The Chehalis River Basin Flood Authority last week toured the site of a proposed dam that would be built to prevent the floods that plague the river basin. The site is on Weyerhaeuser property, a few miles upstream from the town of Pe Ell.
Two types of facilities are being considered: a 238-foot-tall flood storage-only dam and a 288-foot-tall multi-purpose dam which would also provide hydropower.
The idea of a water retention facility was first proposed after the 2007 flood and some members of the Flood Authority are taking steps to make the dam a reality.
Many Lewis County leaders are in favor of the dam, but others — including the Chehalis and Quinault tribes and environmental groups — are already opposed to it.
One problem is the potential effects a dam might have on salmon in the river.
The Flood Authority contracted with Anchor QEA, an environmental science and engineering firm, to determine what those effects would be. According to the firm’s report, which was released earlier this year, the multi-purpose dam is the better, albeit more expensive option: the number of spawning spring Chinook salmon in the river could increase by as much as 140 percent, but the numbers of winter steelhead and coho salmon could decrease by as much as 52 percent each. The dam would cool the water in the summer, which is what scientists hypothesize would cause the 140 percent increase for Chinook.
Anchor QEA is working on a second report to determine how habitat restoration projects along the river could help mitigate impacts of the dam; according to the draft of the report, released in May, those projects could help increase the rate of survival of juvenile salmon from 14 to 73 percent.
Another concern is the potential safety hazard it could have for Pe Ell, a concern which was voiced by members of the public during the meeting Thursday.
The Flood Authority is working to compile a list of flood mitigation projects to present to Gov. Chris Gregoire as she prepares her final budget. The dam is one of the projects being considered.