Landfill site selection utilizing TOPSIS methodology and clay liner geotechnical characterization: a case study for Ankara, Turkey

Abstract

The purpose of this study was to select alternative landfill sites for Ankara based on the growing trends of Ankara toward the Golbasi municipality, and to eventually select the best alternative through the use of decision-making tools. Geographic information systems (GIS) and multi-criteria decision analyses were employed to perform landfill site selection. Several criteria, including geology, slope, proximity to roads, availability and proximity of landfill containment material, settlement, suitability for agriculture, vegetation cover, erosion, and lineament system were gathered in a GIS environment. A weight value was assigned to each criterion by applying the pairwise comparison method and the analytical hierarchy method. An ideal point method, namely, the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) was applied to choose the best alternative landfill site. The geotechnical properties of “Ankara clay”, which shows widespread distribution in Ankara, were reviewed and assessed for the clay's suitability as a single, compacted clay liner and as a component of a geomembrane-compacted clay composite liner for the alternative landfill site selected. The HELP model was employed in order to determine the cumulative, mean leachate head and cumulative, unitized expected leakage rate amounts through the landfill. Four different profiles, from the least conservative to the most conservative, were created and analyzed.