Deep soil mixing (DSM) has been used in European and Asian countries for a few years but was introduced only recently in Australia. DSM is frequently used to improve soft compressible clays where traditional methods such as surcharging and wick drains are not feasible due to either stability reasons or time and/or space constraints. Bridge abutments and road embankments are classic examples where DSM is traditionally used. This paper presents a case study where deep soil mixing was carried out using Cutter Soil Mixing (CSM) equipment. CSM columns were used to support a 53.5m diameter, 20m high, large storage tank instead of founding on deep piles. Analyses using analytical and numerical methods provided confidence that the settlement criteria imposed by the client could be achieved. Numerical analyses were simplified by adopting 2-D axi-symmetric conditions and converting CSM columns into equivalent “doughnuts”. Although laboratory tests were carried out to assess the strength of the mix for different cement volumes, sensitivity studies were carried out numerically to assess the effects due to variations in column strength before finalising the design. Further strength testing was carried out during and following installation to confirm actual strength gain. To improve the stress transfer to the CSM columns, “pile caps” were formed during the installation process. These caps were formed by pre-excavating one metre deep at each column location and using the overflow of cementitious/soil materials to form the cap. This environmentally friendly innovation avoided the removal of excess cementitious material from CSM operations. Settlements were monitored during water testing and results indicated the successful completion of the project.