SF tower settlement 25

[epoxybot]

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.

 

[dik]

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

 

[epoxybot]

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.

 

[dik]

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

Dik

 

[Ingenuity]

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!

 

[dik]

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

Dik

 

[JStephen]

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.

 

[epoxybot]

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.

 

[dik]

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

Dik

 

[jasm]

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?

 

[Ingenuity]

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

...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.

 

[epoxybot]

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

 

[Ingenuity]

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

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

 

[JedClampett]

It hardly seems like a micropile.

 

[Ingenuity]

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 [sup]1[/sup]/[sub]4[/sub]" 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 [sup]3[/sup]/[sub]4[/sub]" weld rings to the outer casing - is tested to 2000 kips.

 

[dik]

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

 

[epoxybot]

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.

 

[dik]

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

Dik

 

[HENRYZAU]

Any update on this great post?

 

[epoxybot]

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.