In Situ Clay Formation: Evaluation of a Proposed New Technology for Stable Containment Barriers

Abstract

Containment of chemical wastes in near-surface and repository environments is accomplished by designing engineered barriers to fluid flow. Containment barrier technologies such as clay liners, soil/bentonite slurry walls, soil/plastic walls, artificially grouted sediments and soils, and colloidal gelling materials are intended to stop fluid transport and prevent plume migration. However, despite their effectiveness in the short-term, all of these barriers exhibit geochemical or geomechanical instability over the long-term resulting in degradation of the barrier and its ability to contain waste. No technologically practical or economically affordable technologies or methods exist at present for accomplishing total remediation, contaminant removal, or destruction-degradation in situ. A new type of containment barrier with a potentially broad range of environmental stability and longevity could result in significant cost-savings. This report documents a research program designed to establish the viability of a proposed new type of containment barrier derived from in situ precipitation of clays in the pore space of contaminated soils or sediments. The concept builds upon technologies that exist for colloidal or gel stabilization. Clays have the advantages of being geologically compatible with the near-surface environment and naturally sorptive for a range of contaminants, and further, the precipitation of clays could result in reduced permeability and hydraulic conductivity, and increased mechanical stability through cementation of soil particles. While limited success was achieved under certain controlled laboratory conditions, the results did not warrant continuation to the field stage for multiple reasons, and the research program was thus concluded with Phase 2. .This page intentionally left blank 5 Preface

Enhanced Attenuation: A Reference Guide On Approaches To Increase The Natural Treatment Capacity Of A System

“…More recently, a wide variety of other types of barriers have been proposed or tested. These include installation of impermeable membranes (e.g., Envirowall, Inc. Gretna, LA), injection of colloidal silica or polysiloxane (Moridis et al, 1996), and methods for catalyzing in situ reactions to form minerals such as clays (Nagy and Fredrich, 2000;Fredrich, et al 2004) or carbonates (Waring and Taylor, 2001) that fill pore spaces to prevent water penetration. Another method involves the localized stimulation of microbial activity to create a biobarrier that physically clogs the aquifer with biofilm (e.g.…”