Deep mixing methods for the construction of cut-off walls or excavation support systems are carried out typically by the use of single or multiple augers to produce a series of circular columns that may be arranged in different patterns. The New CSM method produces well blended rectangular panels of treated soil. They offer a number of advantages over circular column solutions, the most significant of which are: cost, a reduction in the number of joints in a wall, the freedom to use different types of reinforcement. The machines give the possibility of introducing control instrumentation deep in the ground and thereby to monitor and control quality.