Hundreds of outdoors groups, from big game outfitters to fishing groups, are maintaining the pressure on federal officials to ensure that a gold mine proposed to be built near Lake Clark National Park and Preserve does not impair the Bristol Bay watershed and its fisheries.

In a letter (attached below) sent to Environmental Protection Agency Administration Lisa Jackson on Thursday, the coalition of more than 350 groups asked that she "use all the tools at your disposal to protect a sport fishing and hunting destination that is unrivaled in America and perhaps the world, for this and future generations of sportsmen and women."

The Pebble Mine, which also would produce copper and molybednum, is proposed to be developed just 14 miles beyond the preserve portion of Lake Clark's southwestern boundary. The sheer vision of Pebble has spawned a land rush that since 2003 has seen some 1,000 square miles of state lands adjacent to the park staked with mining claims.

Earlier this month, regional EPA officials said they would embark on an effort to gather baseline data from the sprawling Bristol Bay watershed that could come into play with any future decisions concerning the proposed mine.

In their announcement, EPA officials said they would "conduct a scientific assessment of the Bristol Bay watershed to better understand how future large-scale development projects may affect water quality and Bristol Bay’s salmon fishery, an extraordinary salmon resource for the United States. EPA initiated this assessment in response to concerns from federally-recognized tribes and others who petitioned the agency in 2010 to assess any potential risks to the watershed."

In 2010, nine federally-recognized Bristol Bay tribes petitioned EPA to use its authority under the Clean Water Act to protect Bristol Bay, the EPA release said. Their concerns focused on the potential Pebble Mine project. Two other tribes asked EPA to wait for mining projects to submit permit applications before taking action.

On Thursday, representatives from more than 360 organizations held a press conference to relay their fears of what the proposed mine could do to the waters of Bristol Bay.

“A huge open-pit mine in the Bristol Bay region could destroy one of the world’s most productive fish and game habitats, kill tourism to this international hunting and fishing mecca, and eliminate jobs from the United States,” said Brian Kraft, who owns the Alaska Sportsman’s Lodge and Alaska Sportsman’s Bear Trail Lodge.

According to Chris Wood, the president and CEO of Trout Unlimited, which has been running a media campaign against the mine, Bristol Bay is "the single most important wild salmon fishery in the world."

"It generates roughly $450 million a year in economic impact and sustains about 12,000 jobs," he said. "We are confident that after the science and other public input are considered, the EPA and the Obama administration will stand with sport and commercial fishermen and the people of Alaska to protect the extraordinary ecological, economic and cultural value of this place and this fishery."

According to a release from Trout Unlimited, "Bristol Bay is a 40,000-square mile region with nine major rivers, and is home to the world’s largest sockeye salmon run. Pebble Mine would create an open-pit mine up to two miles wide and 1,700 feet deep. Operated by multi-national mining interests, this mine could dump up to 10 billion tons of perpetually toxic waste in the heart of the Bristol Bay watershed. This area is known for frequent earthquakes, which puts the watershed – and all its fish and wildlife - at an even greater risk for long term toxic pollution and severe damage to the fishery."

At the American Fly Fishing Trade Association, Chairman Jim Klug called protecting Bristol Bay the "No. 1 conservation issue for the United States fly fishing industry."

"More than 150 sport fishing product companies have directly signed on to support protecting Bristol Bay’s fish and game habitat and economic resources, and hundreds more have voiced their opposition to Pebble Mine," said Mr. Klug. "We strongly urge the EPA and Obama administration to protect this amazing place.”

In their letter to Administrator Jackson, the organizations thank the EPA for the first step in agreeing to collect baseline data, but urge stronger action to protect Bristol Bay. The EPA has the authority under the Clean Water Act to invoke Section 404(c), which would give Bristol Bay the protection it needs from mining and other large-scale developments.

Next week, representatives of these groups will meet with legislators and agency members in Washington, D.C. to ask for support.

Here's a look at one of the commercials that Trout Unlimited produced to lobby against the mine: