Outer Loop Landfill Bioreactor

This assessment was conducted at the Outer Loop Recycling and Disposal Facility located in Louisville, Kentucky. The site consists of seven individual and separate landfill units, designated Units 1 through 7. The focus of the assessment was the effect of supplemental moisture addition on portions of Unit 5 and Unit 7, which are both permitted, active Subtitle D landfill units. Three types of landfill units were studied—a typical Subtitle D landfill (control, no supplemental moisture addition), a landfill unit retrofitted with moisture addition piping (treatment 1), and a landfill unit constructed with moisture addition piping (treatment 2). The general goals of the study and data analysis included determining if significant trends existed within a study unit, and determining if significant differences existed between the treatment units and the control unit.

    Both qualitative and quantitative statistical tools were utilized to determine if significant trends within a unit or significant differences between units exist. Exploratory data analysis including summary statistics, timeplots, and boxplots was used to qualitatively evaluate trends within landfill units and to evaluate differences between units. Correlation analysis and other multivariate techniques were utilized to quantify relationships between dependent variables of interest or between explanatory variables. Multiple regression analysis was used to determine if suitable linear models exist between the explanatory variables and the dependent variables and if significant temporal trends exist. In addition, diagnostic plots of residuals were investigated to evaluate the underlying statistical assumptions of the linear model.