## 7 Conclusions  
This study investigated the degradation that occurred in the properties of an exposed HDPE geomembrane installed at a gold mining tailing site in Brazil in a warm-hot climate. Non-parametric statistics were applied to help with the analysis. For the specific geomembranes and conditions examined, the following was concluded:  
* The geomembrane exposed showed antioxidant depletion, but considering the average residual values of Std-OIT and HP-OIT for HDPE geomembranes from the literature [30; 31; 35; 83], it is possible that there are still antioxidant stabilizers to be consumed (first stage of degradation) for SP1. SP2 and especially SP3 could be very close to, or have already reached, their residual values.
* After 11 years of exposure, the SCR values of SP2 and SP3 had decreased to 40 and 32% of the reference value [45], implying that the material had reached nominal failure.
* The probability of the geomembrane reaching nominal failure was 0.4% as a function of tensile strength, which translates to a 99.6% probability of success.
* The peel separation showed values higher than the maximum values allowable [45]. Environmental analyses indicated no significant contamination in the area.  
* The geomembrane used in this scenario contributed to SDG 3 (Good Health and Well-Being), SDG 6 (Clean Water and Sanitation), SDG 15 (Life on Land), and SDG 13 (Climate Action). Chemical weathering from seasonal tailings contact (samples SP2 and SP3) and climatic weathering did not significantly degrade the geomembrane compared to sample SP1, which faced only climatic weathering. Varying exposure times prevent definitive conclusions. While the geomembrane's nominal failure may be indicated by the SCR values, this does not imply imminent failure in the field but warns of substantial reductions in its properties and its potential susceptibility to failure based on its remaining resistance and the site conditions. Future research should focus on verifying consistent patterns in the probability density functions (PDFs) by exploring a variety of exposure conditions, durations, and geomembrane types. Such studies are essential to better understand the long-term performance and degradation mechanisms of geomembranes under diverse environmental and operational scenarios. Additionally, investigations into different installation practices and their impact on geomembrane durability will provide valuable insights. By broadening the scope of research to include these variables, it is possible to develop more robust predictive models and enhance the reliability and sustainability of geomembrane applications in mining and other industries. The results obtained using Kernel Density Estimators were promising for evaluating the exhumed geomembrane samples. This methodology may be extended to other engineering projects involving various types of geosynthetics, whether exhumed or aged in a laboratory, thereby enhancing their reliability.  
Conceptualization, B.M.C.U.; data curation, B.M.C.U. and R.S.; formal analysis, B.M.C.U. and R.S.; investigation, R.S.; methodology, B.M.C.U. and A.R.D.; supervision, L.D.F., T.I. and D.C.U.; validation, L.D.F., T.I. and D.C.U.; writing--original draft, B.M.C.U.; writing--review and editing, B.M.C.U., R.S., L.D.F., T.I., D.C.U. and A.R.D. All authors have read and agreed to the published version of the manuscript. A.R.D. received additional support from Federal University of Ouro Preto. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data that support the findings of this study are available from the corresponding author [[PERSON]] upon reasonable request. Acknowledgments: We are grateful to Federal University of Ouro Preto, Osaka University, Japan International Cooperation Agency and Federal Center for Technological Education of Minas Gerais for the support. Conflicts of Interest: The authors declare no conflicts of interest.