Soil mixing is an effective in-situ method to introduce a reagent using excavation and specialized mixing equipment, which alters the chemical or physical condition of the soil while reducing heterogeneity. The reagent is applied at a specific dosage rate and mixed in a one-step process without transporting soil from the treatment area. Cement, polymers, or pozzolanic reagents can be introduced to stiffen or solidify the soil unit, adding compressive strength and reducing permeability.. For environmental applications, this approach can be used to reduce contaminant interaction with the surrounding environment and reduce contaminant leaching.