Army Corps releases NEPA review on proposed dam

Public meetings to be held

By Claudia Yaw

The (Centralia Chronicle

Months after a draft Environmental Impact Statement (EIS) under the State Environmental Policy Act (SEPA) was completed for a proposed flood-retention dam on the Chehalis River, a national review of possible environmental impacts of the project has now been released.

The EIS required by the National Environmental Policy Act was released Friday. It details how the project, estimated to cost more than $400 million, would impact fish species, water quality, wetlands and other environmental facets of the land.

Public meetings will be held from 6 p.m. to 8 p.m. Oct. 8 and 4 p.m. to 6 p.m. Oct. 14, at which individuals can comment on the proposed project. Comments can also be submitted beforehand. Details can be found at https://chehalisbasinstrategy.com/eis/nepa-process/.

The proposed project would create a new 1,550-foot wide dam structure near Pe Ell, which would close only during flooding events. The project would also raise the existing levee near the Chehalis-Centralia airport. The goal is to mitigate the effects of major floods, which occur, on average, every seven years, and catastrophic floods which occur at a 100-year interval. The Quinault Indian Nation and Chehalis Tribe have spoken out against the plan, which would significantly impact fish populations, and have called for a non-dam alternative.

The statement considered the effects of project construction, which is estimated to last five years, as well as its operations after-the-fact.

Chehalis Basin Board Member J. Vander Stoep said the next step is for the board to consider mitigation efforts that could reduce these impacts.

“There is no mitigation plan that has formally been submitted,” Vander Stoep said. “So both the State Department of Ecology and Army Corps are looking at the worst case scenario.”

Ecology completed the state EIS, while the Army Corps of Engineers completed the federal EIS.

One of the major environmental impacts predicted by the statement is “high permanent impairment of habitat function” for fish species. Decreased water quality and increased temperatures would result in significant and long-term impacts for spring-run and fall-run Chinook salmon, coho salmon and steelhead. These impacts would be sustained after construction is finished. However, on the scale of the whole Chehalis Basin, the statement concluded that the impacts would only be high for spring-run Chinook.

Operations of the facility would also significantly decrease habitat for non-salmon fish and impact aquatic plants, even when the dam structure is left open.

Nine endangered species and three threatened species may be present in the project area, and could be impacted due to the 485 acres of land that would need to be cleared of trees and other vegetation.

Construction of the project would also require excavating material and placing it into 1.23 acres of wetlands.

“Those impacts would be direct permanent impacts because the affected resources would cease to exist following excavation and fill placement,” the statement reads.

The tree removal at the reservoir site would significantly impact about 340 acres of wetland and stream buffers and would make the area more vulnerable to invasive plant species. The levee improvements at the airport would also mean a “medium loss” of 4.54 acres of wetlands and 16.61 acres of wetland buffers.

“Although the affected wetlands would continue to exist in the reservoir footprint, the changes in vegetation communities and their associated functions and values would be permanent,” the statement reads.

About 93.65 acres of other waters, including Crim, Rogers, Hull, Big, Lester and Browns Creeks, would also be impacted.

During flooding events, which are likely to happen in late fall and winter, about 500 acres of land could be underwater by the temporary reservoir for anywhere from 4-25 days, killing native species including Douglas firs, red alders, big leaf maples and western hemlocks.

In terms of water quality, several short-term impacts would occur during construction, which would be “low, temporary and limited to the construction phase of the project.” Operation of the facility could also reduce dissolved oxygen concentrations upstream and increase chlorophyll a levels upstream. Groundwater impacts would be low.

A 1,165-foot section of the Chehalis River would be rerouted during construction, and about 450 feet of the river would be permanently replaced by the retention facility, according to the statement. Mahaffey Creek would also need to be temporarily diverted during construction.

The statement also predicted significant long-term impacts from soil erosion around the retention facility.

An alternative project was also considered, which would be largely the same except for its smaller foundation, which would produce less environmental impacts and wouldn’t allow for future expansion of the retention facility.

The application for the project has been received by the U.S. Army Corps of Engineers, but Project Manager Brandon Clinton said there is no immediate timeline for when the review of the application.