Cigar Lake is the world's second largest known high-grade uranium deposit and is located near Waterbury Lake, approximately 660 km north of Saskatoon, northern Saskatchewan, Canada.
The mineral property consists of one mineral lease (ML5521), totaling 308 ha, and another 25 contiguous mineral claims known as the Waterbury property that cover 92,740 ha. The surface lease covers an area of 959 ha of Crown land.
Cigar Lake is owned by joint venture partners Cameco Corporation (50.025%), AREVA Resources Canada Inc. (37.1%), Idemitsu Canada Resources Ltd. (7.875%) and TEPCO Resources Inc. (5.0%). Cameco is the operator and has been since January 2002.
The Cigar Lake uranium deposit was discovered in 1981 by a regional program of diamond drill testing of geophysical anomalies. It occurs at depths ranging between 410 and 450 m below the surface.
The project will be developed as a non-entry underground mine using a jet boring mining method, a full-face tunnel boring machine, and ground freezing techniques. Underground grinding of the ore will take place at Cigar Lake and will be followed by trucking to AREVA's McClean Lake mill for leaching. Final yellowcake production will be split between McClean Lake and Rabbit Lake for a total estimated annual production rate of 18 million pounds U3O8 when the mine is in full operation. Average operating cost is estimated to be Cdn$45.95/lb U3O8. The mine life will be 14.8 years.
Full construction of the Cigar Lake project began in January 2005 and as of October 2006, the capital construction project at the Cigar Lake site was approximately 60% complete. The aggregate capital cost is estimated to be approximately $1.0 billion - costs associated with the remediation activities to address the water inflow incidents are not included. Water inflows are generally uninsurable.
Production was initially scheduled to commence in 2011 but on October 23, 2006 because of water inflow the mine was flooded and underground development suspended.
As of November 2010, Cameco continued to restore the underground mine system and began to freeze the ground around Shaft No. 2 in preparation to resume shaft sinking.
The Cigar Lake mine site is located near Waterbury Lake, approximately 660 km north of Saskatoon, northern Saskatchewan, Canada.
The mine site is in close proximity to two uranium milling operations, McClean Lake is 69 km northeast by road and Rabbit Lake is 87 km east by road. The McArthur Rive mine is 46 km southwest by air from the Cigar Lake site.
The property is accessible all year round by air by using an unpaved airstrip and by an all weather road used to supply the site and truck out the product. To reach the property trucks leaving Saskatoon follow a paved provincial road through Prince Albert and La Ronge and further north along the gravel surfaced Provincial Road 905, and finally to the mine site via a 52 km long, two lane gravel road.
Located about 40 km inside the eastern margin of the Athabasca Basin Region the project area is characterized by a gently rolling terrain covered by 30 to 50 m of overburden, taiga forests and lakes. The mine site elevation is approximately 490 masl.
The climate is typical of the continental sub-arctic region of northern Saskatchewan - short and cool summers and cold and dry winters. Occasional summer temperatures could exceed 30 degree Celsius while winter temperatures could easily drop below minus 40 degree Celsius. The average frost-free period is approximately 90 days. Snow may occur in all months but rarely falls in July or August.
Site activities are carried out throughout the year.
Mining, forestry, fishing and hunting contribute the most to the economy of the sparsely populated northern part of the Saskatchewan province.
The Cigar Lake deposit is a typical Athabascan uranium deposit located at the unconformity contact between rocks of the Athabasca group and underlying lower Proterozoic Wollaston Group metasedimentary rocks. The Athabasca sandstone overlying the basement rocks contains water at high hydrostatic pressure.
The flat lying deposit measures approximately 1950 m long, 20 to 100 m wide, and ranges up to 16 m thick, with an average thickness of about 6 m. Lies at depths ranging between 410 and 450 m below the surface. It is characterized by the occurrence of high-grade uranium concentrations accompanied by massive clays and metallic minerals (oxides, arsenides and sulphides).
Three distinct styles of mineralization occur within the Cigar Lake deposit: high grade mineralization at the unconformity which includes the ore; fracture controlled, vein-like mineralization higher up in the sandstone; and fracture controlled, vein-like mineralization in the basement rock mass. The unconformity ore represents the bulk of the mineral deposit.
Proven and probable mineral reserves total 497,000 t at 20.7% U3O8 containing 226.3 million pounds of U3O8. Measured and indicated amount to 61,000 t grading 4.9% U3O8. The inferred category was estimated at 317,000 t at 16.9% U3O8 for 59.1 million pounds U3O8.
Because of the fact that Athabasca style uranium deposits don't occur at surface geophysical exploration tries to identify buried EM conductors representing graphite, which is generally associated with uranium mineralization.
Mining & Operations
Underground mining of the Cigar Lake deposit faces multiple challenges including groundwater control, weak rock formations and high-radiation environment. A non-entry mining method had been selected for the project.
The ground to be mined is first frozen up by minus 30 degree C calcium chloride pumped from the surface through pipes into freezing holes. It takes one to three years to have the ore and the host rocks freeze at between minus 10 degree C and minus 20 degree C. Freezing the ground provides for a minimized risk of water inflows, reduction of the radon dissolved in water and at the same time increases the stability of the rocks being mined.
Secondly, a mine development system (MDS) would cut through rocks. It is a 5.1 m diameter full-face tunnel boring machine that also provides for the installation of permanent ground support. The MDS will be used on the 480 m level to develop the freeze level crosscuts and on 465 m level to develop production level crosscuts.
Mining would be done by the jet boring method. The method consists of cutting approximately 4.5 m diameter cavities with a high pressure water jet in previously frozen ore. All mining with the Jet Boring System (JBS) will be done from the 465 m production level, located in the basement rock below the ore zone. Following mining, each cavity will be backfilled with concrete backfill.
Although a single JBS unit would be enough to produce the required mine production of 80 to 140 t/d of ore the fleet would comprise three units: one in production, one being moved or set-up, and the third undergoing maintenance.
Two mining shafts having a 4.9 m and 6.1 m in diameter extending to a final depth of 500 m would provide for mining operations taking place at the 420 m and 480 m levels.
The primary ventilation system has been designed to supply a volume of up to 250 m3/s of fresh air to the mine.
On October 23, 2006 because of water inflow the mine was flooded and underground development suspended. As of November 2010, Cameco continued to restore the underground mine system and began to freeze the ground around Shaft No. 2 in preparation to resume shaft sinking.
Because of a challenging hydrogeological environment the risk of water inflows would remain high even in the production stage. That could result in an interruption in planned uranium supply.
Ore mined by the JBS will be mixed with cuttings water and pumped to a ROM ore receiving facility, from which it will be subsequently recovered and it would be fed into an underground crushing and grinding circuit. The resulting finely ground, high density ore slurry will be pumped to surface storage tanks, thickened and loaded into truck mounted containers, similar to those currently being used at McArthur River mine.
Containers of uranium ore slurry will be trucked to AREVA's McClean Lake operations, 70 km to the northeast for leaching. Final uranium processing - yellowcake production - would occur at both the McClean Lake and Rabbit Lake for a total estimated annual production rate of 18 million pounds U3O8.
No tailings will be stored at Cigar Lake because the ore is going to be processed elsewhere.
Environment and Community
The project has regulatory obligations to both the federal and provincial governments. Impact from the Cigar Lake project has been evaluated as part of several environmental assessments going back to 1987.
Local personnel were given priority at hiring. They commute from a number of designated localities by air. Most company employees are on a week-in and week-off schedule. Contractor employees are generally on a longer work schedule.