By Andria Borba

SAN FRANCISCO (KPIX 5) – A major construction fix to stop the city’s Millennium Tower from sinking has been abruptly halted.

Behind the tarps on the corner, heavy equipment sits silent on the corner of Fremont and Mission Streets, as the $100 million fix on the leaning and sinking tower hit a new snag.

UPDATE: Repairs of Leaning San Francisco Skyscraper on Hold; Engineering Expert Blasts Plan

In the past month, during the fix, the building has tilted and sank another inch to the northwest. Oakland consulting structural engineer David Williams calls the development more than disturbing.

“It’s reactivated the settlement and it’s all differential settlement, meaning that it’s going on one side of the building and it’s causing the tilt. The rate of settlement is higher than it’s been throughout the history of settlement of the building,” Williams told KPIX 5 on Wednesday.

Millennium Tower in San Francisco. (CBS)

Millennium Tower in San Francisco. (CBS)

The retrofit is a perimeter pile upgrade along Fremont and Mission, which will drive pilings into the bedrock 10 feet out from the building’s foundation to correct the tilting and sinking.

Williams said, “The loads have to be distributed from the existing foundation out to the perimeter and that’s a pretty risky operation. It will have to be very carefully monitored if they proceed with it.”

The 58-story condo tower, which made headlines as it began to sink, had actually been sinking less in the past few years, before the upgrade work began this year.

Work stoppage on the retrofit has been confirmed by Doug Elmets, spokesperson with the Millennium Tower Association.

Emlets released a statement to KPIX 5, which read in part, “The monitoring has indicated an increased rate of settlement associated with pile installation. Out of an abundance of caution, we have placed a two to four-week moratorium on pile installation while we try to understand better the mechanisms associated with the increased settlement rate and available means of mitigating this.  There has been no material harm to the building and it remains fully safe.”

Williams called the pause a “no brainer” given the amount the building has moved in a month.

“You may expect a little disturbance when you go in and do construction around it, but the rate of settlement is very severe,” he said.