A zinc chloride tank at an industrial site had leaked and released unknown quantities of ZnCl2 into the underground. Over the years, a significant, up to 500 m long contaminant plume developed in the groundwater. The sediment of the aquifer was dominated by medium sand with portions of fine sand. The zinc concentrations in the effluent plume were between 5 and 20 mg / l in the planned range of the in situ barrier. The groundwater velocity was around 0.7 m/day. Due to the active operation of the industrial site and the depth of the aquifer (groundwater level approx. 14 m below ground level), an excavation of the soil was not considered economical. ColFerroX technology was then tested in pilot scale in order to immobilize the pollutant.