Performance assessment modeling is typically done as part of designing engineering barriers such as evapotranspiration (ET) landfills. However, models have limitations for predicting the performance of barriers constructed of native materials for thousands of years since they will change with time because of factors such as soil formation and vegetation succession. To address this, DRI used a series of analog sites in the Great Basin-Mojave Desert transition zone to predict the future condition of landfill covers over a 125,000 year period. Changes in vegetation cover and rooting depth, soil hydraulic properties, and soil morphology were examined. Besides its value for long-term stewardship of engineered barriers, the study provided important insights on coupled physical and biological processes in arid regions.

At Edwards Air Force Base in California, DRI also examined landfills constructed in the 1960s and 1970s to estimate the modes and rates of subsidence on ET landfills, another poorly constrained parameter in predicting engineered barrier performance.

Click here to download article	David Shafer and Julie Miller examine soil development in a trench as part of a study of evapotranspiration landfill subsidence at Edwards Air Force Base.