Fernhill Western Wetlands

CLIENT Clean Water Services

Location Forest Grove, OR

The Fernhill Western Wetlands, a component of Clean Water Services’ innovative Natural Treatment System, are a sustainable and natural solution to treating ammonia in wastewater.

Featuring an 11-million-gallon-per-day vertical flow wetland and associated pump station, pipelines, and other treatment-related elements, the wetlands are designed to remove ammonia that can be harmful to the fish and wildlife that live in the connecting Southern Wetlands.

Shannon & Wilson, Inc., was a subconsultant to Kennedy/Jenks Consultants, and was responsible for the geotechnical engineering of the Fernhill Western Wetlands predesign, design, and construction. The Portland office provided this project with knowledge of the local geologic and seismic conditions.

The subsurface conditions of the site are ideal for wetlands but created challenges when it came to the geotechnical design and earthwork construction of the project. Soft soils, high groundwater, seismic liquefaction settlement susceptibility, and varying excavation depths for the structures that make up the complex ammonia filter system meant that Shannon & Wilson needed to use ingenuity, judgment, and experience to meet Clean Water Services’ goals. Working with Clean Water Services and Kennedy/Jenks, Shannon & Wilson developed tailored solutions to settlement and dewatering issues, helped optimize the site layout to reduce expensive mitigation, and provided expert support during challenging winter construction. The results were cost-effective, geotechnically sound solutions for a complex site so that Clean Water Services could focus resources on the important treatment system portion of the project.

water Rivers / Shorelines / Wetlands Water Supply / Wastewater
Laboratory Geotechnical Engineering Water Resources Construction Management


ACEC Oregon Engineering Excellence 2019 Honor Award


Adrian Holmes

Aimee Holmes
Senior Engineer & Geologist

Alia Hubbard
Senior Environmental Scientist

Jerry Jacksha
Senior Associate

Kyle Romney
Senior Engineer

James Walters

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