The SMW system is an economic method for the construction of cut-off and retaining walls. Mixing self-hardening slurry in-situ with native soil (SMW system) offers a cost-effective technique for the construction of cut-off and retaining walls. Three parallel mixing paddles are driven by three independent rotary drives. They mix the soil with the slurry which is injected through the drill system. A continuous wall is constructed by installing overlapping elements in an alternating sequence.