IN-SITU CAPPING

In-situ treatment risk minimization may be accomplished on some projects through in-situ treatment. Capping of sediments in place can reduce exposure pathways by limiting bioavailability. Caps may be designed to reduce advective flow by creating a hydraulic barrier or to simply create a physical barrier. Recent advancements have been made in the area of cap design that include incorporation of reactive materials into the cap. These reactive materials are capable of either sequestering or treating the contaminates, preventing their release. CETCO offers products that range from impermeable and permeable mats to Reactive Core Mats™ for in-situ capping.

In-situ cap designs may be broken down into either permeable or impermeable. Impermeable caps provide a hydraulic barrier which minimizes contaminate transport through advective flow. Impermeable caps may be constructed using all natural materials or through the use of geosynthetics. CETCO provides Volclay bentonite for use in creating impermeable seals over contaminated sediment. This sediment is typically dispersed over the sediment, as the clay sinks it hydrates into a uniform clay layer. Alternately CETCO GCLs provide a geosynthetic solution. These liners may be deployed over the sediment and subsequently covered with a confining layer. GCLs provide a method of assuring uniform performance over the entire cap.

Permeable caps may also be constructed over contaminated sediment. Designs for these caps typically follow specific guidelines which aid in determining adequate thickness required to allow the cap to provide protection and prevent deleterious effects that that may be caused by natural forces. To augment permeable caps a reactive component may be added. The reactive component acts to sequester or treat the contaminates. By doing so the required cap thickness may be reduced. CETCO provided CETCO Organoclay, an organophyllic, hydrophobic material which sequesters oils and greases or most high molecular weight, low solubility organics. Alternately, Reactive Core Mats may be used to provide a geosynthetic solution. Reactive Core Mats encapsulate the reactive component into geotextiles. This ensures uniform coverage of reactive material over the entire cap.

To ensure that the geosynthetic materials remain in place CETCO can provide Protext 2000. This heavy weight, sand filled geotextile sinks to the bottom of the water column and provides protection and ballast for other geosynthetics.

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All rights reserved. CETCO is a wholly owned subsidiary of AMCOL International Corp.
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