Selecting an appropriate location for a new landfill is a crucial aspect of municipal solid waste management, influenced by many factors. The paper delves into a case study involving the vertical expansion–as a viable solution to extend landfill life–of the Rusino landfill, a non-standardized landfill in the western part of the R. N. Macedonia. Rapid measures have been implemented to enhance its condition, considering the limited access to sanitary landfills there. Vertical expansion, however, concerns about additional subsidence, especially from unsettled waste in the upper layers, necessitates thorough geotechnical investigations. This study describes such investigations on the Rusino landfill, where, among the rest, oedometer tests at varying saturation conditions were conducted on samples to determine parameters and anticipate landfill behaviour during vertical expansion, which was modelled numerically. The paper presents the findings, which can contribute to valuable insights for sustainable waste management practices in regions with limited access to new landfill sites.