The integration of indigenous knowledge into mine site rehabilitation and closure planning at Ok Tedi, Papua New Guinea

Abstract

A critical element of the rehabilitation strategy for the Ok Tedi mine in Papua New Guinea (PNG) is the rehabilitation of the potentially acid forming dredge sand stockpiles at Bige on the banks of the Ok Tedi. Successful long-term mitigation of Acid Rock Drainage (ARD) involves placing a geochemical cover layer over the PAF waste and rehabilitation of the cover. Rehabilitation failure could lead to accelerated erosion, potentially compromising the integrity of ARD mitigation measures. Accordingly, the rehabilitation implemented at Bige must have a high certainty of being self-sustaining in the long-term. Post closure, Ok Tedi Mining Ltd (OTML) will seek to relinquish mine lease areas and rehabilitated lands will form part of the land used by customary landholders for the acquisition of essential natural resources. Any attempt to impose a rehabilitation objective that fails to recognise the potential productivity of the post-mine landscape or the land management techniques used by, and the long-term interests of, local landholders, risks failure. If the landholders reject the post mine land use options created by OTML and implement an alternative land-use, this may affect stockpile stability and compromise ARD mitigation measures. The rehabilitation objectives for Bige needed to address the unique social as well as technical challenges of the site. In the affected area, agriculture is largely subsistence-based, using a system of long fallow (15–30 years or more) shifting cultivation. Traditional lands and forest resources are extensively used for providing food, fibre, medicine and shelter as well as cultural services. The post-mine plant community must therefore provide services that make it sufficiently valuable for affected communities to retain and manage sustainably. In developing the rehabilitation strategy for Bige, information was gathered from local communities on goods and services provided by the surrounding forest, traditional vegetation and land management practices, and recognised cycles of clearing and forest regeneration. This paper describes how the information provided by customary landholders was integrated into the rehabilitation strategy and completion criteria for this part of the Ok Tedi operation.