Tamed a generation ago by four federal dams, the lower Snake River is less a river today than a broad, slow-moving ribbon of commerce.

Near its confluence with the Clearwater River is Potlach Corp.'s mill, where barges load 170,000 tons of pulp and paperboard a year for shipment to the Pacific. To the north lies the Palouse, the rolling wheat country of eastern Washington, its rich bounty contributing to the 3 million tons of grain barged down the Snake every year. Downstream, 37,000 acres of desert-turned-farmland are irrigated by the river's flow, and the transmission lines from Lower Granite Dam pump electricity to Seattle and beyond.

Little wonder, then, that when Interior Secretary Bruce Babbitt stood on the banks of the Kennebec River in Maine two months ago and said the removal of that state's Edwards Dam "is the beginning of something that is going to happen across the nation," it was front-page news in Idaho.

Here, a national debate over tearing down dams as a means of restoring depleted fisheries is a major local issue. In December, the U.S. Army Corps of Engineers will release a long-awaited draft of a massive study of whether to rip out the four federal dams on the 140-mile lower Snake, a $1 billion deconstruction project with enormous economic and social implications for the Pacific Northwest that could determine the fate of some of the region's most imperiled runs of salmon and steelhead.

Constructed in the 1960s and 1970s to provide cheap hydroelectric power, irrigation water and a transportation link to the Pacific rim for grain and wood products from as far away as the northern Great Plains, the four lower Snake impoundments--Lower Granite, Little Goose, Lower Monumental and Ice Harbor--have been the subject of fierce regional arguments for the past decade.

How much of the blame should they shoulder for the precipitous decline of Chinook and sockeye salmon that in their epic migrations to and from the Pacific must struggle past the concrete barriers? Have the billions of dollars in technological fixes to the dams--improved fish passageways, safer turbines, and the barging and trucking of young fish around the dams--made any difference in survival rates for fish? Can the Northwest afford the dislocation and inconvenience of removing the dams? What is a fair price to pay for restoring species that symbolize the Northwest?

The pace of dam deconstruction is picking up across the country and national conservation groups hope to strike a blow on behalf of free-running rivers and fish. Regional politicians--most of whom oppose tearing out the dams--have stepped up their campaign in anticipation of what will ultimately be a congressional decision. More than 100 members of Congress urged President Clinton in August not to rule out dam deconstruction as an option for saving salmon. And presidential candidates are already being drawn into the argument, as Texas Gov. George W. Bush (R) was during a summer visit to Spokane when he said he does not believe the dams have to be breached to save salmon.

Advocates of the commercial interests that depend on the heavily engineered Snake River admit they are surprised that the debate has risen to the point where tearing out the dams is a serious option. "I've been involved in this issue for 10 years and no way would I have thought we'd be talking about dam breaching now," said Bruce Lovelin, executive director of the Columbia River Alliance, a consortium of barge, farm and heavy electric users. "But it's on the table. In spite of our opposition to it, it is here and it's heating up."

It is heating up because the nation's 75,000 dams, once almost universally viewed as marvels of technological prowess, are increasingly regarded as river and fish killers.

"The western landscape is dotted with dead rivers that are now trails of dust and dead cottonwood trees," said Babbitt earlier this summer at the University of Colorado. "We cannot destroy any more rivers."

Many of the nation's older dams, particularly smaller ones in the East and Midwest, have outlived their economic usefulness, and are ripe for removal, said Margaret Bowman, senior director of dam programs for the conservation group American Rivers. Many are being targeted by environmental groups, taking advantage of a wave of license renewal reviews by the Federal Energy Regulatory Commission (FERC), which regulates power-producing dams.

"I think economics is driving it in many places," said Bowman. "We understand better than we did two decades ago how dams affect rivers. It's quite expensive to mitigate for those impacts and for many rivers it is cheaper to remove dams than mitigate."

The removal of the 162-year-old Edwards Dam in Maine, which opens up 17 miles of new spawning habitat for Atlantic salmon, striped bass and sturgeon, is an example of how once-warring interests can come together to restore rivers. The subject of a fierce fight that lasted a decade, the Edwards Dam was ultimately doomed by a 1997 FERC decision that the economic benefits of keeping it in place and producing small amounts of electrical power were outweighed by the environmental rewards of taking it down. A complex settlement followed, involving the dam's owner, the state, the city of Augusta and other industrial users of the Kennebec.

Finding that kind of common ground with larger dams in the West may be another matter. The Interior Department is moving forward with plans to remove two salmon-killing dams on the Elwha River in western Washington, but Babbitt has repeatedly clashed with that state's powerful Republican senator, Slade Gorton, who chairs the appropriations subcommittee that controls Interior's funding.

Gorton opposes removing the four lower Snake dams, a proposal he called "an unmitigated disaster and an economic nightmare" in a speech on the Senate floor in July. As the Army Corps of Engineers studies the social and economic effect of dam removal on the Snake, an effort that will be part of a larger environmental opinion by the National Marine Fisheries Service on the Columbia River basin's hydropower system, the commercial interests that depend on the Snake have geared up for an epic fight.

For all players, the stakes are high. Potlach ships its fiberboard for $4 a ton by barge. It would cost $6 a ton by rail. Grain farmers would pay 28 percent more to ship their produce. Irrigators would lose their farmland, or have to retrofit their pumps. And in a region that enjoys the lowest electric rates in the nation, the loss of 1,200 megawatts of power would cost up to $291 million annually and raise residential rates by $1.50 to $5.30 a month.

"Everybody's business strategy, everybody's transportation, everybody's customer base is built around the river," said Potlach spokesman Frank Carroll.

Among those who would be affected are third-generation farmer Roger Dye and his wife Mary, who grow wheat, bluegrass and canola on 2,500 leased acres in Pomeroy, Wash.. "If they rip those dams out and we lose this life, that's a terribly bitter pill to swallow, and especially tragic if the fish don't come back," said Mary Dye.

The fish, everyone recognizes, are on the brink. As recently as the 1960s, after construction of other dams on the Columbia but before the four on the Snake were erected, 100,000 salmon and steelhead migrated up the Snake. Last year, 9,300 steelhead, 8,426 spring-summer Chinook salmon, 927 fall Chinook and two sockeye made the journey. In this decade, all those species have been put on the endangered or threatened species list, and in the 1980s Snake River coho salmon were declared extinct.

The question is whether removing the dams will make the difference compared with the current system of barging and trucking young fish around the dams, occasionally at a cost of up to $1,000 per fish.

The science is anything but precise. In a report last April, the National Marine Fisheries Service said dam removal is "more likely than any other hydro-system action to meet survival and recovery criteria for the listed species. . . ." However, the agency cautioned that "there are plausible sets of assumptions under which [removal] yields little or no improvement over transportation alone."

Native American tribes, who have relied on salmon for thousands of years, were guaranteed salmon by 19th century treaties through which they gave up millions of acres of land. They have a powerful legal hammer if the federal government does not act to restore the fisheries.

"We know what will not work, the status quo," said Don Sampson, executive director of the Columbia Inter-Tribal Fish Commission, which supports dam removal.

CAPTION: Because of dams on the Snake River, cargo can travel cheaply to the Pacific.