ECNT » Current Campaigns » Mining

1. The proponent (McArthur River Mining) has not provided adequate information to allow an informed decision on the nature of potential impacts associated with the proposed McArthur River and Barney Creek diversions. Key flaws were identified in the modelling undertaken for the Environmental Impact Statement.

- progressive degradation, or erosion, of the McArthur River channel directly upstream of the diversion, causing the destruction of this section of the river. This will occur because streamflow velocities and shear stresses on bedrock and the banks of the channel will be greatly increased in times of a 1 in 2 or a 1 in 5 year flood.

- creation of a long section of sand aggradation, or a ‘sand slug’, downstream of the diversion channel due to the increased sediment load in times of flood. This would bury aquatic habitats and prove a barrier to fish migration upstream. Many of the key concerns about the potential impacts on downstream aquatic environments from increased sedimentation were not however addressed by the proponents.

- continuing erosion of the diversion channel banks. Planted vegetation is unlikely to survive flood events. Revegetation might in fact never occur given the predicted erosion of the diversion channel.

3. The EIS failed to include hydrological information for Barney and Surprise Creeks, even though Barney Creek is to be diverted over 2.5 km. There is potential in larger floods for Barney Creek to pose a greater risk to the mine infrastructure, including the flood bund wall and the waste rock dump, than the diverted McArthur River Channel.

4. On the basis of the information provided in the EIS, it was not possible for the EPA to conclude that contaminants mobilised from the waste rock pile (Overburden Emplacement Facility) would not enter the McArthur River.

5. The EPA had overall concerns about the operation of the tailings storage facility and its potential to impact on the receiving environment due to seepage, ongoing maintenance and monitoring requirements (including beyond mine life).

6. The EPA concluded that there is already probable impact to water quality resulting from mining activity. Zinc levels in Barney Creek were found to be elevated.

7. No sediment data was available for the freshwater reaches of the McArthur River, yet sediment is the ultimate repository for toxicants such as lead and zinc. This lack of data prevented the EPA from making a complete assessment of the environmental risks posed by the proposal.

8. There were concerns regarding the integrity of the bund wall during extreme weather events and the possibility of contaminants from bund wall rupture impacting on the McArthur River aquatic ecosystems either through sedimentation or contaminant transport.

9. There is a lack of substantive data presented in the EIS to demonstrate that the loss of the existing riparian corridors will not cause fragmentation of fauna populations in the short- and longer-terms. This includes loss of habitat for the Commonwealth listed migratory species, the White-browed robin.

10. Groundwater drawdown is expected to occur as a result of dewatering of the open cut. This will affect the extent and depth of Djirrinmini waterhole upstream of the proposed McArthur River diversion channel. The EIS did not consider the ecological impacts of these changes in environmental flows on what is a vital dry season refuge habitat for aquatic species.

11. Insufficient information was provided to enable an adequate assessment of the potential impacts of the project on the critically endangered Freshwater sawfish. Along with impacts on migratory species, the impacts on the Freshwater sawfish are considered a matter of national importance under Commonwealth legislation.

12. The rehabilitation strategy involves leaving the mine pit as a void and breaching the bund wall so that the river flows into the pit every two years or so. The EPA concluded that, “considering that no hydrological information was provided for the Barney Creek diversion and modelling for the McArthur River realignment has been questioned, there remains a high level of uncertainty with regard to the possibility of a major environment incident occurring as a result of the proposal”.