Work on the nearly $100-million perimeter pile upgrade of San Francisco’s sinking Millennium Tower, to prevent significant future settlement, is set to start next month, now that litigation over the problem has been fully resolved.

The 645-ft-tall residential tower settled about 17.3 in. since its completion in 2008.

Millennium Tower Association, the homeowners' group for the 58-story tower, announced the expected start of construction after the end of a dispute that began after the building began settling. “After many years of complex litigation, the association is being fully compensated for retrofitting the building and homeowners are being compensated individually,” says the group, in a release.

Bumper Jack

Shimmick Construction, a subsidiary of AECOM, is the contractor for the pile upgrade, which was engineered by Ronald O. Hamburger, a senior principal with Simpson Gumpertz & Heger.

Work calls for transferring a portion of the building’s weight to bedrock from its existing foundation system. The fix, likened to putting a bumper jack next to a flat tire, relies on drilling and jacking 52 concrete piles—socketed more than 30 ft into the bedrock that starts 220 ft below grade—under the sidewalks along Mission and Fremont streets. Piles would support a new mat section, known as a collar, tied into the existing mat.

Millennium Tower’s original developer, Mission Street Development, an affiliate of Millennium Partners, supported the development of the pile upgrade.

Work will be funded by the many parties that settled the homeowners' claims—and their insurance companies. At least of portion of the settlement will be paid for by California taxpayers because construction of the state-funded Salesforce Transit Center project, which neighbors the tower, was blamed by the Millennium Tower Association for further destabilizing the already sinking building.

In 2018, a San Francisco judge ruled that the Transbay Joint Powers Authority, the state agency that owns the $2.2-billion transit project, had a duty to defend against the homeowners' claims.

Construction on the perimeter pile upgrade is expected to last about two years. All significant components of the government permitting process have been completed.

The dispute resolution involved a private mediation, led by retired Judge Daniel Weinstein, Judge Ronald Sabraw and mediator Gerald Kurland.