On paper, the Blackfoot River, which begins at the Continental Divide and flows 132 miles to the west, doesn't seem poetic. Roads and clear-cuts line its shores. Mining waste runs through its water. In 1975, a tailings dam broke, spilling sludge into the headwaters of the Blackfoot, killing fish and turning the area into a state Superfund site. When Robert Redford filmed the movie version of A River Runs Through It, he decided the Blackfoot had too much logging nearby for the panoramic shots he wanted. He used the Gallatin instead.


So what makes the Blackfoot special?


Fish: The Blackfoot is to anglers what Jerusalem is to monotheism. It houses cutthroat, rainbow and brown trout. It is also one of the Northwest's most important spawning grounds for bull trout, a fish on the verge of being listed as an endangered species.


If the McDonald Mine is built, fish would face a host of dangers:


* Acids and heavy metals - Like Pegasus' Zortman-Landusky Mine, the McDonald Mine isn't expected to mine sulfide ore. Yet if a part of the 450 million tons of waste rock turns out to contain sulfides, groundwater could be contaminated with sulfuric acid, which leaches heavy metals from rock. This toxic brew of "acid mine drainage" has sterilized entire streams and is now a big concern at Zortman-Landusky.


* Dirt - To build the mine, the company plans to move three miles of highway. Sediment from construction could clog stream bottoms and destroy spawning areas.


* Leaking liners - Most liners rip; then cyanide leaks out. Some could make it to the river. A dose as small as a grain of rice kills humans. Much less is fatal to fish.


* Nitrates - Used to blow up the buttes, nitrates in the river could cause large mats of algae to grow, which in turn suck oxygen out of the water, choke fish and clog irrigation ditches.


* De-watering - Since the pit will descend 700 feet below the surface of the water table, pumps will lift water out of the pit and discharge it into the river. This could dry up stream edges, raise water temperatures, destroy spawning areas and strand migrating fish.


*H.A.