Mining Beneath Arctic Lakes – The journey from development to commercial production of the A21 kimberlite pipe at Diavik Diamond Mine

2019

Adan Olivares Castro, Rio Tinto - Diavik Diamond Mines Inc.; Branwen Price, Rio Tinto - Diavik Diamond Mines; Marko Pudar, Rio Tinto - Diavik Diamond Mines

Located 220 km south of the Arctic Circle on a small island in Lac de Gras, Northwest Territories, Canada, the Diavik Diamond Mine (DDMI) uses both open-pit and underground mining methods to extract diamonds from four kimberlite pipes. As the kimberlite pipes are located beneath the lake, water-retaining dikes were required to permit open pit mining. This paper explores the challenges and accomplishments associated with the construction of DDMI’s latest water-retaining dike, the A21 Project. This four-year project consisted of a 2.2 km rockfill embankment that required specialized ground improvement techniques prior to pumping 6.6 million cubic metres of water out of the infield. The engineered designs were supported by an empirical approach where required, to overcome challenges associated with optimizing construction and operation scopes of work. The scopes of work included the construction of a plastic concrete diaphragm cut-off wall, the installation of geotechnical monitoring systems, and tailored blast design practices for drilling and blasting downstream of the water-retaining dike. All of these challenges occurred in the context of sub-zero temperatures, short construction seasons, and a six-week window for freight transportation to the mine via ice road. The A21 Project Team focused on thorough planning/scheduling and engineering solutions to project challenges to successfully construct the dike and transition to operations.

Keywords: Embankment Construction, Ground Improvement, Arctic Engineering, Operational Readiness, Project Management, Empirical Analysis