Carnation Treatment Plant

Wetland enhancement at Chinook Bend Natural Area

Welcome to Chinook Bend Natural Area. Click image for larger view (PDF, 1.1MB).


Signage near the public access, northwest of the bridge. Click image for larger view (JPG).

The Carnation Treatment Plant uses an advanced treatment technology called a membrane bioreactor or MBR. The plant produces reclaimed water that can be used safely as a drought-proof water source for wetland enhancement and other beneficial uses. Reclaimed water is being discharged to a wetland in the county's Chinook Bend Natural Area, next to the plant's river outfall site at the Carnation Farm Road Bridge.

Project design

King County partnered with Ducks Unlimited (external link), a nonprofit group dedicated to wetland conservation, to help design the wetland enhancement project. This partnership helped reduce costs and expedite implementation of the project. The Snoqualmie tribe and other interested stakeholders helped to develop a design for the wetland.

The wetland design focuses on enhancing native plantings and controlling reed canary grass through the use of a water control structure, which allows for moist soil management as well as fish passage. The design included removing an existing culvert and pipe system that drained the former degraded wetland, installing a new water control structure and "daylighting" the water flowing out of the wetland. The design increased the size of the wetland to nearly four acres, benefiting wildlife and enhancing opportunities for passive recreation at Chinook Bend.