[Pedestrian]

Millennium Tower homeowners propose $100 million solution to sinking problem
J.K. Dineen Dec. 3, 2018 Updated: Dec. 3, 2018 8:20 p.m.

Homeowners in the sinking Millennium Tower on Tuesday will submit a permit application to shore up the 58-story building by drilling more than 50 new piles down to bedrock, a nearly $100 million fix.

In an application to be filed with the city’s Department of Building Inspection, the Millennium Tower Association laid out plans for a “perimeter pile upgrade,” 52 steel and concrete piles that would shift a portion of the building’s weight from its existing foundation system to bedrock about 250 feet below.

While the application outlines about $30 million worth of work, the entire pile upgrade would cost nearly $100 million and take 18 months. The contractor would drill 22 new piles along Mission Street and 30 along Fremont Street. Each pile is 24 inches in diameter and weighs 140,000 pounds and would take three or four days to drill into place. A reinforced concrete “inner pile” would be installed within each steel shaft.

That shift would relieve stress on soils that have compressed beneath the building, causing it to settle more than anticipated and to tilt, according to engineer Ronald Hamburger of the firm Simpson Gumpertz & Heger, which designed the plan. The new piles on the north and west sides would limit future settlement of the tower to minimal levels and reverse the building’s tilt, according to Hamburger.

https://www.sfchronicle.com/bayarea/...n-13440479.php