Practice of 2:1 waste rock dump reclamation slope at Batu Hijau - A 20 year journey creating the best legacy

Abstract

The Batu Hijau's orebody is a world-class copper-gold porphyry owned by PT Amman Mineral Nusa Tenggara located in previously uninhabited forestland with sloping terrain southwest of Sumbawa Island. The climatic condition is influenced by two distinct monsoon periods, namely the east monsoon which is characterized by low rainfall and humidity level and extends from May through September, and the west monsoon, which extends from November through March each year. Annual precipitation is 2,511 mm with over 75 percent of rainfall occurring during the west monsoon. The construction phase started in 1997 and it took 3 years before production started in March 2000. Reclamation is performed concurrently and integrated into the annual mine plan update. Numerous studies had been performed since the early stages of exploration that including tree species selection, PROSPER forest vegetation/ soil hydrology model to determine soil thickness, soil water holding capacity, and construction of 2:1 new test slope (NEWTS). This paper outlines the development of a 2: 1 reclamation slope in the waste dump that has been carried out over 20 years from land preparation, erosion control techniques, tree transplanting, monitoring, and evaluation. This achievement assures that Batu Hijau reclamation program's goal to restore the ex-mining area to a forest similar to its pre-mining condition is achievable.