Slurry Cutoff Walls

For environmental applications, slurry cutoff walls offer a cost-effective solution for remedial actions. Additionally, such walls typically eliminate the need for personnel to enter the trench providing an engineering control for worker safety. These nonstructural barriers are constructed to intercept and impede the flow of fluids underground and are effective for underground pollution containment. Constructed by excavating a narrow trench under an engineered fluid, the Geo-Con slurry trench technique permits the installation of deep barriers in all types of soil and groundwater conditions. Our more than 400 installations include the construction of impermeable soil-bentonite, cement-bentonite, and composite slurry walls.

Geo-Con has also pioneered the use of alternative materials such as attapulgite clay, special cements to meet strength requirements, and silicates for cutoff walls where site leachate conditions and incompatibility prohibited the effective use of bentonite. These techniques have been further modified in constructing cement-attapulgite, soil-attapulgite and cement-bentonite-silicate cutoff walls. Additionally, Impermix walls have been constructed where specifications require both strength and permeability requirements.

For projects that have site conditions that prohibit the use of deep (up to 80') slurry trenches due to soft unstable soils, or high levels of contamination, there are alternatives to the conventional hydraulic excavator and/or clamshell method. Where the risk of a trench collapse would be detrimental, Geo-Con can use its DSM procedure to install a deep (up to 120') vertical barrier by continually injecting a slurry with increasing depth, thus mixing with the soils insitu. This technique avoids the excavation of contaminated soils and leaves a waterproof retaining wall in place.

Equipment
Geo-Con owns and operates a fleet of modern slurry wall equipment, much of it designed and built for these special applications. Long-stick hydraulic backhoes have depth capabilities to 80 feet and our clamshell buckets provide for deeper excavations. The company owns a variety of special purpose digging buckets and tools to excavate cemented soil and weathered rock.

Geo-Con owns more than a dozen high-shear, colloidal slurry mixing plants to continuously produce bentonite, cement, cement-bentonite or attapulgite slurry to rigid specifications. A variety of slurry additives can be blended to improve the workability or performance of the slurry in special instances. The Geo-Con slurry plant is designed to produce fully hydrated slurry without storage ponds.

Slurry trench backfill mixtures are blended with conventional construction equipment, power harrow, or special mobile mixing plants to suit project requirements and are placed by a variety of proven methods including tremie, concrete pump, or lead-in trenches.

Design Mix and Compatibility Testing

Geo-Con's commitment to quality in slurry wall construction is demonstrated by all activities being carried out in a consistent, systematic, and controlled manner. Geo-Con implements a three-phase program for all slurry wall operations:

1. Determination of the most technically efficient, yet economical design for the construction materials.

2. Daily onsite QA/QC procedures in accordance with specifications and/or Geo-Con's QC SOPs.

3. Documentation of product performance by laboratory testing of field samples.