Ground water investigations and ground water diversion reports have become the new normal for our clients when building basements which are deep enough to be in this sphere. The level of detail and cost has left us wondering if it was a big scam. And then we read about a 7 year old residential tower in San Francisco that is sinking and we realise it’s a big issue.
For the residents of Millennium Tower in San Francisco there is a real sinking feeling. Since the completion of construction in 2009 the luxury real estate tower has sunk into the ground 40-cms, and begun tilting to the Northwest by 20-cms. And that isn’t even the main problem. The real kicker is that Millennium Tower is also in the middle of an earthquake zone.
While many of the residents are justifiably upset and even taking legal action, the developers maintain they done nothing wrong. There are no San Francisco City requirements to build to bedrock, which is why the foundation of the huge building consists of clay and sand. Millennium Partners argue that the building has only sunk since the construction of a neighbouring transit centre began. Apparently the six billion dollar Transbay Transit Centre, which is currently under construction, have built a giant train tunnel immediately adjacent to the Millennium Tower and then removed the water from the earth. It is for this reason that the Millennium Partners believe they have done nothing wrong.
In Auckland, we are dealing more and more with ground water, ground water monitoring and ground water diversion. The displacement of water and change in underground rivers can affect other buildings foundations. It is our understating that buildings (and the land thereon) in the reclaimed parts of the CBD are moving up and down with the tidal changes.
The level of detail required to manage this issue is building consent like at resource consent. We ask you to plan and prepare for this in terms of scope and cost before embarking on major scale basement work.