Radiological anomalous area on the Nabarlek minesite - visual interpretation of temporal aerial photography


Internal Report 427
Pfitzner K
Supervising Scientist Division
Department of the Environment, Water, Heritage and the Arts

About the report

An area of potentially high erosion rate (described as the ‘badlands’ or ‘Unit 7’) was identified on the rehabilitated Nabarlek site by Grabham (2000). The area lies adjacent to the western side of the mine pit. The area is devoid of vegetation, extremely erodible and highly saline and was the site of stockpiled evaporation pond and processing plant runoff scrapings in 1988 (Grabham 2000). Subsequent analysis of surface soil samples from the site has shown that they have elevated uranium-series radionuclide concentrations (Hancock et al., in prep), and consequently the area has also been called a ‘radiological anomalous area’.

There are therefore two aspects of interest for this area: its high erodibility and radiological nature. Hancock et al. (in prep) provide an erosion and radionuclide assessment of the Nabarlek site. With reference to the area of interest, they found the following: the area has the highest erosion rate determined for the site; is lowering at a rate 300 times that of the background rate and 2500 times that of the adjacent capped pit; has the highest radionuclide concentration (in soil samples); and, contributed the majority of the estimated flux of uranium-series radionuclides (attached to eroded soil particles) to Cooper Creek.

The size, shape and the relationship of this area on the rehabilitated site with previous mining activities has never been accurately defined. This report documents the results of using remotely sensed data to identify the spatial extent of this area during various stages of mining land use. This temporal investigation using aerial photographs was initiated to aid in the planning of a ground-based radiation survey and for defining the location to collect core samples.