GSI staff assisted our client in developing and monitoring a leachate management program that uses hybrid poplar tree plantation to naturally treat the leachate.


The Riverbend Landfill, located near McMinneville, Oregon, generates hundreds of thousands of gallons of leachate annually as a result of precipitation seeping through solid waste. They are required by the state to manage this leachate, and needed to develop and employ an environmentally acceptable and cost effective leachate management program.

GSI’s Solution

We assisted our client with developing a hybrid poplar tree plantation as a natural treatment program for leachate management.The poplar trees take up nitrogen and nutrients, and the root zone actively takes up and transforms other constituents present in the seeping leachate. We then helped develop a soil and groundwater monitoring program for the site that would track the success of the tree plantation and movement of leachate in the soil.

An innovative technology called Time Domain Reflectometry (TDR) was used at this site to provide detailed information on the position of the leachate front in the soil profile, allowing for the leachate application rates to be adjusted and movement of leachate to groundwater minimized. GSI staff was successful in assisting Riverbend in obtaining approval to expand its land application area in order to deal with the record rainfall and leachate production.

The project won a State of Oregon and National Engineering Excellence Award.