Use of deep soil mixing as an alternate verticle barrier to slurry walls

Slurry walls have become an accepted subsurface remediation technique to contain contaminated zones. However, situations develop where conventional slurry wall excavation techniques are not suitable. The use of conventional containment wall construction methods may involve removal and disposal of contaminated soils, stability concerns and the risk of open excavations. For these reasons, other installation techniques have received further consideration. Deep Soil Mixing (DSM) has emerged as a viable alternative to conventional slurry wall techniques. In situations dictating limited soil removal for contamination or stability concerns, or where space is a limitation, DSM can be used for installation of the barrier. Proper installation of a DSM wall requires sufficient monitoring and sampling to evaluate the continuity, mixing effectiveness, permeability and key into the confining layer. This paper describes a case study where DSM was used to cross major highways to avoid open excavation, and along slopes to reduce stability concerns. The DSM barrier was tied to an existing conventional slurry wall that had been installed in more stable areas without highway traffic.