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
69 water management system at Jabiluka including, in a worst case scenario where no other acceptable alternative exists, the pumping of water to the mine void. The analysis presented in this chapter suggests that contingency planning should include the measures discussed below. Rainfall runoff from the ore stockpile represents about 1.5% of the runoff from the remainder of the Total Containment Zone for the Jabiluka Mill Alternative. The water quality of runoff from the stockpile will, however, be much poorer than that from the remainder of the catchment. Hence, in the extreme scenario envisaged in sections 5.3.2 and 5.3.3 where there is a 1 in 50,000 probability that about 200,000 m3 would be discharged from the TCZ to Swift Creek, the volume of poor quality water from the ore stockpile would only be 3000 m3. This volume could easily be accommodated in the freeboard volume of the water retention pond without downgrading the freeboard capacity significantly. It is, therefore, recommended that runoff from the ore stockpile should be isolated from runoff from the remainder of the TCZ so that it is always directed to the pond while, under extreme conditions, runoff from the rest of the TCZ is diverted away from the storage pond. This measure would reduce still further the risk associated with exceeding the capacity of the storage pond. The assessment of the risks associated with overtopping of the water retention pond was based upon the assumption that overtopping would lead to structural failure of the pond embankment and that all of the water in the pond, 855,000 m3, would be discharged to Swift Creek. If the pond were constructed with a properly designed spillway, this would ensure that, even if diversion contingency measures fail, the pond structure would not fail when the overtopping height is reached. This would reduce substantially the impact arising in the event of overtopping because only a small volume of water would be released to the environment rather than the full volume of the pond. It would also, as a by-product, mean that the operation of the mine could continue even following such an extreme event without the need to rebuild the dam. 5.6 Summary of findings on the storage of uranium on the surface Modelling of the water management system at Jabiluka under current climatic conditions This review has included hydrological modelling of the water management system at Jabiluka using a stochastic daily water balance model which incorporates the recommendations of this review on the appropriate rainfall record and evaporation, a realistic distribution of evaporative losses in the ventilation system throughout the year, and a simple soil water capacity model for runoff. The system modelled was the Jabiluka Mill Alternative Original Concept but with tailings returned to the mine void rather than in tailings ponds at the surface. The model has enabled estimates to be made of the storage capacity required as a function of exceedence probability over the 30-year mine life under current climatic conditions. The probability that the pond volume proposed by ERA in the PER (810,000 m3) would be exceeded over the life of the mine is about 1 in 1000. The pond volume required to achieve an exceedence probability of 1 in 10,000 over the life of the mine would be about 940,000 m3.
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