(470f) Organoclays For The Capping Of Contaminated Sediments

Conventional capping of contaminated sediments with sand or other inert materials may not be effective in areas where sediments contain nonaqueous phase liquids (NAPLs) due to displacement or continued migration of NAPLs. The NAPL may migrate as a result of the disturbance associated with capping of the sediment, subsequently during consolidation or as a result of gas release. Organoclays can be an especially effective means of addressing migration of NAPLs and mobile dissolved phase hydrophobic organic compounds. The use of organoclays in laboratory, field demonstration and full-scale field applications will be reviewed. The effectiveness of organoclays in these applications will be summarized. Approaches to effectively place the material in the field will also be summarized.

The potential for organoclay as a capping material will be evaluated primarily on the basis of laboratory measurements of flow and sorption characteristics of organoclay after exposure to water, gas and NAPLs. Organoclays were found to provide good control of both dissolved and nonaqueous phase contaminants. Contact with organoclay gave rise to significant swelling of organoclays and a simultaneous reduction in effective permeability of the organoclay. This could serve to enhance effective utilization of organoclays by forcing lateral migration around seeps but also discourage subsequent migration of NAPLs into a treatment layer. Implications of these results for the design and implementation of organoclays for NAPL control in sediments were assessed.