by Abigail Sterling and Max Darrow
SAN FRANCISCO (KPIX 5) – Days after San Francisco officials put construction to consolidate San Francisco’s leaning Millennium Tower on indefinite hold, there is new evidence that building officials have been warned of the dangers of the fix current.
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The city’s building inspection department said it was looking at an updated construction approach that project engineers came up with after it was discovered that the pile driving activity likely made s ‘push in another inch and tilt five inches.
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“I could see that at some point things were going to go haywire,” geotechnical engineer Robert Pyke said two years ago when he took a closer look at the details of the new plan to stabilize and straighten the tower. San Francisco Millennium Leaning.
The plan was announced at a press conference by prominent San Francisco engineer Ronald Hamburger. “It’s not uncommon to do this sort of thing to a building; it’s called underpinning. What’s unusual about it is the size of the building, very tall, ”Hamburger said at the time.
Pyke’s main concern: The so-called “perimeter pile improvement” calls for connecting only the north and west sides of the sinking building to bedrock, leaving the south and east sides unconnected. “It’s asymmetric. And an asymmetric foundation under seismic load is inherently a very bad thing, ”said Pyke.
So he submitted a letter of concern to the Engineering Design Review Team (EDRT) overseeing the project and to the city, with the headline: “The proposed fix for the Millennium Tower is a joke.
He is not the only engineer who has sounded the alarm. “The problem is, they’ve done a lot of damage already,” says geotechnical engineer Lawrence Karp.
In a report to San Francisco supervisors, Karp and his fellow geotechnical engineer Joshua Kardon warned that the “external asymmetric plane” would cause “further loss of groundwater, which is likely to cause more irreparable damage to the sub- building structure “.
“I see that the groundwater is going down, that’s what we said in our report,” Karp said.
Karp preferred an alternative solution from the New York-based LERA founded by Leslie Robertson, the famous chief engineer of the World Trade Center. The LERA plan called for drilling new piles into bedrock symmetrically on both sides of the building from the inside.
“Everything was inside the building, it went through the foundation mat, so it’s level, it’s masterful,” Karp said.
Karp says he met with city building officials to discuss his concerns, but never received a comment. Pyke says he never got a response either.
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Two years and many lawsuits later, luxury real estate developer Millennium Partners opted for the Hamburger-backed perimeter stack upgrade, while promising to pay for the $ 100 million repair as part of it. ‘a confidential settlement with the owners.
The Building Inspection Department declined our request for an interview, but in a statement told us that a team of experts overseeing the patch on behalf of the city had asked project engineers to respond to critics’ warnings. . Engineers offered assurances and the warnings were dismissed. Now they are coming back to light.
“I am deeply concerned,” said San Francisco supervisor Aaron Peskin, who now wants to have a new independent look at the project before construction resumes.
“I’m frankly concerned that our building inspection department doesn’t have the in-house expertise on something so complicated, from stabilizers to foundation systems, and I want to make sure we have the best people in the country. to examine that, ”Peskin says.
Peskin held hearings in 2016 after the addiction was first detected by residents and then confirmed by experts. He is now calling for new hearings.
“I don’t want to have a Florida situation in San Francisco,” Peskin said, referring to the June collapse of a 12-story condo in Surfside, Florida, which killed 98 people. “I don’t mean to be alarmist, but we have to take this very seriously, we have to be very transparent about it.”
“As a practicing engineer in the Bay Area, I have no concerns about the level of transparency or communications on this particular project,” said Emily Guglielmo, former president of the Structural Engineers Association of Northern California .
Guglielmo told KPIX 5 that the groundwater and asymmetric design criticisms were raised and addressed during the engineering team’s design review period.
“Absolutely suitable for questioning or debating a particular solution,” Guglielmo said. “But it’s also important to understand the level of design, the level of scrutiny, the level of approval that has taken place on this particular project.”
Guglielmo says she doesn’t think a solution like this has been done before with this level of visibility, however, “… the engineering techniques are very consistent. We do this on homes in San Francisco all the time. Supporting, moving loads and foundations is very traditional.
Building officials have asked the Millennium Tower CEO and owners to refrain from resuming construction until DBI and EDRT have reviewed an updated construction approach.
In a statement to KPIX 5, Department of Building and Inspection spokesperson Patrick Hannan said:
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“The Engineering Design Review Team (EDRT) received and reviewed letters from Karp & Kardon and Dr. Pyke as part of EDRT’s review of the Design Foundation Modernization License Application. by SGH (Simpson, Gumpertz and Heger). At that time, EDRT asked SGH to respond to the points raised by the letters regarding the design of the modernization of SGH and EDRT was satisfied with SGH’s responses to these points.