Managing PAF/NAF Overburden Material

Prevention and mitigation of Acid Mine Drainage (AMD) generation especially in open pit coal mine can be done if all potencies of AMD generation in mine site are well identified (i.e. AMD potency from overburden). By preventing and mitigating AMD generation at the beginning, the long term cost to treat AMD can be reduced. Furthermore, successful in managing potency of AMD generation will lead to the success of rehabilitation, reclamation and closure planning.

Potency of AMD generation from overburden is determined by identification of Potentially Acid Forming (PAF) and Non Acid Forming (NAF) materials. PAF materials are generally contains sulphidic compounds (particularly pyrite) in which will be oxidized when exposed to water and oxygen. Therefore, PAF materials should be segregated and handled differently in pit and disposals to minimize AMD generation.  

Overburden geochemical characterization is required to identify and classify PAF/NAF materials. This task will be conducted in yearly basis for Tutupan, Paringin and Wara overburden. Based on the geochemical data, geological model of PAF/NAF distribution will be generated and then used by production planning and operation for special handling PAF/NAF materials to be delivered to disposal area. One of  strategies in mitigating AMD generation from overburden is using dry cover method which is covering up (isolation) of Potentially Acid Forming (PAF) type waste rock with Non Acid Forming (NAF) type waste rock.

Mine water from active mine pits and disposal areas will be treated in different settling ponds dedicated for different catchment area to ensure the water quality is met with applied regulations. Water sourced from active dry cover areas will be monitored for performance evaluation. Final disposals will be reclaimed and rehabilitated in sustainability way.  

The purposes of Integrated AMD Management plan is to: (1) fulfill responsibility to mitigate & minimize AMD generation potential at its source (2) minimize AMD generation from overburden disposals; (3) reduce cost of AMD treatment in the future; (4) remove legacy of potential environmental problem post mine closure; and (5) as part of company’s commitment for environmental protection.