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
33 The recommended value for the 1:10,000 AEP annual rainfall is 2460 mm with 95% confidence limits of 190 mm. This estimate is in very good agreement with the value adopted by ERA, 2450 mm. It is acknowledged that there may be some residual model dependence in the recommended value for the 1:10,000 AEP annual rainfall. However, this is not important for modelling of the Jabiluka water management system in this review because a Monte Carlo simulation method is used based upon stochastically generated rainfall data. Evaporation from open water All of the suggestions made by Wasson et al (1998) to check the validity of the evaporation pan factors used by ERA had already been taken into account in the evaporation calculations presented by ERA in its hydrological modelling of the water management system for the Jabiluka project. Based upon two recent independent reviews, it is recommended that, in all future hydrological modelling of the Jabiluka water management system, the pan factors proposed by the Supervising Scientist in 1987 be used. The difference in annual pond evaporation arising from the use of the pan factors recommended by the Supervising Scientist compared to that obtained using the factors adopted by ERA in the PER for Jabiluka is small (about 2%). This difference is well within current expectations of the accuracy of water management modelling. The volume of the retention pond at Jabiluka would need to be increased by about 3% to take into account the inter-annual variation in evaporation and the inverse relationship relationship between evaporation and rainfall. This estimate is, however, considered to be an overestimate because the relationship between evaporation and rainfall is not linear. Rather, evaporation during the main months of the Wet season tends towards a constant value at high rainfall values. It is recommended that a linear relationship between evaporation and rainfall is incorporated in future water management modelling because this will yield conservative results under high rainfall conditions and more realistic results under drought conditions than would be obtained using the long-term monthly average evaporation. Evaporation in the mine ventilation shafts The observation by Wasson et al (1998) that the latent heat of evaporation needs to be supplied is correct. The conclusion that this results in a major error is, however, invalid because the energy required can be supplied externally, and it was the intention of the design engineer that the optimum way of doing this would be assessed at the detailed design stage once approval for the project to proceed had been given. The capital and operating costs of a humidifier system designed to meet the evaporation energy needs would be high and a cost benefit analysis of various water management options will be required before a final decision on the installation of a humidifier system is made. If it is decided that the cost of installing and running a humidifier system is too high or that the environmental impact is unacceptable, the retention pond at Jabiluka would need to be increased in area from 9 ha to about 13 ha. Given the experience of the Ranger Mine, which has a disturbed area of about 500 ha, this 4 ha increase is not expected to give rise to any detectable environmental impact.