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 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; and 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 ty of molybdenum concentrate containing about 13-million pounds molybdenum.

A single 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 183 m (main embankment) to 18.3 m (east 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
Northern Dynasty Minerals announced in December that its US-based subsidiary, PLP, was ready to file an application for a US Clean Water Act (CWA) 404 permit with the US Army Corps of Engineers.
ached all the targeted milestones.

Northern Dynasty managed to progress the stalled project further along the development timeline, first reaching an agreement in May with the EPA, through which the federal agency agreed to initiate a process to withdraw its proposed determination under Section 404(c) of the CWA, thereby clearing the way for Pebble to apply for a CWA 404 permit with the US Army Corps of Engineers.

Northern Dynasty further announced a framework agreement with First Quantum Minerals, which provides for a future right to acquire a 50% interest in the PLP for a further investment of $1.35-billion.

Northern Dynasty has since confirmed that it received an initial $37.5-million early option instalment payment from First Quantum.

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.