Southwest Alaska's gigantic and controversial Pebble copper and gold prospect keeps growing.
The value of the minerals discovered so far at Pebble is between $345 billion and $500 billion, based on current metal prices, according to 2007 drill results announced on Monday.
Last year's drilling at the deposit, north of Iliamna, added billions of pounds of copper and millions of ounces of gold - an increase valued at $11 billion to $35.4 billion.
The results indicate that Pebble remains likely the second largest copper-gold deposit of its kind in the world, dwarfed only by the Grasberg mine in Indonesia.
"It looks like some really nice numbers but the real key is whether it's economic (to develop) or not," said Steve Borell, executive director of the Alaska Miners Association.
The companies exploring Pebble agree their project is huge, but converting the minerals into dollars at this point is somewhat misleading.
"It's highly unlikely that we'll seek to develop the entirety of the (deposit)," said Sean Magee, spokesman for the Pebble Partnership, the joint venture exploring Pebble. The partnership includes one of the world's largest mining companies, London-based Anglo American, and the junior mining company, Vancouver, British Columbia-based Northern Dynasty Minerals Ltd.
The size of a possible Pebble mine could be curtailed by economics and by feedback from Bristol Bay communities, Magee said.
Developing Pebble is controversial in the region because of the prospect's location in the headwaters of two of the five major river drainages that supply Bristol Bay's world-class salmon runs, which support subsistence, commercial and sport fisheries.
OTHER BIG NUMBERS
Monday's new estimate doesn't take into account the cost of building and operating a mine, or future changes in the price of copper or gold, Magee said.
Building Pebble could cost up to $5 billion and annual operations could cost hundreds of millions, he said.
The new drilling results show copper is still the dominant metal - in volume and potential value - but gold and molybdenum are also major resources.
The updated estimate shows:
* 51.7 billion to 73.7 billion pounds of copper, worth up to $280 billion.
* 66.1 million to 87 million ounces of gold, worth up to $82 billion.
* 2.6 billion to 4.2 billion pounds of molybdenum, worth up to $139 billion.
The reason for the range in the volume of metal is the use of different "cut-off values," which set different criteria for the grades at which copper and gold would be mined.
Mining experts said Monday that they prefer using more conservative "cut-off" values, which correspond to richer grades.
"If the price of metals went down, you could still mine it," said David Szumigala, a geologist with the state Division of Geological and Geophysical Surveys.
Last year's drilling at Pebble helped develop more confidence for the exploring companies about the amount of metal in the deposit. Drilling planned this year will define it even better, Magee said
The mining companies will use the drilling results to prepare a pre-feasibility study, an internal document that they will consult when deciding whether to propose building a mine to their boards, he said.
Anglo American will decide whether to invest more money in Pebble based on the outcome of the study, Magee said.
If the companies decide to pursue a mine, they would likely apply for permits in 2009, and could start producing metal in 2015, according to Northern Dynasty officials.
But a broad coalition of groups opposed to developing Pebble are trying to block the project. One of their tools is a ballot initiative planned for the statewide election this year, which would ban large metallic mines from discharging many pollutants into salmon streams or drinking water sources.
Find Elizabeth Bluemink online at adn.com/contact/ebluemink or call 257-4317.
By ELIZABETH BLUEMINK
Anchorage Daily News