Aug 25 (Reuters) - Alaska's Pebble Mine project, one of the world's largest copper and gold deposits, has been through a roller coaster of regulation over the past 13 years.

The mine would, if brought online, produce 70 million tons of gold, molybdenum and copper ore a year. Opponents say it would permanently damage pristine wilderness and the state's lucrative salmon industry.

The U.S. government on Monday imposed a major regulatory hurdle on the mine's developers, fueling speculation the project will never come online.

Here is a brief history of the project's development.

1987

The Pebble deposit is discovered by a geologist working for a predecessor company to Teck Resources Ltd. Over the next 10 years, geological studies show the deposit is one of the largest gold and copper reserves in the world.

2001

Vancouver-based Northern Dynasty Minerals Ltd secures the rights to develop the Pebble project. The company spends the next few years on further geological tests.

January 2007

Rio Tinto, one of the world's largest mining companies, buys a stake of about 19% in Northern Dynasty.

August 2007

Mining company Anglo American Plc and Northern Dynasty agree to form a 50/50 joint venture to develop Pebble.

February 2008

Major jewelry companies, including Tiffany & Co, come out against the Pebble project, citing concerns over how the mine could affect Alaska's Bristol Bay watershed.

October 2008

Sarah Palin, Alaska's then-governor, becomes the Republican vice presidential candidate and helps bring national attention to the mine. Palin stays officially neutral on the project but is seen as friendly to developers. Other state politicians, including then-Senator Ted Stevens, oppose the project.

April 2009

A delegation from Native tribes in Alaska's Bristol Bay region attends Anglo American's annual shareholder meeting to oppose the Pebble project.

February 2010

A geological study shows the Pebble deposit contains at least 55 billion pounds of copper and 67 million ounces of gold.

November 2012

National Geographic, the prominent conservationist publication, calls the fight over Pebble the "Gettysburg of natural resource conflicts" and praises mine opponents as an "uncommonly savvy patchwork of native groups, commercial fishermen, village councils, local residents, outfitters, conservationists, and others united in the conviction that the environmental risks, especially for salmon, greatly outweigh the economic benefits."

September 2013

Anglo American pulls out of the Pebble project, giving Northern Dynasty full control. Anglo, which walked away having already spent $541 million on the project, said it would focus on "projects with the highest value and lowest risks within our portfolio."

February 2014

The U.S. Environmental Protection Agency under then-President Barack Obama initiated a rarely used process under the Clean Water Act to block Pebble's development. The EPA cited the potential of "irreversible harm" to Alaska's salmon fishery.

April 2014

Rio Tinto gives away its 19% stake in Northern Dynasty to two Alaskan charities, the Alaska Community Foundation and the Bristol Bay Native Corporation Education Foundation. Rio said it had determined that the Pebble project does not fit its strategy. As of August 2020, neither charity remains a Northern Dynasty shareholder, according to Refinitiv data.

May 2017

The EPA agrees to settle several lawsuits related to the Pebble project. The move did not guarantee Pebble would win permit approval, but did, the EPA said, make sure regulatory review would be carried out "in a fair, transparent, deliberate and regular way."

Northern Dynasty told investors it was in discussions "with a number of potential partners," and could form a consortium to develop the mine. The company also said it thought it could get permits "in record time."

January 2018

The EPA pauses its environmental review of the Pebble project, surprising the market because of President Donald Trump's stated goal of boosting U.S. minerals production.

June 2019

The EPA said it would reconsider Pebble. EPA General Counsel Matthew Leopold told staff to reconsider a 2014 decision under Obama's administration that restricted the mine's disposal plans under the auspices of the Clean Water Act.

July 2020

The U.S. Army Corps of Engineers published a final environmental impact statement (EIS) recommending development of the Pebble project. The move was seen as one of the last regulatory hurdles for Pebble to receive necessary federal permits and the company said it could get final permits in as soon as 30 days.

August 2020

Prominent Republicans, including presidential son Donald Trump, Jr., voice opposition to the Pebble project and begin to privately lobby the White House against it. They are concerned the mine could damage a region where they hunt and fish.

Vancouver-based Northern Dynasty insists the project is still moving forward, though rumors circulate Trump could block it.

The Army Corps gives Northern Dynasty 90 days to explain how it would offset "unavoidable adverse impacts" to more than 3,200 acres (1,295 hectares) of wetlands if the mine were developed.

Alaska's U.S. Senators Dan Sullivan and Lisa Murkowski, both Republicans, came out against the mine, saying it could cause significant damage to the Bristol Bay region, popular for fishing and hunting.

Wall Street analysts begin to express doubts that the mine will ever be built. (Reporting by Ernest Scheyder in Houston Editing by Matthew Lewis)