Millennium Tower, seen from Mission Street,
has been slowly sinking right from the start -
17 inches - plus a northern tilt.

Millenium Tower is seen reflected in Salesforce East at 350 Mission Street on Tuesday, July 18, 2017 in San Francisco, Calif. Photo: Lea Suzuki, The Chronicle *

Millenium Tower is seen on Tuesday, July 18, 2017 in San Francisco, Calif. *

16. One Rincon Hill North Tower (left)Year completed: 2014Height: 541 feet Photo: See Notes *

15. One Sansome StreetYear completed: 1984Height: 551 feet Photo: Carlos Avila Gonzalez *

14. Spear TowerYear completed: 1976Height: 564 feet Photo: Google Maps *

13. 44 Montgomery Year completed: 1967Height: 565 feet Photo: John King, The Chronicle *

12. One Embarcadero CenterYear completed: 1971Height: 569 feet Photo: John King *

11. Four Embarcadero Center Year completed: 1984Height: 570 feet Photo: Gabrielle Lurie, Special To The Chronicle *

10. Market Center (center)Year complete: 1975 Height: 573 feet Photo: Google Maps *

9. 50 Fremont Year completed: 1985Height: 600 feet Photo: William A. Porter *

8. 101 CaliforniaYear completed: 1982Height: 600 feet Photo: John King *

7. One Rincon Hill South TowerYear completed: 2008Height: 605 feet Photo: Mike Kepka *

6. Millennium TowerYear completed: 2009Height: 645 feet Photo: John King, The Chronicle *

5. 345 CaliforniaYear completed: 1986Height: 695 feet Photo: John King, The Chronicle *

4. 555 California Year completed: 1969Height: 779 feet Photo: Eric Luse, The Chronicle *

3. 181 Fremont (under construction)Year complete: 2017Height: 802 feet Photo: John King, The Chronicle *

2. Transamerica PyramidYear completed: 1972Height: 853 feet Photo: Katy Raddatz, The Chronicle *

1. Salesforce Tower (under construction)Year complete: 2018Height: 1,070 feet Photo: Noah Berger, Special To The Chronicle

* Millennium Tower, seen from Mission Street, has been slowly sinking right from the start - 17 inches - plus a northern tilt. <#photo-13263068> * Millenium Tower is seen reflected in Salesforce East at 350 Mission Street on Tuesday, July 18, 2017 in San Francisco, Calif. <#photo-13263074> * Millenium Tower is seen on Tuesday, July 18, 2017 in San Francisco, Calif. <#photo-13263075> *

A fix appears to be in the works for San Francisco's sinking and tilting Millennium Tower - just as a new report estimates the 58-story luxury high-rise has sunk yet another inch in the past seven months.

City officials and other sources familiar with the situation tell us that the building has now dropped 17 inches since construction got under way in 2005 and continues to descend into the bay fill at Mission and Fremont streets. The sinkage is more pronounced on the northern side, the direction in which the tower is leaning, said the sources, who spoke on condition of anonymity because the Millennium's problems are the subject of numerous lawsuits.

That lean is now up to nearly 14 inches at the building's roof - an additional 2-plus inches more than the tilt measured in January.

The good news for the tower's well-heeled residents, who paid from $1.6 million to $10 million for their condominiums, is that a pair of engineering firms hired by developer Millennium Partners and other parties involved in the dispute think they have a solution that will stabilize the tower and prop it back upright.

San Francisco's "leaning tower" is sinking faster than previously thought.

Media: ZMG San Francisco

ALSO

* Former San Francisco 49er quarterback Joe Montana is seen on Monday, March 30, 2010 in the Club Level of the Millennium Tower in San Francisco, Calif. where he and his wife, Jennifer, have recently moved into a condominium.

Joe Montana sues SF's Millennium Tower developers

* The view from the 62nd floor of the Salesforce Tower in San Francisco on January 13, 2017.

Milestone for Salesforce Tower: Now the tallest in the West

The firms, Arup Group and LERA, say the problem can be remedied by drilling 50 to 100 new piles down to bedrock from the building's basement. Each pile would be anywhere from 10 inches to a foot in diameter.

After we first reported the Millennium Tower's problems in August, the developer insisted that its decision not to anchor the foundation to bedrock in the first place had nothing to do with the building's sink and lean - and that the ground under the building had been destabilized by neighboring construction.

The high-rise's 900 piles now descend 60 to 91 feet - well short of the 200 feet to bedrock.

The engineering firms estimate the fix will cost $100 million to $150 million - more than your average home foundation repair, but a lot less than the billion-dollar-plus price tag that some experts have feared.

Like so many other things involving the slow-motion fiasco, just who would pay the bill would be the subject of negotiation, and possibly litigation, involving Millennium Partners, the homeowners association and the public agency building the Transbay Transit Center next door, which the developer and condo owners insist bears some responsibility.

One source told us that residents would probably be able to stay in the building while the repairs were under way.

"Conceptually, it's workable, but they need to vet it out," the source said.

Another source told us the vetting needed to be done quickly. "There is a sense that we need to start doing something sooner rather than later because of the continuing sinkage," the source said.

That sinkage shows no sign of easing up. The new engineering report by Arup shows that the rate of sinking remains steady. There is also evidence of continued cracking in the basement, according to the report we've obtained.

"It's approximately the same rate of sinking and tilting as before," said one of the sources.

P.J. Johnston, spokesman for Millennium Partners, declined to comment on the talks or the latest engineering report, but said, "Our highest priority has always been to fix the building.

"We've been working closely with the (homeowners association) throughout the mediation process, and we're optimistic that we'll reach an agreement on the fix," Johnston said. "To do so, it's imperative that we respect the confidentiality of the mediation process. Any proposed solutions are preliminary until an agreement is reached."

Jack Gallagher, a spokesman for the San Francisco city administrator's office, which is reviewing all downtown high-rise construction in the wake of the Millennium Tower's problems, said no repair plan has been submitted to the city for permits. "And since we haven't seen any of their plans, we have nothing we can comment on," he said.

Bill Strawn, spokesman for the Department of Building Inspection, said his office had just received the latest engineering report on the building's slippage, and had sent it to the city's data engineers for review.

In the meantime, he said, the department sent out a team of inspectors Tuesday to follow up on a report done six months ago detailing cracking and other damage from the building's movement, and a list of repairs that needed to be done in the short term. The initial repairs were done, and the latest inspection is expected to reveal whether more work is needed.

The city is involved in part because it's the lead in the multiagency Transbay Joint Powers Authority, which is building the Transbay Transit Center next door. Millennium Partners says the tower's problems were caused by construction crews pumping groundwater from the adjacent site, which the developer says destabilized the soil under the tower.

The transbay authority argues that the slippage has continued long after the pumping ended, proving that the culprit was the developer's decision not to drive piles all the way to bedrock. However, Millennium Partners has also said it suspects construction of the nearby Salesforce Tower has since added to the problems.

Before it became a national punch line, the Millennium was a prestige address for big-name buyers like former 49ers great Joe Montana*.* Despite the tower's problems, the city and developer say the building is still safe - but that's more than you can say for the value of the condos, which has tumbled.

About 100 condo owners got a small break this week, when city Assessor Carmen Chu began notifying them that their 2017 property-tax bills are being reduced by about $3,000 apiece - reflecting an average $320,000 drop in value on each of their units.

Another 100 or so owners also petitioned to have their taxes reduced, but Chu said no.

"It really depends on when you bought your property," she said. "If it was at the height of the market, you were probably impacted" by the recent revelations.

On the other hand, Chu said, if an owner bought "at a low in the market" - for example, right after the 2008 economic crash - "you probably have seen a lot of appreciation" in value over the years, so "you are not going to get as much of a reduction."

Tell that to Jerry and Pat Dodson, who bought their 42nd-floor condo soon after the building's 2009 opening, when prices were still relatively low - and are not expected to benefit from the 2017 reassessments.

"Our unit is assessed at $2.3 million - but I doubt we could sell it for half that," Pat Dodson said.

Chu notes that those who don't get a reassessment can take their case to the city Assessment Appeals Board. But that's not good enough, say the Dodsons, who have filed their own lawsuit against Millennium Partners and the city.

"We would not be in this problem if city officials had done their job," Pat Dodson said. "They issued the certificate of occupancy knowing that the building had already sunk and tilted."

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross

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