The Diavik mine is operated by Diavik Diamond Mines Inc., a member of the Rio Tinto Group and is located in the Northwest Territories in Canada, approximately 220 kilometers south of the Arctic Circle. A deep cut-off wall was required for the 2.2 km perimeter dike enabling open-pit mining under the waters of Lac de Gras. A combination of different techniques was implemented to execute the task. The foundation works stared with vibro densification strengthening the filled dike body. The actual bedrock below the dike was sealed with a grout curtain to a depth of nearly 60 m. More than 19,000 m² Cutter-Soil-Mixing (CSM) cut-off wall was installed through the densified dike into natural soil below. The works on the cut-off wall were completed with jet grouting to close the gap between the bottom of the already installed CSM wall and the installed lower grout curtain.