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. The deposit also contains palladium and rhenium.

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 stockpile. The mining rate will average 90-million tons a year, with 58-million tons of mineralised material being processed through the mill every 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), a low-grade-ore 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 construction material for on-site roads and TSFs embankments. 

A small amount of waste rock considered non-PAG will be stored in a lined low-grade-ore 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, 1.6-million ounces of silver and 15 000 t/y of molybdenum concentrate containing about 13-million pounds of 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 PLP is one step closer to completing the federal permitting process for the Pebble project, after a US federal district court judge dismissed action brought by a collection of activist groups.

The ruling should pave the way for a final environmental-impact statement (EIS) and record-of-decision on the Pebble project by mid-2020, PLP CEO Tom Collier said in a statement on April 18.

Judge Sharon Gleason granted the Environmental Protection Agency’s (EPA's) “motion to dismiss” case brought by the activist groups, declaring that they had “failed to state a claim upon which relief can be granted”.

The Bristol Bay Defense Alliance, comprising Bristol Bay Native Association, United Tribes of Bristol Bay and others, sued the EPA in October last year for changing course on Obama-era restrictions that had halted the development of the Pebble mine.

The litigation challenged the EPA's July 2019 decision to formally withdraw its prior regulatory action under Section 404(c) of the Clean Water Act (CWA),

Collier said the US legal system had reaffirmed the Pebble project's right to receive a fair and objective permitting review under the CWA and National Environmental Policy Act (NEPA).

While PLP believes that the project can be developed without harm to the Bristol Bay fishery and for the benefit of the region. Groups opposing the project have expressed their disappointment and vowed to continue to fight the development of the mine.

“This ruling does nothing to change the scientific fact that Pebble mine cannot coexist with Bristol Bay fisheries. Removing the proposed protections was a short-sighted decision and we cannot allow that to harm the fishery that has sustained Bristol Bay cultures and communities for thousands of years. We will never allow this mine to be built in our region,” United Tribes of Bristol Bay executive director Alannah Hurley has said.

Bristol Bay Economic Development Corporation CEO Norm Van Vactor has added that communities and fishermen in the region had sustainably harvested salmon for more than a century. “The science is clear that to ensure this continues, we must protect the fishery from the disruption and devastation that Pebble would cause. We will do everything we can to ensure that there are many more seasons to come.”

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

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