Abstract
Rum Jungle is one of the world’s iconic legacy sites in the history of ARD assessment and management. A major program of rehabilitation works was implemented in the mid-1980s, resulting in a 70% reduction of metal loads and substantial improvement in aquatic ecosystem health downstream. However, this improvement was not sufficient to meet contemporary environment protection standards. This issue amongst others prompted the Australian and Northern Territory Governments to set up a National Partnership Agreement to develop and implement a rehabilitation plan to bring the site to current standards.
The development of locally derived water quality criteria for ecosystem protection (performance objectives) and the geochemical characterisation underpinning the works needed to meet these objectives will be described. A particular issue for legacy sites, in contrast to operating sites that are mining and managing fresh material, is that the sulfidic waste is often already substantially oxidised. Achieving protection of the receiving environment from this partly oxidised material can be more complex than for fresh waste rock where exclusion of oxygen alone can be an effective management strategy.
The rehabilitation proposed for Rum Jungle will involve a combination of below water placement (pit backfill) for the highest sulfide waste and a newly constructed above ground waste storage facility for the lower sulfide material. For both strategies the existing contained acidity will need to be neutralised to prevent it from being a future source of metals and acidity to ground and surface waters, respectively. Estimating the dosing rate of neutralant needed to account for this acidity (a combination of titratable and jaroasite acidity) was a key project requirement and the methods used to do this will be described.