Nabarlek Pit decommissioning migration of sulphate, nitrate and radium ions in groundwater - preliminary modelling
E-Publications; E-Books; PublicationNT; Report ; 41/1984
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Dept. of Transport and Works
Report ; 41/1984
Check within Publication or with content Publisher.
Technical Report WRD84041 Viewed at 14:07:09 on 29/07/2010 Page 15 of 34. I -----~~ I I I I I I I I I I I I I I I I I I I I .--~--"'f'''~----~ During the remaining life of the Nabarlek mine, pit water levels will be 10m higher than present levels, and this will cause groundwater outflows from the pit to take place. The duration of this initial seepage pulse will be four years, as after this time water will be pumped out of the pit as part of the mine rehabilitation procedures. An analytical solution to describe the motion of a seepage pulse in an isotropic porous medium is given by Van Genuchten (1981): C(x,t) ( CoA(X,t) + c. Q (t) - c. G(x, t) o <t", t - \ ~ ~ 0 ( ~ A (x, t) + c. Q (t) - c. G(x,t) -C (x t-t ) ~ 0 ~ l o ' 0 t>t 0 where C(x,t) = concentration of a solute as a function cf time and space Co - initial concentration C. - background concentration in groundwater ~ to = duration of seepage pulse (assumed to be 4 years here) . A(X,t), G(x,t), Q(t) are functions (see Appendix A) An important parameter which has to be input into this solute transport equation is a dispersion coefficient. This was determined by assuming that the dispersion coefficient for the fractured rock aquif-er near the water management ponds also applies to the area to the south east of the pit. Seepage from the water management ponds occurred in 1982 and 1983 and breakthrough curves for sulphate ion at various times (assuming the SPROP to be the seepage source) are shown in Fig 5.1. SA2/11 :TJ