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Sensors Installed To Measure Sinking Of Millennium Tower

SAN FRANCISCO (CBS SF) -- Engineers hired by the Millennium Tower Association on Monday started to install data collection devices around the building to monitor and collect settlement data.

The luxury high-rise in the South of Market area is gradually sinking and tilting.

There will be three drill sites where the devices will be installed. Two will be on Mission Street and the third will be on Fremont Street.

All three holes will be drilled into the bedrock.

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At a press conference Monday morning, questions like 'Why is the tower sinking?' weren't answered. Instead, the focus was on how the problem would get fixed. Before that can be fully understood, data needs to be collected.

"What I want to do is to try to bring some clarity and some information to a process that has sort of been fast-paced and moving," said Evette Davis of BergDavis Public Affairs, speaking on behalf of the Millennium Tower Association.

Settlement extensometers are a critical part to this process. They will go at various intervals in the Old Bay clay, which is underneath the Colma sand.

Patrick Shires is the soil engineer the Millennium Homeowners Association hired to conduct an investigation independent of others that have been done.

"What they will tell you is where is the soil compressing, where is it settling," said Shires. "And that's important, because if you know where it's settling, you can determine which part hasn't settled yet."

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Once that is figured out, then engineers will have a better understanding of how long the building will keep settling and at what rate.

The drill work will take three weeks to complete, but it still may be five or six months before the results of these tests are made public.

The city attorney's office issued a subpoena to the developers last week.

Millennium Partners insist the building is safe and structurally sound.

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