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Nabarlek Pit decommissioning migration of sulphate, nitrate and radium ions in groundwater - preliminary modelling



Nabarlek Pit decommissioning migration of sulphate, nitrate and radium ions in groundwater - preliminary modelling


Appleyard, S.


E-Publications; E-Books; PublicationNT; Report ; 41/1984




Made available via the Publications (Legal Deposit) Act 2004 (NT).





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Dept. of Transport and Works

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Report ; 41/1984

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Technical Report WRD84041 Viewed at 14:07:09 on 29/07/2010 Page 3 of 34. I I I I I I I I I I I I I I I I I I I I 1. INTRODUCTION 1.1 Objectives of the Modelling Exercise The Nabarlek mine pit contains water which has high concentrations of the ions calcium, magnesium, aITIDonium, radium, sulphate ar-d nitrate, and high levels of manganese. Queensland Mines Limited have requested that their authorisation be amended such that the water level in the pit be allowed to rise to RL 70m, a level IThere groundwater outflows from the pit will take place. It is envisaged that this high pit Ivater level will be maintained for a period of four years, after '''hich time water will be removed and the pit will be rehabilitated. This discussion paper will examine the possible impact of contaminants in groundv.rater outflohl's from the pit on Cooper Creek which is situated about 1 km to the south-east. 1.2 Identi~ication of Major Poliutants Fresh and weathered rock possess a natural capacity to remove many cations from solution through the processes of irreversible adsorption and ion exchange. Observations from uranium mines in fuuerica (see e.g. Rouse and Williams, 1983) have indicated that heavy , metals and ammonium ion are totally removed from seeping mine waste water within a fevl metres of the seepage source, and this is also expected to be the case for water discharging from the Nabarlek pit. The major pollutants that will reach Cooper Creek are those that will not be adsorbed by mineral surfaces. The most important pollutants reaching Cooper Creek are therefore expected to be the anions nitrate and sulphate. Another possible contaminant that could reach Cooper Creek is radium ion; radium is extremely toxic in 1m, concentrations and can be concentrated to a large extent by organisms such as freshwater shellfish. SA2/11 :TJ .. - ~