Lac de Gras Lac de Gras Lac de Gras is a lake approximately north east of Yellowknife, in the Northwest Territories of Canada. Lac de Gras was the centre of the diamond rush of the 1990s. There are two working, and one closed, diamond mines in the area, Diavik Diamond Mine, Ekati Diamond Mine, and the care and maintenance Snap Lake Diamond Mine. It was called Ekati by aboriginal peoples. The lake is ultraoligotrophic but supports a slow-growing but stable population of some eight species of cold-water fishes, including round whitefish, cisco, and lake trout. Lake trout dominate the lake, both numerically and
Underground mine ventilation the permafrost heating may not take place to prevent melting the permafrost. "Cold mines" such as Raglan Mine and Nanisivik Mine are designed to operate below 0°C. The wet bulb temperature in any working place does not exceed 33.5°C and where the wet bulb temperature exceeds 30.5°C arrangements are made to ventilate the same with a current of air moving at a speed of not less than one metre per second; Underground mine ventilation Underground mine ventilation provides a flow of air to the underground workings of a mine of sufficient volume to dilute and remove dust and noxious gases