COGEMA Resources Inc. operates the uranium mines and mill at Cluff Lake in Northern Saskatchewan. Several uranium deposits have been mined or are currently being mined by either open pit or underground methods at the Cluff Lake site. One of these deposits, the “D” deposit, was discovered in 1970 and mined as an open pit in 1979 and 1980. The deposit yielded 150 000 tonnes of ore at an average grade of 3.0% uranium.
Since the mining of the ’D” pit was completed, the surface facilities have been removed and the area has been recontoured, covered with a layer of local overburden and revegetated. Vegetation was reestablished by hydroseeding the area with a seed mix that was developed on site and which was suited to local soil conditions. The overburden at the “D” site is virtually barren of nutrients when compared to farmlands in the southern part of the province and required the addition of fertilizer at a rate of 850 kg/ha. In addition mulch is also required along with tackifier when seeding on steeper slopes. A thick thatch developed within a few years after completion of the revegetation program. This thatch initially inhibited the invasion of native plants but now shrubs and trees are starting to invade the area.
The water collecting in the former open pit, the groundwater and surface waters have been monitored extensively since 1985 as part of the mine site license requirements. Results to date indicate that the upper 10 metres of water in the pit will meet Saskatchewan Surface Water Quality Objectives (SSWQO). If the water were to overflow the pit area into Boulder Creek it is expected that these objectives would still be met. Also the pit water has had no detectable effect on the surrounding ground water chemistry.