Millennium Tower

San Francisco's Millennium Tower ‘Fix' Moves to Ear-Splitting Next Stage

"I am now warning that there are many uncertainties associated with the excavation that is necessary to construct the mat extensions"

NBC Universal, Inc.

Work began this week on a new phase of the retrofit of the sinking and tilting Millennium Tower – an operation that one critic calls “very risky” because it involves digging and removing  tons of supportive dirt on two sides of the already troubled foundation.

Millennium Tower officials notified residents in a memo on Tuesday that construction work was moving into the fourth, and final stage, with digging needed to expand the existing mat foundation that will be supported by new support piles anchored in bedrock. Residents were told to expect “some drilling sounds” as well as vibration associated with the work, which is expected to last through September.

As work on that final stage begins, monitoring data shows the tower is leaning 27 inches to the northwest at the top. Since work started in May, the tower has tilted 10 inches more at the top, according to that monitoring data.

Work on the Millennium Tower is getting noisier as crews continue to work on preventing more leaning and sinking. Monitoring data shows the tower is now leaning 27 inches at the top, which is an additional 10 inches sine work on the so-called fix started last year. NBC Bay Area's Investigative Reporter Jaxon Van Derbeken has more details.

Millennium fix designer Ron Hamburger has indicated the building is expected to tilt a little more by the time work is done, but experts fear the new digging to make way for an expanded foundation could make the building sink and tilt more than anticipated.

“I think it’s very risky,” said veteran local geotechnical engineer Bob Pyke, who has repeatedly warned city officials about the viability of the fix. In a March 14 letter to building official Neville Pereira, Pyke wrote, “I am now warning that there are many uncertainties associated with the excavation that is necessary to construct the mat extensions.”

Pyke says he’s concerned that digging down 25 feet and removing dirt on two sides of the structure – where it currently is leaning the most – will mean the loss of earth that is currently buttressing the existing foundation. He says the work could result in as much as two inches of additional settlement. That’s equivalent to how much the building has sunk since the so-called fix began. That work-related settlement has resulted in about 10 inches of additional tilt.

“It could be anything from zero to six inches – I don’t know,” Pyke said of the amount of settlement that the building could suffer at the corner. “That’s the problem – no one knows.”

City officials said in a statement that they’ll halt digging if settlement during the work exceeds established limits. But they stressed that despite the new phase of work, the city has yet to sign off on the Millennium fix engineer’s plan to use just 18 piles to support the building instead of the originally planned 52.

While tower residents were alerted to the prospect of some added noise, several told NBC Bay Area’s Investigative Unit that the constant jack-hammering work so close to their windows has been ear-splitting. Millennium officials told them to expect the work to go on between 7 a.m. and 8 p.m. on weekdays and sometimes weekends as well.

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