Commonly the terms Slurry Wall, Slurry Trench, or Slurry Cutoff Wall refer to non-structural vertical cutoff walls constructed using the slurry trench installation method. The slurry trench installation method refers to construction practices that utilize an engineered fluid (normally consisting of some mixture of clay and water) to hold open the sidewalls of an excavation thereby permitting the excavation of deep and narrow trenches without the need for other conventional excavation support systems. Slurry walls are mainly constructed to slow the flow of groundwater. Occasionally, these walls are also intended to slow the migration of subsurface contaminants, namely by slowing the flow of the groundwater carrying the contaminants. Slurry walls have been employed at thousands of sites across the United States and internationally in a variety of applications; at waste sites to contain contaminated groundwater, at "clean" sites to dewater excavations, and to stabilize dams, levees, and similar structures. Click on the links at the left to learn more about the various types of slurry walls.
Most slurry walls are excavated with backhoes which can be modified to dig up to 90 feet deep. Deeper depths are possible with clamshell excavators. When the excavation is complete, the trench is filled with a low permeability mixture (normally less than 1 x 10-7 cm/sec) called backfill. Normally backfill consists of a blend of soil and bentonite; soil, cement, and bentonite; or cement and bentonite. Composite barriers using synthetic materials (such as HDPE liners) or composite trench systems are also possible.