WASHINGTON -- The Environmental Protection Agency's independent inspector general has found no evidence of bias or predetermination in the agency's effort to review the potential impacts of the proposed Pebble mine on the Bristol Bay watershed, according to a new report out Wednesday.

But the inspector general did raise questions about potentially inappropriate efforts by one EPA employee to aid opponents of the mine, though he was retired by the time the agency proposed to block mining in portions of the Bristol Bay watershed.

The report marks a major step in a years-long fight over the potential mine that has been subject to calls of federal overreach by the company hoping to mine the massive deposits of gold and copper in Southwest Alaska. The inspector general reviewed EPA's actions from over a year: May 2014 to October 2015, including an assessment of more than 8,000 emails involving EPA officials, the report said.

"First of all, based on the information available to us, we found no evidence of bias in how the EPA conducted its Bristol Bay watershed assessment, or that the EPA pre-determined the assessment outcome" to allow the agency to bar mining in parts of the watershed, said Randy Holthaus, of the inspector general's office, in a podcast released with the report. The EPA followed the rules in its scientific process for assessing the potential impacts to the watershed and the subsequent peer review, the report found.

"We're very pleased that at the end of the day they concluded that the science was done consistently with all of our guidance and procedures and requirements," said Dennis McLerran, head of the EPA's regional office that includes Alaska. "And we feel that the science that we've done up there is rock solid and this is an indication of that."

Clearly pleased with the outcome, EPA attorneys quickly filed a copy of the report Wednesday with U.S. District Court in Anchorage in an ongoing case over the agency's efforts to block the mine in Bristol Bay.

Pebble Limited Partnership CEO Tom Collier struck back against the inspector general's findings, asserting the EPA reached a decision to block the mine before undertaking the scientific inquiry. He said the EPA "inappropriately colluded with environmental activists, [and] that it had manipulated the scientific process and lied about its intentions."

Collier called the report "an embarrassing failure" and said he hopes Congress will push forward with further investigation into EPA's actions.

The inspector general's inquiry sprang from multiple requests from members of Congress and Pebble Limited Partnership to investigate the EPA's efforts leading up to the watershed assessment. The inspector general's office set out to find out why EPA did the review; if it was done in a biased manner or had a predetermined outcome; and if the agency followed correct policies, processes and procedures during the watershed assessment and the peer review that followed.

Mining companies have been considering developing the area since 2001, when Northern Dynasty Minerals Ltd. began surveying the site. The EPA got involved in 2003, and annual meetings with company, state and federal officials began a year later. The Pebble Limited Partnership -- a joint venture of mining companies Northern Dynasty and Anglo American -- was launched in 2007. Anglo American dropped out of the project in 2013.

After ongoing requests and concerns about the project, and Pebble's repeated unfulfilled promises to submit a permit application, EPA agreed to launch a scientific study, based largely information about mine plans Northern Dynasty submitted to the U.S. Securities and Exchange Commission in 2011. That information is required to be accurate.

Pebble "told us many times, and people in Alaska many times, that the permit application was going to come next month, next year, very soon. And we felt that they would likely file a permit application during the time that we were doing the watershed assessment. But they didn't," McLerran said. The company can still file a permit application, he added.

In July 2014, EPA issued a proposed decision to restrict certain parts of the watershed from mining activities, but that decision has not been made final due to ongoing litigation.

Groups opposed to the mine development lauded the report, saying it proves the EPA acted fairly and its findings are legitimate. Statements from representatives of Salmon State, Sportsman's Alliance for Alaska, the Natural Resources Defense Council and the United Tribes of Bristol Bay, among others, said the report should put to rest many concerns about the agency's actions.

Kim Williams, executive director Nunamta Aulukestai, a nonprofit association of Bristol Bay Native organizations opposed to the mine, said the "report shows that EPA is on the right track and they need to get back to work. Pebble asked for this report, and now that they don't like the findings, they are trying to undercut it with their paid lobbyists."

"Today's news confirms what we in Bristol Bay have known since the beginning: that EPA acted fairly, at the request of Bristol Bay's tribes, to protect our invaluable salmon cultures and the world's last great salmon fishery," said Alannah Hurley, director of United Tribes of Bristol Bay. "The baseless accusations made against the EPA by foreign corporations and Outside Congressmen have once again failed to stand up to the facts."

Nelli Williams, director of Trout Unlimited's Alaska Program, said the group hopes the report will allow the agency to quickly resume its efforts to block mining in the watershed. "The Pebble Limited Partnership has employed a series of expensive delay and deception tactics to mislead the public on the truth behind the EPA's fair and transparent steps to protect Bristol Bay," Williams said, adding that the report shows the agency's efforts "are based on science and common sense."

The EPA employee in question

The EPA inspector general said an EPA employee may have acted inappropriately in helping tribes submit a petition to stop the mine, though that petition was not initially successful.

The employee is not identified in the report but acknowledged by the agency and Pebble to be retired staffer Phil North, an agency ecologist who oversaw Clean Water Act requirements for parts of Alaska and was "was one of 20 authors of, and an EPA technical lead for, the assessment," the report said.

The inspector general said, however, North's actions did not undermine the whole process, though it did recommend additional training to ensure clearer lines between staff and groups working with the agency. EPA agreed to that recommendation.

North has been a key focus for Pebble, given 25 months of missing emails from 2007 to 2009. The inspector general also tried to subpoena North's personal emails but couldn't find him, and North's attorney wouldn't accept a subpoena on his behalf.

From what the inspector general could find, the former EPA employee may have misused his position, Holthaus said. There "are basic standards of ethical conduct that executive branch employees must follow and one of those is that federal employees remain impartial in dealings with outside parties — especially if those parties are considering petitioning or have petitioned the agency to take action on a particular matter," he said.

The main evidence of bias was in a stretch of emails between North and an attorney representing mine opponents where North suggested edits to the petition that asked agency to stop the mine.

"The Region 10 employee provided six edits on word choice and one comment to add some language on ecological effects not directly related to fisheries. The final tribal petition letter sent to then EPA Administrator [Lisa] Jackson included changes suggested by the Region 10 employee," the report said.

EPA rules state if an employee uses a personal account for any reason, the employee is required to forward the emails to a work account for record keeping. The investigators could find no evidence North did so, though EPA did note as the sole employee in a remote Alaska office. "telecommunication challenges occasionally required" he use his personal email account.

"We don't condone the activities that were identified there," McLerran said in an interview Wednesday. "But what is very clear is that Phil North was not the decision-maker here. I was the decision-maker, in consultation with headquarters folks," he said. And the decision was to undergo a scientific assessment, not to grant the tribes' petition, he noted.

"And Phil North retired from EPA" before the assessment was finished, "and certainly before we made any decisions about restrictions on mining in the watershed," McLerran said.

"There's a narrative that Pebble Partnership has put forward" that the agency believes is "a false narrative," McLerran said. The "process here was done appropriately and was done with independent reviews by independent peer reviewers. So we feel comfortable and solid with the work as a whole."

Pebble: the report is too limited

Pebble argued the investigation was too narrow, focusing on only a few employees, and the email search was particularly limited — including only three employees with no way of gathering potentially deleted emails.

"We are by no means through making our case that EPA acted inappropriately and perhaps illegally with respect to Alaska's Pebble Project," Collier said in response to the report.

"We will have the opportunity to depose as many as 35 senior EPA officials, insiders and others in the environmental community" in ongoing litigation, and congressional investigations may yield "fresh insights," Collier said. But Pebble has already lost in court in its efforts to force activists outside the EPA to testify or turn over evidence and there's no indication from the judge that Pebble will get another chance.

Some employees at the EPA did know about North's efforts to help the tribes with their petition, Pebble argues, focusing on an email showing they knew the petition was coming.

The inspector general acknowledged some at the agency believed there was sufficient evidence to make a determination about the mine, but notes the agency decided to go ahead with the three-year watershed assessment anyway, marking it up to internal deliberations. But Pebble argues that is evidence the decision was already made at the outset.

Pebble has sought numerous records in its litigation over the case, including North's email records. In November, a federal judge ruled the company could not force opposing environmental and fishing groups to turn over years of records or to require testimony by two individuals fighting the massive proposed mine. The individuals said Pebble was using the subpoenas to harass them and violate their rights to oppose the mine.

The company issued its own independent review of the process last year that raised concerns about the fairness of the process.