Diavik Diamond Mine (located in the Northwest Territories, approximately 300 kilometres northeast of Yellowknife) is in the process of developing the last of four kimberlite pipes in Lac de Gras, called the A21 pipe. In order to construct an open pit mine, a 2.2 km dike must be constructed and the water pumped out. In preparation for building the dike, JJM Construction Ltd. was awarded a contract to remove and dispose of soft lakebed sediments within the dike footprint and prepare the foundation for dike construction.
Diavik Diamond Mines (2012) Inc.
November, 2014 - January, 2017
Work under the contract consists of the removal and disposal of soft lakebed sediment and boulders using clamshell dredging and cutter suction dredging methodologies. JJM must then install a filter blanket – a 1.1 metre thick layer of 50mm minus graded crushed rock on the dredged surface – as well as installation of stability buttresses in areas of adverse lakebed bathymetry, in preparation for the embankment placement. JJM is also responsible for the installation and maintenance of a turbidity curtain that protects Lac de Gras from sediment dispersal from the project site. Work within the lake can only take place during the ice-free period that typically runs from late June or early July through September, so there is a very intense period of activity during this short season.
The project presents significant logistical challenges, since transportation of construction equipment and materials can only be done via ice road hauling in the late winter. Working with the team at Diavik, JJM has mobilized to the project site 4 sectional flat barges, 3 hopper barges, 3 tug boats, 2 crawler cranes (175 ton capacity), a cutter suction dredge unit with 3 booster pumps, 3 survey/work boats, a Hitachi EX1200 excavator, a service truck, and multiple container loads of spare parts, small tools and consumables.