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Hillsboro Landfill Wetlands Outfall Channel and No-Rise Documentation

Hillsboro Figure with labelsClient: Latimer Environmental

The Hillsboro Landfill is a construction-demolition waste landfill situated on 400 acres south of Hillsboro, Oregon between SE Minter Bridge Road and the Tualatin River. With the landfill operations located at the northeast end of the property, the south and west sides of the property contain wetland mitigation sites adjacent to the Tualatin River. Waterways was retained to design an outfall from the constructed wetlands located at the south end of the property that provides a geomorphically stable discharge into the Tualatin River. 


Waterways conducted a topographic survey of the outfall location, modeled and analyzed hydraulics to size the outfall opening, and developed engineering drawings for construction. The outfall is planned for construction in 2016. In addition, Waterways performed a hydraulic analysis of the final landfill closure conditions to ensure that no rise in the 100 year FEMA water surface elevation occurs from this development.