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

Location
South-west Alaska, US.

Client
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; and 4.46-billion tonnes in the inferred category, containing 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 TSF embankments. 

A small amount of waste rock considered 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.

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

Duration
Not stated.

Latest Developments
The US Army Corps of Engineers' Alaska District will shortly publish a notice of intent in the US federal register to prepare a draft environmental-impact statement (EIS) to review PLP's application to discharge fill material into US waters to develop the Pebble project.

The public scoping period is slated to start on April 1 and conclude on April 30.

Scoping is the process used to determine the appropriate contents of an EIS, and the objective is to identify specific elements of the environment that might be affected by the applicant’s proposal.

The permit application was made publically available on January 5, and continues to be available on the Corps' website.

Public meetings will be hosted by the Corps during the scoping period in Alaska's regional centres Anchorage, Homer, King Salmon and Dillingham, as well as in villages in close proximity to the Pebble project, including Iliamna, Igiugig, Nondalton and Kokhanok.

In addition to seeking public and stakeholder input during scoping, the Corps will facilitate a formal consultation and public comment process following publication of the Pebble draft EIS – expected in 2019. The Corps' current timeline estimates the final EIS for the Pebble project to be completed within 24 months.

The Corps announced in February that it had appointed a third-party contractor to undertake the EIS.

In December, Northern Dynasty announced a framework agreement with First Quantum Minerals anticipating that an affiliate of First Quantum would subsequently execute a $150-million option agreement with Northern Dynasty, which provides for a future right to acquire a 50% interest in PLP for a further investment of $1.35-billion.

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 allow 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.