Take Note: This San Francisco Luxury High-Rise is Sinking at an Alarming Rate
Leaning towers aren’t exclusive to Italy anymore.
San Francisco has one of its very own, and its residents are suing the building’s designers and developers.
The leaning tower in question is Millennium Tower at 301 Mission Street, a neighbor to the ever-present and thrusting Salesforce Tower. The 58-story luxury high-rise opened to residents in 2009, and continues to “settle at a rate of about one-half inch per year and to tilt at a rate of about three inches per year,” said Ronald O. Hamburger at a city hearing last Thursday. In other words, it’s sinking.
Hamburger, the structural engineer responsible for divining a fix, warned that Millennium Tower could reach a 40-inch tilt within a few years, “the point at which the elevators and plumbing may no longer operate.” According to NBC Bay Area, the tower is currently tilting “some 26 inches north and west” at the corner of Fremont and Mission Streets.
The intended fix will be an installation of 18 steel piles to bedrock 250 feet below the tower, in order to anchor the building on its foundation of “rapidly compressing clay and sand soil.” Hamburger claims the building remains safe for residents, but advises that this construction should be accomplished “quickly.”
This construction actually started last August, but potentially destructive delays ensued. In order to install the first six piles, several tons of soil were removed from beneath the tower. The void created by this soil removal was meant to be filled with concrete grout in a timely manner, but the drilling logs indicated a “1 to 4 day gap” between the soil removal and grout installation.
Apparently, this gap was not in compliance with project specifications, and in fact may have accelerated the building’s settlement. The delay risked “collapse of soils locally under piles” and a “general collapse of the foundation,” foundation engineer David Williams told NBC Bay Area last week.
“It’s very disconcerting.”
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