In Situ Capping of Contaminated Sediments with Organophilic Clay

Port authorities are seeking innovative ways to conduct remediation of contaminated sediments. In-situ capping involves the placing of a subaqueous cover over contaminated sediments to stabilize sediments, minimize their re-suspension and transport, and reduce dissolved contaminant transport into surface waters. In-situ capping can be limited by concerns regarding navigation, uniform cap placement, bio-intrusion and geotechnical stability. A potential solution for many in-situ capping concerns is the use of an active material cap. Reactive or adsorptive materials, such as organophilic clay, can provide higher retardation capacity of the contaminants than sand or gravel. Over the past several years organophilic clay has been used at several sites for in-situ capping of contaminated sediments. Organophilic clay may be mixed with sand or pea gravel and placed in bulk. Alternatively, a reactive mat that encapsulated organophilic clay between two geotextiles and/or a marine mattress can be used. The reactive material is armored as needed to protect it from erosion.