Slurry Cut-Off Walls Stop the Flow of Groundwater

Slurry Trenches can stop groundwater and help to dewater jobsites

slurry wall hazardous waste containment long stick excavator

Slurry trench being excavated with a long stick excavator

Commonly the terms Slurry Wall, Slurry Trench, or Slurry Cut-Off 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 1000s 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 below to learn more about the various types of slurry walls.

These pages describe the relative advantages and disadvantages of each of these wall types as well as explaining differences in construction materials and procedure

Most slurry walls are excavated with backhoes which can be modified to dig up to 90 ft 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/s) 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.

The Use of Bentonite in Excavating Slurry Trenches

Slurry Mixing Plant

Bentonite slurry mixing plant

Slurry walls are constructed by excavating a narrow trench under an engineered fluid.  The most common engineered fluid in this application is a colloidal suspension of bentonite clay in water.  Bentonite clay used in slurry wall applications is typically a sodium based bentonite that is formed from the weathering of volcanic ash.  Bentonite is capable of absorbing a significant amount of water, so much so that individual particles can swell up to 6 times their original volume!  This property makes bentonite useful in creating medium to high viscosity engineered fluids.  The mixture of bentonite and water is commonly referred to as bentonite slurry or just simply slurry.  Even below the water table the slurry stabilizes the excavation and prevents the trench walls from collapsing.  

Geo-Solutions' Experience with Slurry Wall Construction

The staff of Geo-Solutions has been involved in the construction of over a thousand slurry walls.  We’ve authored or co-authored numerous publications on the construction of slurry walls.  the We have a variety of different business models tailored to meet the demands of each unique project.  Most often we serve as the prime contractor for projects on which a slurry wall makes up the largest contract item.  On projects where the slurry wall is an ancillary item we serve as the slurry wall subcontractor.  For smaller or remote domestic and international projects we provide on-site technical assistance services to general contractors seeking to bid and execute the slurry wall work with their own forces.  Additionally, we frequently serve as consultants to Owners/Engineers that are investigating the economics or feasibility of barrier wall options.  Our consulting involvement varies from project to project, but normally consists of bid document review, feasibility studies for barrier wall options, and bench scale studies to devise practical, low-permeability, contaminant-resistant backfill mixtures.

slurry wall movie

Slurry Wall Movie
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Why Use Geo-Solutions for Your Slurry Walls

Geo-Solutions staff has the construction experience and technical knowhow to help you during every stage of your project.  We believe that our combination of experience and knowledge makes us unique in that we can help design and execute the work.  Our specialty equipment fleet, including high-production batch plants, excavator stick extensions, trenching buckets, drill rigs, and clamshells, is state-of-the-art and is a key to our continued success.  In addition to full scale contracting, we can provide supervision and all the specialty equipment necessary for slurry cut-off wall and other specialty construction projects.  On these projects we bring just what you need to the project and no more.  The result is an economical project constructed under our expert technical guidance which results in a project with a smaller likelihood of subcontractor hassles and unnecessary costs.

Design Mix Studies

Given our unique experience, contractors with technical backgrounds, we can provide useful insights to projects at the bench scale level.  Bench scale testing requires a detailed knowledge of how the wall will be constructed on a full scale level to ensure that the bench scale procedures result in a mix that will closely resemble the wall’s macro behavior. For more information on how we may assist you in your design mix study or bench scale testing check out our design support page.

Learn More about Slurry Cut-Off Walls

Slurry Wall Sample Specifications

  • Read and download Geo-Solutions sample specs for soil bentonite slurry cut-off walls, cement bentonite slurry walls, soil-cement-bentonite slurry walls, composite slurry walls, bio-polymer slurry groundwater collector trenches.

Contact Us

For help with slurry cut-off walls utilizing various types of bentonite slurry mixes, call us at 724-335-7273 or click here.