The San Rafael Mine, which is operated by Minsur S.A. (Minsur), is an underground mine located 120 km from the city of Puno in southeast Peru, in the eastern cordillera of the Andes at 4,500 masl. It is the third largest tin producer in the world.
The B4 tailings storage facility (TSF) began construction in 2020 and is in the operations stage. It has a projected capacity of 8 Mt and will be raised using the central axis method, reaching a height of 75 m at the fifth raise.
The geological conditions of the site are complex because of areas with potential for karstification and the presence of local and regional faults. Engineering designs, therefore, were developed that allowed for the adequate performance of the TSF during its useful life. During the design process, procedures were developed for the treatment of karst zones and faults that were found during the excavation of the foundation of the dam and the impoundment of B4 TSF. In addition, to limit possible seepage from the tailings impoundment, a grout curtain was installed in the dam axis, and a lining system was constructed in the impoundment of B4 TSF.
Knight Piésold was appointed by Minsur as the civil-geotechnical designer for the project in 2014. Since then, Knight Piésold has provided the following services: geological, geotechnical, and geochemical characterization; water balance; hydraulic and civil design; slope stability and deformation analysis; risk management support; and other services. Knight Piésold has also provided technical assistance and continuous quality control during construction of B4 TSF, verifying compliance with the design intent.
Moremore, Knight Piésold was assigned as the Engineer of Record (EoR) for B4 TSF in 2020 and has since been providing technical assistance for all stages of its life cycle and participating in monitoring, performance evaluation, and risk management. One of the main challenges of this project is appropriately integrating strategic aspects of tailings management with mining operational activities.
The first raise of B4 TSF (4,334 masl) was completed, and Knight Piésold is currently providing support to promote the formation of tailings beaches. Knight Piésold is also continuing to assist with tailings management to fulfill Minsur’s commitment to the International Council on Mining and Metals in adhering to the Global Industry Standard on Tailings Management.