While many may have given up hope that a large-scale project to address flooding in Centralia, Chehalis and the surrounding area would ever materialize, the Chehalis Basin Board just took a big step on deciding once and for all which project — or projects — deserves buy-in.
Chehalis Basin Board members spent Friday, June 6, in Lacey at the Washington state Department of Ecology headquarters deciding on six combinations of projects — seven, in the end — to study in depth over the next six months. The board plans to make a final decision on which large-scale projects it will pursue to lessen the impacts of severe flooding and address fish habitat restoration in the early months of 2026.
The analysis will look at how combinations of projects will impact the upper basin in 13 different categories, including agriculture, forestry, commercial fishing, infrastructure, transportation, public health and tribal cultural values. The analysis will use a range of methods to measure impact, including modeling virtual flood scenarios, calculating financial impact and holding public comment sessions to understand the experiences of basin residents.
At the center of each of the seven packages are three major infrastructure projects: a proposed flow-through dam that would be built near Pe Ell referred to as flood retention expandable (FRE) combined with a levee wall around the Chehalis-Centralia airport; the Local Actions Non-Dam Alternative (LAND), which is a system of levees around Chehalis and Centralia to protect homes and important infrastructure; and potential changes made to the Skookumchuck Dam ranging from leaving it as is, removing or something in between.
Each package is a decision to build entirely, in part or not at all, each of the three major infrastructure projects. Board members also decided how much they would support funding seven other efforts that the board and Office of Chehalis Basin currently fund. Among them are the Aquatic Species Restoration Project, Flood Authority projects and the flood warning system.
The meeting last week marks the beginning of final decision making. As part of the process, the Office of Chehalis Basin will begin community outreach over the next six months to present designs for the wide range of projects and hear feedback and concerns from basin residents.
The Office of Chehalis Basin was most recently funded with $75 million from the state Legislature for use on flood mitigation and habitat restoration over the next biennium.
The following is a summary of each of the three major projects being considered by the Chehalis Basin Board. To get more information about the process, visit the Office of Chehalis Basin website at https://officeofchehalisbasin.com/lts/.
Flood Retention Expandable
Ultimately, three of the scenarios selected by the board included constructing a flow-through dam in the headwaters of the Chehalis River near Pe Ell. It would hold back water only during major flood events to reduce the impacts of catastrophic flooding in and around Centralia and Chehalis. At times when flooding is not predicted, the structure would remain open, allowing fish and other species to move up the river.
Unlike the other two projects, board members provided a simple yes or no “all or nothing” choice on the construction of the flow-through dam and Chehalis-Centralia Airport levee. That being said, some board members noted that if the dam was built, they would like to take the “E” out of the FRE, signaling that they wouldn’t endorse efforts to expand the structure beyond its initial size and function.
An initial design for the dam was reviewed by the Washington state Department of Ecology and the U.S. Army Corps of Engineers in 2020. The reports from the state and federal governments laid out potential environmental impacts for the dam and led to it being redesigned. The new design, taking into account the potential impacts, is currently under review, with the state’s findings expected near the end of the year.
If the Chehalis Basin Board chose to construct the flow-through dam, it would also have to take measures to mitigate the environmental impacts of the project, which could include restoring fish habitat to make up for any adverse impacts the facility has on fish in the river.
The construction of the dam was first proposed many years ago in the aftermath of the historic 2007 Chehalis River flood and is supported primarily by the Chehalis River Basin Flood Control Zone District, which is the flood arm of Lewis County. The three Lewis County commissioners double as the leaders of the district.
The district’s website shares information on the proposed project, including 3D renderings, answers to frequently asked questions and informational videos showing how the flow-through dam would work.
For more information, visit https://chehalisriverbasinfczd.com/.
Local Actions Non-Dam
The Local Actions Non-Dam alternatives project in its entirety proposes constructing eight levees and relocating the Mellen Street bridge. The levees are designed to protect homes and infrastructure while also lowering flood water levels on I-5 and other vital roads. All but two of the project packages chosen Friday include at least one aspect of the levee project, with two calling for constructing all proposed levees.
The Chehalis Basin Board and the Office of Chehalis Basin are currently contracting an engineering firm, Moffat and Nichol, to plan out the levee system. The firm gave an updated presentation to the Chehalis Basin Board on Thursday, June 5, ahead of the big decision.
As part of the update, the firm showed how the project could be built in sections as funding became available without worsening flood impacts. The first of three phases would see construction of three levees — two along the Skookumchuck and one along China and Salzer creeks — along with the relocation of the Mellen Street bridge.
While the project was originally pitched as an alternative to a flow-through dam, the Chehalis Basin Board has increasingly considered the possibility of building just some of the phases or levees in conjunction with a flow-through dam or other infrastructure.
Skookumchuck Dam
Of the seven packages selected, three would make changes to the Skookumchuck Dam located east of Bucoda on the Skookumchuck River. Options being considered for the dam are to either leave it as is, remove it entirely or modify it in some way to improve fish passage, flood mitigation or both.
The dam is believed to have provided some level of flood mitigation during the catastrophic flooding in 2007 as the reservoir behind the dam was low before the flood began and stored some of the flood waters mitigating damages to Bucoda and parts of Centralia. Flood control is not part of its design, though.
The dam, however, is also considered a major obstacle to fish habitat restoration efforts. According to the Office of Chehalis Basin, the dam blocks Chinook and coho salmon as well as steelhead trout from miles of spawning habitat upstream.
Any changes to the study would still be years out as the office, unlike for the other two projects, would still have to begin engineering any changes and go through a review process, which altogether could take years.
The other major obstacle is that the dam is currently owned and operated by TransAlta, which uses water from the dam reservoir at its nearby coal power plant. Even with that plant closing this year, TransAlta will still own water rights on the river and would have to be involved in any changes made to the dam.
