State environmental review of proposed Chehalis River Basin Flood Damage Reduction Project

The State Environmental Policy Act (SEPA) outlines a process to identify and analyze potential environmental impacts associated with government decisions like building public facilities, issuing permits for private projects, or adopting regulations, policies, and plans.
 
The SEPA review process helps agency decision-makers, applicants, and the public understand how the entire proposal will affect the environment. SEPA can be used to modify or deny a permit in order to avoid, reduce, or compensate for probable impacts.
 
The environmental review may include an Environmental Impact Statement (EIS). An EIS begins with scoping, which sets up participation from the public, local and tribal governments, and other state and federal agencies to comment on a proposal’s alternatives, impacts, and potential mitigation measures to be analyzed in the EIS.

Basin communities are working with the Chehalis Basin Board to develop the long-term Chehalis Basin Strategy to reduce flood damage and restore habitat for aquatic species through an array of small- and large-scale projects and short- and long-term actions in Washington’s second-largest river basin.

The Chehalis River Basin Flood Damage Reduction Project is one of the large-scale Strategy actions under consideration to reduce flood-related damage in the basin. We prepared a draft state Environmental Impact Statement (EIS) for the Chehalis River Basin Flood Control Zone District’s (Flood District) proposal which evaluates probable impacts from the proposed project.

The draft EIS is required under the State Environmental Policy Act to provide information about the project’s likely significant and adverse environmental impacts. In 2017, we completed a “programmatic” EIS for the basin-wide Chehalis Basin Strategy. That EIS found a flood-retention dam on the Chehalis River was likely to have significant impacts. The 2020 draft EIS is the state’s initial, but comprehensive, evaluation of the Flood District’s proposal.

The state’s draft environmental review analyzed:

• Probable, adverse environmental impacts from the proposed project — including the 5-year construction period and 50-year operations period for the project.
• A major flood, catastrophic flood, and recurring flood scenarios.
• A No Action and a Local Actions Alternative.

Yes. We will release the revised draft EIS for public review and comment in fall 2025. 

When we released the original draft state EIS on Feb. 27, 2020, we took public comments through May 27, 2020. We also provided opportunities to share information and take substantive comments from people interested in commenting on the draft state EIS. We held online public comment opportunities on April 2 and April 21, 2020.

The EIS analysis found the proposed project would have significant impacts, mainly along the Chehalis River in the area above the proposed dam and downstream to the confluence with the South Fork of the Chehalis River. There would be adverse effects on salmon and other fish, including their habitat; some wildlife such as amphibians; water quality; the Chehalis River channel; and recreation. There also would be an increase in greenhouse gas emissions and could significantly impact tribal and cultural resources.

Since the project design has changed, some of these impacts may be different. 

• What is a significant and unavoidable impact?
• What is a substantive comment?
• Does it matter how many times a comment is made?
• How are the EIS and the plan to restore aquatic species habitat in the Chehalis River basin related? Should they be reconciled?
• How does the EIS evaluate the effects of climate change?
• What kind of flood scenarios did the 2020 draft EIS evaluate?
• Did the EIS assess potential impacts from a large earthquake?
• How will the EIS be used?
• Will the new revised draft EIS replace the 2020 draft EIS?

In the EIS, a significant and unavoidable impact is a major environmental impact that cannot be offset or reduced to a lower level. The EIS contains proposed mitigation for the Flood District to develop and implement. However, we don’t know if mitigation is technically feasible or economically possible. The EIS identifies this uncertainty.

Substantive comments provide facts and information for us to consider. Comments simply in support of or opposition to the project proposal are not considered substantive. Public comments can address issues such as:

• Likely environmental impacts and potential mitigation measures.
• Degree to which various types of resources could be affected.
• Project alternatives and methodologies.
• New data or studies to consider.

We will consider all substantive comments we get during the comment period. It does not matter how many times the same comment is made. Duplicate comments will not increase the value or weight of a substantive comment.

The Chehalis Basin Board will consider both the EIS and aquatic species restoration program as part of their recommendation for an integrated long-term Chehalis Basin Strategy to reduce flood-related damage and restore species aquatic habit in the basin. The Board and Flood District will also consider measures to offset — or mitigate— the adverse environmental impacts identified in the draft state EIS.

Climate change will drive more frequent floods, higher flood levels, and will put native fish runs at higher risk in the future, absent significant restoration efforts. In all the future scenarios we evaluated, we included climate change predictions such as changes in rainfall frequency and intensity, sea-level rise, increased flooding frequency and intensity, and increased air and water temperatures.

The environmental review looked at three scenarios in the future:

• Major flood: A flood with a 1-in-4 (25 percent) chance of happening in any given year, similar to the 2009 flood.
• Catastrophic flood: A flood with a 1-in-7 (4 percent) chance of happening in any given year, similar to the 1996 flood.
• Recurring flood: A flood happening every year for three consecutive years.

Yes. While highly unlikely, if ground shaking from a large earthquake happened while the temporary reservoir was holding water and the dam structure failed, the water would significantly affect people, buildings, roads, and the environment downstream from the facility.

The EIS is required under the State Environmental Policy Act to provide information about potential impacts at the early stage of a proposal. The EIS provides critical information we anticipate will be used by the Chehalis Basin Board, local and tribal governments, state agencies, the public, and other decision makers.