The Crow Butte operation uses the in situ recovery (ISR) mining method. ISR mining produces no waste rock or tailings and results in minimal disturbance to the surface and underground areas mined.
Uranium at Crow Butte occurs in sandstone aquifers as coatings on sand grains at up to 300 metres underground. Uranium is removed using a grid of injection and production wells.
The uranium is insoluble in the native groundwater. Small amounts of oxygen and bicarbonate (baking soda) are added to the injection stream to dissolve the uranium. The uranium solution, less than 1/10 of 1% uranium, is then pumped from a production well to a satellite facility where the uranium is transferred to ion exchange resin beads similar to the sand from which it was extracted. The uranium-bearing resin is then pumped to a processing plant where it is removed from the beads, precipitated and dried to become the final product, yellowcake.
This is essentially a closed-loop recirculation system. Water from the production wells is reintroduced in the injection wells. Slightly less water is injected than withdrawn to ensure the fluids are confined to the ore zones intended for extraction. Monitor wells are installed to allow testing of groundwater quality above, below and around the target zones to ensure fluids do not move outside those areas.