Territory Stories

Assessment of the Jabiluka Project : report of the Supervising Scientist to the World Heritage Committee

Details:

Title

Assessment of the Jabiluka Project : report of the Supervising Scientist to the World Heritage Committee

Creator

Johnston, A.; Prendergast, J. B.; Bridgewater, Peter

Collection

E-Publications; E-Books; PublicationNT; Supervising Scientist Report; 138

Date

1999

Location

Alligator Rivers Region

Table of contents

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.

Language

English

Subject

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

Publisher name

Environment Australia

Place of publication

Canberra (A.C.T.)

Series

Supervising Scientist Report; 138

Format

1 volume (various pagings) : illustrations, maps

File type

application/pdf

ISBN

642243417

Use

Copyright

Copyright owner

Environment Australia

License

https://www.legislation.gov.au/Details/C2019C00042

Parent handle

https://hdl.handle.net/10070/264982

Citation address

https://hdl.handle.net/10070/462402

Related items

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

Page content

86 Carlo calculations show that migration up to 1200 m is possible but with a very low probability. Kalf and Dudgeon (1999) conclude that radium and uranium will remain at background levels in the floodplain. Kalf and Dudgeon (1999) also concluded that there is negligible likelihood of a major fracture system in the rock aquifer that could cause significant pollution in downstream waterways. 6.4 Risk assessment on the long-term storage of tailings A risk assessment of the probable impact on people and the wetlands of Kakadu National Park arising from the long-term storage of tailings in the mine void and the silos has not been carried out to the extent that was developed in chapter 5 for storage of uranium on the surface. To carry out such an assessment would require the extension of the analysis of groundwater dispersion to the quantitative prediction, using Monte Carlo analysis methods, of the concentrations of solutes in the waters of the Magela floodplain and the probability with which these concentrations will occur. The range and quality of existing hydrogeological data do not enable such a detailed analysis to be carried out. However, the Monte Carlo analyses of solute concentrations in the deep aquifer and the information on the vertical component of groundwater flow presented in section 6.3 demonstrate that the concentrations of the tailings derived solutes in surface waters of the Magela floodplain will remain at their natural values and will not be affected by dispersion of solutes from the tailings repositories. 6.5 Summary of findings on long-term storage of tailings Erosion of tailings in the long-term Once the Jabiluka mine is backfilled and sealed following completion of mining, the only mechanism for physical dispersal of the tailings solids will be erosion of the overlying bedrock. Since the mine void and the tailings silos will be about 100 m below the surface and the upper surface of these is below sea level, the whole land mass would need to be eroded away and by that time the wetlands of Kakadu would no longer exist. Thus, physical dispersal of the tailings does not pose a threat to the wetlands of Kakadu. Using the mean measured denudation rate for the region of 0.04 mm per annum, the time required to erode the bedrock overlying the tailings in the mine void and the silos would be about 2 million years. Hence the excess concentrations all of the radioactive progeny will have decayed away by the time the tailings are exposed and they will be in approximate equilibrium with the residual uranium. Dispersal of tailings in the very long term will not constitute a hazard for future generations. Hydrogeological features of the area The permeability of the Cahill Formation schists west of the orebody is significantly greater than that of the Kombolgie sandstone to the east. For this reason, it is recommended that the additional tailings silos should be excavated in the Kombolgie sandstone east of the orebody, as is currently planned by ERA. This choice of location will minimise potential environmental impacts. The excavation of the silos will result in additional material being placed on the surface. The location of the silos in the sandstone rather than in the schists to the west is also


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