Three months after they dipped their canoe into the Boundary Waters of Northern Minnesota, Dave and Amy Freeman stepped ashore on the banks of the Potomac to plead their case in the nation's capital.

For three months, the couple paddled, sailed and portaged the 2,000 miles from the Boundary Waters Canoe Area Wilderness, retracing the path of the French fur-trading

voyageurs of centuries before. Their canoe is covered, inside and out, with thousands of signatures from people they met along the way, all petitioning the federal government to protect the Boundary Waters from a copper-nickel mining operation proposed near its borders.

"We met people from all across the country who love the Boundary Waters. It's not just people in Minnesota who visit – it's truly a national treasure," said Dave Freeman, who has logged thousands of miles of adventures with his wife and fellow wilderness guide, Amy.

The couple, who were named National Geographic's 2014 Adventurers of the Year wrapped up this year's adventure on the banks of the Potomac Tuesday. Over the past decade, they have trekked around the country and beyond by kayak, canoe, backpack and dogsled; paddled an 1,100-mile loop around Lake Superior; and once let schoolchildren pick part of their route on a 11,647 mile trek across North America.

But always, waiting for them at the end of their travels, was the peace and tranquility of the Boundary Waters, a million square acres of lakes, rivers and wilderness along the U.S.-Canada border. This year marks the 50th anniversary of the Wilderness Act that set aside 9.1 million acres, including the vast stretches of the Northern Minnesota preserve.

Photo credit: Nate Ptacek

The visitors they guide there, Freeman said, "come for the pristine environment, the solitude, being able to sit out in the middle of the lake in your canoe or walk out onto the lake with your snowshoes on – and you can't hear any sounds, there's no lights, there's nothing around you at all. Just the wilderness."

Now, they worry, the peace and pristine beauty of the boundary waters could be in jeopardy from the proposed sulfide-ore operation on its borders. Already, Freeman said, he can hear the clatter of test drilling.

Proposed copper-nickel mining operations have divided northern Minnesota communities between those eager for the jobs and economic boost the operations could provide, and those worried about pollution, light and noise spoiling the peace of a region that lures visitors from around the globe to paddle, hike, camp and trek through the wilderness.

"These types of mines have a very long track record of pollution. This type of mine in a sulfide-ore body, has never been done anywhere in the world without causing significant pollution, both to surface water and ground water," Freeman said. "The Boundary Waters is a maze of interconnected lakes and rivers. It's really one of the worst places that we could try and put this type of mine."

On Tuesday, exactly 101 days after they set out, the Freemans paddled up the Potomac through a cold, driving rain. Waiting for them along the Georgetown waterfront was a small flotilla of local canoers, waiting to welcome them to the end of their trek.

The Freemans plan to plead their case -- and present their canoe/petition -- to federal officials they hope can intervene to block the mining operation. The alternative, they fear, will be scenes like the Hudson River Superfund site they paddled through – a place "where you don't even want to touch the water," Freeman said.

"Everyone we met, all along the route, in these non-wild areas, they were all trying to clean up the rivers, they were all trying to gain access to the water," he said. "We have such a special thing in Northern Minnesota. You can just go onto the lake and dip your cup in and drink. We just don't feel it's worth the risk these sulfide-ore mines would bring."

For more information about the "Paddle to D.C." trek, visit www.savetheboundarywaters.org.