Ok Tedi Copper Mine

Ok Tedi Mining Limited (OTML), in Papua New Guinea, have been monitoring the effects of pipeline ruptures which released pyrite concentrate (PCon) into upland creeks of the Fly River system. To reduce the risk of ARD on the Fly River floodplain, pyrite is removed from the mine tailings stream and piped from the mill, 120 km to the lowland floodplain, where it is buried in cells below the water table.

In 2011 the pipeline ruptured in several locations, with PCon flowing into a series of small rainforest creeks. Spills were contained with sediment traps constructed in creeklines, and the concentrate manually collected and removed. However, because of the steep terrain, some pyrite passed down the creeklines, leaving residual material on the creek bed.

To assess the impact of the spills on the creeks, a total of 6 creeks were sampled; 2 un-impacted reference systems and 4 creeks exposed to different sized spills. On each creek, water, sediment and the aquatic macroinvertebrate fauna were sampled at multiple sites along a downstream gradient.

Data detected a minor impact to water quality, sediment, and aquatic fauna at the two larger spill locations, but with impacts localised to sites closest to the spills (i.e. within 500 m). Sites further downstream showed comparable water quality, diversity and composition of macroinvertebrate fauna to nearby control creeklines. There was no detectable impact to the macroinvertebrate fauna where the two smaller PCon spills took place. Recovery of the remaining pyrite has continued. It is intended to resample the creeks to assess recovery.