For the first time, a radical departure from solidly established concepts and practices based on the use of bentonite for trenching under slurry, is proving itself as a viable alternative. It is even more so in this age of acute environmental sensitivity. The role played by polymers, and in particular a synthetic biodegradable polymer, are taking an increasing role in geotechnical construction: cohesionless sands can be cored with 100% recovery and small and large diameter soft ground tunnels are being bored with greater ease. Of interest to the field of slurry trenched excavations is the new ability to excavate under slurry, be it for continuous deep french drain or for a panelized reinforced concrete diaphragm wall, using a same and totally new kind of slurry. This slurry is a solution of polymers combined with either natural fines or added colloids. Since the slurry is naturally biodegradable, it can be used in all situations. The biodegradation can be deferred by inhibitors and with pH control while regulating it according to needs.
Leachate collection or recharge french drains installed under slurry are presented from the conceptual and QC perspectives. Since most structural slurry wall projects are in urban areas, where working with clay muds is problematic for many reasons, the writer examines the advantages of going from bentonite to polymer slurries. The limitations of the new technology are also discussed.