Derived from landfill practice, the application of liners to control seepage from Tailings Storage Facilities (TSF) has also increasing through the years. Environmental acceptability of liner design will depend on post closure, long term liner performance and contingency measures and can be a key environmental issue in TSF permitting. The suitability of geosynthetics for long-term applications for waste containment in the mining industry is still being scrutinized. According Renken, K. et al (2005), although laboratory tests predict lifespans of up to several hundred years for materials such as HDPE (Koerner, 2004), manufacturers are willing to warranty their products (materials and their replacement) for up to 20-30 years (e.g. Colorado Lining International, 2005). While short and medium term (up to ~ 30 years) geosynthetics performance data is available, long-term field performance data is non-existent and available predictions have been based on a variety of laboratory tests and modeling to date. These factors may be contributing reasons for the limited use of geosynthetics to address long-term issues such as the control of Metal Leaching (ML) and acid rock drainage (ARD). In order to bring contribution to the understanding of field performance of liners applied to control seepage in a TSF for leach tailings containment, this paper presents results from mechanical assessments on an exhumed HDPE geomembrane submitted during a year to several environmental conditions, such as changes temperature, changes in pH and changes in mechanical stress, that in synergy can accelerate degradation.