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
66 It should be noted that if a properly engineered spillway were installed in the wall of the retention pond, the dam would be protected from destruction under overtopping. This would result in the loss of much lower volumes of water over a longer period and would fully protect both Swift Creek and the Magela floodplain under the conditions considered here. It is recommended that such a spill-way be incorporated in the design of the retention pond. Static failure of the retention pond structure Static failure of the water retention pond could, in principle, occur as a result of piping (the erosive action of water passing through or under the dam wall) or slope failure (the downward and outward movement of a mass of soil beneath the dam wall) as a result of excessive pressures being applied. Failure as a result of piping is not considered to be an issue with the specific design adopted by ERA because there is a double impermeable liner on the floor of the dam and on the inner walls. In addition, a seepage detection system has been included in the design so that, were the liner to be damaged, seepage would be detected at an early stage and repair action implemented. The retention pond structure has been designed with a factor of safety (FS) of 1.7 against slope failure. This FS was calculated under circumstances in which the pond is at its full capacity with the liner intact. Hence, the probability of slope failure should be less than the probability of overtopping which was estimated above to be about 0.0005 or 5 in 10,000. Since slope failure would only arise under circumstances similar to those considered for overtopping, the estimates of environmental impact derived above for overtopping would also apply to slope failure. Table 5.3.4 Variation return period with peak ground acceleration arising from an earthquake for a site near Darwin Return Period (Years) Peak Ground Acceleration mm/s2 1 98 10 218 100 484 500 842 1000 1068 2000 1349 3000 1544 5000 1834 Failure due the occurrence of a severe earthquake The factor of safety of 1.7 for the designed retention pond structure was derived by considering not only conditions that would lead to static failure but also ground level motions with an acceleration of 0.08 g arising from an earthquake, where g is the acceleration due to gravity. (The acceleration 0.08 g is that specified in the relevant Australian standard for normal structures.) The engineering consultant responsible for the design of the retention pond, Golder Associates, has advised the Supervising Scientist (private communication) that the acceleration corresponding to a safety factor of 1.0, at which dam failure could commence, is 0.39 g (3830 mm/s2).
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