Reszat, TR, Balding, G & Fawcett, M 2009, 'Remediation of small scale uranium mining activities in the South Alligator Valley, Kakadu National Park', in AB Fourie & M Tibbett (eds), Mine Closure 2009: Proceedings of the Fourth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 213-228, https://doi.org/10.36487/ACG_repo/908_15
(https://papers.acg.uwa.edu.au/p/908_15_Reszat/)
Abstract: The director of National Parks has initiated works to remediate, over four years, 13 abandoned uranium 
mines and related sites in the Gunlom Aboriginal Land Trust (GLT) area located in the upper South 
Alligator River Valley of Kakadu National Park. There are two categories of abandoned uranium mines and 
related sites in the GLT area: namely, non-radiologically contaminated sites (termed Part A sites); and sites 
containing residual quantities of tailings and run-of-mine wastes with low levels of radiological 
contamination (termed Part B sites). 
The portion of the works discussed in this paper involves characterisation of the Part B sites and the design 
of an engineered containment facility suitable for low level radiologically contaminated materials. Site 
remediation and engineered containment design involved a comprehensive and critical assessment of both 
the waste sites and the containment area. Sites investigated and characterised included Battery Bund, El 
Sherana Mine, El Sherana Village, Palette Mine, tailings residues near Rockhole Creek, South Alligator 
Village and Weighbridge. 
Physical, geochemical and radiological material characterisation of waste was undertaken to assess which 
materials are at risk and require additional works to supplement previous remediation. Radiological 
assessment included gamma measurements and radiometric laboratory analyses. Geochemical assessment 
involved sampling and characterisation based on in-field gamma measurements and sampling of known 
waste materials from a non-radiological perspective. Geochemical characterisation of samples involved 
solids and leach extraction chemistry, and testing to assess acid rock drainage (ARD) potential. Laboratory 
geochemical and radiological results were assessed through geochemical modelling to predict pore-water 
speciation of all wastes and the likelihood of solute migration. 
Containment site assessment involved geochemical and radiological characterisation to obtain base-line 
conditions and considered geochemical mixing and speciation modelling to predict the effects of containment 
leachate on-site base-line chemistry, should migration of solutes occur. The containment was designed using 
industry best practice using site-specific physical characteristics to develop the optimum design option, and 
considered geotechnical, hydrological, erosional and geochemical processes. Design alternatives were 
considered using soil-atmosphere, seepage and regional groundwater modelling including full sensitivity 
analyses to ensure proper design specifications were met.  
The preferred design alternative includes a robust cover system to limit net percolation of water into the 
waste and consists of a thick growth medium underlain by a compacted clay layer (CCL). The containment is 
located in the vadose zone, 5 m above maximum groundwater levels, in low permeability, clay-rich 
materials, and includes a secondary containment method consisting of a CCL at the base of the waste. The 
design includes automated instrumentation for monitoring and surveillance including: soil suction, 
temperature, and moisture sensors throughout the profile; provision of radon gas egress monitoring though 
the cover system; vibrating wire piezometers and lysimeters at the base to assess seepage and pore-water 
pressures; cover erosion and runoff measurements; piezometers appropriately sited to intercept potential 
seepage and monitor hydraulic heads through the containment area; and meteorological instrumentation. 
Remediation of small scale uranium mining activities in the South Alligator Valley, Kakadu National Park T.R. Reszat et al. 
214 Mine Closure 2009, Perth, Australia