The Leaning Millennium Tower of San Francisco
San Francisco, CA was previously known for its low-rise infrastructures. When technologies boom and architectural trends reached the place, everything started to change. However, in the earthquake-prone San Francisco, there is an overlooked fine print — that most of its buildings including the new skyscrapers stand in a group of squishy land reclaimed from the bay. One of its new buildings, the Millennium Tower is now 16-inches shorter than before. It has engulfed into the ground and the condominium continues to sink unevenly.
Aaron Peskin, a member of San Francisco Board of Supervisors, had revealed evidence that the inspection department has raised the sinking issue a few years ago before its launch, thus making it sound political.
A letter sent to the engineering section spoke about “larger than usual” settlement of the building and if the consequences were thoroughly studied.
Despite the serious allegation, in August 2009, the city announced the building ‘safe’ for people to move in.
Mr. Peskin questioned this decision of the state , “I believe, and I know this is a very serious allegation.” He also trusts his gut feel, “that there was some level of political interference.”
Property owners of the condominium are making moves to recover loss in property values.
In August, a group of lawyers filed a class-action lawsuit against the developers of the Millennium Tower. The Transbay Joint Powers Authority was also listed down by the complainants as their construction site for a transportation hub building may have affected the sinking of the condominium.
One of the lawyers, Mark Garay says that it is too early to tell exactly what and who to blame. He informed everyone of the fact that the sinking is already happening before the construction of the transportation hub.
“What we do know is that the foundation of this building does not go into bedrock,” said Garay. “It’s all landfill. It used to be part of the bay.”
It is clear that the sinking of the Millennium Tower is just the beginning of a very long story.
Are buildings on reclaimed land in Singapore safe?
Singapore – Nearly 20% of the current land space in Singapore is reclaimed from the sea. The bulk of this reclaimed land is used to build the airport terminals in Changi, the industrial areas in Tuas and Jurong island, as well as the new Central Business District (CBD) at Marina Bay.
On top of the reclaimed land at Marina Bay sits the iconic Marina Bay Sands and many new skyscrapers like Marina Bay Financial Centre (MBFC) and upcoming projects like Marina One Residences and many more to come.
To ensure that reclaimed land will be stable enough to hold buildings, Singapore lets the land lay fallow for about 20 years to allow the sand to settle.
But is that enough to be safe?
Engineers say that reclaimed land may be prone to sinking due to difficulties in compacting the sand and draining the water trapped inside the reclaimed plot, which causes reclaimed land to subside more easily.
Japan’s Kansai International Airport, the world’s first airport built on reclaimed land, has sunk more than 11.5 metres since construction began in 1987.
However, buildings on reclaimed land will not sink if they are supported by steel or concrete columns that are hammered all the way into the seabed, although the streets circling the buildings may sink alongside the drooping land, engineers say.
It is fortunate that Singapore does not lie in an earthquake zone.
During an earthquake, sand in reclaimed land slides like liquid when saturated with water, in a process called liquefaction, according to Fan Sau Cheong, an engineering professor at Singapore’s Nanyang Technological University.
This makes it more likely for buildings to sink into the reclaimed land, in earthquake-prone cities like San Francisco and Tokyo.
Notwithstanding this, property values in the reclaimed Marina Bay are one of the highest in Singapore, like the upcoming Marina One Residences fetching more than $2,500 PSF.