Nabarlek Pit decommissioning migration of sulphate, nitrate and radium ions in groundwater - preliminary modelling
Appleyard, S.
E-Publications; E-Books; PublicationNT; Report ; 41/1984
1984-04-01
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Date:1984-04
English
Dept. of Transport and Works
Darwin
Report ; 41/1984
application/pdf.
Check within Publication or with content Publisher.
https://hdl.handle.net/10070/228496
https://hdl.handle.net/10070/674076
Technical Report WRD84041 Viewed at 14:07:09 on 29/07/2010 Page 9 of 34. I ~-- ~~ I I I I I I I I I I I I I I I I I I I I or more of these parameters. If the curve shovm in Fig ~ 3.1 is assumed, the value of the ratio CICo is about 10-13 , which is equivalent to a discharge concentration -13 of radium in Cooper Creek of about 10 Bq/L. The above ratio applies only as t ~ 00, ie. radium is given ample time to reach the creek. If the flow rate is increased by an order of magnitude or if the rate constant or cross-sectional area is decreased by an order of magnitude, the value of the ratio CICo will be approximately 0.1, ie. the discharge concentration of radium in Cooper Creek will be one tenth that contained in the pit after rehabilitation. Similarly, if the floVl rate of radium ions is decreased by an order of magnitude, or if the cross sectional area or rate contant is increased by an order of magnitude, effectively no radium will reach Cooper Creek. The family of curves that result if the bulked constant term! K, is varied by an order of magnitude is shown in Fig 3.2. The terms G, A and k in equation (6) are all imprecisely knmvn largely because of lack of detailed knowledge about the degree to which a hydraulic connection exists between poorly transmissive rock near the pit and highly transmissive rock to the south-east. Geophysical work , test pumping will be carried out in the area to the south east of the pit by AGC this year, and data obtained from these studies may lead to better estimates of fracture density in this area, which in turn will lead to better estimates of the terms k, A and G being made. However, it must be stressed again that the above analytical solution was derived for t = roo AGe (1984) laboratory tests place the radium ions at Nabarlek in groundwater velocity of -6 the range 5 x 10 to 2 x -7 I . 10 m s, Vlh~ch suggests that Ra will not appear at Cooper Creek for about 5 x 105 years. SA2/l1 :TJ