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DESIGNING WITH GEOSYNTHETIC CLAY LINER FOR BAUXITE RESIDUE STORAGE

Zhou, Y. Cooling, D.J.

Current state-of-practice liner for containing bauxite residue consists of a geomembrane overlaying a compacted clay liner (CCL). Sourcing quality clay at or near every site is becoming a challenge, as the limited clay supply for existing facilities is exhausted, or at facilities where clay is geologically unavailable. As a substitute for clay, geosynthetic clay liner (GCL) has been successfully used in waste containment for decades. However, the alkalinity of bauxite residue deters the application of GCL in the industry, because bentonite, the key ingredient of GCL, reacts adversely with alkaline leachate. Over the past ten years, Alcoa has been working with GCL researchers and GCL manufacturers to develop GCLs suitable for bauxite residue storage. With up-to-date scientific research, and newly available non-traditional GCLs, Alcoa has been able to develop an engineering approach for designing and constructing GCL-lined facilities that will meet long term performance requirements. This approach covers GCL compatibility with location-specific residue, engineering evaluations and design guidelines, GCL types and liner system configurations suitable for site geological and hydro-geological conditions, long term performance and stability, GCL seaming requirements for varying site conditions, and procedures of GCL construction quality control (CQC) and quality assurance (CQA). Using this approach, Alcoa has designed and constructed two full scale bauxite residue storage areas with GCLs, saving tens of millions of dollars in capital investments, while providing better liner quality, shorter construction time, and improved overall facility sustainability. Alcoa believes that the GCL design guidelines that have been developed as a part of this work pave the way for GCL applications in our industry, opening up much needed opportunities in constructing improved storage facilities at lower capital costs.