Diavik Diamond Mines Inc.

Diavik Diamond Mines Project, Northwest Territories, Canada

Diavik is a joint venture between Diavik Diamond Mines Inc. (60%), a subsidiary of Rio Tinto plc, and Aber Diamonds Ltd. (40%).  The Diavik Mine is located 300 km northeast of Yellowknife, Northwest Territories.  Diavik's kimberlite lies at lake floor of the Lac de Gras Lake.  To access the kimberlite it was necessary to construct dikes. A154 kimberlite pipe was the 1st dike of its kind constructed in Canada.  Diavik Diamond Mine became Canada’s 2nd major diamond mine with a project captial cost of $1.3 billion.

Nuna's Role

NUNA has been involved as a construction contractor since Diavik’s early exploration days. NUNA cleared the land and built the exploration camps, constructed the first small airstrip (to land Twin Otters) and the winter ice strip (to land larger planes), built the drill pads and assisted with the original sampling of the Lac de Gras Lake bottom.

NUNA's transportation services involved:

  • 3,000 tonne bulk sample from the A154 site to pilot plant in Yellowknife;

  • inbound supplies to support the drilling and bulk sample program; and

  • transported Jet B fuel drums from Yellowknife to site for helicopter and aircraft support.

NUNA's support and logistics services included:

  • drill support for a diversified drilling program; and

  • constructability advise to the Diavik feasibility study prepared by Nishi-Nhon/SNC Lavalin Limited.

Our ice roads and ice pad work involved:

  • construction and maintenance of annual winter road; and

  • establishment of drill pads on the Lac de Gras ice for the annual drill program (to ensure bearing capacity of the ice, it was necessary to determine the ice thickness using NUNA's subsurface radar system).

Our earthworks and runways services covered:

  • earth moving for the preparation of the exploration site and placement of facilities; and

  • reparation of the decline tunnel entrance.

Lac de Gras Constructors Joint Venture's Role

Lac de Gras Constructors (LDGC) is a joint venture between NUNA Logistics Limited and Peter Kiewit Sons, formed to construct the Diavik Diamond Mines' A154 Dike, North Inlet Dike, A418 Dike, raising of the Processed Kimberlite Containment (PKC) Dam and various other earthworks projects.

A154 Kimberlite Pipe Dike Construction, De-watering & Pre-stripping - 2001 / 2002

A154 is the 1st dike of its kind constructed in Canada. Located 20 m below water off an island in Lac de Gras lake.  The A154 kimberlite pipe required construction of a 3.8 km long, up to 25 m high dike to enclose an area of 1.5 km2.

During 2001 season 5,000,000 m3 of rock was excavated and 6,000,000 tonnes of crushed granular aggregates was produced and placed to complete the dike. Excavation along the central core of the dike allowed the installation of a bentonite cut-off wall of 51,000 m2.

Work included, installation of turbidity curtains, foundation preparation (dredging), placement of filter material on lake bed floor, placement of embankment,(3 types of materials), vibrodensification of materials, excavation through central core to facilitate cutoff wall.  Trenching on land and in shallow waters for cutoff wall in some areas, placement of abutment insulations which included thermosyphons, drainage and toe berms, relief wells and installation of geotechnical instrumentation. Jet grouting was required along the entire length of the dike between the cutoff/bedrock interface and curtain grouting below the cutoff in the bedrock.

A418 Kimberlite Pipe Dike Construction, De-watering & Pre-stripping, 2005 / 2006

Water retaining dike and cutoff wall for kimberlite pipe A418. A418 dike is 1.2 km long, required approximately 1.1 m3 of rockfill and is built in water up to 32 m deep.

A418 dike joins the existing A154 dike with construction methods being similar as those used in A154 dike - various sizes of rockfill, a central plastic concrete cut-off-wall, jet and curtain grouting and installation of instrumentation.  A significant crushing facility prepared much of the rock before placement using rock from the A154 open pit. The rockfill portion of the A418 dike was completed in 2005, and the cutoff wall completed in 2006.

North Inlet Dike

The North Inlet dike was constructed prior to the A154 dike and provided a test platform to confirm the cut-off wall constructability criteria. This project consisted of backfilling the core with granular material, vibrodensification and jet grouting columns.

Earthworks and Runways

  • developed site earthworks including a permanent 1,600 m airstrip able to handle large jets and a commercial Hercules cargo aircraft;

  • on-site haul roads built of rock quarried near the mine’s island-based infrastructure;

  • concrete foundations plant site;

  • kimberlite containment facilities;

  • civil infrastructure which included pads, tank farm containments, installation of Hilfiker wall; and

  • supply and placement of structural concrete.