Pebble Mine - Possible Mining Plan

Possible Mining Plan

The exact nature and scope of proposed mining activities at Pebble are yet to be finalized - but the general outline of the plan is known. A contiguous body of ore is known as Pebble West where mineralization locally extends to the surface, and as Pebble East where it is a deeply buried (off to the east) root of the deposit.

Pebble West would probably be mined as an open pit. The open pit preliminarily envisioned by Pebble Mines Corp. is two miles (3 km) wide and several thousand feet deep. Most of the rock removed from the pit will be waste, up to 10 billion tons of waste rock. That waste rock material, along with allowed discharge chemicals, would be stored (forever) in two artificial lakes behind massive earthen dams. The largest of the dams containing these lakes would be 740 feet (230 m) tall and 4.3 miles (6.9 km) long. The Pebble East part of the deposit would most likely be mined using underground methods.

Only a huge mine benefiting from economies of scale is feasible at Pebble, due to the low-grade character of the ore. Development and construction of a mine at Pebble would be a massive industrial project, taking years and costing billions of dollars. It will require many miles of roads and bridges across currently wild and undeveloped land, pipelines for fuel and for rock slurries, the use of great amounts of process water, impoundment of great amounts of surface water, electric powerlines, and constant transport and use of fuel and industrial and domestic chemicals and supplies.

Some design possibilities being considered include: construction of a port on Iniskin Bay of Cook Inlet with a private two-lane freight road roughly 104 miles (167 km) long built along the north side of Lake Iliamna between the mine and the new port; trucks hauling ore concentrate on that road to the port; several pipelines along the road which would carry fuel and a slurry of metal concentrate from the minesite to the portsite. The slurry would be dewatered at the port before being shipped to a smelter, with a pipeline returning the water to the mine. Power to operate the mine would possibly come from a combination of overhead powerlines and a submarine cable across Cook Inlet.

Feasibility studies (detailed mine construction and operation plans) are being prepared by Pebble Mines Corp. The company expects to apply for permits in 2012, at the earliest.

If Pebble is fully developed, it will be roughly operationally similar to existing large copper porphyry mines such as Chuquicamata, Bingham Canyon, and Ok Tedi - although the environmental setting and some technical considerations of Pebble vary widely from these desert and tropical examples.