What caused the millenium tower to sink in san francisco?
The critics blame the city for allowing Millennium partners to anchor the building into packed sand rather than bedrock. The problem with Millennium tower arose because the 60 to 90-foot-long friction piles supporting it were driven into sandy soil rather than the bedrock, 200 feet down.
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.
### Instruction: What caused the millenium tower to sink in san francisco?
### Input: 
### Response: The critics blame the city for allowing Millennium partners to anchor the building into packed sand rather than bedrock. The problem with Millennium tower arose because the 60 to 90-foot-long friction piles supporting it were driven into sandy soil rather than the bedrock, 200 feet down.