A clay barrier constructed in the subsurface to prevent the spread of contaminants by preventing water flow.

Construction method used in wet, unstable soil. As the trench is excavated, it is filled with bentonite slurry. This fluid mixture allows the excavation to continue while preventing the passage of groundwater or the collapse of the trench walls. The trench is later backfilled with other material, forms for poured concrete walls, or pre-fabricated wall sections.

the three-foot-thick concrete perimeter wall that forms the World Trade Center site's east and west bathtubs, supported laterally by high-strength tieback anchors

A slurry wall is a type of wall used to build tunnels, open cuts and foundations in areas of soft earth close to open water or with a high ground water table.