SAN FRANCISCO - Engineers in San Francisco on Tuesday will try out a new strategy to keep the Millennium Tower from from continuing to sink.
The building is about 58-stories and it has sunk about 19 inches since 2009.
Over the summer, the original plan was to install 52 concrete piles into the ground's bed rock. But once crews noticed the soil excavation, and drilling caused the building to sink even more, they had to stop. They only installed about 30.
Engineers will now install one more three-foot steel sleeve about 100 feet into the ground along the Fremont Street side of building, first reported by the San Francisco Chronicle and confirmed later by KTVU.
This time, sensors will determine how the building reacts to the construction.
"The machines that are putting them in are being put on rubber mats to reduce the vibration," said District 3 Supervisor Aaron Peskin. "Other precautions are being taken to make sure they don't over excavate dirt."
This tower is mostly made up of apartments owned by residents.
Many sued the building for a decrease in property values and a lawsuit
A lawsuit settled within the year.
This new strategy will likely cause the tower to sink, but the project will be immediately halted if the building sinks more than ¼ of an inch.
The installation should last about two to three days. If crews manage to keep the sinking to a minimum, then they'll install more casings over the next few weeks.