This article concentrates on the impact of two parameters that define landfill base grades, namely the leachate collection pipe slope and base slope. In many occasions, the designer selects certain pre-determined slope values for the pipe and base of the landfill cells, values that have been used in previous designs or values that have been set by the firm to be used in all designs. This form of selection overrides the necessity of performing a sensitivity analysis to determine impacts of selected slope values on construction cost and available airspace. The task of performing sensitivity analysis can be costly, especially if the design includes many disposal cells. The formulation discussed in the article can potentially cut back on the cost of a sensitivity analysis in a dramatic way. The developed formulation is based on a rectangular cell with grades in accordance with the herringbone concept. The sensitivity analysis begins by considering a second set of slope values for the pipe and base and the formula provides the volume difference between the initial and the second surfaces. This allows the designer to evaluate the impact of the pipe and base slopes on the quantity of the structural fill needed for the construction of the cell and the airspace that will be made available for waste disposal.
Written and presented by Ali Khatami, Ph.D., P.E., L.E.P., and SCS vice president. For more information or questions please contact Dr. Khatami by clicking here.