1000 m² 50m long curtain
Capital Regional District (CRD) needed to remediate the right abutment of Butchart Dam No.5 in the Goldstream Watershed of the Regional Water Supply System located near Victoria, BC.
The bedrock of the embankment had a high permeability due to the fractured karts limestone since the dam was filled to the total capacity. The seepage of water has led to the formation of sinkholes on the downstream toe of the embankment. Multiple remediation efforts in the past have tried to limit the seepage pathway by creating a barrier and decreasing the permeability of the bedrock.
Menard performed Permeation/Foundation Grouting to create a grout curtain along the alignment of the dam crest, thus a barrier for the flow of water downstream. The grout curtain was constructed in a grid pattern extending 20m below the dam crust.
Permeation Grouting is a widely accepted methodology to stabilize a structure’s foundation through grout injection and to fill the voids. Grout is pumped through a specialized Grout pipe/Tube with perforations and ballons to ensure a controlled injection of grout into the fractured bedrock. Boreholes were drilled from the dam crest until the treatment depth to insert the tube. This technique allows the flow of a sufficient volume of grout at a very low pressure to avoid any appreciable movement of the bedrock surrounding the tube. The grout is pumped in multiple phases by both Gravitational fillings and a specialized setup until all the voids are filled. The main advantage of this technique is the formation of a strong bond that is both waterproof and permanent. The whole execution is clean, non-intrusive, and non-destructive.
The results from this technique were observed almost immediately by the drop in the water level leaking downstream.