The seepage from flows coming from the tailings disposed in an impoundment that usually does not have any type of liner system for impermeabilization may cause consequences or impacts in the ecosystem or in underground water that do not have direct contact with tailings. The impact magnitude depends on the acidity generation degree that tailings may have, amount of concentration of metal precipitated in seepage flow and the amount of seepage from tailings. If these impacts finally occur, lawsuit and penalties can generate loss of reputation for the mine and the industry. However, in any case, the use of a liner system must depend on a rigorous technical evaluation instead of just trying to meet the needs of the nearby population or the regulatory agencies.

When a liner system is required in a tailings storage facility, the selection of the proper geomembrane is important because the area to be lined has to be prepared for receiving the geomembrane and the amount of earthworks needs to be optimized in order to reduce costs. Currently, there is a wide variety of geosynthetics that could be used as liner system, for example HDPE or LLDPE geomembranes, PVC geomembranes and FPP geomembranes. The chosen one must be justified by the project needs which depend on foundation material and tailings characteristics, as well as their own cost.

The objective of this paper is to evaluate and select the best liner system that reaches the requirements of a tailings storage facility located in the Peruvian Andes through the alternative selection methodology CBA (choosing by advantages). This methodology allows decision-makers to separate the economic aspect of each alternative from the technical aspect suported by studies carried out for each alternative, in this way, CBA prevents a bad alternative being compensated by its low cost in its final weight and CBA gives an objective decision of the chosen geosynthetic.

In the technical aspect, the geosynthetics will be evaluated by their performance against differential settlements, which was one of the most important factors in this particular case, as well as by their deficiencies. On the other hand, in the economic aspect, the costs of supply and installation of the geosynthetics and the complementary activities that are necessary for the geosynthetics installation, mainly the earthworks, will be considered.