ABSTRACT:The aim of this study is to investigate the causes of the landslide occurred on 18 February 2013 at the NW–facing slope of the Harmandalı waste disposal site located in İzmir–Çiğli a n d the reactivation potential of the same circular slip surface. In the light of the geological a n d geotechnical studies resumed in September–2016; the reactivation potential has been evaluated. An embankment (a barrier) was built as a protection structure in front of the slopes of solid waste in 2010. It was determined from the readings in the inclinometer boreholes drilled right after the landslide that the sliding slowed down gradually after the initial landslide. A 64.5 mm displacement occurred in horizontal direction towards NW along the circular slip surface passing through the high plasticity clay band located under the embankment. This movement caused cracks on the walls of the administration buildings, disruption of the main connection road, a n d deformation such as buckling indicating the effect of compression within the embankment. The longitudinal cross-section showing the sliding mechanism has been prepared basedon the pressuremeter tests a n d the readings taken from the inclinometer boreholes drilled at different locations in March–2013 a n d September–2016. In addition, the engineering properties of high plasticity clays (CH), which are the weathering products of the andesitic tuffs that cause sliding, have been investigated.