The sinking and leaning Millennium Tower may now be partly supported to bedrock, but a glass industry veteran says he is concerned about the ongoing risk from its windows after two failed during a windstorm earlier this year.
It was on March 21, the second of two windstorms that hit the city, that an open 49th floor window partly broke free from the tower, sending glass into the unit and some down to Mission Street below.
While the independent investigation into that failure is still pending, a Millennium-hired engineer’s report obtained by NBC Bay Area’s Investigative Unit under the state's Public Records Act, includes photographs showing large pieces of broken glass inside the 49th floor unit.
“This is extraordinary,” said Bill Thomas, a Southern California-based window inspector and consultant. “In my opinion, this is a very dangerous situation and it could very well result in very serious injury or death.”
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The photo is marked with several red arrows pointing to larger pieces of glass both on the window seat and the floor of the unit. Millennium engineers said in the report that those glass fragments from the inner pane fell mostly into the unit when the window broke free from its supporting arms and slammed into the building.
Thomas says it’s the large pieces that have him so concerned, given the potential that they could inflict serious injury to anyone near that window in the room.
“If you look at the picture, you will see very large chunks of heat, broken heat-strengthened glass on the on the window seat right below the window and more importantly on the floor,” Thomas said.
Normally, windows that open in high rises have to be safety glass, so the inner pane will either hold together or break into small harmless pieces if something goes wrong.
But Thomas says safety glass is not required for windows that are 18 or more inches above floor level, like the one on the 49th floor. That’s because windows that are 18 inches high or more are considered less of a risk to children.
San Francisco Supervisor Aaron Peskin, who has held several hearings on the status of the troubled Millennium Tower, says the risk of glass hitting someone in a unit is unacceptable.
“This seems to be part of an ongoing pattern at the Millennium as it relates to their operable windows,” Peskin said.
And while Millennium officials say they’re installing more than 3,000 new stay arms to better secure the windows, Peskin says he remains skeptical. “I have serious questions at this point as to whether or not the stay arms are actually going to even fix the problem.”
Meanwhile, the same report written by Millennium engineers shows that a second window, on the 47th floor, failed during the same windstorm. The engineer’s report to Millennium management indicates the second window failed because it was loose in its steel frame and shifted, causing it to crack.
Fortunately, Thomas says, the cracked outer window that failed had a protective layer that prevented the pane from breaking completely, so no shards fell onto the street – and people – below.
But Thomas says that layer wouldn’t be much protection if an entire window broke loose from its frame and fell – a potential danger if the glass should become loose enough in a frame.
“That’s the last thing you want is any glass shifting in your frames,” Thomas said.
The Millennium Tower homeowners association initially said the second window failure was unrelated to the weather event, but now says the independent firm commissioned by the city confirmed the 47th floor failure concluded the failure was, in fact, due to winds.
The final report from the glass experts into what triggered window failures in seven separate San Francisco high-rises is due out later this summer.
