Case Study: Landfill Closure / Environmental Instrumentation

Client: Confidential public agency Location: Western WA Contact for environmental projects: Doug Hillman

Project Background & Challenges

A public agency client required support in designing an effective landfill cover system to control infiltration of rainwater at a rural western Washington facility. The client wanted to integrate an innovative design, which would limit the quantity of leachate generation, as well as comply with regulatory closure standards.

Solution

Aspect Consulting provided technical support in the implementation of a poplar tree cover on the closed landfill as a water management tool. The cover consists of four species of hybrid poplars planted into the existing soils covering municipal solid waste. Approximately 10,000 poplar seedlings were planted in April 2000. Because of their vigorous root systems, poplars utilize soil moisture to depths much greater than grasses, creating a reservoir for moisture during the dormant winter months. To evaluate the success of the project, Aspect Consulting designed and operates a monitoring system for the cover which includes continuous soil moisture measurement using time domain reflectometry (TDR) probes, precipitation, runoff, climate parameters necessary for computation of evapotranspiration, and canopy interception.