Assessment of the Jabiluka Project : report of the Supervising Scientist to the World Heritage Committee
Johnston, A.; Prendergast, J. B.; Bridgewater, Peter
E-Publications; E-Books; PublicationNT; Supervising Scientist Report; 138
Alligator Rivers Region
Main report--Appendix 2 of the Main Report. Submission to the Mission of the World Heritage Committee by some Australian Scientists ... --Attachment A. Johnston A. and Needham S. 1999. Protection of the environment near the Ranger uranium mine--Attachment B. Bureau of Meteorology 1999. Hydrometeorological analysis relevant to Jabiluka--Attachment C. Jones, R.N., Hennessy, K.J. and Abbs, D.J. 1999. Climate change analysis relevant to Jabiluka--Attachment D. Chiew, F and Wang, Q.J. 1999. Hydrological anaysis relevant to surface water storage at Jabiluka--Attachment E. Kalf, F. and Dudgeon, C. 1999. Analysis of long term groundwater dispersal of contaminants from proposed Jabiluka mine tailings repositories--Appendix 2 of Attachment E. Simulation of leaching on non-reactive and radionuclide contaminants from proposed Jabiluka silo banks.
Uranium mill tailings - Environmental aspects - Northern Territory - Alligator Rivers Region; Environmental impact analysis - Northern Territory - Jabiluka; Uranium mines and mining - Environmental aspects - Northern Territory - Jabiluka; Jabiluka - Environmental aspects
Supervising Scientist Report; 138
1 volume (various pagings) : illustrations, maps
https://hdl.handle.net/10070/462403; https://hdl.handle.net/10070/462400; https://hdl.handle.net/10070/462405; https://hdl.handle.net/10070/462406; https://hdl.handle.net/10070/462408; https://hdl.handle.net/10070/462409; https://hdl.handle.net/10070/462411
56 concentrations of a range of important constituents of the effluent to ensure a very high level of ecosystem protection. Implicit in this approach, however, is the assumption that significant quantities of water could regularly be discharged from the mine site provided that the appropriate standards are met. While this might be sound on a scientific level, the Aboriginal people of the region have been consistent in their opposition to the discharge of mine waters and, because of these deeply felt concerns, ERA has adopted a policy of not releasing any water from those parts of the mine site containing the mill, ore stockpiles and any material with a concentration of uranium of greater than 0.02%. Only inert waste rock would be outside this Total Containment Zone. Thus the size of the pond has been determined on social grounds rather than scientific grounds. The issue that will be addressed in this section is the quantification of the risk to people and downstream ecosystems arising from any particular choice of storage capacity. In particular, we will assess the risks associated with the particular storage pond proposed by ERA in the Public Environment Report. This will be followed by an assessment of the risk associated with dam failure. 5.3.1 Water quality of runoff from the ore stockpile Prior to estimating the risks associated with discharges of water from the ore stockpile to the environment beyond the mine site, it is necessary to estimate the concentrations of the principal constituents in runoff water. In Appendix B1 of the PER, ERA reviewed the information available on runoff water quality. It identified the principal constituents as uranium and its radioactive progeny, and magnesium sulphate. The information obtained from kinetic testing of a number of samples of the Jabiluka ore showed that, while a number of metals and metalloids were present in the ore at concentrations greater than average in the earths crust, none other than uranium was at a concentration that, under the general chemical environment of the ore stockpile, will present a threat to ecosystems or people beyond the mine site. The Supervising Scientist agrees with this assessment. ERA, based upon a review of water quality in the ore stockpile sump at Ranger, estimated that concentrations of uranium in runoff water are likely to be in the range 5000 10,000 g/L. Based upon the concentrations of uranium in the sump in recent years, this estimate appears to be valid. However, in earlier years of the Ranger operation, concentrations as high as 50,000 g/L were observed. In addition, it is necessary to take into account the higher concentration of uranium in the ore at Jabiluka (0.46%) compared to that at Ranger (0.3%). On this basis, a value of 80,000 g/L has been adopted as a worst case scenario for this risk assessment. This converts to 1000 Bq/L in radioactivity units. ERA estimated the concentration of 226Ra at 100 mBq/L based upon relatively infrequent measurements of radium concentrations in the stockpile sump at Ranger. While this may well be a reasonable estimate, a more conservative approach has been adopted in this review. The concentrations of all of the other long-lived radionuclides of the uranium series in runoff from the Jabiluka ore stockpile have been estimated using the observed ratios of the concentrations of these radionuclides (Martin et al 1998) to concentrations of uranium in Retention Pond No 2, which collects water from the ore stockpiles and water transferred from the mine pit at Ranger.