The framework of the deal "ensures that our customers will be protected at every step along the way," Greg Abel, PacifiCorp's chairman and chief executive, said in a prepared statement.

The deal between PacifiCorp, the Interior Department and California and Oregon was reached after three years of negotiations with environmental, tribal and farmer groups. The parties hope to finalize the agreement by June. The dams' removal is subject to approval by federal officials, after reviews that are expected to take four years.

"This marks the first step in a future process, but it's a giant step," Interior Secretary Dirk Kempthorne said at a new conference Thursday.

Oregon Gov. Ted Kulongoski added, "While many months of work [lie] ahead, this historic agreement provides a path forward to achieve the largest river and salmon restoration effort ever undertaken."

Most groups didn't get everything they wanted. The American Rivers environmental group, for example, was pushing for the dams to be removed by as soon as 2015. And farmers who depend on irrigation from the river stand to get less water in dry years than they do now.

But most of the parties sounded pleased that a deal could be reached to end the dispute.

The conflict turned so ugly in 2001 that federal marshals had to be called in after angry farmers seeking water turned on spigots that the U.S. government had closed during a drought year.

In 2002, environmentalists became enraged after tens of thousands of salmon died in the river when the government diverted more water to the farmers.

"The bottom line is we tried to find common ground and compromise, and that is the only way something like this could have happened," said Martin Goebel, president of Sustainable Northwest, a Portland-based environmental group.