Millennium Tower fix engineers have scrapped an elaborate strategy designed to prevent more tilting at the troubled high-rise as they push to complete the project – a shift in strategy that critics say amounts to gambling, but monitoring data suggests is paying off so far.
Back in June, after the building tilted nearly three more inches to the west toward Fremont Street in a matter of months, engineers halted work on an underground support wall along Fremont. They proposed continuing to work around the corner along Mission Street, then propping up the building on one corner by extending the foundation and attaching it to piles already sunk to bedrock. The prop-up strategy, engineers said, would support the tower enough to prevent any more tilting to the west when work resumed on that shoring wall designed to protect Fremont Street.
But monitoring reports on file with the city show last month, crews resumed digging along Fremont Street – without first propping up the structure at the corner.
Documents show the first of the newly installed piles on Fremont went in Oct. 8. So far, there has been no “noticeable impact” on the structure’s tilt, said lead engineer Ronald Hamburger in a statement.
“Resumption of shoring wall work on Fremont street is intended to move the project towards an earlier conclusion according to the original schedule,” Hamburger said, adding that the work is subject to constant oversight and cannot go forward each day without his release.
Millennium Tower Association spokesman Doug Elmets said in a statement that the city’s appointed engineering and design review panel signed off on scrapping the corner prop-up plan, but city officials say Hamburger’s team made the final call on how to proceed.
Elmets added, “we resumed work on Fremont Street a month ago without any further tilting.”
“They’re gambling,” says veteran geotechnical engineer Bob Pyke, a longtime critic of the fix. He says the work being done along Fremont Street to finish that underground wall is essentially the same digging that led to the tower’s leaning nearly three more inches in the first part of the year.
Pyke says the soil being removed to construct the wall serves to buttress the sides of the tower’s foundation against more tilting. Although tilting data is holding steady so far, Pyke is skeptical that will continue given the project’s troubled track record.
“They simply don’t understand geotechnical issues, which is why they’ve had one problem after another,” Pyke says.
Meanwhile, the homeowners association has alerted residents about the resumed work along Fremont, saying the goal is to hasten project completion. The association warns that residents can expect a new round of jackhammering as crews dig along Mission Street to extend the foundation out to those existing support pilesthat have been sunk to bedrock.
Source: NBC Bay Area