by Abigail Sterling and Max Darrow
SAN FRANCISCO (CBS SF) -- Limited work on a fix for San Francisco's leaning Millennium Tower has resumed, but at least one leading structural engineering consultant believes it's time to put the brakes on the entire project.
Construction crews were busy on the corner of Mission and Fremont Thursday as work on part of San Francisco's leaning Millennium Tower retrofit resumed.
Work on the fix was paused just before Labor Day once it became apparent construction methods were actually making the problem worse.
"We haven't got to the worst part of the fix yet, the most risky part of the fix," said David Williams, a structural engineer and deep foundation expert.
In 2017, concerned Millennium Tower unit owners hired Williams as a consultant after learning their luxury high rise, barely 7 years old, had sunk more than a foot and was leaning to the northwest.
"There was evidence of a lot of places with water intrusion," said Williams.
Williams noted some extensive water damage in the garage, but he says the floor of the Millennium Tower's basement exposed what appeared to be an even bigger problem: It was dipping in the middle, something referred to as dishing.
"The dishing of the floor there, which is the dishing of the mat, 10 foot thick mat, was significant. Clearly it had been distressed," said Williams.
He predicts the current Perimeter Pile Upgrade may run into serious problems when new piles anchored to bedrock are connected to the building's weakened foundation.
"When they start jacking, then they're doing a load redistribution and they're really dependent on the integrity of the existing structure," said Williams.
Williams hopes the foundation issues will be discussed when San Francisco Board of Supervisors holds hearings on how to fix the leaning high rise next week.
Supervisor Aaron Peskin called for the hearings, set to begin next Thursday.
"The building today is not in any imminent threat of structural failure," Peskin said. "The question that has not been satisfactorily answered as far as I'm concerned is at what point is the point of no return."
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