A Consolidation and Contaminant Transport Device for Assessing Reactive Mat Effectiveness for Subaqueous Sediment Remediation

This paper describes the design and fabrication of a new laboratory testing column to assess the effectiveness of a permeable reactive mat for in situ sediment remediation. After the composite mat, which consists of top and bottom filtering geotextile layers and a middle reactive core, is placed on the sediment surface, hydrodynamic dispersion and pore fluid flow carry contaminants through the mat. In the reactive layer, the contaminants react with one or more amendments. A thin cap of new sediment material can be placed on top of the geocomposite to promote a new, healthy benthic community. The processes controlling these geocomposites have not been physically modeled to assess their effectiveness. The new device is fundamentally a sediment column, but with the capability to apply a constant, overlying stress to the sediment-reactive mat column to cause its consolidation. Pressure-volume controllers at the top and bottom of the sediment column allow in situ pressure conditions to be imposed and allow for chemical sampling of inflow/outflow fluids.