This project presents a methodology for the reliability-based design of tailings dam built using sand by the downstream method. The main purpose of this document is the generation of a design guide for this type of mine waste retaining dams. The four most common failure modes were identified: piping, stability (static and pseudo-static), liquefaction and overtopping erosion. For each failure mode a probability of dam failure was calculated using a reliability analysis from typical values and literature reviews, after of it is possible to determine a total probability of failure of the dam, including the design criteria involved in the analysis. With this information a design guide that provides information about the parameters to be taken into account when building these dams and further recommends criteria most suitable and reliable for the design of this type of dam design was generated.