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This case study is copyright (©)1997 by Kevin A. Morin and Nora M. Hutt, and is adapted from Case Study 6.2-2 in Environmental Geochemistry of Minesite Drainage: Practical Theory and Case Studies.
2 The Rum Jungle Minesite is located in the Northern Territory of Australia, approximately 150 km south-southwest of Darwin. The climate is tropical and annual rainfall averages 1.5 m with approximately 80% falling between December and March. Monthly mean daily temperature varies from 25C in July to 30C in November.
Mining for uranium began at this site in 1954 with White's orebody, depleted in 1958 (Harries and Ritchie, 1982). This was followed by Dyson's and Intermediate orebodies, with all mining ceasing in 1965 or 1971. By the time mining ceased, there were three pits and three waste-rock dumps (White's, Dyson's, and Intermediate), a copper heap-leach pile, and a tailings impoundment (Figure 1). Acidic drainage caused by sulfide oxidation and the accompanying metal leaching led to significant releases from these minesite components (Table 1).
Click on Figure 1 to enlarge it
Metal-Release Rates from Various Minesite Components during the 1973-1974 Wet Season at the Rum Jungle Minesite
(adapted from Harries and Ritchie, 1982, and Bennett and Lawton, 1995)
|Component||Cu (t/yr)||Mn (t/yr)||Zn (t/yr)|
|White's Waste-Rock Dump||29-53||11-19||17-31|
|Intermediate Waste-Rock Dump||16-30||2.5-4.5||13-25|
|Dyson's Waste-Rock Dump||0.2||5||-|
|Copper Heap-leach Pile||32-42||-||-|
|Old Acid Dam||-||12||-|
After 1958, Whites Pit flooded quickly to its equilibrium static level with the assistance of diverted river water, and at that time had a pH of 4.75 and a sulfate concentration of 180 mg/L. However, unneutralized tailings and treatment raffinate were dumped into the pit through the 1960's so that by 1974 pH had fallen to 2.4 and sulfate increased to 9000 mg/L. The annual flow of water through Whites Pit was estimated at 19,000,000 m3, but did not include subsurface inflow and outflow.
The East Finniss River which runs through the site (Figure 1) carried elevated levels of metals even before closure. The river was devoid of biological species up to 8.5 km downstream, with reduced biodiversity over another 15 km (Bennett and Lawton, 1995). In late 1983, a rehabilitation program was started and eventually completed in early 1987 at a cost of AUS$18,600,000. This program was designed to reduce metal levels in the East Finniss River by up to 70%, reduce on-site pollution, and revegetate the minesite. Ryan and Joyce (1991) concluded that the first and primary objective was not accomplished and that diversion of the river may have been a more successful option than all the on-site remediation. On the other hand, Bennett and Lawton (1995) state that metal levels were successfully reduced, but a five-year program is currently underway to delineate carefully the degree of success.
The on-site remediation program included:
Water balances for White's and Intermediate Dumps shows that a major portion of the water reported to the underlying groundwater system. The loadings to the underlying groundwater and the nearby river were expected to continue for 10-20 years, apparently reflecting the release of retained reaction products.
After White's Dump was covered as explained above, oxygen levels throughout most of the dump decreased, and remained high (>5% O2) only within a few meters of the slopes and top surface. Afterwards, these profiles of oxygen, carbon dioxide, and temperature with depth showed minor changes over five years of monitoring. This was taken as evidence that oxygen entry was controlled by diffusion, except for convection in one large area of the dump.
There have been debates in Australia over the general success and return-on-investment of the Rum Jungle remediation. The Australian Nuclear Science and Technology Organisation (ANSTO, see Links to Related Sites), which has carried out the remediation and monitoring, is conducting a five-year review and investigation to better define the degree of success.
In contrast to debates over the success of remediation at Rum Jungle, the nearby Rum Jungle South open-pit uranium mine was successfully remediated. Despite some acidic drainage, the pit was flooded and evolved to a slightly alkaline lake. The adjacent waste-rock dump with an average of 0.29%S was recontoured and covered with soil. The minesite is now a pleasant park and swimming area, with only small localized seeps of acidic drainage occasionally seen near the dump.
© Kevin A. Morin and Nora M. Hutt, 1997
Bennett, J.W., and M.D. Lawton. 1995. Assessment of the Rum Jungle Strategy for acid mine drainage control. IN: N.J. Grundon and L.C. Bell, eds., Proceedings of the Second Australian Acid Mine Drainage Workshop, Charters Towers, Queensland, Australia, March 28-31.
Harries, J.R., and A.I.M. Ritchie. 1982. Pyrite oxidation in mine wastes: its incidence, its impact on water quality and its control. IN: E.M. O'Loughlin and P. Cullen, eds., Prediction in Water Quality: Proceedings of a Symposium on the Prediction in Water Quality, Australian Academy of Science and the Institute of Engineers, Canberra, November 30-December 2, p.347-377.
For more details and case studies, see Environmental Geochemistry of Minesite Drainage: Practical Theory and Case Studies.
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Created by K.Morin