In the broadest use of term, in-situ chemical reduction (ISCR) refers to the use of chemical reduction (removal of oxygens) for the in place remediation of contaminants. In practice, the term is often used to describe process of injection or direct mixing of reactive chemical reducers with the soil and groundwater for the purpose of reducing chemical contaminants in place. Within the context of soil mixing, this term refers to the use of chemical reducers delivered and mixed with the soil, via soil mixing, for the purposes of in place treatment. The most common type of soil mixing used for ISCR is large diameter single auger soil mixing, but the technique can be accomplished using excavator buckets and rotary tools too. Soil mixing offers numerous technical advantages over alternative reducing agent delivery methods, with the largest advantage being that intimate contact between the reducing agent and contaminants in guaranteed with soil mixing, independent of soil lithology. Other methods like direct injection are not effective in certain soil types and, even in soil types that are conducive to direct injection, the injection program can have variable effectiveness in achieving reducing agent / contaminant contact. Other reducing agents, e.g. iron, are not easily applied using direct injection.
Geo-Solutions has completed a number of soil mixing projects for accomplishing in-situ chemical reduction objectives. The most common application of ISCR via soil mixing is for the injection of zero valent iron (ZVI) and bentonite for the treatment of chlorinated solvents.
