The Department of Ecology on Thursday released a draft environmental impact statement for the Chehalis Basin Strategy, a state initiative to limit flood damage and restore habitat throughout the Chehalis River Basin.

Ecology is planning two public hearings within the affected region, in Montesano at 6 p.m. Oct. 27 at City Hall. A short presentation will be given at 6:30 p.m. followed by the public hearing at 7 p.m.

A public hearing also will be held at the same time on Oct. 18 at Veterans Memorial Museum in Chehalis (100 S. W. Veterans Way).

The draft EIS can be viewed in full online at bit.ly/2cZlbOd.

The Governor’s Chehalis Basin Work Group released a 2014 recommendation report which proposed, among other actions, a dam near Pe Ell.

The EIS is a “programmatic EIS,” which looks at broad impacts of the project rather than specifics.

“With this broad scope and evaluation comes a degree of uncertainty, whether it be from predicting the magnitude of effects from climate change, or the willingness of landowners to take voluntary actions that may affect their homes or livelihood,” the EIS notes.

Background information within the EIS suggests a need for action, highlighting that five of the largest floods in the history of the Chehalis Basin have occurred in the last 30 years. In 2007 and 2009, the EIS notes, two extreme floods occurred only 13 months apart.

“Repeated flooding makes it difficult to attract new industry to the Chehalis Basin, and the emotional and psychological costs to communities are significant,” the EIS states.

The public can comment on the draft EIS until Oct. 31.

Comments can be submitted online via email to info@chehalisbasinstrategy.com, or at either of the public hearings.

Comments also can be mailed to Chehalis Basin Strategy EIS, c/o Anchor QEA, 720 Olive Way, Suite 1900, Seattle, WA 98101.

The EIS looked at four “action alternatives,” as well as the possibility of taking no action.

Alternative 1 (the 2014 Governor’s Work Group Recommendation) included a dam and reservoir, airport levee improvements in Chehalis and the Aberdeen/Hoquiam North Shore Levee.

“Compared to the other alternatives, Alternative 1 would result in the greatest reduction in flood depth and extent in the Chahalis River floodplain during a major flood,” the EIS reports.

Damage would be reduced in the upper and middle basin, as well as in Aberdeen and Hoquiam. Some areas would no longer be inundated and some would have a 10-foot reduction in inundation (though most areas would experience a .1-foot to .5-foot reduction in inundation.

The dam could reduce water quality by increasing water temperature, decreasing oxygen levels and increasing turbidity). Landslides could become more frequent along the perimeter of the proposed reservoir, and any failure in design of the reservoir in the event of a major earthquake could affect downstream communities.

There would be permanent losses of wetlands and forested vegetation, primarily because of the dam. Fish would be temporarily or permanently affected.

“The dam would have a significant adverse impact on the native species that use this area of the river,” according to the draft environmental impact statement.

Building a dam is generally contentious, the document notes.

According to the EIS, more than 1,000 structures would see reduced damage through Alternative 1. The North Shore levee would protect an additional 2,715 structures.

Alternative 2 does not include a dam, but it includes both the airport and North Shore levees. Also included in Alternative 2 are projects along I-5.

Alternative 2 results in a give and take of sorts, with floodwater depths reducing by .1 foot and 1 foot in parts of Chehalis and Centralia, but areas upstream of the levees and walls could see an increase in flood water by depths of .1 foot and .9 foot.

“Alternative 2 is anticipated to result in greater benefits to aquatic species habitat function than Alternative 1 because it would exclude the permanent and large-scale changes to the Chehalis River and floodplain results from the Flood Retention Facility (dam),” the EIS states.

Permanent loss of wetlands are expected where the levees and I-5 projects would be constructed, but it would have fewer adverse impacts on wetlands than Alternative 1.

Nine hundred structures would see reduced flood damage through Alternative 2. The North Shore levee would protect an additional 2,715 structures.

Alternative 3 relies on local projects to protect important buildings and infrastructure. While it would reduce damage to particular structures, it is not meant to be a basin-wide solution. Aberdeen and Hoquiam would continue to be at risk from coastal flooding without the levee, the EIS notes.

There are few adverse impacts, but the EIS noted continued flooding along I-5 and at the Chehalis-Centralia Airport.

“Alternative 3 has the potential to reduce threats to human health and safety when compared to the No Action Alternative because Alternative 3 would protect structures in the floodplain and allow people the option of safely waiting out many floods in their homes,” the EIS notes. “However, Alternative 3 would not improve the ability to access critical medical facilities as compared to the No Action Alternative …”

About 800 structures would see reduced flood damage through Alternative 3.

Alternative 4 focuses on restoring natural flood protection by reversing landscape changes that contribute to downstream flooding and erosion.

Engineered large wood and plantings would be added to create flow resistance to river channels and would reconnect river channels to floodplain storage. Some 21,000 acres of floodplain would face increased flooding through the reconnected channels. Alternative 4 looks at buy-outs, flood proofing and easements to address the increased flooding. Alternative 4 relies on landowner participation.

Some 16,000 acres of managed forestland would need to be converted, impacting current vegetation.

Alternative 4 also is incompatible with existing land uses, impacting some 12,000 acres of active farmland. And in relocating land uses, public utilities would need to be moved or decommissioned.

I-5, local roads and the Chehalis-Centralia Airport would continue to see flooding. And some roadways would see increased closures. During a 100-year flood, State Route 6 would be closed for four additional days, State Route 506 by one or two more days, and State Route 508 by two days.

More than 1,200 structures would see reduced flood damage through Alternative 4.

With no action, more than 1,300 structures are flooded during each 100-year flood.

A scoping meeting for the EIS was held in Montesano and Chehalis late last year. The Montesano meeting was not well attended with project representatives greatly outnumbering the public.

The scoping meeting was intended to guide the EIS by accepting suggestions for areas the EIS should study.