<p>An upstream tailings dam closure process involves reincorporating the structure into the surrounding terrain, a conception that relies on adequately characterising the hydraulically deposited tailings to obtain representative parameters. Nevertheless, laboratory tests seldom fully represent the on-field tailings conditions because of difficulties in obtaining undisturbed samples or reproducing the original fabric using reconstituted specimens. Accordingly, this work evaluates the response of iron ore tailings deposited within a dam slated for decommissioning using field and laboratory tests in conjunction with a pilot excavation plan. A CPTu test enabled the division of the deposited tailings into two different materials: coarser and finer. Representative samples of each tailings were retrieved and tested in drained and undrained triaxial compression tests to determine the critical state parameters. These parameters, along with the CPTu data, helped define the in-situ state of the material. The experimental excavation was monitored with inclinometers and monitoring points, confirming the stability of the deposited material throughout the process. This research demonstrates a robust integrated methodology for validating tailings stability, providing critical data for safe and effective decommissioning designs.</p>