In 2008 BAUER Foundations Canada Inc. (BFC) was awarded by Shell to execute a 70.000 m2 “Soil-Bentonite Cut-off-Wall” at Albian Sands Expansion I. The purpose of the wall was to establish environmental protection for the adjacent Jackpine River next to the new mine facility. The scope was the installation of a 2.6 km long and up to 50 m deep cut-off wall.
After the installation of a 40 m wide working platform, up to 8 m high, the excavation of the trench was performed by a long-boom-long-stick excavator (“Long-stick”) down to an average depth of 18 m. The further excavation of the trench to the final depth of max 50 m, including the key into the naturally impermeable oil sand layer, was executed by crane mounted clamshells.
The partially very hard soils required additional measures during excavation. Chisels were used to break up local obstructions like boulders in the trench. Part of the area to be trenched was crossed by very dense sands and sandstone layers. These were predrilled by our strong BG 28 drill rigs to a max depth of 48 m to loosen the soil.
The trench being 90 cm wide was filled with a soil-bentonite mix, thus giving the wall a permeability of 1x10-9 m/sec. Permanent on site laboratory facilities and personnel guarantied the quality of the soil-bentonite mixture and placement.