Construction will continue during summer months for five years.

The plan includes replacing turbines, building underwater walls to redirect currents and improving the labyrinthlike fish ladders at the T.W. Sullivan Plant.

"When this is done, the fish will have the best access they've ever had to the Willamette," including before the dam was built in the late 1800s, said John Esler, project manager for PGE. Fish survival rates are expected to increase to at least 98 percent, 3 percent higher than the current average.

The project is a condition of PGE's settlement agreement to gain relicensing with the Federal Energy Regulatory Commission. PGE consulted with Native American tribes, environmental groups, state and federal agencies and nongovernmental groups for about a year to form the plan. PGE will continue to work with the groups as the plan progresses.

PGE shut down the plant and diverted water over the falls in mid- June and plans to have the first construction phase finished by Nov. 1.

This summer's construction includes replacement of two turbines with newer, more efficient models that will not harm as many fish. In the next five years, 10 of 13 turbines will be replaced. This week, crews will add concrete walls to the river floor in front of the dam to subtly change the current.

"We can actually sweep the fish right past the entrances" of the turbines, Esler said, so that fish will naturally be directed toward the sides and away from the turbines.

PGE officials said they plan to drain the area every summer and work for four to five months, which will disturb fish the least. The hydroelectric plant will not be able to produce power during these months.

While the changes are primarily designed to help salmon and steelhead, lampreys also will be helped. PGE has commissioned research to determine how best to help the eellike fish traditionally harvested by Native Americans.

PGE has agreed to make whatever changes are determined by the research.

The utility also will build a gate to concentrate water flow over the center of the Willamette Falls, which will prevent fish from getting swept to a steeper, more dangerous area. Esler said the fish were getting swept over the falls and dying on the rocks and in shallows.

Most of the changes to the falls will be invisible, especially when the water is high.

"In the context of the whole Columbia Basin, these changes are all incremental things that, in total, make a difference," Esler said.