The recent collapse of Champlain Towers South in Surfside, Florida has attracted attention to the stability of tall buildings around the world. Now one of San Francisco’s newest towers has shown mysterious signs of sinking and tilting since 2016. The recent discovery of additional subsidence has caused engineers to halt an ambitious repair scheme that was begun in November 2020. A review of the history of Millennium Tower at 301 Mission Street in San Francisco shows how such problems can be difficult to detect and even more difficult to cure.
First problems at Millennium Tower
Millennium’s problems began in 2016 when residents were informed that the tower was sinking. The building’s foundation was not built on top of bedrock. Instead, the tower’s foundation rested on deep, dense sand. Then, an inspection in 2018 determined that the northwest corner of the building had sunk more than 18 inches into the fill on the intersection of Mission and Fremont Streets. Engineers studying the problem recommended a “perimeter pile upgrade,” which involves placing pilings to a depth of 250 feet along the north and west sides of the tower. The new pilings were intended to be connected to the original pilings beneath the sidewalk. After 39 of the intended 52 pilings had been installed, engineers detected a new problem.
More sinking at Millennium Tower
After the 39th new piling had been installed, engineers detected a sudden drop of one inch on the Fremont Street side of the building. Crews had reportedly completed drilling half way down to bed rock to install the new pilings. The additional sinking has moved the 58th floor five inches away from true vertical. When the additional sinking was discovered a few days ago, the engineering firm supervising the project halted all work.
A litigation tsunami
As might be expected, a flood of lawsuits hit the courts when the first sinking was detected. The homeowners’ association sued the general contractor and the developer. The city sued the tower’s developer. The developer blamed the problem on the Transbay Joint Powers Authority, which built the adjacent Transbay Transit Center. The suits were settled in part by the payment of the cost of the “perimeter pile upgrade.”
Anyone who works on large buildings, especially architects and engineers, can be expected to be drawn into a litigation nightmare when such defects are reported. Retaining an experienced construction lawyer as soon as possible may be the most effective way to avoid significant exposure to a large award of damages.