Minerals

Minerals

Pebble’s downsized mine
Anchorage’s Dena’ina Center was packed last week during the U.S. Army’s Corps of Engineers hearing on the Pebble Mine Draft Environmental Impact Statement. While the opposition to the mine from fisheries and tribal groups are well documented, the details of Pebble’s scaled-down project are less known. A smaller mine, which is proposed in the applications to the Corps, covers a much smaller “footprint,” Pebble said. The plan eliminates the large-scale use of cyanide and makes major changes in the “tailings,” or waste rock, storage.

One change that is important is that the mine facilities have been relocated outside the Upper Talarik Creek watershed, from where waters flow to Lake Iliamna and eventually Bristol Bay. However, they are still in another watershed supporting the Koktuli River, which flows into the Mulchatna River to the Nushagak River and then to Bristol Bay. The concern is that any contamination to these watersheds could affect salmon spawning streams. At the mine itself there would be a large bulk-tailings facility holding 85 percent of the waste rock which will be basically inert. A smaller facility would hold a quantity of “pyritic” tailings that have the potential for generation of acid drainage. The smaller pyritic tailings facility would be lined with an impermeable layer, following advanced industry practice, to prevent seepage. When the mine is decommissioned these will be moved to the main mine pit and be covered by water, which will prevent contact with air and the formation of acidic fluid.

The large bulk tailings facility, meanwhile, will incorporate a “flow-through” design to allow water to flow through the dam structure to a storage area. This would prevent a buildup of water above the dam, which would create pressure as water ac- cumulated. This design concept was not used in tailings dams that have failed, such as the Mount Polley dam failure in British Columbia, and recent dam failures in Brazil. At mine closure the inert rock in the large bulk storage area will be covered with a liner and layer of soil, which would allow vegetation to grow.

A unique aspect to the Pebble design is a system to control the release of water at optimal times for the support of fish habitat. If Pebble is developed it will have major benefits to the state’s economy as well as small communities near the mine and the Lake and Peninsula Borough. The mine would pay an estimated $20 million a year in taxes to the borough and $66 million a year in taxes and royalties to the state.

If it goes ahead Pebble would employ about 2,000 in construction and about 850 in production jobs. Mining jobs pay well, averaging about $100,000 a year. That’s $85 million a year in annual payroll When indirect employments effects are added the total jobs created will be about 2,000.

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