Nabarlek Pit decommissioning migration of sulphate, nitrate and radium ions in groundwater - preliminary modelling
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Dept. of Transport and Works
Report ; 41/1984
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Technical Report WRD84041 Viewed at 14:07:09 on 29/07/2010 Page 20 of 34. I I I I I I I I I I I I I I I I I I I I 6. DISCUSSION The above calculations suggest that the ion most likely to reach Cooper Creek at high levels in water seeping from the pit is sulphate ion. The greatest impact -that sulphate ion could have on the Cooper Creek ecosystem would be if this anion was precipitated in creek sediments in soluble salts (probably as MgS0 4 .7H20). and then redissolved in first flush <;;aters. Sulphate ion is non-toxic, but high concentrations of this ion will increase the total dissolved salt load of a given water, and high TDS levels can interfere with fish breeding patterns, kill young waterfowl and wither plants [Train, 1979). The U ~ S ~ Env iro::r;\lental P::-otection Agency recoJ:imend that 'TDS levels in water of the composition of Coope~ Creek water (TDS ::;:. 10-50 mg/L) should not vary by more than 10% from the natural salinity range. At very low groundwater flow rates (~-e-. dispersior1 of sulphate ion in. grou:1dwater is important) r l'D8 level increases in first flush flows tvill be negligible. However, if goundwater flow is rapid and dispersion of sulphate ion in groundidater between the pit and Cooper Creek 1''':'1 --h .lS neg ....... lg..:..D_e, L..:. .. en high TDS levels will occur in first flush flows in this creek for at least a four year period. A more "-a.ccu!:'at.e assessment of the impact of 804 ~ from pit seepage \>later on Cooper Creek cannot be made ;,..;i thout more detailed , kno~dledge of the nature of groundwater floVl between the pit and Cooper Creek. '~~O/l' m-,:;I:~L ..I.: ..L0