If you are wanting build anything substantial in the inner West you will need to be aware of the floaters.

Just under the surface of the Western suburbs acid clay lurks a menace, floating rocks the size of Volkswagons that make for unstable footing under older houses. Larger developments like the 3 storey apartments next door require removal of these rocks so that excavation can proceed. They are clawed out then broken up prior to removal.

Below a pile nearly all broken up from a small area to begin the process.