Water quality

Water is a necessary part of the Montana Resources mine operation. We have in place a closed circuit water system wherein all water used in the mine and concentrator is recycled through the process, with zero discharge to the outside environment.

A pulverized rock slurry emerging from the concentrator and thickener tanks is pumped to the Yankee Doodle Tailings Pond where the flour-sized byproduct of the milling process settles out before the water is piped back to the mine operation. From this closed circuit not a drop of water leaves the site. Copper is also extracted from water taken from the nearby Berkeley Pit in precipitation cells, taking advantage of that resource, and the water is afterward returned to the Pit.

Montana Resources also monitors water level and conditions in the Berkeley Pit and together with Atlantic Richfield funds the Berkeley Pit Public Education Committee.

Left: A view of the Montana Resources water treatment plant.

Air Quality

Mining is about rock and machines and is bound to raise dust, for which every effort is made to minimize. Water trucks constantly wet down haul roads in never-ending circuits.

Montana Resources has upgraded its haul truck fleet with new trucks with 240 ton capacity. The larger trucks move more ore per trip, using less fuel per ton than previous 170 ton trucks, and create less overall dust and diesel emissions.

At the crusher dump, a suction dust collection system and water sprays are used to capture the fugitive dust.

In dry weather, water trucks constantly wet down haul roads in never-ending circuits.

Waste Rock

Once waste rock is identified, it is hauled to either a waste rock repository or used in the tailings dam construction. All of Montana Resources’ waste rock repositories are designed to prevent the generation of acid mine drainage. Any waste rock determined to contain high-sulfide materials with capability of creating acidic compounds is encapsulated inside the repository to be capped, contoured and revegetated.

Reclamation

Commonly, an open pit mine is active for the entire life of the pit, only reclaimed when it becomes dormant. Montana Resources practices concurrent reclamation, reclaiming as soon as possible while mining operations continue. Soil is saved and stockpiled whenever it is available. Completed waste rock dumps undergo surface shaping, being recontoured to prescribed slopes in a layer thickness determined by the slope profile. The result creates grassy rolling hills inhabited by deer and other wildlife. Montana Resources maintains an active noxious weed control program on mine property.

Waste rock is the first layer, followed by pH-neutral alluvium. (For example the reclamation plan specifies slopes less than 5% to receive 28 inches of pH-neutral alluvium with the top 6 inches of alluvium amended to contain 1.5% organic material by weight.) The recontoured area is then seeded with a site-specific recipe of native grasses approved by the Montana Department of Environmental Quality including bluebunch and crested wheatgrass, blue flax, hard fescue and Russian wild rye.