TORONTO (miningweekly.com) – Vancouver-based Northern Dynasty Minerals on Thursday reported that the office of the inspector general of the US Environmental Protection Agency (EPA) would carry out an investigation into the EPA's conduct in preparing its assessment on the Pebble copper/gold/molybdenum project, known as the Bristol Bay assessment.

From the time the report, 'An assessment of potential mining impacts on salmon ecosystems of Bristol Bay, Alaska', was published in January, Northern Dynasty had submitted three protest letters to the EPA inspector general.

Environmental regulators have moved to block development of the Pebble mine, citing potential "irreversible harm" to the state's salmon fishery.

TSX- and NYSE-listed Northern Dynasty maintained that the report raised serious issues of bias, process irregularities and collusion with environmental organisations in the federal agency's preparation of the assessment.

In response to congressional and other requests, the inspector general's office announced this week that it would start preliminary research to determine whether the EPA had adhered to laws, regulations, policies and procedures in developing its assessment of potential mining impacts in Bristol Bay.

“While the documents we've received to date through the Freedom of Information Act requests are sparse and heavily redacted, they paint the picture of an agency launching a 'watershed assessment' to justify a predetermined outcome,” Northern Dynasty president and CEO Ron Thiessen said.

“We are thankful that the inspector general's office has initiated this action, and hopeful that EPA's failure to conduct an objective, transparent and defensible scientific investigation will ultimately come to light.”

Northern Dynasty and the Pebble Limited Partnership had in the past called on the EPA to suspend the regulatory process under Section 404(c) of the Clean Water Act that it initiated on February 28.

The companies said that despite the absence of a proposed development plan, the EPA was threatening to take pre-emptive action to either veto or restrict development at Pebble – citing the assessment as the main evidence to do so.

Northern Dynasty, the Pebble Partnership and the State of Alaska had encouraged the EPA to wait for the submission of a proposed development plan for the Pebble project and to participate in the federal and state permitting process under the National Environmental Policy Act (NEPA), including the preparation of a comprehensive environmental-impact statement (EIS), before taking any regulatory action.

"Not only does EPA not have the statutory authority to undertake pre-emptive action at Pebble, they are threatening to do so based on a flawed study that is now the subject of an investigation by their own agency,” Thiessen said.

“There is absolutely no reason for EPA to press on with its pre-emptive regulatory process for Pebble when, by its own admission, an EIS process under NEPA will provide a more comprehensive, definitive and robust assessment of the true effects of mineral development in south-west Alaska.”

Last month, mining major Rio Tinto gave away its 19.1% holding in the company to two Alaskan charities.

The decision followed the strategic review announced last year of Rio Tinto's interest in Northern Dynasty, which concluded the Pebble project did not fit with Rio Tinto's strategy. Anglo American pulled out in September, as part of its plan to cut the cost of future options.