Chehalis River Flood Damage Reduction Project Environmental Impact Statement

To reduce flood damage in the Chehalis River basin, the Chehalis River Basin Flood Control Zone District is proposing to construct a new flood retention facility and temporary reservoir near the Lewis County town of Pe Ell, and make levee improvements around the Chehalis-Centralia Airport.

Our role in reviewing the District's proposed flood damage reduction project will be to:

  • Conduct the state environmental review process under the State Environmental Policy Act (SEPA).
  • Offer public engagement opportunities during scoping and for the draft Environmental Impact Statement (EIS).
  • Should the project proceed after the environmental review is complete, issue environmental permits consistent with state and federal laws and rule.

Scoping has been completed and work has started on the SEPA draft EIS.

We determined the proposal would have significant adverse environmental impacts and are conducting a formal study through the state EIS process. See our Determination of Significance for the project proposal.

The U.S. Army Corps of Engineers (USACE), the lead federal environmental agency, will conduct a separate review under the National Environmental Policy Act. No permit decisions can happen until after the state and federal environmental reviews are complete.

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Work underway on draft EIS

The scoping comments we received are now being used to develop the draft EIS under SEPA. We anticipate providing information regarding the scope of the EIS and alternatives in February 2019. Please sign up to be notified about new information related to the SEPA EIS.

Scoping period closed

Scoping is the first step in the environmental review process. We and USACE head a joint SEPA-NEPA EIS scoping period from Sept. 28 through Oct. 28, 2018, including two public scoping meetings. During scoping, the public, local and tribal governments, state and federal agencies, businesses, and organizations provided input on the scope of the SEPA EIS to help identify project alternatives, probable significant adverse impacts, and potential mitigation measures.

The SEPA EIS Scoping Summary Report provides a summary of scoping comments and outreach. This report will be included in the SEPA draft EIS as well. Visit the EIS Scoping page for more information and to view scoping materials.

Proposed project details

The EIS scoping period will help us and the USACE decide what resources and impacts to analyze for the proposed Chehalis River Basin Flood Damage Reduction Project that includes:
  • Building a new flood retention facility and temporary reservoir near the town of Pe Ell in Lewis County. The proposed structure would have an expandable foundation.
  • Making levee improvements around the Chehalis-Centralia Airport. 
Open the map to see location details for the proposed project.

Proposed flood retention facility would only operate during major floods

The Chehalis River Basin Flood Control Zone District's proposed project involves constructing a new floodwater retention facility and temporary reservoir on the Chehalis River near the town of Pe Ell in Lewis County.

During a major flood, the proposed facility is designed to substantially reduce flood damages in parts of the Chehalis River basin by storing up to 65,000 acre feet of water in a temporary reservoir. When it is safe to do so, retained floodwater water would be released slowly back to the river over a period of time. Most of the time, however, the Chehalis River would flow through the structure's low-level outlet works at the river's normal rate of flow and volume — allowing fish to pass upstream and downstream.

The flood retention facility is not designed to protect communities from all flooding, nor would it stop regular annual flooding from the Chehalis River.

Proposed flood retention facility details

The top of the proposed flood retention structure would be 1,220 feet long and up 254 feet high — including three to five feet of freeboard for safety and a 210 foot-wide emergency spillway. The structure would be built on a foundation that could be expanded should a permanent reservoir and additional water retention capability be needed in the future. However, any structure expansion or major operational changes would require new environmental reviews and permits.

To construct the retention facility and reservoir, trees and vegetation at the site would need to be removed. A new power line would be constructed to operate the dam’s pumps, gates, instruments, and other controls. The project also would include developing a quarry, material storage and processing sites, and setting aside areas for offices and storing equipment.

Proposed Chehalis-Centralia Airport levee improvements

To protect the Chehalis-Centralia Airport, local businesses, and area transportation from damages from 100-year floods, the district also proposes raising the existing airport levee and part of Airport Road. The project would:
  • Add four to seven feet to the height of the existing 9,500 foot-long levee by adding earthen materials or flood walls.
  • Raise about 1,700 feet of Airport Road along the southern extent of the airport.
  • Potentially change the northwest corner of the levee to avoid interfering with the runway glide path.
  • Include utility infrastructure and other transportation improvements.

Next steps

Now that scoping is complete, the next environmental review step will be developing a draft and then a final EIS for the project proposal. The USACE will follow similar steps. The EIS process provides many opportunities for public involvement, guidance, and comments. Each agency will summarize the comments received during scoping into a summary document, and make the summaries available on the project website. No permit decisions can be made until after the final EIS is issued.

Administrative and SEPA process questions

What is SEPA? Why are Environmental Impact Statements being done for the proposed Chehalis basin project? Who decides what the Environmental Impact Statements will evaluate? What is a substantive scoping comment? Does it matter how many times a comment is made? Where can I find a response to my scoping comment? Will comments at meetings be more valued? I made a comment on the programmatic EIS for the Chehalis basin. Will it be automatically included?