As presenters rose to pitch a new flood control project just outside of Pe Ell during Tuesday's meeting of the Chehalis River Basin Flood Control Zone District, the message remained consistent: the proposal would be unlike anything ever built in North America.
“At the beginning of this, the initial design concept was more of a traditional dam,” said Lewis County Commissioner and Flood District Supervisor Scott Brummer. “Working with our partners in the basin, both the tribes and the agencies, we recognized that we need to differ so that we ensure that we reduced impacts to both fish habitats and aquatic species, and that we also balance that so that we ensure that we get some flood protection for the folks in Lewis County and this basin.”
The update Tuesday brought together state and local lawmakers, county officials and project planners to discuss a project they hope will prevent a flood similar to the 2007 event that devastated Lewis County.
The flood and its aftermath caused more than $900 million in damage to the river basin as almost 300,000 acre-feet of water went down the Chehalis River.
During the flood, Interstate 5 was shut down for nearly a week as water covered much of the roadway while more than 1,300 homes were destroyed.
“I know for many of us that have spent time during these floods helping our neighbors pull installation and clean up and sweep mud and doing the types of activities that we do here in Lewis County to help each other out, you realize how much it has impacted,” Brummer said. “And I know that I myself have seen a lot of devastation, just on a personal level.”
Fear of a future flood devastating the county is one of the reasons officials are optimistic about the structure, which, according to a new video created by the Chehalis River Basin Flood Control Zone District, would be “tailored to the unique needs of the Chehalis Basin.”
When activated, which would only occur when flooding is forecasted, the facility’s reservoir could hold approximately 62,000 acre-feet of water.
“Does that eliminate a flood? No, you still have a lot of water,” said J. Vander Stoep, an Office of Chehalis Basin (OCB) board member. “But what you have is the difference between a big flood and a catastrophic flood, and that’s what this is aiming to do.”
While residents would need to continue to take steps to reduce their flood risk, Vander Stoep said the proposal is the “only answer” that would reduce the flood risk to communities along the river.
“We’re not proposing a traditional dam,” said Matt Dillin, project manager for the Flood District. “What we’re proposing here is a flow-through dam. It’s a different type of dam than you’ve seen in the country.”
Unlike dams seen on the Columbia River, the structure, he said, would not retain a permanent pool of water. At the base of the structure, conduits designed to mimic the flow and current of the Chehalis River would allow fish to swim up and down the river unimpeded.
“It’s a different type of structure than what you think of when you hear the word dam,” Dillin said.
Officials say they have addressed many of the concerns identified in state and federal environmental reviews through the redesign of the dam, which will now be reviewed again by agencies involved.
Other questions remain unanswered.
Cost estimates for the project are still “being refined” Dillin said Tuesday, though the redesign will cost more than initial estimates.
Dillin said one of the “big pieces” the flood control district is doing next will identify when the structure is closed. According to the district, the structure would have been activated three times in the past two decades.
“One of the things we want to avoid is operating if we’re not going to have a positive benefit,” Dillin said. “We’re refining those operations to make sure we’re operating when we have that benefit, and not having an environmental impact when we don’t have one.”
Aiming to address concerns
Earlier this year, the district submitted a revised mitigation plan for the project, Dillin said, which resolved several of the problems identified in the planning process.
According to Dillin, the redesigned structure addresses several concerns identified in the state environmental impact statement (EIS). Released in 2020, the EIS outlined a series of concerns state officials had for the project.
The draft EIS found construction of the project would have a “significant impact” on fish, according to Dillin. The determination, he said, was based on an initial plan to fully block the river and truck fish to the other side of the structure.
As part of a redesign, Dillin said the district proposed an open channel that would mimic the natural river that would allow fish to move up and down the river during construction.
“This is a pretty major redesign on our part to address this impact identified in the draft EIS,” Dillin said.
Conduits at the base of the project, he said, are also a key aspect of the district’s plan to address concerns that the project could negatively impact the passage of fish on the Chehalis River.
According to Dillin, the state’s EIS found the proposal would also result in a “significant” increase in greenhouse gas emissions as a result of clear-cutting the area in preparation for construction, which had been based on burning the material. Dillin said the district has committed to using the material for “habitat restoration” since the EIS was released.
“So putting wood back into the Chehalis restoration projects or mitigation projects,” Dillin said.
The EIS identified other concerns with the clearing of vegetation, which it said would reduce shade on the river and allow the warm summer sun to raise water temperatures.
“What the district is proposing is a vegetation management plan. So we wouldn’t go through and clear-cut everything,” Dillin said. “We’d actually adaptively manage the vegetation in this reservoir and transition from flood intolerant species … to deciduous trees.”
The district has also committed to funding the engineering upgrades needed in the town of Pe Ell to ensure the project does not disrupt the town’s water supply, according to Dillin.
While the EIS addressed environmental and other concerns that would likely occur during construction and operation, engineers have also had to address less likely scenarios.
The project was designed to account for a “catastrophic” earthquake occurring while the facility was retaining water. According to Dillin, the odds of such a scenario occurring are one in 2.5 billion.
“Even though it’s such a rare event that’s unlikely to occur, our engineers are designing this project assuming the reservoir is full and we have a catastrophic earthquake,” Dillin said.
According to Dillin, planners addressed concerns that the structure would eliminate miles of recreational area on the Chehalis River. The proposed structure, he said, is “behind locked gates” on private property.
“So we actually see more opportunities for recreation having this project in place,” he said.
While the new facility would be one facet of the project, the proposal also includes raising levies around the Chehalis Airport. In doing so, Dillin said, the state assumed in the EIS that the renovation would disrupt nearby wetlands as it widened the structure.
“Our engineers have looked at this and have concluded that there are technologies and construction methods that you’ll find to raise the airport levies in the same footprint, so we’d not be eliminating all of those wetlands,” Dillin said.
A revised EIS for the project is scheduled to be released in the fall of 2025, and a final EIS is scheduled to be released in early 2026.
