BAUER Foundations Canada Inc. (BFCA) was contracted in 2020 by Pomerleau-
Bessac to execute the Jet Grouting and Ground Improvement works for the new Outfall and Effluent Shafts at the Annacis Wastewater Treatment Plant (WWTP).
Annacis is one of the largest WWTP in Vancouver region serving 14 municipalities in the area. The new shafts would increase the capacity of the current facility to meet the needs of region’s growing population and ensure it continues to protect both the public and the environment.
The project involved the construction of a 1 km-long tunnel about 40 m below the surface that would extend from the existing plant to a shaft and diffuser valves in the Fraser River.
BFCA’s scope of works included the Ground Improvement of Outfall and Effluent Shafts, Jet Grout columns 40 m below surface and 10 m long columns with drilling up to 51 m.
The ground improvement purpose was to mitigate the liquefaction hazard in case of a seismic event with the soil ratio replacement of approximately 7 % of the total volume of the ground below slab.
The works also consisted of 2 TBM Break-Out blocks for the Outfall Shaft (44 columns in total) and one TMB Break-In block for the Effluent Shaft (29 columns in total). Overlapping Jet Grout columns were to form blocks with a target column diameter of 2.2 m.
One BAUER BG 18 was mobilized to site including Jet Grouting equipment.