Proposed new dam on Chehalis to address chronic flooding raises many questions | KNKX

Proposed new dam on Chehalis to address chronic flooding raises many questions

Mar 4, 2020

The Chehalis River has flooded 18 times in the past 20 years, sometimes submerging Interstate 5 near Olympia. The local Flood Control Zone District is proposing a new dam to prevent extreme high water. A draft environmental impact statement is now out for public comment.  

The new dam would only trap water when the river reaches a certain volume. This is what’s known as a “run of the river” dam; under normal conditions, it would let the Chehalis run. 

It's designed with fish passage through underground tunnels and there are mechanisms for a gradual release from the reservoir after any damming. But the structure would require clearing forest land along the river — and it would be massive.

An image, from the state's Draft Environmental Impact Statement, of the proposed "run of the river" dam for flood control, to be built near the town of Pe Ell on the Chehalis River.
Credit Courtesy of the Chehalis River Basin Flood Zone District

“There’s unavoidable impacts on salmon, steelhead, as well as access to our treaty resources and cultural resources,” says Tyson Johnston.

He is vice president of the Quinault Indian Nation, which has treaty rights in the Chehalis flood plain — so they’re concerned about the impacts of such a huge new structure.

But he says they've also experienced a big increase in destructive flooding and sea-level rise over the past few decades, so they want to take a thorough look at the proposal and give it a fair shot.

“As a tribe, whose principal village is on the ocean, we really get the need to address the flooding issue for our communities," Johnston says. "But, as far as having a dam being the primary solution to that? I don’t think the nation is really sold on that yet."

Johnston says there may be more equitable and less expensive solutions: things like reconnecting the river to its flood plains or building small levies in specific areas.

Curt Hart, with the Washington Department of Ecology, says this is the state's second-largest watershed. And although the fish runs on the Chehalis are down by about 80 percent of their levels from 100 years ago, the river is one of very few with no species listed as endangered or threatened under federal law. Hart says the state wants to keep it that way.

“We want to try to work with the community to bring salmon back – their habitat back – while we also work to reduce damages from floods,” he said.

He says late last year, the department released a draft plan to restore habitat for aquatic species on the Chehalis flood plain and the proposed dam needs to take them into consideration as well.

Comments on the draft environmental impact statement are open through April 27. There also will be two public meetings before then, in Centralia and Montesano.