Case study: Design-build of a cement-bentonite groundwater cutoff wall in Fort-McMurray

ABSTRACT: In 2018, Canada Geo-Solutions Inc. (CGSI) completed a design-build project for the installation of a groundwater cutoff wall in Fort McMurray, AB. The purpose of the cutoff wall is to minimize off-lease seepage of process affected water (PAW) beneath the planned Northeast Closure Dam (NECD). The PAW is generated during the mining and processing of synthetic crude at a large oil sands mine. The requirements of the cutoff wall included a maximum hydraulic conductivity of 10-9 m/sec, a minimum unconfined compressive strength of 1 MPa, a 2 m penetration into the underlying McMurray Formation, and tie-in to an existing cut off wall previously installed for an existing tailings settling basin. Based on the complex project requirements, CGSI selected a self-hardening cement-bentonite slurry wall as the groundwater barrier. This paper provides details of this project from the design and bench scale study to completion of the cutoff wall installation and provides lessons learned through the performance of the project.