Terrain hazard around the Ok Tedi copper mine, Papua New Guinea

• Published in: Land Surface Evaluation for Engineering Practice Vol. 18; pp. 143 - 149
• Main Authors: Hearn, G. J., Blong, R., Humphreys, G.
• Format: Book Chapter
• Language: English
• Published: The Geological Society of London 01.01.2001
• Series: Geological Society, London, Engineering Geology Special Publications
• ISBN: 9781862390843; 1862390843
• ISSN: 0267-9914; 2041-4730
• DOI: 10.1144/GSL.ENG.2001.018.01.21

Rationale Located in the remote Star Mountains of Western Province, Papua New Guinea, the Ok Tedi open-cut copper mine operates under conditions of particular topographical and geotechnical adversity. Slopes are frequently steep, rocks are highly fractured and weakened due to tectonics and weathering, and rainfall is world record-breaking, with annual totals exceeding 10 m in the vicinity of the mine (Jones & Maconochie 1990). The mine is planned to occupy an area of 2 km diameter with a depth of 500 m at an altitude of 1800 m a.s.l. The mine supply corridor, along which power, food and other essential materials are brought in and copper concentrate is piped out, is 160 km long, and is itself at risk from slope, flooding and erosional hazards. The threat posed by these hazards to the operation of the mine and the viability of its supply corridor has been recognized and evaluated by the geotechnical department of Ok Tedi Mining Ltd (OTML) since the project‘s inception. However, the severity and proximity of this risk were perhaps not fully realized until 1989 when a rock avalanche involving perhaps as much as 70 x 106 m3 of material occurred within a very short distance of the mine office. The collapse of the mountainside was dramatic and was considered to have been responsible for the seismic event recorded at the time of failure in Port Moresby, approximately 800 km away. Although the infrastructure of the mine was not directly affected by this failure, it served as a