Fernhill South Wetlands Natural Treatment System

Former sewage lagoons are converted into a valuable resource that provides wildlife habitat and recreational opportunities as it cools and cleans water that is discharged into the Tualatin River.

Clean Water Services (CWS), an Oregon utility, wanted to restore three former sewage lagoons associated with the Forest Grove Wastewater Treatment facility. They turned to Biohabitats to lead the design team. Though the ponds were occasionally visited for wildlife viewing, they held untapped ecological and recreational potential. Biohabitats’ design transformed the lagoons into a rich, 90-acre mosaic of riparian wetlands that provide natural wastewater treatment while enhancing ecological function and recreational and educational opportunities along the Tualatin River floodplain.

The restoration first involved draining the lagoons, drying more than 200,000 cubic yards of soil, and moving the soil to create precise contours and depths. Control structures were strategically placed to encourage the growth and establishment of 750,000 native wetland plants and 3.5 billion seeds. 180 logs and snags were anchored into place to provide wildlife habitat.

The wetlands reduce the temperature of the treated wastewater flowing into the Tualatin River, and regenerate the complex systems of life and nutrients that exist in healthy waters. The treatment facility can treat 5-18 million gallons per day throughout the year. The project accommodates diurnal and seasonal variation in the wetland system, giving flexibility to provide important ecosystem functions. With wetland hydraulic control structures, CWS can manipulate water levels in the wetland cells to more closely mimic typical seasonal variations.

Habitats created by the restoration included open water, mudflat, emergent marsh, scrub-shrub, and upland areas that support wildlife. The enhanced habitat for waterfowl and shorebirds has helped make the wetlands an important stopover site in the Pacific Flyway. Birds and wildlife have taken to the site, and human visitors are flocking to enjoy trail improvements, outdoor classrooms, and views of the wetlands. By creating a wetland system that provides benefits in water quality, wildlife habitat, recreation, and education, CWS and Biohabitats are making a long-term investment in the health and resilience of the Tualatin River.

TAGS

• Analysis+Planning
• Assessment+Monitoring
• Design
• Ecological Restoration
• Resilient Water Systems