At the site of the former steelworks in Newcastle (New South Wales), Menard constructed a soil-bentonite wall, the deepest in the world, designed to prevent leaching of contaminants into the Hunter River. The up-gradient cut-off wall, 1.5 km long and 28 m to 49 m deep, was constructed to isolate the contaminated zone from the groundwater. The system is completed by constructing a low permeability horizontal cap effectively preventing ingress of surface water. As a result, the hydraulic gradient between the river and the contaminated zone is progressively exhausted with the amount of contaminants leaching into the river falling rapidly below acceptable levels.