Daybreak on August 8 found me on a bank of the North Fork of the Flathead River in northwestern Montana, among the mixed tracks of deer, otters, and grizzly bears, marveling, as I have a thousand times before, at the near-magical transparency of these waters.

The bottom stones stood out as if on display under glass. Decades ago, my wife and I built a cabin nearby.

Across the river on the east bank, in Glacier National Park, the campers were stirring in their tents and the first cars were snaking up the Going to the Sun Road. But I was headed west that day, into the Whitefish Range, to see a man about the future of this valley.

Later that morning, I started up the Glacier View Mountain Trail above Big Creek, a tributary of the North Fork. In a month or two bull trout, a threatened species, would be swimming up the creek to spawn. The trail wound up a mountainside that had burned in 2001 and was now dotted with gray, weathered snags. Young lodgepole pines were growing in among them, along with Douglas fir and wild rose and blossoming fireweed. The pines offered the only shade as the day's temperature rose into the 80s.

After the better part of a mile, I heard the scrape and ping of tempered steel on stone. A trail crew from the Montana Conservation Corps was digging into the steep slope to widen a series of switchbacks. Small plumes of dust drifted from their shovels and pickaxes. I met young recruits from places like Ohio and Brooklyn. I also met a 71-year-old guy in a hard hat, jeans, and sweaty, dirt-smudged T-shirt, who was whacking away at the slope with a pickax.

That was the man I'd come for: Montana Senator Max Baucus, current chairman of the powerful Senate Finance Committee. Today was one of his periodic "work days" back home, when he joins fellow Montanans at their jobs, and he had invited a few reporters to join him on the crew's lunch break. He wanted to talk about something close to his heart: the North Fork Watershed Protection Act.

When You Float It You Understand

The North Fork begins in British Columbia and flows 45 miles (72 kilometers) through undeveloped provincial forest there. After crossing into Montana, it continues for an approximately equal distance, defining the western boundary of Glacier National Park, before joining the Flathead's Middle Fork. The North Fork Valley is a corridor for wolves and lynx as well as grizzlies and bull trout, and a haven for an incredible diversity of plants and aquatic insects.

Only a tiny percentage of the valley is private property; most is public land. My own 32-acre patch of paradise is surrounded on three sides by the Flathead National Forest, and on the fourth by the river. But public land can be leased for mining, oil and gas drilling, and other purposes. For decades the valley has faced one industrial threat after another.

Baucus's commitment to safeguarding it began shortly after he was first elected to the House of Representatives in 1974. A Toronto-based mining corporation had proposed a massive open-pit coal-mining operation and coal-fired power plant near Cabin Creek, a Canadian tributary of the North Fork, just six miles from the northwestern corner of Glacier Park.