Engineers paused work for at least two weeks on the $100-million foundation upgrade for San Francisco's 645-ft-tall Millennium Tower high-rise residential condominium after measurements showed increased settlement during the installation of pile casings for the new piles.

The work has been stopped "out of an abundance of caution" for two to four weeks, said a statement from Ronald O. Hamburger, the senior principal with Simpson Gumpertz & Heger, who designed the upgrade scheme. The pause, which began Aug. 20, will allow the engineers "to understand better the mechanisms associated with the increased settlement rate" and ways to mitigate it, he explains.