Name of the Project
Pebble copper/gold/molybdenum project.

Location
South-west Alaska, US.

Project Owner/s
Pebble Limited Partnership (PLP), wholly owned by Northern Dynasty Minerals.

Project Description
The Pebble project is the world’s largest undeveloped copper and gold resource. The project’s tonnes, grade, metallurgy and geometry have the potential to support a modern, long-life mine.

The project’s current resource estimate includes 6.44-billion tonnes in the measured and indicated categories containing 57-billion pounds of copper, 70-million ounces of gold, 3.4-billion pounds of molybdenum and 344-million ounces of silver. The inferred category of 4.46-billion tonnes contains 24.5-billion pounds of copper, 37-million ounces of gold, 2.2-billion pounds of molybdenum and 170-million ounces of silver. Palladium and rhenium also occur in the deposit.

The PLP is proposing to develop the Pebble copper/gold/molybdenum porphyry deposit as an openpit mine, with associated on- and off-site infrastructure including:
• a 230 MW power plant located at the mine site;
• a 134 km transport corridor from the mine site to a port site on the west side of Cook Inlet;
• a permanent, year-round port facility near the mouth of Amakdedori Creek on Cook Inlet; and
• a 303 km natural gas pipeline from the Kenai Peninsula to the Pebble project site.

The proposed mine will operate for about 20 years. This includes 14 years of mining using conventional drill-blast-shovel operations, followed by six years of milling material from a low-grade-ore (LGO) stockpile. The mining rate will average 90-million tons a year, with 58-million tons of mineralised material being processed through the mill each year for an extremely low life-of-mine waste-to-ore ratio of 0.1:1.

Mine site facilities will include an openpit mine, tailings storage facilities (TSFs), an LGO stockpile, overburden stockpiles, quarry sites, water management ponds, milling and processing facilities, as well as supporting infrastructure such as the power plant, water treatment plants, camp facilities and storage facilities.

The openpit will be developed in stages and will eventually be 1 981 m long, 1 676 m wide and between 405 m and 533 m deep. A total of 1.2-billion tons of material will be mined, including 1.1-billion tons to be processed through the mill and 100-million tons of waste rock.

Nonpotentially acid-generating (non-PAG) waste rock will be used as a construction material for on-site roads and TSFs embankments. 

A small amount of waste rock considered non-PAG will be stored in a lined LGO stockpile until mine closure, at which time it will be back-hauled to the openpit for permanent subaqueous storage.

Mineralised material will be processed using conventional froth flotation. On average, the process plant will produce about 600 000 t/y of copper/gold concentrate containing an estimated 287-million pounds of copper, 321 000 oz of gold and 1.6-million ounces of silver, and 15 000 t/y of molybdenum concentrate containing about 13-million pounds molybdenum.

A TSF located in the North Fork Koktuli drainage will store 1.1-billion tons of tailings generated over 20 years of mine operations. About 88% will be non-PAG bulk tailings; the remaining 12% will be pyritic PAG tailings, which will be stored subaqueously in a separate, fully lined cell within the TSF. Four TSF embankments, ranging from 18.3 m (east embankment) to 183 m (main embankment) in height, will be developed, with centre-line or downstream construction methods used for all external embankments. A conservative 2.6:1 (horizontal:vertical) slope is targeted to ensure safety and stability under all operating conditions, including maximum possible flood and seismic events.

Potential Job Creation
The Pebble project will directly employ about 2 000 workers during its four-year construction phase and an estimated 850 workers during its 20-year operations phase.

Net Present Value/Internal Rate of Return
Not stated.

Capital Expenditure
Capital expenditure on Pebble is estimated at between $6-billion and $8-billion.

Planned Start /End Date
Not stated.

Latest Developments
The Justice and Corporate Accountability Project (JCAP), on behalf of Earthworks, has said it will file a request for a compliance investigation into Northern Dynasty Minerals.

The complainants will raise serious issues concerning alleged “misleading claims” with the British Columbia Securities Commission and the US Securities and Exchange Commission.

According to a statement issued by Earthworks, the complainants will show that Northern Dynasty was allegedly misleading investors in four major ways concerning the proposed Pebble gold/copper/molybdenum mine.

The environmental organisation contends that the 20-year-old Pebble mine plan is controversial because it is located at the headwaters of Alaska’s Bristol Bay watershed, which produces roughly half of the world’s supply of wild sockeye salmon.

The draft environmental-impact statement for the mine allegedly estimated that about 130 km of rivers and streams would be permanently lost and the resulting openpit would contain more contaminated water (estimated at 61-billion gallons) than the Berkeley pit (estimated at 50-billion gallons), which is one of the largest superfund sites in the US.

Superfund sites are polluted locations requiring a long-term response to clean up hazardous material contaminations.

Key Contracts and Suppliers
Wardrop Engineering (preliminary assessment report).

On Budget and on Time?
The Pebble deposit has inspired intense controversy, as a broad and bipartisan coalition – including environmentalists, Alaska natives and commercial fishermen – has fought its planned development, resulting in the EPA stopping the project in 2014. The election of US President Donald Trump, however, has fuelled hopes that a more mining-friendly EPA will enable the project to progress.

Contact Details for Project Information
PLP, tel +1 907 339 2600, fax +1 877 450 2600 or email receptionist@pebblepartnership.com.