not be happy.

San Francisco has the Maher Ordinance for portions of San Francisco that are built on bay fill & they have Supervisor Aaron Peskin's Slope Protection Ordinance but they don't have anyone on staff that has the required knowledge & experience to actually review a Geotechnical Report. The city with the most infamous & dramatic examples of what earthquakes can do to a city doesn't feel compelled to hire one Geotechnical Engineer at SFDBI. Since Millennium Tower they have crafted, not a Geotechnical Administrative Bulletin but a more rigorous Structural - Tall Building & Performance Design Administrative Bulletin, essentially engineering their way around, doing the obvious. Now, they require not one but TWO geotechnical engineers or some such nonsense. Seattle, Los Angeles, San Diego all have well developed Geotechnical Teams in their building departments but not San Francisco. Even San Jose, which doesn't have much need for a Geotechnical Engineer has a City Geologist that decides if a project requires deeper scrutiny.

It is not just SFDBI, it is the City. A look an employment website confirms the Bay Area has more Geotechial Engineers than anywhere else in the world but when SF needed one for the 301 Seismic Safety Committee PEER Review, apparently the only one they could find was a former founding employee, 16 year alumnus of Treadwell & Rollo who started out with Frank Rollo Sr. at Harding/Lawson pre-1989.

There was a time that a former SFDBI employee was forging an Architect's & a Structural Engineer's seal on documents submitted to SFDBI. Supposedly it took years for his former colleagues to become suspicious. If he had chosen a Geotechnical Engineers seal, he might still be at it.

Before the City of San Francisco decides to waste any more time on Administrative Bulletins, they need to hire a Geotechnical Engineer. It also doesn't take an Administrative Bulletin to require that going forward all Major Buildings & PEER Review Kick-off meeting will be attended by all engineers of record on the project, including the Geotech. The City of San Francisco deservedly should have to deal with this mess on its own. The TJPA did all their due diligence.

The SG&H 2017 Seismic Report Supplement largely crafted to address the suggestion by Sen, Dianne Feinstein that a committee be formed to investigate the troubles at 301 Mission is a bit sloppy, considering the company that authored it & the people impaneled by the City to review the data. The Long-term Static Axial Pile capacity is described at having it's lowest capacity to the North & East but it appears to be to the North & West, which is an area that SFDBI expressed concern about. Also, the description of the tops of the piles in the report has the numbers jumbled in two different parts of the report and the description is not in agreement with the shop drawings supplied by the pile producer. While most of the numbers on the pile shop drawing are in mathematical agreement, there is a number shown at the sum of the strands that is clearly not correct.

SG&H describes the piles as having 8ea x 23ft-6in of #8 or #9, suggesting 12ft-3in could be removed with 12ft-3in left to develop pile capacity. In fact there are 4ea x 23ft-6in of #8 & 4 ea x 7.5ft #9 bars grouted into 17.5ft sleeves. It isn't so much that there are a large number of piles that were cut but that SG&H really fails to explain with clarity how the piles are up to the task or how many are deficient. There was something else that was off about the report but it escapes me at the moment.

RE: SF tower settlement

Awesome post, epoxybot! Very informative.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: SF tower settlement

This will be winding its way through the courts long after its 'best by' date... The malfeasance starts right at the top... Excellent post, Epoxybot... wish I could give you a handful of stars.

Dik

RE: SF tower settlement

In case anyone's curious about the abbreviations:

BIC
[San Francisco] Building Inspection Commission
CDSM
Cement Deep Soil Mixing
CRSI
Concrete Reinforcing Steel Institute
DBI
[San Francisco] Department of Building Inspection
EIR
Environmental Impact Report
EOR
Engineer of Record
GFRP
Glass Fiber Reinforced Polymer
HOA
Homeowners’ Association
PG&E
Pacific Gas and Electric
SEAONC
Structural Engineers Association of Northern California
SFDBI
San Francisco Department of Building Inspection
SFDPW
San Francisco Department of Public Works
SFPUC
San Francisco Public Utilities Commission
SGH
Simpson Gumpertz & Heger
SG&H
Simpson Gumpertz & Heger
T&R
Treadwell & Rollo
TJPA
Transbay Joint Powers Authority
WTC
World Trade Center

RE: SF tower settlement

JAE: Modified... you note I didn't say 'corrected'.

Dik

RE: SF tower settlement

San Francisco Supervisor Aaron Peskin has subpoenaed Ramin Golesorkhi, PhD, PE, GE, F. ASCE. Dr. Golesorkhi & Christopher A. Ridley, G.E. were the Geotechnical Engineers at Treadwell Rollo who made the soil determinations & piling recommendations for the 301 Mission Project. Dr. Golesorkhi is currently the V.P. and a Principal at the San Francisco offices of Langan Engineering & Environmental Services Inc. The engineering services of the San Francisco office were formerly a Treadwell & Rollo enterprise. Langan acquired Treadwell & Rollo in late 2010.

The founder of Treadwell & Rollo, Don Treadwell passed away in 2016. Link

Dr. Ramin Golesorkhi was originally subpoenaed to testify before the S.F. Government Audit and Oversight Committee on Apr. 4, 2018 but it seems a copy of the subpoena was later served to legal representation and the hearing will commence at 10AM PST next Wednesday the 18th of April. The hearing will become available for online viewing the following week. Link

The subpoena seeks to have Dr. Golesorkhi provide testimony regarding the tower foundation at 301 Mission and also the Treadwell & Rollo foundation for the controversial, approx 50 story concrete tower originally proposed at 80 Natoma. The 301 Mission project was determined to be on much poorer soil that 80 Natoma.

Indeed, the Transbay Joint Powers Authority's (TJPA) own Seismic modeling of the new Transbay Center & Train Box separates the ground along the train box foot print into 4 separate zones with the ground immediately adjacent to the Millennium Tower in one soil zone and the new Sales Force Tower across Fremont St. and West of the Millennium Tower in another soil zone. The TJPA modeled the section of the train box adjacent to Millennium Tower, not only on the basis of the soil conditions but also concerning the interactions with 301 Mission & the new 199 Fremont tower. The two towers bookend the Transbay Center which require a considerable number of micropiles to keep it from popping out of the ground. The conclusions were that the neighboring structures played a greater influence on the way the Train box responded to a seismic event than the poor soil conditions. The report also concludes that some ground motions were also faster. They may be faster than have been calculated for the Millennium Tower in the SG&H Seismic Report. Then again the SG&H report isn't worth the paper it was printed on if the Seismic Soil Class for the 301 Mission Tower was Type "E" instead of the Type "D" as designed. Unfortunately the article does not indicate what the Seismic Soil classification was determined to be. Link

Surprisingly after more than 8 hearings regarding 301 Mission and in 2004 perhaps 12 to 16 hearings & meetings over the 80 Natoma project, no one has sufficiently explained to any of the officials in San Francisco, up to & including the engineering staff at San Francisco's Dept of Building Inspection the "Compensation" part of a Compensated (Fully/Partially) Raft Foundation.

Dr. Ramin Golesorkhi is also one of the co-authors of the 2016 publication "Performance-Based Seismic Design for Tall Buildings" published by the Council on Tall Buildings & Urban Habitat. The other co-authors are Leonard Joseph P.E., S.E. - Principal, Thornton Tomasetti, Ron Klemencic P.E., S.E. - President, Magnusson Klemencic Associates, David Shook P.E., S.E. - Skidmore Owings & Merrill LLP & John Viise P.E., S.E. - Thornton Tomasetti. Link

Christopher A. Ridley, G.E., who has not thus far been subpoenaed departed Treadwell & Rollo and along with Frank Rollo have formed Rollo and Ridley. Geotechnical Rngineers.

RE: SF tower settlement

Quote (epoxybot)

Christopher A. Ridley, G.E., who has not thus far been subpoenaed departed Treadwell & Rollo and along with Frank Rollo have formed Rollo and Ridley. Geotechnical Rngineers.

Don't know why he wasn't included... he was involved from day 1.

Dik

RE: SF tower settlement

Yesterday's hearing was postponed. Supervisor Peskin, the hearing sponsor had a family emergency. Industry experts have apparently weighed in on the cost of installing 275 to 300 micropiles and give estimates of $200 to $500 million. Link

There is a some thought to installing piles with the prospect that once installed and the building settles on these piles that "with luck" it will start to tilt back in the other direction. I find this highly unlikely. 1) It was never suppose to sink in the first place. Expecting piles to now perform in a manner they were not suppose to behave in the first place is wishful thinking. 2) The piles on the east side of the tower have higher blow counts than to the west. 3) The largest number of pile that were cut short of their specified depth are on the east side of the tower. These piles represent, Combined friction & end resistance piles. 4) Settlement Data from ARUP seems to indicate that the west end of the 1500sf PG&E utility vault under the 3 ft cantilever slab, flying off the south end of the mat foundation has dipped ever so slightly towards Fremont St (West).

The weight of the tower & settling has to be creating a great deal of stress across the mat/cantilever connection. The piling scheme would have to proceed carefully not to make it worse. Still not a peep about the PG&E vault from Millennium Partners, the HOA or LERA/Swinerton. Dealing with the utility vault, ought to be part of early work of any remedial scheme.

RE: SF tower settlement

A million dollars a micropile is a little steep... even in this area...

Dik

RE: SF tower settlement

From Epoxybot's 19 Apr 18 23:10 link the 13-5/8" cased micropile is double-walled?



So 300 micropiles at 300 feet deep for $300M - so $3,000 + per foot!

I wonder what the basement height is - limited-access drilling!

RE: SF tower settlement

Ingenuity: I thought a little pricey... and the work, likely, comes with no guarantees...

Dik

RE: SF tower settlement

Maybe it's the malpractice insurance that drives the cost up. I know that is not a job anybody is going to get involved in for cheap.

RE: SF tower settlement

2
Here are links to the drawings for the test piles designed by LEAR or perhaps more precisely by Hayward-Baker. Link

Here is the test pile SE Review: Link

Here are the drawings for the Shoring Wall Investigation: Link

Here is the shoring wall SE Review: Link

I didn't post these back on April 2nd because, if SF Planning posted them in error, I thought I'd wait to see if they were removed but since the news has broken to a wider extent, so be it.

RE: SF tower settlement

I'd love to see the seismic lateral calculations for this project... just to see that it stands up...

Dik

RE: SF tower settlement

How much would the tower cost to demolish? If the piles are already more than the build cost, shouldn't people be thinking about starting over rather than incurring the risk that the attempted fix will not work as expected?

RE: SF tower settlement

epxoybot: A purple star for you. Great 'googling' with those info links. Well done.

Quote (epoxybot)

...or perhaps more precisely by Hayward-Baker.

Or even more precisely, Nicholson/Haywood-Baker - JV.



Nice project for a JV - get two of the most experienced and technically knowledgeable geo-structural contractors in the US to jointly design/build/engineer a solution - and presumably limit some (?) of their liability.


RE: SF tower settlement

I honestly don't understand why the Millennium Homeowners don't do Crosshole Seismic Testing through the sidewalk on Fremont St from the driveway to the corner of Fremont & Mission and then along Mission from the corner of Fremont & Mission for the width of the tower. For all the bole holes they have now had performed, they could have done Crosshole Seismic Testing and probably had some far better data.

The SF Dept. of Building Inspection (SFDBI) is in the process of re-writing their criteria for Performance Based Buildings and one of their IDEAS is that from now on the Geotech must sign off on all the soil related below grade engineering. Foundation, Piles, Shoring, Tie-Backs, the works. Also PEER review, if I followed it correctly would have Two (2) Geotechs. So what happens when there is insufficient data? Two Geotechs don't make fuzzy data better. Insufficient data by default is Seismic Soil Class "D". Tag-team Geotechs for PEER Review, One Geotech to Rule them All for the site work. You really start to get the feeling that SFDBI has an aversion to hiring a Geotech themselves. Yet they look silly, if not incompetent, compared to their like circumstance, west coast, big city, earthquake zone Building Dept. siblings

The piles on Fremont St. between the super columns/out-rigger connection, for all intents never reached resistance. They just ran out of pile. The majority of the site data and soil sampling was done for a 4 level basement and even there it is not particularly plentiful. A lot of the sampling was done at the bottom end of a soil layer. You almost get an itch, that the contract was lump sum. I've read elsewhere that Treadwell & Rollo were known to be ~aggressive~ with their competitors.

The Geotechnical Report advised that pile jacking was a possibility, due to ground water and soil conditions, yet the Restrike was done 24 hours after it had been driven. Even if it is a good restrike, when compared to the blow counts for the piles between the Super Columns on Fremont St. you realize the Restrike pile isn't a very good representation of this group of low blow count piles. How did they figure the remodeling of the soil around the follower? The list of questions becomes lengthy.

I'm not to sure how much the HOA represents the sole interests of the Condo Owners. They had that report about the curtain wall separation & fire hazard and instead issued a redacted copy to the residents. Maybe the insurance companies will require them to do shear wave velocity testing. If the Fremont St. face of the building turned out to be Seismic Soil Class "E" and the building was designed to Seismic Soil Class "D", would any insurance company be willing to insure it?

All that said, the building is in all likelihood safe but lawyers just make the information feed behave like a blocked artery. Heck, back in the mid 80's T.Y. Linn built a 30 floor, 3 building (tri-star arrangement), 583 apartment project across the bay in Emeryville on soil that is much the same. The Pacific Park Plaza. It came through the Loma Prieta quake very well. It was also instrumented and the Earthquake Engineering Research Center just on the other side of Interstate 80 has looked at it 6 way to Sunday. One of the buildings also has a tilt. You can only see it when you stand at the base of a seismic joint between two of the towers. It about doubles in width as it goes up. Link

RE: SF tower settlement

From epoxybot's link above - Link - the micropile cross section is pretty impressive:

#28 grade 75 bar, 1-1/8" thick wall x 9-5/8" dia inner casing, weld beads around outer casing at 6" c/c:



RE: SF tower settlement

It hardly seems like a micropile.

RE: SF tower settlement

I am posting a clarification to the TEST PILE PROGRAM - it is actually a MICROPILE CONNECTION TEST PROGRAM, and as the name implies, is a test of the transfer/connection between the existing mat and the proposed micropiles.

Micropile TEST #1 is only 10 ft deep - cored into the existing 10 ft thick mat foundation. This test uses 1/4" weld beads around the outer casing circumference and tested to 2000 kips - yes 2,000,000 lb.f!!!



If TEST #1 is NOT satisfactory, then TEST #2 - with 3/4" weld rings to the outer casing - is tested to 2000 kips.



RE: SF tower settlement

Quote (epoxybot)

The SF Dept. of Building Inspection (SFDBI) is in the process of re-writing their criteria for Performance Based Buildings and one of their IDEAS is that from now on the Geotech must sign off on all the soil related below grade engineering. Foundation, Piles, Shoring, Tie-Backs, the works. Also PEER review,

Given the seismic area, I think this is a great solution to a problem similar to Millennium Towers... they should also have a geotekkie on staff to review the submissions by the added geotekkies.

Dik

RE: SF tower settlement

Ingenuity - Thanks for the clarification. I kept looking at the drawings and feeling they were short on some piling information but it now seems clear, this is just to test/prove the mats capacity to develop/sustain a highly loaded connection. So the beading on the outer casing is transforming it into a deformed casing (rebar-like) and the concentric casings serve to increase the shear perimeter.

Dik - It is great for the Geotech firm to not have to wheel & deal al carte but serving two masters; the developer & the GC will be ugly.

RE: SF tower settlement

epoxybot... and the homeowners, too...

Dik

RE: SF tower settlement

Any update on this great post?

RE: SF tower settlement

Unfortunately, news about the SF Millennium Tower has gone dark for the most part. Unless you want to include the grand opening of the world's most luxurious & expensive BUS STATION! It is rather ironic that the Temporary Bus Terminal built for about $10 million got good reviews by commuters and this in spite of the fact that the awnings neither sheltered people from the rain or provided shade, or did the design provided much seating. I'm sure the $2.5 Billion Bus Station is definitely a step up..., except it too is lacking of seating.

I always thought a drinking fountain, a public toilet & a place to sit down were 3 of the things that made America just a bit better than other countries. Foreigners though find our public toilets unsettling, the gaps top & bottom, plus the poor fit of the doors, irks them greatly.

Obviously everyone from the City of San Francisco, the developer & the condo owners want to blame the TJPA for their woes. So it is disappointing that the SF Bay Area news services don't do a better job on reporting the legal side of this fiasco. Whatever the TJPA spends on Millennium Tower, in one way or another the Bay Area, State & US Taxpayers are footing the bill for.

Apart from the Pile Testing permits, the only other work has been in the Northwest corner of the parking garage at the 4th & 5th levels. This area does share the Tower/Podium shoring wall, so the problems could be related. There has been problems with cracks, water infiltration & odor. The odor seems to be Ammonia. Environmental testing does show it to be higher than acceptable limits, so work is being done to determine the cause. It is suspected that the Waterproofing Admixture used in the Parking Garage basement levels may be the source.

The last hearing of the SF Government Audit & Oversight Committee was May 16, 2018, where Ramin Golesorkhi of Langan Engineering (formerly of Treadwell & Rollo) testified. It wasn't particularly eventful and nothing new came to light. Langan does have another building tilting in SF. They were the Geo-Tech for a new building and had determined that the adjacent building (FDIC) would not require underpinning. About a quarter if the way into excavating the basement for the new building the adjacent building had sunk 1-1/2 inches.

RE: SF tower settlement

This kind of post fascinates me. One thing I don't understand is the settlement timeline posted by Ingenuity. It shows the original T&R estimate was 4.5-5.5" yet by end of construction they already had 6" of settlement and merely updated their prediction to show 10.3-12.3". Not being structural/geo I don't understand. If you exceeded your lifetime settlement estimate just at the completion of construction, you can simply update the estimate?

RE: SF tower settlement

"If you exceeded your lifetime settlement estimate just at the completion of construction, you can simply update the estimate?"
Why not? We discovered an earthquake fault during construction of a Navy wharf. We just lowered the specified safety factors on everything.

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