Pebble Mine
Pebble Mine is the common name of a proposed copper-gold-molybdenum mining project in the Bristol Bay region of Southwest Alaska, near Lake Iliamna and Lake Clark. It was discovered in 1987, optioned by Northern Dynasty Minerals in 2001, explored in 2002, and drilled from 2002 to 2013 with discovery in 2005. Preparing for the permitting process began and administrative review lasted over 13 years.
the mine developer, Northern Dynasty Minerals, still sought federal permits from the United States Coast Guard and the Bureau of Safety and Environmental Enforcement. State permitting would then follow, which the developer expected to take up to three years. In November 2020, the U.S. Army Corps of Engineers denied a permit for the proposed mine discharge plan.
On September 9, 2021, it was reported that the United States Environmental Protection Agency had "asked a federal court to allow for Clean Water Act protections for parts of the bay." On January 31, 2023, the EPA effectively vetoed the project, using a rarely invoked power to restrict development to protect watersheds.
Background
Geography
The Pebble prospect is in a remote, wild, and generally uninhabited part of the Bristol Bay watershed in Southwest Alaska. The nearest communities, about distant, are the villages of Nondalton, Newhalen, and Iliamna. The site is southwest of Anchorage, Alaska.Pebble is approximately north of, and upstream of, Lake Iliamna, and near Lake Clark. The deposit area is characterized by relatively flat land dotted by glacial ponds, interspersed with isolated mountains or ranges of hills rising one or two thousand feet above the flats. Pebble is under a broad flat valley at about above sea level dividing the drainages of Upper Talarik Creek and the Koktuli River.
Upper Talarik Creek flows into Lake Iliamna, which flows through the Kvichak River into Bristol Bay. Waters in the Koktuli River drain into the Mulchatna River, a tributary of the Nushagak River which empties into Bristol Bay at Dillingham. Water from Lake Clark, approximately east of Pebble, flows down the Newhalen River to Lake Iliamna.
Geology
Regional
The Kahiltna terrain is interpreted to represent a sediment trough formed on the landward side of the Wrangellia volcanic arc terrane, prior to collision of Wrangellia with Alaska. The Wrangellia and Kahiltna terrains docked to Alaska in the Cretaceous Period. This part of the Kahiltna terrane is dominated by Late Triassic basalt, andesite and sedimentary rocks overlain by Jurassic-Cretaceous andesitic turbidites. Cretaceous granitic intrusive activity was widespread in the Kahiltna terrane. Tertiary volcanic and sedimentary rocks, and Quaternary glacial deposits, developed over the older rocks.The Lake Clark fault, or a splay, probably lies within of the Pebble deposits and possibly much closer. The fault is a major right-lateral strike-slip crustal feature, considered to be a westward expression of the Castle Mountain fault. The actual ground trace of the fault and its splays are unknown in the Pebble area, due to extensive ground cover. A 2007 report indicates that magnitude 7.1 quakes occur on the fault on a 700-year cycle. The Lake Clark fault several hundred miles to the north is sub-parallel to the Denali fault and considered to be of similar nature. A magnitude 7.9 quake struck the Denali fault in 2002.
The subduction zone of the Aleutian Trench lies approximately south of Pebble. This zone was the source of the 1964 Good Friday earthquake of magnitude 9.2. The Augustine Volcano, which lies 25 miles offshore, last erupted in 2006.
The ore body
A contiguous body of ore is known as Pebble West where mineralization locally extends to the surface and as Pebble East where it is deeply buried. Pebble holds mostly low-grade ore, requiring a large-scale operation to economically recover it.The Pebble deposit is hosted in porphyritic granodiorite to tonalite of Upper Cretaceous age intruded into deformed sedimentary rocks of the Jurassic to Cretaceous Kahiltna flysch terrane.
The copper ore is a calc-alkali porphyry copper-gold-molybdenum deposit. The ore body extends from the surface to at least depth. In the western part of the orebody, mineralization occurs in a complex of several small granodiorite cupolas, diorite sills, older intrusions, breccias, and sediments. The western part of the deposit is locally exposed at the surface; thin gossans are developed and oxidation reaches in depth. The orebody extends eastward across a fault contact, at depth. East of the fault mineralization occurs in abundant sills and in the intruded sediments. Farther east, and deeper, the sills coalesce into a deeply buried granodiorite pluton. Mineralization and ore continue into the pluton. The eastern part of the deposit was eroded when it was exposed at the surface millions of years ago. It has since been buried by a thickening-to-the-east wedge of post-mineralization-age Tertiary sedimentary and volcanic sedimentary rocks.
Mineralization at Pebble is aged from 90.4 ±0.6 MYA to 89.5 ±0.3 MYA.
Metallic minerals identified at Pebble include pyrite, chalcopyrite, molybdenite, and bornite, along with minor covellite, chalcocite, digenite and magnetite.
Resources
In 2008, Pebble was estimated to be the second-largest ore deposit of its type in the world in terms of the value of the contained metal, slightly smaller than Indonesia's Grasberg Mine, which contains more metal in a smaller amount of ore than Pebble.The last resource estimate for Pebble, as at December 2017, was a measured and indicated resource of 6.46 billion tonnes of ore grading 0.40% copper, 0.34 g/t gold, 1.7 g/t silver and 240 ppm molybdenum. Contained metals in the resource were 56.9 billion pounds of copper, 70.6 million troy ounces of gold, 3.4 billion pounds of molybdenum and 344 million ounces of silver. The estimate used a 0.3% copper equivalent cutoff.
gross value of the contained metals, 57% was from copper, and 27% from gold and 14% from molybdenum. Co-products including silver, rhenium, and palladium might also be recoverable.
Fisheries
All five Eastern Pacific salmon species spawn in Bristol Bay's freshwater tributaries. The bay is home to the world's largest commercial sockeye salmon fishery. The Kvichak River has the world's single largest sockeye run. The Kvichak drains from Lake Iliamna, which is downstream of the deposit. Salmon, herring and other fisheries account for nearly 75% of local jobs.Sport fishing is another important local industry. Many lodges cater for sport fishermen exploiting the salmon and trout populations in the freshwater tributaries. Freshwater species include humpback whitefish, Dolly Varden trout, arctic grayling and rainbow trout.
Seasonal harvesting of salmon and year-round harvesting of freshwater fish is a critical part of life for rural residents, most of whom live downstream of the mine site.
Human populations
The Pebble site is within Lake and Peninsula Borough, about 1,600 inhabitants as of 2010 United States census, adjacent to the Bristol Bay Borough of about 1000 inhabitants and the Dillingham Census Area, 4,800 inhabitants. Some 7,500 people live largely rural lifestyles within or near the area downstream of the Pebble site. The populations of Lake Clark National Park and other parts of the Bethel Census Area are upstream of the site or in a different watershed.The populations in the area rely heavily on wild resources for subsistence, harvesting moose, caribou and salmon. Wild resources play an important part in the region's cultural heritage. There are more than 30 Alaskan native tribes in the region that depend on salmon to support their traditional subsistence ways of life, in addition to other inhabitants and tourists in the area.
History
Discovery
In 1987 Cominco Alaska Exploration collected mineralized surface samples at the Pebble site from color anomalies visible from aircraft. Geologist Phil St. George was credited with the discovery. He led early exploration efforts, drilling out the first half billion tons of the deposit. The first two exploration holes were drilled in 1988; in 1989 twelve more drill holes, soil sampling, and geophysical surveys indicated that the Pebble West occurrence was part of a large copper porphyry system. CAE continued drilling and other work through 1992, with a second drill campaign in 1997, with the resource doubled from 500M short tons to 1B short tons.In 2001, Northern Dynasty Minerals, Ltd. optioned the property from Teck Cominco, the successor to CAE's parent company. Northern Dynasty Minerals began exploration in 2002, which continued through 2013. In 2005, Northern Dynasty discovered the Pebble East deposit and acquired 100% ownership of the Pebble mining claims.
Project funding
In 2008, $140 million was budgeted and approximately of additional drilling was completed.In 2009, $70 million was budgeted, to complete a preliminary feasibility study, or "prefeasibility" study, and to prepare the project for permitting.
In 2010, $73 million was budgeted towards the pre-feasibility report, environmental studies, and various administrative and community-relations work. Applications for development and operations permits were not planned until after 2010.
For 2011, $91 million was budgeted to complete the pre-feasibility study, leading to permit applications in 2012. Environmental and engineering studies including of drilling to decide on mine design and a complete environmental baseline.
By 2017, over $150 million had been spent on environmental and social impact assessments.
In 2022, an additional $9.4 million was received from a private asset management company, with the potential to invest up to $47 million total over a two-year period.
Project particulars
Project ownership
The land is owned by the State of Alaska. Pebble Mines Corp. holds mineral rights for of the area, an area that includes the Pebble deposits, as well as other, less explored, mineral deposits. A sequence of mining companies and partnerships have owned the Alaska mining claims at and around Pebble since the initial claim staking by Cominco in 1987.The Pebble Limited Partnership was once one of the largest multinational mining corporations made up of South African company Anglo American, along with Northern Dynasty Minerals, a junior mining company headquartered in Canada. After a few investors walked away, Northern Dynasty was the only company left seeking development.
The Pebble Limited Partnership is now 100% owned by The Northern Dynasty Partnership, which is a wholly owned Canadian-based subsidiary of Northern Dynasty Minerals, Limited.
Three of the world's largest mining companies purchased shares of Northern Dynasty or became partners in the Pebble Limited Partnership through obligations to fund exploration and development. All have since divested their interests.
Mitsubishi Corporation sold its 9.1% interest in Northern Dynasty Minerals in 2011.
Anglo American, a South African mining company, struck a deal with Northern Dynasty to earn a 50% interest in a newly created Pebble Limited Partnership, the other 50% belonging to Northern Dynasty; between 2007 and 2013 Anglo American spent over half a billion dollars on the project. In December 2013 Anglo American walked away from the project, losing its 50% interest, which reverted to Northern Dynasty Minerals Limited.
Rio Tinto Group, through its wholly owned subsidiary Kennecott Utah Copper purchased, for 87 million dollars, a 9.9% ownership of Northern Dynasty Minerals Limited in July 2006, and in 2007 doubled that to 19.8% ownership, for an additional 94 million dollars.
On December 23, 2013, Rio Tinto announced it reviewed its $200 million investment in Northern Dynasty Minerals, and considered divesting. On April 7, 2014, Rio Tinto divided its 19% holdings in the project equally between the Bristol Bay Native Corporation, which had opposed the mine, and the Alaska Community Foundation, which had cooperated with Northern Dynasty in managing the Pebble Fund, a financier of grants to organizations in the Bristol Bay area. In April 2014, the Rio Tinto Group gifted its shares, worth only approximately 18 million by then, to two Alaskan charitable foundations.
Northern Dynasty is one of several public mining companies controlled by Hunter Dickinson, a Vancouver-based Canadian mining corporation.
All but one of Hunter Dickinson Corporation's board members are also on the Northern Dynasty board. Most of the senior management of Northern Dynasty also hold senior management positions at Hunter Dickinson Corporation.
As reported on February 13, 2019, Kopernik Global Investors beneficially owns 6.17% of Northern Dynasty Minerals, which is an increase of 11% in their ownership stake from their prior reported position reported in February 2018. Based on filings, Kopernik has held a position in NAK since at least as early as 2015, when they owned 19.99%.