Any final action by the federal government blocking large-scale mining in the Bristol Bay region will likely have to wait until the next presidential administration, a top Environmental Protection Agency official said Monday.

Dennis McLerran, administrator for EPA's Pacific Northwest region, said litigation by the company seeking to build the controversial Pebble Mine has forced a delay in action on the agency's plan to use a Clean Water Act provision to prevent a big mine from being built in the salmon-rich region.

EPA's Bristol Bay Watershed Assessment, launched in 2011 in response to concerns in Alaska about Pebble impacts, resulted in a 2014 decision to start a Clean Water Act process precluding development of large-scale metals mining there.

Three lawsuits filed by the Pebble Limited Partnership have prevented EPA from carrying out that administrative action, allowed under Section 404(c) of the Clean Water Act, McLerran said. But the watershed assessment justifies such action, he said.

"The science that we've done is clear. That will stand the test of time," said McLerran, who was in Anchorage to take part in the Alaska Forum on the Environment in Anchorage. "In some ways, it's unfortunate that we won't be able to, likely during this year, finalize 404 (c) action on this. But future administrations and career staff will have that work in hand when the litigation's resolved."

The three lawsuits were filed in 2014 in U.S. District Court in Alaska.

One of them, a complaint challenging EPA's authority to conduct the watershed assessment, was dismissed in 2014 by U.S. District Court Judge Russel Holland. That dismissal was upheld last May by the 9th U.S. Circuit Court of Appeals.

The other two are still pending. One is a complaint alleging that EPA's Bristol Bay Watershed Assessment was the product of collusion with anti-mine environmentalists in violation of the Federal Advisory Committee Act. Both sides are collecting testimony and other evidence, McLerran said.

"That's going to take a while to play out," he said. "It'll be probably late this year, at the earliest, before the discovery phase is completed." After that, the Department of Justice will face a decision about whether to seek dismissal on behalf of EPA, he said.

The third lawsuit concerns the Pebble Limited Partnership's claims that EPA has violated the Freedom of Information Act.

McLerran said EPA is confident it will prevail in both cases.

The Bristol Bay Watershed Assessment concluded that a mine of the size and scope that Pebble has proposed in financial reports would cause significant harm to the region's fisheries.

McLerran said the assessment has been upheld through two peer reviews and, most recently, a review by EPA's Office of Inspector General that found EPA's work had been conducted without bias and without a predetermined outcome. That Inspector General report was issued last month. McLerran said the next presidential administration could use the report as the basis for a future Section 404(c) ruling or in any future permitting review.

"That work is extremely important and solid work that will stand the test of time," he said. "We may not be able to complete the work under section 404(c) during this administration, but the science is there."

The Pebble Limited Partnership is vowing to push forward with its litigation. A company statement issued on Jan. 13, the day the Office of Inspector General report was issued, promised an extensive discovery process in the lawsuit over allegations that EPA violated the Federal Advisory Committee Act.