SEATTLE - Opponents of a plan to deepen a 103-mile stretch of the Columbia River have filed suit, challenging the federal government's approval of the $136 million project.

Earthjustice, a public interest law firm representing Northwest Environmental Advocates, argued that dredging 3 feet from the river's 600-foot-wide shipping channel from the Pacific Ocean to Portland would devastate salmon habitat and worsen erosion of Washington and Oregon beaches.

"This project is wrong for salmon and other species, it's wrong for Washington and Oregon, and it's wrong for the American taxpayers," said Nina Bell, executive director of Northwest Environmental Advocates. "It's shocking that the federal agency in charge of salmon can approve further degrading the estuary that is so critical to salmon survival."

Brian Gorman, spokesman for the National Oceanic and Atmospheric Administration's Fisheries office in Seattle, said Tuesday the agency had not reviewed the lawsuit yet and he could not comment on it.

But he noted that when NOAA Fisheries approved the dredging plan in May 2002, it stated that restoring salmon habitat is a priority.

"We were really very clear in our biological opinion that any possible harm to fish that might occur during the actual dredging operations needed to be offset by some benefit for the estuary," Gorman said. "It's crucial that we treat that body of water very carefully."

The U.S. Army Corps of Engineers' plan is designed to open the river to the latest models of deep-draft container ships and grain vessels, helping Portland and five downriver ports compete for Pacific Rim business.

Critics noted that in 1999, NOAA Fisheries scientists called the channel-deepening plan "an incremental insult to an already degrading ecosystem," citing erosion of coastal beaches and deterioration of narrow inlets that serve as crucial salmon habitat.

"NOAA Fisheries disregarded its own scientific findings when it approved this project," said Todd True, a lawyer for Seattle-based Earthjustice. "All the science shows that dredging and dams on the Columbia have taken an enormous toll on salmon and it's outright illegal to approve more.

The lawsuit, filed Tuesday in U.S. District Court in Seattle, challenges both routine maintenance dredging and the channel-deepening plan on grounds that they fail to protect 12 stocks of Columbia River salmon.

"There's no analysis there of what current dredging is doing to salmon and salmon habitat," Bell said.

The Corps has said it would work to offset environmental damage with projects aimed at restoring the ecosystem, such as dumping some dredged sand and mud from the center of the river to its edges, creating habitat for juvenile salmon.

Other dredge spoils would get dumped into the Pacific Ocean, which critics say would smother a swath of sea bottom teeming with juvenile Dungeness crabs that feed in the nutrient-rich waters at the mouth of the river.