We have been following this one for some time. As you might recall, the Millennium Tower, a “pricey” 58-story luxury condominium tower at 301 Mission Street was built on a site of sand and fill from the time when part of the bay was filled to make way for additional development in the City by the Bay.
The foundation is a 10-foot-deep concrete mat with piers 60-90 feet deep that were supposed to anchor the building in one place. The New York developer, Related Companies, did not engineer the piers down to bedrock and in the first six years since construction was completed and the units sold to notables like Joe Montana, the building has sunk and tilted. Currently, according to the article, the 58-story tower has sunk 16 inches, tilted 14 inches to the west and 6 inches toward the north. Truly a leaning tower.
As we reported in our last post, the dewatering of an adjacent site for a transit center has, according to the developers’ lawyers, caused the entire issue and negotiations have been on-going as to how the problem will be fixed. And it won’t be cheap.
Now, according to an article in the San Francisco Chronicle titled “Pricey retrofit proposed for sinking Millennium Tower in SF," the engineers have proposed boring 275 to 300 “micro-piles” to anchor the building to bedrock, but first the building has to be stabilized and that means placing the piles on the sinking side of the tower and waiting for the other sides of the tower to “catch up” or sink to the same level as the lowest side is today. Only then would the additional piers be drilled. Once the piles are all in place, a process that could “take from two to five years.” The building should be stabilized, and the sinking and leaning should be solved.
The general contractor and engineers are working on the approvals and permits needed to start the retrofit.
Oh yes, there is the cost. It is estimated that the cost of the retrofit will be somewhere between $200 and 500 million. The original cost of the concrete frame tower was estimated at $350 million.
The value of the units has dropped like a rock. According to an article in the SF Business Times, “A two-bedroom penthouse in San Francisco's sinking, tilting Millennium Tower has sold for 29 percent less than what it sold for 22 months ago.
A buyer paid $5.75 million last Friday at closing. The luxury unit was initially listed at nearly $9 million last November.
"Purchased for $8.1 million in mid-2015, the two-bedroom plus den penthouse unit #1A on the 58th floor of San Francisco’s Millennium Tower, a 2,700-square-foot unit with two parking spaces which has been remodeled with an 'ultra-contemporary design' and 'only the finest materials, procured from around the globe," SocketSite reports.
We will continue to monitor the progress of this rebuild.