Environmental contamination is a worldwide problem due to the persistence of chlorinated hydrocarbons and toxic metals in the soil and groundwater. Often these contaminants are located in regions very difficult to reach by conventional methods. However, suspensions of specifically tailored zerovalent iron particles transport through packed beds or soil to effectively remediate halogenated hydrocarbon contaminants, such as trichloroethylene (TCE), by chemical reduction to non-toxic products. In order to study the transport of particles through the subsurface, sand and soil packed columns were designed. With these columns, it is possible to quantify the amount of iron retained by the column and determine where in the column the iron particles are retained. Experimental elution results were compared to contemporary transport models based on particle filtration through granular media. Control experiments showed that unmodified iron particles rapidly agglomerated in water, and were filtered efficiently by the columns. However, colloidal suspensions formed by combining iron particles with anionic transport agents achieved drastically improved iron particle elution through sand and soil packed columns. Additional experiments showed that adding specific combinations of anionic hydrocolloids and polyelectrolytes to iron suspensions further enhanced particle transport, mainly by controlling particle aggregation. Iron particle aggregation and subsequent sedimentation resulted for higher iron particle concentrations. The incorporation of anionic hydrocolloids was found to affect aggregation, though further studies are underway. Through collaboration with industry, this technology has already been successfully implemented in full-scale remediation field studies.