The U.S. Army Corps of Engineers (USACE) today published a notification that the permit application submitted by the Pebble Limited Partnership (PLP) has been accepted. This formally begins the permitting process under the rigorous National Environmental Policy Act (NEPA) review process and other permitting efforts associated with the project. PLP’s application incorporates more than a decade of extensive third-party environmental research. The application and supporting documentation can be viewed via the USACE website:
Pebble Partnership CEO Tom Collier reiterated that the Pebble team has taken great strides in recent years to re-design its project in response to stakeholder concerns. The development proposed in Pebble’s Project Description is substantially smaller than previous iterations, and presents significant new environmental safeguards, including:
- a development footprint less than half the size previously envisaged;
- the consolidation of most major site infrastructure in a single drainage (the North Fork Koktuli), and the absence of any primary mine operations in the Upper Talarik drainage;
- a more conservative Tailings Storage Facility (“TSF”) design, including enhanced buttresses, flatter slope angles and an improved factor of safety;
- separation of potentially acid generating (“PAG”) tailings from non-PAG bulk tailings for storage in a fully-lined TSF;
- no permanent waste rock piles; and
- no cyanide usage.
“These are very substantial improvements that we have made over the past few years in response to issues and concerns raised by project stakeholders,” Collier said. “We believe that as Alaskans become more familiar with our proposed project design and the environmental safeguards it incorporates, there will be an increasing degree of support for the project, and the significant economic potential it represents for the State of Alaska.”
The Proposed Pebble Mine
The Pebble Partnership is proposing to develop the Pebble copper-gold-molybdenum porphyry deposit in southwest Alaska as an open pit mine, with associated on and off-site infrastructure, including:
- a 230 megawatt power plant located at the mine site;
- an 83-mile transportation 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 188-mile natural gas pipeline from the Kenai Peninsula to the Pebble Project site.
Following four years of construction activity, the proposed Pebble mine will operate for a period of 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 per year, with 58 million tons of mineralized material going through the mill each year (160,000 tons per day), for an extremely low life-of-mine waste to ore ratio of 0.1:1.
Mine Site Facilities and Operations
- Mine site facilities will include: an open pit; a TSF; a 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 open pit will be developed in stages with final dimensions of ~6,500 feet in length, ~5,500 feet in width and depths between 1,330 and 1,750 feet. 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.
- Non-PAG waste rock will be used as a construction material for on-site roads and TSF embankments. The minority 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 open pit for permanent sub-aqueous storage.
- Mineralized material will be processed via conventional froth flotation. On average, the process plant will produce ~600,000 tons of copper-gold concentrate each year, containing ~287 million lb copper, ~321,000 oz gold and 1.6 million oz silver, and ~15,000 tons of molybdenum concentrate each year, containing ~13 million lb 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 sub-aqueously in a separate, fully-lined cell within the TSF. A total of four TSF embankments ranging from 600 (main embankment) to 60 feet (east embankment) in height will be developed, with center-line or downstream construction methods used for all external embankments, and a conservative 2.6:1 (horizontal:vertical) slope applied to ensure safety and stability under all operating conditions (including maximum possible flood and seismic events).
- Pebble has proposed an 83-mile transportation corridor from the mine site to a port site on the west side of Cook Inlet. The proposed road corridor has been designed to minimize impact on wetlands, minimize stream crossings and avoid areas of known subsistence and recreational use.
- The transportation corridor includes: a 30-mile private, 30-foot wide gravel road from the mine site to a ferry terminal on the north shore of Lake Iliamna; an 18-mile crossing of Iliamna Lake using a custom- designed ice-breaking ferry; and a 35-mile private, 30-foot wide gravel road from the south shore of Iliamna Lake to a port site at Amakdedori. Spur roads will connect the Pebble transportation system to the villages of Iliamna, Newhalen and Kokhanok.
- Daily transportation of mineral concentrate, mining equipment and supplies will require up to 35 round trips by truck each day, and one round trip by ferry.
- A permanent, year-round port facility constructed at Amakdedori on the west side of Cook Inlet will facilitate the direct loading of mineral concentrate onto Handysize bulk carrier vessels, as well as the delivery via barge of mining equipment and supplies.
- The port will include shore-based facilities to receive and store containers and fuel, as well as two two- megawatt natural gas power generators, associated infrastructure and facilities. The port’s marine component will include a causeway extending out to a marine jetty in 15-feet on natural water depth to facilitate roll-on/roll-off barge access and a separate berth for Handysize vessels. A dredged channel will be required to access the berth for Handysize ships.
- Port operations will facilitate up to 25 concentrate shipments via Handysize bulk carrier vessels each year, and up to 30 marine barge loads of mining equipment and supplies.
Power Plant & Natural Gas Pipeline
- To meet the mine’s power requirements while providing sufficient peaking capacity and N+1 redundancy, a 230 megawatt power plant utilizing a high-efficiency combustion turbine or reciprocating engine generators operating in a combined-cycle configuration will be built at Pebble. Waste heat from the power plant will be used to heat mine buildings and supply process heat to water treatment plants.
- The mine site power plant, as well as smaller generating facilities at the port site and ferry landing sites, will be supplied by a 188-mile pipeline to connect with existing natural gas supply infrastructure near Happy Valley on the Kenai Peninsula.
- From Happy Valley, a buried steel pipeline will travel south for nine miles to a compressor station near Anchor Point, which will feed a 94-mile subsea pipeline across Cook Inlet to come ashore at the Amakdedori port site. From the port site, the natural gas pipeline will traverse 81 miles to the mine site in three sections. It will be buried in a trench adjacent to the road prism on the south and north sides of Iliamna Lake, and run under Iliamna Lake for a distance of 18 miles between ferry landing sites.
- Pebble has proposed a comprehensive water management plan to provide sufficient water for mine operations, to minimize the volume of water diverted from natural flows, to discharge surplus waters captured at the mine site in a strategic manner to optimize downstream habitat conditions for salmon and other species, and to ensure water quality is maintained in all local streams.
- The Pebble mine will employ two water treatment plants to ensure that surplus water discharged into nearby streams meets applicable water quality standards, and is properly conditioned for aquatic life. Sufficient water storage, pumping capacity and treatment plant redundancy has been incorporated into the design to ensure that water management goals can be achieved under all operating conditions.
Reclamation and Closure
- The Pebble Project has been ‘designed for closure’, in order that facilities can be removed and land reclaimed in such a way that it can be returned to a stable and productive state.
- Reclamation and closure activities will include: removal of mill and other facilities not required in the post- closure period; hauling of PAG waste rock into the open pit for sub-aqueous storage; recontouring of disturbed areas and placement of overburden for revegetation; installation of water management features to provide for long-term water quality monitoring and treatment.
- Prior to commencing construction, a Project Reclamation and Closure Plan must be approved and an associated financial assurance mechanism be put in place to ensure that the required financial resources are available at all time to fund costs associated with physical closure of the project and long-term post- closure monitoring, water treatment and site maintenance.
- By regulation, Pebble’s Project Reclamation and Closure Plan must be updated every five years to address any changes in closure and post-closure requirements, and associated financial obligations.
The Pebble Project will directly employ ~2,000 workers during its four-year construction phase, and ~850 workers during its 20-year operations phase.
The Pebble Deposit is an important statewide economic asset, located on State of Alaska land designated for mineral exploration and development. The area was acquired by the State of Alaska in 1974 via an historic land exchange with the federal government and Cook Inlet Region, Inc. With the growing worldwide consumption and dependence upon technical products powered by critical minerals such as copper, the expanding demand for renewable energy technologies, and the development of projects with strategic national significance, the Pebble Deposit has the potential to generate hundreds of millions in annual economic activity for Alaska, as well as significant revenues for state and local governments. It will also create high-wage, year-round jobs and training opportunities in Southwest Alaska, and supply and service contracts for local businesses.